libmicrohttpd

libmicrohttpd.texi (133273B)

---

 \input texinfo
 @setfilename libmicrohttpd.info
 @documentencoding UTF-8
 @include version.texi
 @settitle The GNU libmicrohttpd Reference Manual
 @c Unify all the indices into concept index.
 @syncodeindex vr cp
 @syncodeindex ky cp
 @syncodeindex pg cp
 @copying
 This manual is for GNU libmicrohttpd
 (version @value{VERSION}, @value{UPDATED}), a library for embedding
 an HTTP(S) server into C applications.
 
 Copyright @copyright{} 2007--2019 Christian Grothoff
 
 @quotation
 Permission is granted to copy, distribute and/or modify this document
 under the terms of the GNU Free Documentation License, Version 1.3
 or any later version published by the Free Software Foundation;
 with no Invariant Sections, no Front-Cover Texts, and no Back-Cover
 Texts.  A copy of the license is included in the section entitled "GNU
 Free Documentation License".
 @end quotation
 @end copying
 
 @dircategory Software libraries
 @direntry
 * libmicrohttpd: (libmicrohttpd).       Embedded HTTP server library.
 @end direntry
 
 @c
 @c Titlepage
 @c
 @titlepage
 @title The GNU libmicrohttpd Reference Manual
 @subtitle Version @value{VERSION}
 @subtitle @value{UPDATED}
 @author Marco Maggi (@email{marco.maggi-ipsu@@poste.it})
 @author Christian Grothoff (@email{christian@@grothoff.org})
 @page
 @vskip 0pt plus 1filll
 @insertcopying
 @end titlepage
 
 @summarycontents
 @contents
 
 @c ------------------------------------------------------------
 @ifnottex
 @node Top
 @top The GNU libmicrohttpd Library
 @insertcopying
 @end ifnottex
 
 @menu
 * microhttpd-intro::            Introduction.
 * microhttpd-const::            Constants.
 * microhttpd-struct::           Structures type definition.
 * microhttpd-cb::               Callback functions definition.
 * microhttpd-init::             Starting and stopping the server.
 * microhttpd-inspect::          Implementing external @code{select}.
 * microhttpd-requests::         Handling requests.
 * microhttpd-responses::        Building responses to requests.
 * microhttpd-flow::             Flow control.
 * microhttpd-dauth::            Utilizing Authentication.
 * microhttpd-post::             Adding a @code{POST} processor.
 * microhttpd-info::             Obtaining and modifying status information.
 * microhttpd-util::             Utilities.
 
 Appendices
 
 * GNU-LGPL::                    The GNU Lesser General Public License says how you
                                  can copy and share almost all of `libmicrohttpd'.
 * eCos License::                The eCos License says how you can copy and share some parts of `libmicrohttpd'.
 * GNU-GPL::                     The GNU General Public License (with eCos extension) says how you can copy and share some parts of `libmicrohttpd'.
 * GNU-FDL::                     The GNU Free Documentation License says how you
                                 can copy and share the documentation of `libmicrohttpd'.
 
 Indices
 
 * Concept Index::               Index of concepts and programs.
 * Function and Data Index::     Index of functions, variables and data types.
 * Type Index::                  Index of data types.
 @end menu
 
 @c ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 
 @c ------------------------------------------------------------
 @node microhttpd-intro
 @chapter Introduction
 
 
 @noindent
 All symbols defined in the public API start with @code{MHD_}.  MHD
 is a small HTTP daemon library.  As such, it does not have any API
 for logging errors (you can only enable or disable logging to stderr).
 Also, it may not support all of the HTTP features directly, where
 applicable, portions of HTTP may have to be handled by clients of the
 library.
 
 The library is supposed to handle everything that it must handle
 (because the API would not allow clients to do this), such as basic
 connection management. However, detailed interpretations of headers,
 such as range requests, are left to the main application.  In
 particular, if an application developer wants to support range
 requests, he needs to explicitly indicate support in responses and
 also explicitly parse the range header and generate a response (for
 example, using the @code{MHD_create_response_from_fd_at_offset} call
 to serve ranges from a file).  MHD does understands headers that
 control connection management (specifically, @code{Connection: close}
 and @code{Expect: 100 continue} are understood and handled
 automatically).  @code{Connection: upgrade} is supported by passing
 control over the socket (or something that behaves like the real
 socket in the case of TLS) to the application (after sending the
 desired HTTP response header).
 
 MHD largely ignores the semantics of the different HTTP methods,
 so clients are left to handle those.  One exception is that MHD does
 understand @code{HEAD} and will only send the headers of the response
 and not the body, even if the client supplied a body.  (In fact,
 clients do need to construct a response with the correct length, even
 for @code{HEAD} request.)
 
 MHD understands @code{POST} data and is able to decode certain
 formats (at the moment only @code{application/x-www-form-urlencoded}
 and @code{multipart/form-data}) using the post processor API.  The
 data stream of a POST is also provided directly to the main
 application, so unsupported encodings could still be processed, just
 not conveniently by MHD.
 
 The header file defines various constants used by the HTTP protocol.
 This does not mean that MHD actually interprets all of these values.
 The provided constants are exported as a convenience for users of the
 library.  MHD does not verify that transmitted HTTP headers are
 part of the standard specification; users of the library are free to
 define their own extensions of the HTTP standard and use those with
 MHD.
 
 All functions are guaranteed to be completely reentrant and
 thread-safe.  MHD checks for allocation failures and tries to
 recover gracefully (for example, by closing the connection).
 Additionally, clients can specify resource limits on the overall
 number of connections, number of connections per IP address and memory
 used per connection to avoid resource exhaustion.
 
 @section Scope
 
 MHD is currently used in a wide range of implementations.
 Examples based on reports we've received from developers include:
 @itemize
 @item Embedded HTTP server on a cortex M3 (128 KB code space)
 @item Large-scale multimedia server (reportedly serving at the
       simulator limit of 7.5 GB/s)
 @item Administrative console (via HTTP/HTTPS) for network appliances
 @c If you have other interesting examples, please let us know
 @end itemize
 
 @section Thread modes and event loops
 @cindex poll
 @cindex epoll
 @cindex select
 
 MHD supports four basic thread modes and up to three event loop
 styles.
 
 The four basic thread modes are external sockets polling (MHD creates
 no threads, event loop is fully managed by the application), internal
 polling (MHD creates one thread for all connections), polling in
 thread pool (MHD creates a thread pool which is used to process all
 connections) and thread-per-connection (MHD creates one thread for
 listen sockets and then one thread per accepted connection).
 
 These thread modes are then combined with the evet loop styles
 (polling function type).  MHD support select, poll and epoll. select
 is available on all platforms, epoll and poll may not be available on
 some platforms.  Note that it is possible to combine MHD using epoll
 with an external select-based event loop.
 
 The default (if no other option is passed) is ``external select''.
 The highest performance can typically be obtained with a thread pool
 using @code{epoll}.  Apache Benchmark (ab) was used to compare the
 performance of @code{select} and @code{epoll} when using a thread pool
 and a large number of connections. @ref{fig:performance} shows the
 resulting plot from the @code{benchmark.c} example, which measures the
 latency between an incoming request and the completion of the
 transmission of the response.  In this setting, the @code{epoll}
 thread pool with four threads was able to handle more than 45,000
 connections per second on loopback (with Apache Benchmark running
 three processes on the same machine).
 @cindex performance
 
 
 @float Figure,fig:performance
 @image{libmicrohttpd_performance_data,400pt,300pt,Data,.png}
 @caption{Performance measurements for select vs. epoll (with thread-pool).}
 @end float
 
 
 Not all combinations of thread modes and event loop styles are
 supported.  This is partially to keep the API simple, and partially
 because some combinations simply make no sense as others are strictly
 superior.  Note that the choice of style depends first of all on the
 application logic, and then on the performance requirements.
 Applications that perform a blocking operation while handling a
 request within the callbacks from MHD must use a thread per
 connection.  This is typically rather costly.  Applications that do
 not support threads or that must run on embedded devices without
 thread-support must use the external mode.  Using @code{epoll} is only
 supported on some platform, thus portable applications must at least
 have a fallback option available.  @ref{tbl:supported} lists the sane
 combinations.
 
 @float Table,tbl:supported
 @multitable {@b{thread-per-connection}} {@b{select}} {@b{poll}} {@b{epoll}}
 @item                           @tab @b{select} @tab @b{poll} @tab @b{epoll}
 @item @b{external}              @tab  yes       @tab no       @tab yes
 @item @b{internal}              @tab  yes       @tab yes      @tab yes
 @item @b{thread pool}           @tab  yes       @tab yes      @tab yes
 @item @b{thread-per-connection} @tab  yes       @tab yes      @tab no
 @end multitable
 @caption{Supported combinations of event styles and thread modes.}
 @end float
 
 
 @section Compiling GNU libmicrohttpd
 @cindex compilation
 @cindex embedded systems
 @cindex portability
 
 MHD uses the standard GNU system where the usual build process
 involves running
 @verbatim
 $ ./configure
 $ make
 $ make install
 @end verbatim
 
 MHD supports various options to be given to configure to tailor the
 binary to a specific situation.  Note that some of these options will
 remove portions of the MHD code that are required for
 binary-compatibility.  They should only be used on embedded systems
 with tight resource constraints and no concerns about library
 versioning.  Standard distributions including MHD are expected to
 always ship with all features enabled, otherwise unexpected
 incompatibilities can arise!
 
 Here is a list of MHD-specific options that can be given to configure
 (canonical configure options such as ``--prefix'' are also supported, for a
 full list of options run ``./configure --help''):
 
 @table @code
 @item ``--disable-curl''
 disable running testcases using libcurl
 
 @item ``--disable-largefile''
 disable support for 64-bit files
 
 @item ``--disable-messages''
 disable logging of error messages (smaller binary size, not so much fun for debugging)
 
 @item ``--disable-https''
 disable HTTPS support, even if GNUtls is found; this option must be used if eCOS license is desired as an option (in all cases the resulting binary falls under a GNU LGPL-only license)
 
 @item ``--disable-postprocessor''
 do not include the post processor API (results in binary incompatibility)
 
 @item ``--disable-dauth''
 do not include the authentication APIs (results in binary incompatibility)
 
 @item ``--disable-httpupgrade''
 do not build code for HTTP ``Upgrade'' (smaller binary size, binary incompatible library)
 
 @item ``--disable-epoll''
 do not include epoll support, even if it supported (minimally smaller binary size, good for portability testing)
 
 @item ``--enable-coverage''
 set flags for analysis of code-coverage with gcc/gcov (results in slow, large binaries)
 
 @item ``--with-threads=posix,w32,none,auto''
 sets threading library to use. With use ``none'' to not support threads. In this case, MHD will only support the ``external'' threading modes and not perform any locking of data structures! Use @code{MHD_is_feature_supported(MHD_FEATURE_THREADS)} to test if threads are available. Default is ``auto''.
 
 @item ``--with-gcrypt=PATH''
 specifies path to libgcrypt installation
 
 @item ``--with-gnutls=PATH''
 specifies path to libgnutls installation
 
 @end table
 
 To cross-compile MHD for Android, install the Android NDK and use:
 @verbatim
 ./configure --target=arm-linux-androideabi --host=arm-linux-androideabi --disable-doc --disable-examples
 make
 @end verbatim
 
 Similar build commands should work for cross-compilation to other platforms.
 Note that you may have to first cross-compile GnuTLS to get MHD with TLS support.
 
 
 @section Validity of pointers
 
 MHD will give applications access to its internal data structures
 via pointers via arguments and return values from its API.  This
 creates the question as to how long those pointers are assured to
 stay valid.
 
 Most MHD data structures are associated with the connection of an
 HTTP client.  Thus, pointers associated with a connection are
 typically valid until the connection is finished, at which point
 MHD will call the @code{MHD_RequestCompletedCallback} if one is
 registered.  Applications that have such a callback registered
 may assume that keys and values from the
 @code{MHD_KeyValueIterator}, return values from
 @code{MHD_lookup_connection_value} and the @code{url},
 @code{method} and @code{version} arguments to the
 @code{MHD_AccessHandlerCallback} will remain valid until the
 respective @code{MHD_RequestCompletedCallback} is invoked.
 
 In contrast, the @code{upload_data} argument of
 @code{MHD_RequestCompletedCallback} as well as all pointers
 from the @code{MHD_PostDataIterator} are only valid for the
 duration of the callback.
 
 Pointers returned from @code{MHD_get_response_header} are
 valid as long as the response itself is valid.
 
 
 @section Including the microhttpd.h header
 @cindex portability
 @cindex microhttpd.h
 
 Ideally, before including "microhttpd.h" you should add the necessary
 includes to define the @code{va_list}, @code{size_t}, @code{ssize_t},
 @code{intptr_t}, @code{off_t}, @code{uint8_t}, @code{uint16_t},
 @code{int32_t}, @code{uint32_t}, @code{int64_t}, @code{uint64_t},
 @code{fd_set}, @code{socklen_t} and @code{struct sockaddr} data types.
 Which specific headers are needed may depend on your platform and your
 build system might include some tests to provide you with the
 necessary conditional operations.  For possible suggestions consult
 @code{platform.h} and @code{configure.ac} in the MHD distribution.
 
 Once you have ensured that you manually (!) included the right headers
 for your platform before "microhttpd.h", you should also add a line
 with @code{#define MHD_PLATFORM_H} which will prevent the
 "microhttpd.h" header from trying (and, depending on your platform,
 failing) to include the right headers.
 
 If you do not define MHD_PLATFORM_H, the "microhttpd.h" header will
 automatically include headers needed on GNU/Linux systems (possibly
 causing problems when porting to other platforms).
 
 @section SIGPIPE
 @cindex signals
 MHD does not install a signal handler for SIGPIPE.  On platforms where
 this is possible (such as GNU/Linux), it disables SIGPIPE for its I/O
 operations (by passing MSG_NOSIGNAL or similar).  On other platforms,
 SIGPIPE signals may be generated from network operations by MHD and
 will cause the process to die unless the developer explicitly installs
 a signal handler for SIGPIPE.
 
 Hence portable code using MHD must install a SIGPIPE handler or
 explicitly block the SIGPIPE signal.  MHD does not do so in order to
 avoid messing with other parts of the application that may need to
 handle SIGPIPE in a particular way.  You can make your application
 handle SIGPIPE by calling the following function in @code{main}:
 
 @verbatim
 static void
 catcher (int sig)
 {
 }
 
 static void
 ignore_sigpipe ()
 {
   struct sigaction oldsig;
   struct sigaction sig;
 
   sig.sa_handler = &catcher;
   sigemptyset (&sig.sa_mask);
 #ifdef SA_INTERRUPT
   sig.sa_flags = SA_INTERRUPT;  /* SunOS */
 #else
   sig.sa_flags = SA_RESTART;
 #endif
   if (0 != sigaction (SIGPIPE, &sig, &oldsig))
     fprintf (stderr,
              "Failed to install SIGPIPE handler: %s\n", strerror (errno));
 }
 @end verbatim
 
 @section MHD_UNSIGNED_LONG_LONG
 @cindex long long
 @cindex MHD_LONG_LONG
 @cindex IAR
 @cindex ARM
 @cindex cortex m3
 @cindex embedded systems
 
 Some platforms do not support @code{long long}.  Hence MHD defines a
 macro @code{MHD_UNSIGNED LONG_LONG} which will default to
 @code{unsigned long long}.  For standard desktop operating systems,
 this is all you need to know.
 
 However, if your platform does not support @code{unsigned long long},
 you should change "platform.h" to define @code{MHD_LONG_LONG} and
 @code{MHD_UNSIGNED_LONG_LONG} to an appropriate alternative type and
 also define @code{MHD_LONG_LONG_PRINTF} and
 @code{MHD_UNSIGNED_LONG_LONG_PRINTF} to the corresponding format
 string for printing such a data type.  Note that the ``signed''
 versions are deprecated.  Also, for historical reasons,
 @code{MHD_LONG_LONG_PRINTF} is without the percent sign, whereas
 @code{MHD_UNSIGNED_LONG_LONG_PRINTF} is with the percent sign.  Newly
 written code should only use the unsigned versions.  However, you need
 to define both in "platform.h" if you need to change the definition
 for the specific platform.
 
 
 @section Portability to W32
 
 libmicrohttpd in general ported well to W32. Most libmicrohttpd features
 are supported. W32 do not support some functions, like epoll and
 corresponding MHD features are not available on W32.
 
 
 @section Portability to z/OS
 
 To compile MHD on z/OS, extract the archive and run
 
 @verbatim
 iconv -f UTF-8 -t IBM-1047 contrib/ascebc > /tmp/ascebc.sh
 chmod +x /tmp/ascebc.sh
 for n in `find * -type f`
 do
   /tmp/ascebc.sh $n
 done
 @end verbatim
 to convert all source files to EBCDIC.  Note that you must run
 @code{configure} from the directory where the configure script is
 located.   Otherwise, configure will fail to find the
 @code{contrib/xcc} script (which is a wrapper around the z/OS c89
 compiler).
 
 
 
 @c ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 
 @c ------------------------------------------------------------
 @node microhttpd-const
 @chapter Constants
 
 
 @deftp {Enumeration} MHD_FLAG
 Options for the MHD daemon.
 
 Note that MHD will run automatically in background thread(s) only if
 @code{MHD_USE_INTERNAL_POLLING_THREAD} is used. Otherwise caller
 (application) must use @code{MHD_run} or @code{MHD_run_from_select} to
 have MHD processed network connections and data.
 
 Starting the daemon may also fail if a particular option is not
 implemented or not supported on the target platform (i.e. no support
 for @acronym{TLS}, threads or IPv6). TLS support generally depends on
 options given during MHD compilation.
 
 @table @code
 @item MHD_NO_FLAG
 No options selected.
 
 @item MHD_USE_ERROR_LOG
 If this flag is used, the library should print error messages and
 warnings to stderr (or to custom error printer if it's specified by
 options).  Note that for this run-time option to have any effect, MHD
 needs to be compiled with messages enabled. This is done by default
 except you ran configure with the @code{--disable-messages} flag set.
 
 @item MHD_USE_DEBUG
 @cindex debugging
 Currently the same as @code{MHD_USE_ERROR_LOG}.
 
 @item MHD_USE_TLS
 @cindex TLS
 @cindex SSL
 Run in HTTPS-mode.  If you specify @code{MHD_USE_TLS} and MHD was
 compiled without SSL support, @code{MHD_start_daemon} will return
 NULL.
 
 @item MHD_USE_THREAD_PER_CONNECTION
 Run using one thread per connection.
 
 @item MHD_USE_INTERNAL_POLLING_THREAD
 Run using an internal thread doing @code{SELECT}.
 
 @item MHD_USE_IPv6
 @cindex IPv6
 Run using the IPv6 protocol (otherwise, MHD will just support IPv4).
 If you specify @code{MHD_USE_IPV6} and the local platform does not
 support it, @code{MHD_start_daemon} will return NULL.
 
 If you want MHD to support IPv4 and IPv6 using a single socket, pass
 MHD_USE_DUAL_STACK, otherwise, if you only pass this option, MHD will
 try to bind to IPv6-only (resulting in no IPv4 support).
 
 @item MHD_USE_DUAL_STACK
 @cindex IPv6
 Use a single socket for IPv4 and IPv6.  Note that this will mean
 that IPv4 addresses are returned by MHD in the IPv6-mapped format
 (the 'struct sockaddr_in6' format will be used for IPv4 and IPv6).
 
 @item MHD_USE_PEDANTIC_CHECKS
 @cindex deprecated
 Deprecated (use @code{MHD_OPTION_STRICT_FOR_CLIENT}).
 Be pedantic about the protocol.
 Specifically, at the moment, this flag causes MHD to reject HTTP
 1.1 connections without a @code{Host} header.  This is required by the
 standard, but of course in violation of the ``be as liberal as possible
 in what you accept'' norm.  It is recommended to turn this @strong{ON}
 if you are testing clients against MHD, and @strong{OFF} in
 production.
 
 @item MHD_USE_POLL
 @cindex FD_SETSIZE
 @cindex poll
 @cindex select
 Use @code{poll()} instead of @code{select()}. This allows sockets with
 descriptors @code{>= FD_SETSIZE}.  This option currently only works in
 conjunction with @code{MHD_USE_INTERNAL_POLLING_THREAD} (at this point).
 If you specify @code{MHD_USE_POLL} and the local platform does not
 support it, @code{MHD_start_daemon} will return NULL.
 
 @item MHD_USE_EPOLL
 @cindex FD_SETSIZE
 @cindex epoll
 @cindex select
 Use @code{epoll()} instead of @code{poll()} or @code{select()}. This
 allows sockets with descriptors @code{>= FD_SETSIZE}.  This option is
 only available on some systems and does not work in conjunction with
 @code{MHD_USE_THREAD_PER_CONNECTION} (at this point).  If you specify
 @code{MHD_USE_EPOLL} and the local platform does not support it,
 @code{MHD_start_daemon} will return NULL.  Using @code{epoll()}
 instead of @code{select()} or @code{poll()} can in some situations
 result in significantly higher performance as the system call has
 fundamentally lower complexity (O(1) for @code{epoll()} vs. O(n) for
 @code{select()}/@code{poll()} where n is the number of open
 connections).
 
 @item MHD_USE_TURBO
 @cindex performance
 Enable optimizations to aggressively improve performance.
 
 Currently, the optimizations this option enables are based on
 opportunistic reads and writes.  Basically, MHD will simply try to
 read or write or accept on a socket before checking that the socket is
 ready for IO using the event loop mechanism.  As the sockets are
 non-blocking, this may fail (at a loss of performance), but generally
 MHD does this in situations where the operation is likely to succeed,
 in which case performance is improved.  Setting the flag should generally
 be safe (even though the code is slightly more experimental).  You may
 want to benchmark your application to see if this makes any difference
 for you.
 
 
 @item MHD_USE_SUPPRESS_DATE_NO_CLOCK
 @cindex date
 @cindex clock
 @cindex embedded systems
 Suppress (automatically) adding the 'Date:' header to HTTP responses.
 This option should ONLY be used on systems that do not have a clock
 and that DO provide other mechanisms for cache control.  See also
 RFC 2616, section 14.18 (exception 3).
 
 
 @item MHD_USE_NO_LISTEN_SOCKET
 @cindex listen
 @cindex proxy
 @cindex embedded systems
 Run the HTTP server without any listen socket.  This option only makes
 sense if @code{MHD_add_connection} is going to be used exclusively to
 connect HTTP clients to the HTTP server.  This option is incompatible
 with using a thread pool; if it is used,
 @code{MHD_OPTION_THREAD_POOL_SIZE} is ignored.
 
 
 @item MHD_USE_ITC
 @cindex quiesce
 Force MHD to use a signal inter-thread communication channel to notify
 the event loop (of threads) of our shutdown and other events.  This is
 required if an application uses @code{MHD_USE_INTERNAL_POLLING_THREAD}
 and then performs @code{MHD_quiesce_daemon} (which eliminates our
 ability to signal termination via the listen socket).  In these modes,
 @code{MHD_quiesce_daemon} will fail if this option was not set.  Also,
 use of this option is automatic (as in, you do not even have to
 specify it), if @code{MHD_USE_NO_LISTEN_SOCKET} is specified.  In
 "external" select mode, this option is always simply ignored.
 
 Using this option also guarantees that MHD will not call
 @code{shutdown()} on the listen socket, which means a parent
 process can continue to use the socket.
 
 @item MHD_ALLOW_SUSPEND_RESUME
 Enables using @code{MHD_suspend_connection} and
 @code{MHD_resume_connection}, as performing these calls requires some
 additional inter-thred communication channels to be created, and code
 not using these calls should not pay the cost.
 
 @item MHD_USE_TCP_FASTOPEN
 @cindex listen
 Enable TCP_FASTOPEN on the listen socket.  TCP_FASTOPEN is currently
 supported on Linux >= 3.6.  On other systems using this option with
 cause @code{MHD_start_daemon} to fail.
 
 
 @item MHD_ALLOW_UPGRADE
 @cindex upgrade
 This option must be set if you want to upgrade connections
 (via ``101 Switching Protocols'' responses).  This requires MHD to
 allocate additional resources, and hence we require this
 special flag so we only use the resources that are really needed.
 
 
 @item MHD_USE_AUTO
 Automatically select best event loop style (polling function)
 depending on requested mode by other MHD flags and functions available
 on platform.  If application doesn't have requirements for any
 specific polling function, it's recommended to use this flag.  This
 flag is very convenient for multiplatform applications.
 
 @item MHD_USE_POST_HANDSHAKE_AUTH_SUPPORT
 Tell the TLS library to support post handshake client authentication.
 Only useful in combination with @code{MHD_USE_TLS}.
 
 This option will only work if the underlying TLS library
 supports it (i.e. GnuTLS after 3.6.3). If the TLS library
 does not support it, MHD may ignore the option and proceed
 without supporting this features.
 
 @item MHD_USE_INSECURE_TLS_EARLY_DATA
 Tell the TLS library to support TLS v1.3 early data (0-RTT) with the
 resulting security drawbacks. Only enable this if you really know what
 you are doing. MHD currently does NOT enforce that this only affects
 GET requests! You have been warned.
 
 This option will only work if the underlying TLS library
 supports it (i.e. GnuTLS after 3.6.3). If the TLS library
 does not support it, MHD may ignore the option and proceed
 without supporting this features.
 
 @end table
 @end deftp
 
 
 @deftp {Enumeration} MHD_OPTION
 MHD options.  Passed in the varargs portion of
 @code{MHD_start_daemon()}.
 
 @table @code
 @item MHD_OPTION_END
 No more options / last option.  This is used to terminate the VARARGs
 list.
 
 @item MHD_OPTION_CONNECTION_MEMORY_LIMIT
 @cindex memory, limiting memory utilization
 Maximum memory size per connection (followed by a @code{size_t}).  The
 default is 32 kB (32*1024 bytes) as defined by the internal constant
 @code{MHD_POOL_SIZE_DEFAULT}.  Values above 128k are unlikely to
 result in much benefit, as half of the memory will be typically used
 for IO, and TCP buffers are unlikely to support window sizes above 64k
 on most systems.
 
 @item MHD_OPTION_CONNECTION_MEMORY_INCREMENT
 @cindex memory
 Increment to use for growing the read buffer (followed by a
 @code{size_t}).  The default is 1024 (bytes).  Increasing this value
 will make MHD use memory for reading more aggressively, which can
 reduce the number of @code{recvfrom} calls but may increase the number
 of @code{sendto} calls.  The given value must fit within
 MHD_OPTION_CONNECTION_MEMORY_LIMIT.
 
 @item MHD_OPTION_CONNECTION_LIMIT
 @cindex connection, limiting number of connections
 Maximum number of concurrent connections to accept (followed by an
 @code{unsigned int}).  The default is @code{FD_SETSIZE - 4} (the
 maximum number of file descriptors supported by @code{select} minus
 four for @code{stdin}, @code{stdout}, @code{stderr} and the server
 socket).  In other words, the default is as large as possible.
 
 If the connection limit is reached, MHD's behavior depends a bit on
 other options.  If @code{MHD_USE_ITC} was given, MHD
 will stop accepting connections on the listen socket.  This will cause
 the operating system to queue connections (up to the @code{listen()}
 limit) above the connection limit.  Those connections will be held
 until MHD is done processing at least one of the active connections.
 If @code{MHD_USE_ITC} is not set, then MHD will continue
 to @code{accept()} and immediately @code{close()} these connections.
 
 Note that if you set a low connection limit, you can easily get into
 trouble with browsers doing request pipelining.  For example, if your
 connection limit is ``1'', a browser may open a first connection to
 access your ``index.html'' file, keep it open but use a second
 connection to retrieve CSS files, images and the like.  In fact, modern
 browsers are typically by default configured for up to 15 parallel
 connections to a single server.  If this happens, MHD will refuse to
 even accept the second connection until the first connection is
 closed --- which does not happen until timeout.  As a result, the
 browser will fail to render the page and seem to hang.  If you expect
 your server to operate close to the connection limit, you should
 first consider using a lower timeout value and also possibly add
 a ``Connection: close'' header to your response to ensure that
 request pipelining is not used and connections are closed immediately
 after the request has completed:
 @example
 MHD_add_response_header (response,
                          MHD_HTTP_HEADER_CONNECTION,
                          "close");
 @end example
 
 @item MHD_OPTION_CONNECTION_TIMEOUT
 @cindex timeout
 After how many seconds of inactivity should a connection automatically
 be timed out? (followed by an @code{unsigned int}; use zero for no
 timeout).  The default is zero (no timeout).
 
 @item MHD_OPTION_NOTIFY_COMPLETED
 Register a function that should be called whenever a request has been
 completed (this can be used for application-specific clean up).
 Requests that have never been presented to the application (via
 @code{MHD_AccessHandlerCallback()}) will not result in
 notifications.
 
 This option should be followed by @strong{TWO} pointers.  First a
 pointer to a function of type @code{MHD_RequestCompletedCallback()}
 and second a pointer to a closure to pass to the request completed
 callback.  The second pointer maybe @code{NULL}.
 
 @item MHD_OPTION_NOTIFY_CONNECTION
 Register a function that should be called when the TCP connection to a
 client is opened or closed. The registered callback is called twice per
 TCP connection, with @code{MHD_CONNECTION_NOTIFY_STARTED} and
 @code{MHD_CONNECTION_NOTIFY_CLOSED} respectively. An additional
 argument can be used to store TCP connection specific information,
 which can be retrieved using @code{MHD_CONNECTION_INFO_SOCKET_CONTEXT}
 during the lifetime of the TCP connection. 
 Note @code{MHD_OPTION_NOTIFY_COMPLETED} and the @code{req_cls} argument
 to the @code{MHD_AccessHandlerCallback} are per HTTP request (and there
 can be multiple HTTP requests per TCP connection). 
 
 This option should be followed by @strong{TWO} pointers.  First a
 pointer to a function of type @code{MHD_NotifyConnectionCallback()}
 and second a pointer to a closure to pass to the request completed
 callback.  The second pointer maybe @code{NULL}.
 
 @item MHD_OPTION_PER_IP_CONNECTION_LIMIT
 Limit on the number of (concurrent) connections made to the
 server from the same IP address.  Can be used to prevent one
 IP from taking over all of the allowed connections.  If the
 same IP tries to establish more than the specified number of
 connections, they will be immediately rejected.  The option
 should be followed by an @code{unsigned int}.  The default is
 zero, which means no limit on the number of connections
 from the same IP address.
 
 @item MHD_OPTION_LISTEN_BACKLOG_SIZE
 Set the size of the @code{listen()} back log queue of the TCP socket.
 Takes an @code{unsigned int} as the argument.  Default is the
 platform-specific value of @code{SOMAXCONN}.
 
 @item MHD_OPTION_STRICT_FOR_CLIENT
 Specify how strict we should enforce the HTTP protocol.
 Takes an @code{int} as the argument.  Default is zero.
 
 If set to 1, MHD will be strict about the protocol.  Specifically, at
 the moment, this flag uses MHD to reject HTTP 1.1 connections without
 a "Host" header.  This is required by the standard, but of course in
 violation of the "be as liberal as possible in what you accept" norm.
 It is recommended to set this to 1 if you are testing clients against
 MHD, and 0 in production.
 
 If set to -1 MHD will be permissive about the protocol, allowing
 slight deviations that are technically not allowed by the
 RFC. Specifically, at the moment, this flag causes MHD to allow spaces
 in header field names. This is disallowed by the standard.
 
 It is not recommended to set it to -1 on publicly available servers as
 it may potentially lower level of protection.
 
 @item MHD_OPTION_SERVER_INSANITY
 @cindex testing
 Allows the application to disable certain sanity precautions in MHD. With
 these, the client can break the HTTP protocol, so this should never be used in
 production. The options are, however, useful for testing HTTP clients against
 "broken" server implementations.  This argument must be followed by an
 @code{unsigned int}, corresponding to an @code{enum MHD_DisableSanityCheck}.
 
 Right now, no sanity checks can be disabled.
 
 @item MHD_OPTION_SOCK_ADDR
 @cindex bind, restricting bind
 Bind daemon to the supplied socket address. This option should be followed by a
 @code{struct sockaddr *}.  If @code{MHD_USE_IPv6} is specified,
 the @code{struct sockaddr*} should point to a @code{struct sockaddr_in6},
 otherwise to a @code{struct sockaddr_in}.  If this option is not specified,
 the daemon will listen to incoming connections from anywhere.  If you use this
 option, the 'port' argument from @code{MHD_start_daemon} is ignored and the port
 from the given @code{struct sockaddr *} will be used instead.
 
 @item MHD_OPTION_URI_LOG_CALLBACK
 @cindex debugging
 @cindex logging
 @cindex query string
 Specify a function that should be called before parsing the URI from
 the client.  The specified callback function can be used for processing
 the URI (including the options) before it is parsed.  The URI after
 parsing will no longer contain the options, which maybe inconvenient for
 logging.  This option should be followed by two arguments, the first
 one must be of the form
 @example
  void * my_logger(void * cls, const char * uri, struct MHD_Connection *con)
 @end example
 where the return value will be passed as
 @code{*req_cls} in calls to the @code{MHD_AccessHandlerCallback}
 when this request is processed later; returning a
 value of @code{NULL} has no special significance; (however,
 note that if you return non-@code{NULL}, you can no longer
 rely on the first call to the access handler having
 @code{NULL == *req_cls} on entry)
 @code{cls} will be set to the second argument following
 MHD_OPTION_URI_LOG_CALLBACK.  Finally, @code{uri} will
 be the 0-terminated URI of the request.
 
 Note that during the time of this call, most of the connection's state
 is not initialized (as we have not yet parsed he headers).  However,
 information about the connecting client (IP, socket) is available.
 
 @item MHD_OPTION_HTTPS_MEM_KEY
 @cindex SSL
 @cindex TLS
 Memory pointer to the private key to be used by the
 HTTPS daemon.  This option should be followed by an
 "const char*" argument.
 This should be used in conjunction with 'MHD_OPTION_HTTPS_MEM_CERT'.
 
 @item MHD_OPTION_HTTPS_KEY_PASSWORD
 @cindex SSL
 @cindex TLS
 Memory pointer to the password that decrypts the
 private key to be used by the HTTPS daemon.
 This option should be followed by an
 "const char*" argument.
 This should be used in conjunction with 'MHD_OPTION_HTTPS_MEM_KEY'.
 
 The password (or passphrase) is only used immediately during
 @code{MHD_start_daemon()}.  Thus, the application may want to
 erase it from memory afterwards for additional security.
 
 @item MHD_OPTION_HTTPS_MEM_CERT
 @cindex SSL
 @cindex TLS
 Memory pointer to the certificate to be used by the
 HTTPS daemon.  This option should be followed by an
 "const char*" argument.
 This should be used in conjunction with 'MHD_OPTION_HTTPS_MEM_KEY'.
 
 @item MHD_OPTION_HTTPS_MEM_TRUST
 @cindex SSL
 @cindex TLS
 Memory pointer to the CA certificate to be used by the
 HTTPS daemon to authenticate and trust clients certificates.
 This option should be followed by an "const char*" argument.
 The presence of this option activates the request of certificate
 to the client. The request to the client is marked optional, and
 it is the responsibility of the server to check the presence
 of the certificate if needed.
 Note that most browsers will only present a client certificate
 only if they have one matching the specified CA, not sending
 any certificate otherwise.
 
 @item MHD_OPTION_HTTPS_CRED_TYPE
 @cindex SSL
 @cindex TLS
 Daemon credentials type.  Either certificate or anonymous,
 this option should be followed by one of the values listed in
 "enum gnutls_credentials_type_t".
 
 @item MHD_OPTION_HTTPS_PRIORITIES
 @cindex SSL
 @cindex TLS
 @cindex cipher
 SSL/TLS protocol version and ciphers.
 This option must be followed by an "const char *" argument
 specifying the SSL/TLS protocol versions and ciphers that
 are acceptable for the application.  The string is passed
 unchanged to gnutls_priority_init.  If this option is not
 specified, ``NORMAL'' is used.
 
 @item MHD_OPTION_HTTPS_CERT_CALLBACK
 @cindex SSL
 @cindex TLS
 @cindex SNI
 Use a callback to determine which X.509 certificate should be used for
 a given HTTPS connection.  This option should be followed by a
 argument of type "gnutls_certificate_retrieve_function2 *".  This
 option provides an alternative to MHD_OPTION_HTTPS_MEM_KEY and
 MHD_OPTION_HTTPS_MEM_CERT.  You must use this version if multiple
 domains are to be hosted at the same IP address using TLS's Server
 Name Indication (SNI) extension.  In this case, the callback is
 expected to select the correct certificate based on the SNI
 information provided.  The callback is expected to access the SNI data
 using gnutls_server_name_get().  Using this option requires GnuTLS 3.0
 or higher.
 
 @item MHD_OPTION_HTTPS_CERT_CALLBACK2
 @cindex SSL
 @cindex TLS
 @cindex SNI
 @cindex OCSP
 Use a callback to determine which X.509 certificate should be
 used for a given HTTPS connection.  This option should be
 followed by a argument of type `gnutls_certificate_retrieve_function3 *`.
 This option provides an
 alternative/extension to #MHD_OPTION_HTTPS_CERT_CALLBACK.
 You must use this version if you want to use OCSP stapling.
 Using this option requires GnuTLS 3.6.3 or higher.
 
 @item MHD_OPTION_GNUTLS_PSK_CRED_HANDLER
 @cindex SSL
 @cindex TLS
 @cindex PSK
 Use pre-shared key for TLS credentials.
 Pass a pointer to callback of type
 @code{MHD_PskServerCredentialsCallback} and a closure.
 The function will be called to
 retrieve the shared key for a given username.
 The key must be at least 16 bytes long, as required by RFC 4279
 section 7.1; MHD fails the authentication for a shorter one.
 
 @item MHD_OPTION_DIGEST_AUTH_RANDOM
 @cindex digest auth
 @cindex random
 Digest Authentication nonce's seed.
 
 This option should be followed by two arguments.  First an integer of
 type "size_t" which specifies the size of the buffer pointed to by the
 second argument in bytes.  Note that the application must ensure that
 the buffer of the second argument remains allocated and unmodified
 while the daemon is running.  For security, you SHOULD provide a fresh
 random nonce when using MHD with Digest Authentication.
 
 @item MHD_OPTION_NONCE_NC_SIZE
 @cindex digest auth
 @cindex replay attack
 
 Size of an array of nonce and nonce counter map.  This option must be
 followed by an "unsigned int" argument that have the size (number of
 elements) of a map of a nonce and a nonce-counter.  If this option
 is not specified, a default value of 4 will be used (which might be
 too small for servers handling many requests).  If you do not use
 digest authentication at all, you can specify a value of zero to
 save some memory.
 
 You should calculate the value of NC_SIZE based on the number of
 connections per second multiplied by your expected session duration
 plus a factor of about two for hash table collisions.  For example, if
 you expect 100 digest-authenticated connections per second and the
 average user to stay on your site for 5 minutes, then you likely need
 a value of about 60000.  On the other hand, if you can only expect
 only 10 digest-authenticated connections per second, tolerate browsers
 getting a fresh nonce for each request and expect a HTTP request
 latency of 250 ms, then a value of about 5 should be fine.
 
 
 @item MHD_OPTION_LISTEN_SOCKET
 @cindex systemd
 Listen socket to use.  Pass a listen socket for MHD to use
 (systemd-style).  If this option is used, MHD will not open its own
 listen socket(s). The argument passed must be of type "int" and refer
 to an existing socket that has been bound to a port and is listening.
 
 @item MHD_OPTION_EXTERNAL_LOGGER
 @cindex logging
 Use the given function for logging error messages.
 This option must be followed by two arguments; the
 first must be a pointer to a function
 of type 'void fun(void * arg, const char * fmt, va_list ap)'
 and the second a pointer of type 'void*' which will
 be passed as the "arg" argument to "fun".
 
 Note that MHD will not generate any log messages without
 the MHD_USE_ERROR_LOG flag set and if MHD was compiled
 with the "--disable-messages" flag.
 
 @item MHD_OPTION_THREAD_POOL_SIZE
 @cindex performance
 Number (unsigned int) of threads in thread pool. Enable
 thread pooling by setting this value to to something
 greater than 1. Currently, thread mode must be
 MHD_USE_INTERNAL_POLLING_THREAD if thread pooling is enabled
 (@code{MHD_start_daemon} returns @code{NULL} for an unsupported thread
 mode).
 
 @item MHD_OPTION_ARRAY
 @cindex options
 @cindex foreign-function interface
 This option can be used for initializing MHD using options from an
 array.  A common use for this is writing an FFI for MHD.  The actual
 options given are in an array of 'struct MHD_OptionItem', so this
 option requires a single argument of type 'struct MHD_OptionItem'.
 The array must be terminated with an entry @code{MHD_OPTION_END}.
 
 An example for code using MHD_OPTION_ARRAY is:
 @example
 struct MHD_OptionItem ops[] = @{
  @{ MHD_OPTION_CONNECTION_LIMIT, 100, NULL @},
  @{ MHD_OPTION_CONNECTION_TIMEOUT, 10, NULL @},
  @{ MHD_OPTION_END, 0, NULL @}
 @};
 d = MHD_start_daemon(0, 8080, NULL, NULL, dh, NULL,
                      MHD_OPTION_ARRAY, ops,
                      MHD_OPTION_END);
 @end example
 For options that expect a single pointer argument, the
 second member of the @code{struct MHD_OptionItem} is ignored.
 For options that expect two pointer arguments, the first
 argument must be cast to @code{intptr_t}.
 
 @item MHD_OPTION_UNESCAPE_CALLBACK
 @cindex internationalization
 @cindex escaping
 
 Specify a function that should be called for unescaping escape
 sequences in URIs and URI arguments.  Note that this function will NOT
 be used by the MHD_PostProcessor.  If this option is not specified,
 the default method will be used which decodes escape sequences of the
 form "%HH".  This option should be followed by two arguments, the
 first one must be of the form
 
 @example
   size_t my_unescaper(void * cls, struct MHD_Connection *c, char *s)
 @end example
 
 where the return value must be @code{strlen(s)} and @code{s} should be
 updated.  Note that the unescape function must not lengthen @code{s}
 (the result must be shorter than the input and still be 0-terminated).
 @code{cls} will be set to the second argument following
 MHD_OPTION_UNESCAPE_CALLBACK.
 
 
 @item MHD_OPTION_THREAD_STACK_SIZE
 @cindex stack
 @cindex thread
 @cindex pthread
 @cindex embedded systems
 Maximum stack size for threads created by MHD.  This option must be
 followed by a @code{size_t}).  Not specifying this option or using
 a value of zero means using the system default (which is likely to
 differ based on your platform).
 
 @item MHD_OPTION_TCP_FASTQUEUE_QUEUE_SIZE
 @cindex listen
 When the flag @code{MHD_USE_TCP_FASTOPEN} is used, this option sets the
 connection handshake queue size for the TCP FASTOPEN connections.  Note
 that a TCP FASTOPEN connection handshake occupies more resources than a
 TCP handshake as the SYN packets also contain DATA which is kept in the
 associate state until handshake is completed.  If this option is not
 given the queue size is set to a default value of 10.  This option must
 be followed by a @code{unsigned int}.
 
 @item MHD_OPTION_HTTPS_MEM_DHPARAMS
 @cindex TLS
 @cindex SSL
 @cindex DH
 Memory pointer for the Diffie-Hellman parameters (dh.pem) to be used
 by the HTTPS daemon for key exchange.  This option must be followed by
 a @code{const char *} argument.  The argument would be a zero-terminated
 string with a PEM encoded PKCS3 DH parameters structure suitable
 for passing to @code{gnutls_dh_parms_import_pkcs3}.
 
 @item MHD_OPTION_LISTENING_ADDRESS_REUSE
 @cindex bind, restricting bind
 @cindex reusing listening address
 This option must be followed by a @code{unsigned int} argument.
 If this option is present and true (nonzero) parameter is given, allow reusing
 the address:port of the listening socket (using @code{SO_REUSEPORT} on most
 platforms, and @code{SO_REUSEADDR} on Windows).  If a false (zero) parameter is
 given, disallow reusing the the address:port of the listening socket (this
 usually requires no special action, but @code{SO_EXCLUSIVEADDRUSE} is needed on
 Windows).  If this option is not present @code{SO_REUSEADDR} is used on all
 platforms except Windows so reusing of address:port is disallowed.
 
 @end table
 @end deftp
 
 
 @deftp {C Struct} MHD_OptionItem
 Entry in an MHD_OPTION_ARRAY.  See the @code{MHD_OPTION_ARRAY} option
 argument for its use.
 
 The @code{option} member is used to specify which option is specified
 in the array.  The other members specify the respective argument.
 
 Note that for options taking only a single pointer, the
 @code{ptr_value} member should be set.  For options taking two pointer
 arguments, the first pointer must be cast to @code{intptr_t} and both
 the @code{value} and the @code{ptr_value} members should be used to
 pass the two pointers.
 @end deftp
 
 
 @deftp {Enumeration} MHD_ValueKind
 The @code{MHD_ValueKind} specifies the source of the key-value pairs in
 the HTTP protocol.
 
 @table @code
 @item MHD_HEADER_KIND
 HTTP header.
 
 @item MHD_COOKIE_KIND
 @cindex cookie
 Cookies.  Note that the original HTTP header containing the cookie(s)
 will still be available and intact.
 
 @item MHD_POSTDATA_KIND
 @cindex POST method
 @code{POST} data.  This is available only if a content encoding
 supported by MHD is used (currently only @acronym{URL} encoding), and
 only if the posted content fits within the available memory pool.  Note
 that in that case, the upload data given to the
 @code{MHD_AccessHandlerCallback()} will be empty (since it has
 already been processed).
 
 @item MHD_GET_ARGUMENT_KIND
 @code{GET} (URI) arguments.
 
 @item MHD_FOOTER_KIND
 HTTP footer (only for http 1.1 chunked encodings).
 
 @end table
 @end deftp
 
 
 @deftp {Enumeration} MHD_RequestTerminationCode
 The @code{MHD_RequestTerminationCode} specifies reasons why a request
 has been terminated (or completed).
 
 @table @code
 @item MHD_REQUEST_TERMINATED_COMPLETED_OK
 We finished sending the response.
 
 @item MHD_REQUEST_TERMINATED_WITH_ERROR
 Error handling the connection (resources exhausted, other side closed
 connection, application error accepting request, etc.)
 
 @item MHD_REQUEST_TERMINATED_TIMEOUT_REACHED
 No activity on the connection for the number of seconds specified using
 @code{MHD_OPTION_CONNECTION_TIMEOUT}.
 
 @item MHD_REQUEST_TERMINATED_DAEMON_SHUTDOWN
 We had to close the session since MHD was being shut down.
 @end table
 @end deftp
 
 
 @deftp {Enumeration} MHD_ResponseMemoryMode
 The @code{MHD_ResponeMemoryMode} specifies how MHD should treat
 the memory buffer given for the response in
 @code{MHD_create_response_from_buffer}.
 
 @table @code
 @item MHD_RESPMEM_PERSISTENT
 Buffer is a persistent (static/global) buffer that won't change
 for at least the lifetime of the response, MHD should just use
 it, not free it, not copy it, just keep an alias to it.
 
 @item MHD_RESPMEM_MUST_FREE
 Buffer is heap-allocated with @code{malloc} (or equivalent) and
 should be freed by MHD after processing the response has
 concluded (response reference counter reaches zero).
 
 @item MHD_RESPMEM_MUST_COPY
 Buffer is in transient memory, but not on the heap (for example,
 on the stack or non-malloc allocated) and only valid during the
 call to @code{MHD_create_response_from_buffer}.  MHD must make its
 own private copy of the data for processing.
 
 @end table
 @end deftp
 
 
 @deftp {Enumeration} MHD_ResponseFlags
 Response-specific flags.  Passed as an argument to
 @code{MHD_set_response_options()}.
 
 @table @code
 @item MHD_RF_NONE
 No special handling.
 
 @item MHD_RF_HTTP_VERSION_1_0_ONLY
 Only respond in conservative HTTP 1.0-mode.   In particular,
 do not (automatically) sent "Connection" headers and always
 close the connection after generating the response.
 
 By default, MHD will respond using the same HTTP version which
 was set in the request. You can also set the
 @code{MHD_RF_HTTP_VERSION_1_0_RESPONSE} flag to force version 1.0
 in the response.
 
 @item MHD_RF_HTTP_VERSION_1_0_RESPONSE
 Only respond in HTTP 1.0-mode. Contrary to the
 @code{MHD_RF_HTTP_VERSION_1_0_ONLY} flag, the response's HTTP version will
 always be set to 1.0 and ``Connection'' headers are still supported.
 
 You can even combine this option with MHD_RF_HTTP_VERSION_1_0_ONLY to
 change the response's HTTP version while maintaining strict compliance
 with HTTP 1.0 regarding connection management.
 
 This solution is not perfect as this flag is set on the response which
 is created after header processing. So MHD will behave as a HTTP 1.1
 server until the response is queued. It means that an invalid HTTP 1.1
 request will fail even if the response is sent with HTTP 1.0 and the
 request would be valid if interpreted with this version. For example,
 this request will fail in strict mode:
 
 @verbatim
 GET / HTTP/1.1
 @end verbatim
 
 as the ``Host'' header is missing and is mandatory in HTTP 1.1, but it
 should succeed when interpreted with HTTP 1.0.
 
 @item MHD_RF_INSANITY_HEADER_CONTENT_LENGTH
 Disable sanity check preventing clients from manually
 setting the HTTP content length option.
 
 @end table
 @end deftp
 
 
 @deftp {Enumeration} MHD_ResponseOptions
 Response-specific options.  Passed in the varargs portion of
 @code{MHD_set_response_options()}.
 
 @table @code
 @item MHD_RO_END
 No more options / last option.  This is used to terminate the VARARGs
 list.
 @end table
 @end deftp
 
 
 @c ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 
 @c ------------------------------------------------------------
 @node microhttpd-struct
 @chapter Structures type definition
 
 
 @deftp {C Struct} MHD_Daemon
 Handle for the daemon (listening on a socket for HTTP traffic).
 @end deftp
 
 
 @deftp {C Struct} MHD_Connection
 Handle for a connection / HTTP request.  With HTTP/1.1, multiple
 requests can be run over the same connection.  However, MHD will only
 show one request per TCP connection to the client at any given time.
 @end deftp
 
 
 @deftp {C Struct} MHD_Response
 Handle for a response.
 @end deftp
 
 
 @deftp {C Struct} MHD_IoVec
 An element of an array of memory buffers.
 @end deftp
 
 
 @deftp {C Struct} MHD_PostProcessor
 @cindex POST method
 Handle for @code{POST} processing.
 @end deftp
 
 
 @deftp {C Union} MHD_ConnectionInfo
 Information about a connection.
 @end deftp
 
 
 @deftp {C Union} MHD_DaemonInfo
 Information about an MHD daemon.
 @end deftp
 
 
 
 @c ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 
 @c ------------------------------------------------------------
 @node microhttpd-cb
 @chapter Callback functions definition
 
 
 @deftypefn {Function Pointer} enum MHD_Result {*MHD_AcceptPolicyCallback} (void *cls, const struct sockaddr * addr, socklen_t addrlen)
 Invoked in the context of a connection to allow or deny a client to
 connect.  This callback return @code{MHD_YES} if connection is allowed,
 @code{MHD_NO} if not.
 
 @table @var
 @item cls
 custom value selected at callback registration time;
 @item addr
 address information from the client;
 @item addrlen
 length of the address information.
 @end table
 @end deftypefn
 
 
 @deftypefn {Function Pointer} enum MHD_Result {*MHD_AccessHandlerCallback} (void *cls, struct MHD_Connection * connection, const char *url, const char *method, const char *version, const char *upload_data, size_t *upload_data_size, void **req_cls)
 Invoked in the context of a connection to answer a request from the
 client.  This callback must call MHD functions (example: the
 @code{MHD_Response} ones) to provide content to give back to the client
 and return an HTTP status code (i.e. @code{200} for OK, @code{404},
 etc.).
 
 @ref{microhttpd-post}, for details on how to code this callback.
 
 Must return @code{MHD_YES} if the connection was handled successfully,
 @code{MHD_NO} if the socket must be closed due to a serious error while
 handling the request
 
 @table @var
 @item cls
 custom value selected at callback registration time;
 
 @item url
 the URL requested by the client;
 
 @item method
 the HTTP method used by the client (@code{GET}, @code{PUT},
 @code{DELETE}, @code{POST}, etc.);
 
 @item version
 the HTTP version string (i.e. @code{HTTP/1.1});
 
 @item upload_data
 the data being uploaded (excluding headers):
 @cindex POST method
 @cindex PUT method
 
 @code{POST} data @strong{will} be made available
 incrementally in @var{upload_data}; even if @code{POST}
 data is available, the first time the callback is
 invoked there won't be upload data, as this is done
 just after MHD parses the headers.  If supported by
 the client and the HTTP version, the application can
 at this point queue an error response to possibly
 avoid the upload entirely. If no response is generated,
 MHD will (if required) automatically send a 100 CONTINUE
 reply to the client.
 
 Afterwards, POST data will be passed to the callback
 to be processed incrementally by the application. The
 application may return @code{MHD_NO} to forcefully
 terminate the TCP connection without generating a
 proper HTTP response. Once all of the upload data has
 been provided to the application, the application
 will be called again with 0 bytes of upload data.
 At this point, a response should be queued to complete
 the handling of the request.
 
 @item upload_data_size
 set initially to the size of the @var{upload_data} provided; this
 callback must update this value to the number of bytes @strong{NOT}
 processed; unless external select is used, the callback maybe
 required to process at least some data.  If the callback fails to
 process data in multi-threaded or internal-select mode and if the
 read-buffer is already at the maximum size that MHD is willing to
 use for reading (about half of the maximum amount of memory allowed
 for the connection), then MHD will abort handling the connection
 and return an internal server error to the client.  In order to
 avoid this, clients must be able to process upload data incrementally
 and reduce the value of @code{upload_data_size}.
 
 @item req_cls
 reference to a pointer, initially set to @code{NULL}, that this callback can
 set to some address and that will be preserved by MHD for future
 calls for this request;
 
 since the access handler may be called many times (i.e., for a
 @code{PUT}/@code{POST} operation with plenty of upload data) this allows
 the application to easily associate some request-specific state;
 
 if necessary, this state can be cleaned up in the global
 @code{MHD_RequestCompletedCallback} (which can be set with the
 @code{MHD_OPTION_NOTIFY_COMPLETED}).
 @end table
 @end deftypefn
 
 
 @deftypefn {Function Pointer} void {*MHD_RequestCompletedCallback} (void *cls, struct MHD_Connectionconnection, void **req_cls, enum MHD_RequestTerminationCode toe)
 Signature of the callback used by MHD to notify the application about
 completed requests.
 
 @table @var
 @item cls
 custom value selected at callback registration time;
 
 @item connection
 connection handle;
 
 @item req_cls
 value as set by the last call to the
 @code{MHD_AccessHandlerCallback};
 
 @item toe
 reason for request termination see @code{MHD_OPTION_NOTIFY_COMPLETED}.
 @end table
 @end deftypefn
 
 
 @deftypefn {Function Pointer} enum MHD_Result {*MHD_KeyValueIterator} (void *cls, enum MHD_ValueKind kind, const char *key, const char *value, size_t value_size)
 Iterator over key-value pairs.  This iterator can be used to iterate
 over all of the cookies, headers, or @code{POST}-data fields of a
 request, and also to iterate over the headers that have been added to a
 response.
 
 @table @var
 @item cls
 custom value specified when iteration was triggered;
 
 @item kind
 kind of the header we are looking at
 
 @item key
 key for the value, can be an empty string
 
 @item value
 value corresponding value, can be NULL
 
 @item value_size
 number of bytes in @code{value}. This argument was introduced in
 @code{MHD_VERSION} 0x00096301 to allow applications to use binary
 zeros in values.  Applications using this argument must ensure that
 they are using a sufficiently recent version of MHD, i.e. by testing
 @code{MHD_get_version()} for values above or equal to 0.9.64.
 Applications that do not need zeros in values and that want to compile
 without warnings against newer versions of MHD should not declare this
 argument and cast the function pointer argument to
 @code{MHD_KeyValueIterator}.
 
 @end table
 
 Return @code{MHD_YES} to continue iterating, @code{MHD_NO} to abort the
 iteration.
 @end deftypefn
 
 
 @deftypefn {Function Pointer} ssize_t {*MHD_ContentReaderCallback} (void *cls, uint64_t pos, char *buf, size_t max)
 Callback used by MHD in order to obtain content.  The callback has to
 copy at most @var{max} bytes of content into @var{buf}.  The total
 number of bytes that has been placed into @var{buf} should be returned.
 
 Note that returning zero will cause MHD to try again.
 Thus, returning zero should only be used in conjunction
 with @code{MHD_suspend_connection()} to avoid busy waiting.
 
 While usually the callback simply returns the number of bytes written
 into @var{buf}, there are two special return value:
 
 @code{MHD_CONTENT_READER_END_OF_STREAM} (-1) should be returned
 for the regular end of transmission (with chunked encoding, MHD will then
 terminate the chunk and send any HTTP footers that might be
 present; without chunked encoding and given an unknown
 response size, MHD will simply close the connection; note
 that while returning @code{MHD_CONTENT_READER_END_OF_STREAM} is not technically
 legal if a response size was specified, MHD accepts this
 and treats it just as @code{MHD_CONTENT_READER_END_WITH_ERROR}.
 
 @code{MHD_CONTENT_READER_END_WITH_ERROR} (-2) is used to indicate a server
 error generating the response; this will cause MHD to simply
 close the connection immediately.  If a response size was
 given or if chunked encoding is in use, this will indicate
 an error to the client.  Note, however, that if the client
 does not know a response size and chunked encoding is not in
 use, then clients will not be able to tell the difference between
 @code{MHD_CONTENT_READER_END_WITH_ERROR} and
 @code{MHD_CONTENT_READER_END_OF_STREAM}.
 This is not a limitation of MHD but rather of the HTTP protocol.
 
 @table @var
 @item cls
 custom value selected at callback registration time;
 
 @item pos
 position in the datastream to access; note that if an
 @code{MHD_Response} object is re-used, it is possible for the same
 content reader to be queried multiple times for the same data; however,
 if an @code{MHD_Response} is not re-used, MHD guarantees that
 @var{pos} will be the sum of all non-negative return values obtained
 from the content reader so far.
 @end table
 
 Return @code{-1} on error (MHD will no longer try to read content and
 instead close the connection with the client).
 @end deftypefn
 
 
 @deftypefn {Function Pointer} void {*MHD_ContentReaderFreeCallback} (void *cls)
 This method is called by MHD if we are done with a content reader.
 It should be used to free resources associated with the content reader.
 @end deftypefn
 
 
 @deftypefn {Function Pointer} enum MHD_Result {*MHD_PostDataIterator} (void *cls, enum MHD_ValueKind kind, const char *key, const char *filename, const char *content_type, const char *transfer_encoding, const char *data, uint64_t off, size_t size)
 Iterator over key-value pairs where the value maybe made available in
 increments and/or may not be zero-terminated.  Used for processing
 @code{POST} data.
 
 @table @var
 @item cls
 custom value selected at callback registration time;
 
 @item kind
 type of the value;
 
 @item key
 zero-terminated key for the value;
 
 @item filename
 name of the uploaded file, @code{NULL} if not known;
 
 @item content_type
 mime-type of the data, @code{NULL} if not known;
 
 @item transfer_encoding
 encoding of the data, @code{NULL} if not known;
 
 @item data
 pointer to size bytes of data at the specified offset;
 
 @item off
 offset of data in the overall value;
 
 @item size
 number of bytes in data available.
 @end table
 
 Return @code{MHD_YES} to continue iterating, @code{MHD_NO} to abort the
 iteration.
 @end deftypefn
 
 
 @c ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 
 @c ------------------------------------------------------------
 @node microhttpd-init
 @chapter Starting and stopping the server
 
 @deftypefun {void} MHD_set_panic_func (MHD_PanicCallback cb, void *cls)
 Set a handler for fatal errors.
 
 @table @var
 @item cb
 function to call if MHD encounters a fatal internal error.  If no handler was set explicitly, MHD will call @code{abort}.
 
 @item cls
 closure argument for cb; the other arguments are the name of the source file, line number and a string describing the nature of the fatal error (which can be @code{NULL})
 @end table
 @end deftypefun
 
 @deftypefun {struct MHD_Daemon *} MHD_start_daemon (unsigned int flags, unsigned short port, MHD_AcceptPolicyCallback apc, void *apc_cls, MHD_AccessHandlerCallback dh, void *dh_cls, ...)
 Start a webserver on the given port.
 
 @table @var
 @item flags
 OR-ed combination of @code{MHD_FLAG} values;
 
 @item port
 port to bind to;
 
 @item apc
 callback to call to check which clients will be allowed to connect; you
 can pass @code{NULL} in which case connections from any @acronym{IP} will be
 accepted;
 
 @item apc_cls
 extra argument to @var{apc};
 
 @item dh
 default handler for all URIs;
 
 @item dh_cls
 extra argument to @var{dh}.
 @end table
 
 Additional arguments are a list of options (type-value pairs,
 terminated with @code{MHD_OPTION_END}). It is mandatory to use
 @code{MHD_OPTION_END} as last argument, even when there are no
 additional arguments.
 
 Return @code{NULL} on error, handle to daemon on success.
 @end deftypefun
 
 
 @deftypefun MHD_socket MHD_quiesce_daemon (struct MHD_Daemon *daemon)
 @cindex quiesce
 Stop accepting connections from the listening socket.  Allows clients
 to continue processing, but stops accepting new connections.  Note
 that the caller is responsible for closing the returned socket;
 however, if MHD is run using threads (anything but external select
 mode), it must not be closed until AFTER @code{MHD_stop_daemon} has
 been called (as it is theoretically possible that an existing thread
 is still using it).
 
 This function is useful in the special case that a listen socket
 is to be migrated to another process (i.e. a newer version of the
 HTTP server) while existing connections should continue to be
 processed until they are finished.
 
 Return @code{-1} on error (daemon not listening), the handle to the
 listen socket otherwise.
 
 @end deftypefun
 
 
 @deftypefun void MHD_stop_daemon (struct MHD_Daemon *daemon)
 Shutdown an HTTP daemon.
 @end deftypefun
 
 
 @deftypefun enum MHD_Result MHD_run (struct MHD_Daemon *daemon)
 Run webserver operations (without blocking unless in client callbacks).
 This method should be called by clients in combination with
 @code{MHD_get_fdset()} if the client-controlled @code{select}-method is used.
 @cindex select
 @cindex poll
 
 This function will work for external @code{poll} and @code{select} mode.
 However, if using external @code{select} mode, you may want to
 instead use @code{MHD_run_from_select}, as it is more efficient.
 
 @table @var
 @item daemon
 daemon to process connections of
 @end table
 
 Return @code{MHD_YES} on success, @code{MHD_NO} if this daemon was not
 started with the right options for this call.
 @end deftypefun
 
 
 @deftypefun enum MHD_Result MHD_run_from_select (struct MHD_Daemon *daemon, const fd_set *read_fd_set, const fd_set *write_fd_set, const fd_set *except_fd_set)
 Run webserver operations given sets of ready socket handles.
 @cindex select
 
 This method should be called by clients in combination with
 @code{MHD_get_fdset} if the client-controlled (external)
 select method is used.
 
 You can use this function instead of @code{MHD_run} if you called
 @code{select} on the result from @code{MHD_get_fdset}.  File descriptors in
 the sets that are not controlled by MHD will be ignored.  Calling
 this function instead of @code{MHD_run} is more efficient as MHD will
 not have to call @code{select} again to determine which operations are
 ready.
 
 @table @var
 @item daemon
 daemon to process connections of
 @item read_fd_set
 set of descriptors that must be ready for reading without blocking
 @item write_fd_set
 set of descriptors that must be ready for writing without blocking
 @item except_fd_set
 ignored, can be NULL
 @end table
 
 Return @code{MHD_YES} on success, @code{MHD_NO} on serious internal
 errors.
 
 @end deftypefun
 
 
 
 @deftypefun void MHD_add_connection (struct MHD_Daemon *daemon, int client_socket, const struct sockaddr *addr, socklen_t addrlen)
 Add another client connection to the set of connections
 managed by MHD.  This API is usually not needed (since
 MHD will accept inbound connections on the server socket).
 Use this API in special cases, for example if your HTTP
 server is behind NAT and needs to connect out to the
 HTTP client, or if you are building a proxy.
 
 If you use this API in conjunction with a internal select or a thread
 pool, you must set the option @code{MHD_USE_ITC} to
 ensure that the freshly added connection is immediately processed by
 MHD.
 
 The given client socket will be managed (and closed!) by MHD after
 this call and must no longer be used directly by the application
 afterwards.
 
 @table @var
 @item daemon
 daemon that manages the connection
 @item client_socket
 socket to manage (MHD will expect to receive an HTTP request from this socket next).
 @item addr
 IP address of the client
 @item addrlen
 number of bytes in addr
 @end table
 
 This function will return @code{MHD_YES} on success,
 @code{MHD_NO} if this daemon could
 not handle the connection (i.e. malloc failed, etc).
 The socket will be closed in any case; 'errno' is set
 to indicate further details about the error.
 @end deftypefun
 
 
 @c ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 
 @c -----------------------------------------------------------
 @node microhttpd-inspect
 @chapter Implementing external @code{select}
 
 
 @deftypefun enum MHD_Result MHD_get_fdset (struct MHD_Daemon *daemon, fd_set * read_fd_set, fd_set * write_fd_set, fd_set * except_fd_set, int *max_fd)
 Obtain the @code{select()} sets for this daemon. The daemon's socket
 is added to @var{read_fd_set}. The list of currently existent
 connections is scanned and their file descriptors added to the correct
 set.
 
 When calling this function, FD_SETSIZE is assumed to be platform's
 default.  If you changed FD_SETSIZE for your application,
 you should use @code{MHD_get_fdset2()} instead.
 
 This function should only be called in when MHD is configured to use
 external select with @code{select()} or with @code{epoll()}.  In
 the latter case, it will only add the single @code{epoll()} file
 descriptor used by MHD to the sets.
 
 After the call completed successfully: the variable referenced by
 @var{max_fd} references the file descriptor with highest integer
 identifier. The variable must be set to zero before invoking this
 function.
 
 Return @code{MHD_YES} on success, @code{MHD_NO} if: the arguments are
 invalid (example: @code{NULL} pointers); this daemon was not started with
 the right options for this call.
 @end deftypefun
 
 
 @deftypefun enum MHD_Result MHD_get_fdset2 (struct MHD_Daemon *daemon, fd_set * read_fd_set, fd_set * write_fd_set, fd_set * except_fd_set, int *max_fd, unsigned int fd_setsize)
 Like @code{MHD_get_fdset()}, except that you can manually specify the value of FD_SETSIZE used by your application.
 @end deftypefun
 
 
 @deftypefun enum MHD_Result MHD_get_timeout (struct MHD_Daemon *daemon, unsigned long long *timeout)
 @cindex timeout
 Obtain timeout value for select for this daemon (only needed if
 connection timeout is used).  The returned value is how many
 milliseconds @code{select} should at most block, not the timeout value
 set for connections.  This function must not be called if the
 @code{MHD_USE_THREAD_PER_CONNECTION} mode is in use (since then it is
 not meaningful to ask for a timeout, after all, there is concurrenct
 activity).  The function must also not be called by user-code if
 @code{MHD_USE_INTERNAL_POLLING_THREAD} is in use.  In the latter case, the
 behavior is undefined.
 
 @table @var
 @item daemon
 which daemon to obtain the timeout from.
 @item timeout
 will be set to the timeout (in milliseconds).
 @end table
 
 Return @code{MHD_YES} on success, @code{MHD_NO} if timeouts are not used
 (or no connections exist that would necessitate the use of a timeout
 right now).
 @end deftypefun
 
 
 @c ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 
 @c -----------------------------------------------------------
 @node microhttpd-requests
 @chapter Handling requests
 
 
 @deftypefun int MHD_get_connection_values (struct MHD_Connection *connection, enum MHD_ValueKind kind, MHD_KeyValueIterator iterator, void *iterator_cls)
 Get all the headers matching @var{kind} from the request.  The @var{kind}
 argument can be a bitmask, ORing the various header kinds that are
 requested.
 
 The @var{iterator} callback is invoked once for each header, with
 @var{iterator_cls} as first argument.  After version 0.9.19, the
 headers are iterated in the same order as they were received from
 the network; previous versions iterated over the headers in reverse
 order.
 
 @code{MHD_get_connection_values} returns the number of entries
 iterated over; this can be less than the number of headers if, while
 iterating, @var{iterator} returns @code{MHD_NO}.
 
 @var{iterator} can be @code{NULL}: in this case this function just counts
 and returns the number of headers.
 
 In the case of @code{MHD_GET_ARGUMENT_KIND}, the @var{value} argument
 will be @code{NULL} if the URL contained a key without an equals operator.
 For example, for a HTTP request to the URL ``http://foo/bar?key'', the
 @var{value} argument is @code{NULL}; in contrast, a HTTP request to the URL
 ``http://foo/bar?key='', the @var{value} argument is the empty string.
 The normal case is that the URL contains ``http://foo/bar?key=value''
 in which case @var{value} would be the string ``value'' and @var{key}
 would contain the string ``key''.
 @end deftypefun
 
 
 @deftypefun enum MHD_Result MHD_set_connection_value (struct MHD_Connection *connection, enum MHD_ValueKind kind, const char *key, const char *value)
 This function can be used to append an entry to
 the list of HTTP headers of a connection (so that the
 @code{MHD_get_connection_values function} will return
 them -- and the MHD PostProcessor will also
 see them).  This maybe required in certain
 situations (see Mantis #1399) where (broken)
 HTTP implementations fail to supply values needed
 by the post processor (or other parts of the
 application).
 
 This function MUST only be called from within
 the MHD_AccessHandlerCallback (otherwise, access
 maybe improperly synchronized).  Furthermore,
 the client must guarantee that the key and
 value arguments are 0-terminated strings that
 are NOT freed until the connection is closed.
 (The easiest way to do this is by passing only
 arguments to permanently allocated strings.).
 
 @var{connection} is the connection for which
 the entry for @var{key} of the given @var{kind}
 should be set to the given @var{value}.
 
 The function returns @code{MHD_NO} if the operation
 could not be performed due to insufficient memory
 and @code{MHD_YES} on success.
 @end deftypefun
 
 
 @deftypefun {const char *} MHD_lookup_connection_value (struct MHD_Connection *connection, enum MHD_ValueKind kind, const char *key)
 Get a particular header value.  If multiple values match the
 @var{kind}, return one of them (the ``first'', whatever that means).
 @var{key} must reference a zero-terminated ASCII-coded string
 representing the header to look for: it is compared against the
 headers using (basically) @code{strcasecmp()}, so case is ignored.
 @end deftypefun
 
 @deftypefun {const char *} MHD_lookup_connection_value_n (struct MHD_Connection *connection, enum MHD_ValueKind kind, const char *key, size_t key_size, const char **value_ptr, size_t *value_size_ptr)
 Get a particular header value.  If multiple values match the
 @var{kind}, return one of them (the ``first'', whatever that means).
 @var{key} must reference an ASCII-coded string
 representing the header to look for: it is compared against the
 headers using (basically) @code{strncasecmp()}, so case is ignored.
 The @var{value_ptr} is set to the address of the value found,
 and @var{value_size_ptr} is set to the number of bytes in the
 value.
 @end deftypefun
 
 
 @c ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 
 @c ------------------------------------------------------------
 @node microhttpd-responses
 @chapter Building responses to requests
 
 
 @noindent
 Response objects handling by MHD is asynchronous with respect to the
 application execution flow. Instances of the @code{MHD_Response}
 structure are not associated to a daemon and neither to a client
 connection: they are managed with reference counting.
 
 In the simplest case: we allocate a new @code{MHD_Response} structure
 for each response, we use it once and finally we destroy it.
 
 MHD allows more efficient resources usages.
 
 Example: we allocate a new @code{MHD_Response} structure for each
 response @strong{kind}, we use it every time we have to give that
 response and we finally destroy it only when the daemon shuts down.
 
 @menu
 * microhttpd-response enqueue:: Enqueuing a response.
 * microhttpd-response create::  Creating a response object.
 * microhttpd-response headers:: Adding headers to a response.
 * microhttpd-response options:: Setting response options.
 * microhttpd-response inspect:: Inspecting a response object.
 * microhttpd-response upgrade:: Creating a response for protocol upgrades.
 @end menu
 
 @c ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 
 @c ------------------------------------------------------------
 @node microhttpd-response enqueue
 @section Enqueuing a response
 
 
 @deftypefun enum MHD_Result MHD_queue_response (struct MHD_Connection *connection, unsigned int status_code, struct MHD_Response *response)
 Queue a response to be transmitted to the client as soon as possible
 but only after MHD_AccessHandlerCallback returns.  This function
 checks that it is legal to queue a response at this time for the
 given connection.  It also increments the internal reference
 counter for the response object (the counter will be decremented
 automatically once the response has been transmitted).
 
 @table @var
 @item connection
 the connection identifying the client;
 
 @item status_code
 HTTP status code (i.e. @code{200} for OK);
 
 @item response
 response to transmit.
 @end table
 
 Return @code{MHD_YES} on success or if message has been queued.  Return
 @code{MHD_NO}: if arguments are invalid (example: @code{NULL} pointer); on
 error (i.e. reply already sent).
 @end deftypefun
 
 
 @deftypefun void MHD_destroy_response (struct MHD_Response *response)
 Destroy a response object and associated resources (decrement the
 reference counter).  Note that MHD may keep some of the resources
 around if the response is still in the queue for some clients, so the
 memory may not necessarily be freed immediately.
 @end deftypefun
 
 
 An explanation of reference counting@footnote{Note to readers acquainted
 to the Tcl API: reference counting on @code{MHD_Connection}
 structures is handled in the same way as Tcl handles @code{Tcl_Obj}
 structures through @code{Tcl_IncrRefCount()} and
 @code{Tcl_DecrRefCount()}.}:
 
 @enumerate
 @item
 a @code{MHD_Response} object is allocated:
 
 @example
 struct MHD_Response * response = MHD_create_response_from_buffer(...);
 /* here: reference counter = 1 */
 @end example
 
 @item
 the @code{MHD_Response} object is enqueued in a @code{MHD_Connection}:
 
 @example
 MHD_queue_response(connection, , response);
 /* here: reference counter = 2 */
 @end example
 
 @item
 the creator of the response object discharges responsibility for it:
 
 @example
 MHD_destroy_response(response);
 /* here: reference counter = 1 */
 @end example
 
 @item
 the daemon handles the connection sending the response's data to the
 client then decrements the reference counter by calling
 @code{MHD_destroy_response()}: the counter's value drops to zero and
 the @code{MHD_Response} object is released.
 @end enumerate
 
 
 @c ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 
 @c ------------------------------------------------------------
 @node microhttpd-response create
 @section Creating a response object
 
 
 @deftypefun {struct MHD_Response *} MHD_create_response_from_callback (uint64_t size, size_t block_size, MHD_ContentReaderCallback crc, void *crc_cls, MHD_ContentReaderFreeCallback crfc)
 Create a response object.  The response object can be extended with
 header information and then it can be used any number of times.
 
 @table @var
 @item size
 size of the data portion of the response, @code{-1} for unknown;
 
 @item block_size
 preferred block size for querying @var{crc} (advisory only, MHD may
 still call @var{crc} using smaller chunks); this is essentially the
 buffer size used for @acronym{IO}, clients should pick a value that is
 appropriate for @acronym{IO} and memory performance requirements;
 
 @item crc
 callback to use to obtain response data;
 
 @item crc_cls
 extra argument to @var{crc};
 
 @item crfc
 callback to call to free @var{crc_cls} resources.
 @end table
 
 Return @code{NULL} on error (i.e. invalid arguments, out of memory).
 @end deftypefun
 
 
 
 @deftypefun {struct MHD_Response *} MHD_create_response_from_fd (uint64_t size, int fd)
 Create a response object.  The response object can be extended with
 header information and then it can be used any number of times.
 
 @table @var
 @item size
 size of the data portion of the response (should be smaller or equal to the
 size of the file)
 
 @item fd
 file descriptor referring to a file on disk with the data; will be
 closed when response is destroyed; note that 'fd' must be an actual
 file descriptor (not a pipe or socket) since MHD might use 'sendfile'
 or 'seek' on it.  The descriptor should be in blocking-IO mode.
 @end table
 
 Return @code{NULL} on error (i.e. invalid arguments, out of memory).
 @end deftypefun
 
 
 @deftypefun {struct MHD_Response *} MHD_create_response_from_pipe (int fd)
 Create a response object.  The response object can be extended with
 header information and then it can be used ONLY ONCE.
 
 @table @var
 @item fd
 file descriptor of the read-end of the pipe; will be
 closed when response is destroyed.
 The descriptor should be in blocking-IO mode.
 @end table
 
 Return @code{NULL} on error (i.e. out of memory).
 @end deftypefun
 
 
 @deftypefun {struct MHD_Response *} MHD_create_response_from_fd_at_offset (size_t size, int fd, off_t offset)
 Create a response object.  The response object can be extended with
 header information and then it can be used any number of times.
 Note that you need to be a bit careful about @code{off_t} when
 writing this code.  Depending on your platform, MHD is likely
 to have been compiled with support for 64-bit files.  When you
 compile your own application, you must make sure that @code{off_t}
 is also a 64-bit value.  If not, your compiler may pass a 32-bit
 value as @code{off_t}, which will result in 32-bits of garbage.
 
 If you use the autotools, use the @code{AC_SYS_LARGEFILE} autoconf
 macro and make sure to include the generated @file{config.h} file
 before @file{microhttpd.h} to avoid problems.  If you do not have a
 build system and only want to run on a GNU/Linux system, you could
 also use
 @verbatim
 #define _FILE_OFFSET_BITS 64
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <fcntl.h>
 #include <microhttpd.h>
 @end verbatim
 to ensure 64-bit @code{off_t}.  Note that if your operating system
 does not support 64-bit files, MHD will be compiled with a 32-bit
 @code{off_t} (in which case the above would be wrong).
 
 @table @var
 @item size
 size of the data portion of the response (number of bytes to transmit from the
 file starting at offset).
 
 @item fd
 file descriptor referring to a file on disk with the data; will be
 closed when response is destroyed; note that 'fd' must be an actual
 file descriptor (not a pipe or socket) since MHD might use 'sendfile'
 or 'seek' on it.    The descriptor should be in blocking-IO mode.
 
 @item offset
 offset to start reading from in the file
 @end table
 
 Return @code{NULL} on error (i.e. invalid arguments, out of memory).
 @end deftypefun
 
 
 @deftypefun {struct MHD_Response *} MHD_create_response_from_buffer (size_t size, void *data, enum MHD_ResponseMemoryMode mode)
 Create a response object.  The response object can be extended with
 header information and then it can be used any number of times.
 
 @table @var
 @item size
 size of the data portion of the response;
 
 @item buffer
 the data itself;
 
 @item mode
 memory management options for buffer; use
 MHD_RESPMEM_PERSISTENT if the buffer is static/global memory,
 use MHD_RESPMEM_MUST_FREE if the buffer is heap-allocated and
 should be freed by MHD and MHD_RESPMEM_MUST_COPY if the
 buffer is in transient memory (i.e. on the stack) and must
 be copied by MHD;
 @end table
 
 Return @code{NULL} on error (i.e. invalid arguments, out of memory).
 @end deftypefun
 
 
 @deftypefun {struct MHD_Response *} MHD_create_response_from_buffer_with_free_callback (size_t size, void *data,  MHD_ContentReaderFreeCallback crfc)
 Create a response object.  The buffer at the end must be free'd
 by calling the @var{crfc} function.
 
 @table @var
 @item size
 size of the data portion of the response;
 
 @item buffer
 the data itself;
 
 @item crfc
 function to call at the end to free memory allocated at @var{buffer}.
 @end table
 
 Return @code{NULL} on error (i.e. invalid arguments, out of memory).
 @end deftypefun
 
 @deftypefun {struct MHD_Response *} MHD_create_response_from_data (size_t size, void *data, int must_free, int must_copy)
 Create a response object.  The response object can be extended with
 header information and then it can be used any number of times.
 This function is deprecated, use @code{MHD_create_response_from_buffer} instead.
 
 @table @var
 @item size
 size of the data portion of the response;
 
 @item data
 the data itself;
 
 @item must_free
 if true: MHD should free data when done;
 
 @item must_copy
 if true: MHD allocates a block of memory and use it to make a copy of
 @var{data} embedded in the returned @code{MHD_Response} structure;
 handling of the embedded memory is responsibility of MHD; @var{data}
 can be released anytime after this call returns.
 @end table
 
 Return @code{NULL} on error (i.e. invalid arguments, out of memory).
 @end deftypefun
 
 
 Example: create a response from a statically allocated string:
 
 @example
 const char * data = "<html><body><p>Error!</p></body></html>";
 
 struct MHD_Connection * connection = ...;
 struct MHD_Response *   response;
 
 response = MHD_create_response_from_buffer (strlen(data), data,
                                             MHD_RESPMEM_PERSISTENT);
 MHD_queue_response(connection, 404, response);
 MHD_destroy_response(response);
 @end example
 
 
 @deftypefun {struct MHD_Response *} MHD_create_response_from_iovec (const struct MHD_IoVec *iov, int iovcnt, MHD_ContentReaderFreeCallback crfc, void *cls)
 Create a response object from an array of memory buffers.
 The response object can be extended with header information and then be used
 any number of times.
 @table @var
 @item iov
 the array for response data buffers, an internal copy of this will be made; however, note that the data pointed to by the @var{iov} is not copied and must be preserved unchanged at the given locations until the response is no longer in use and the @var{crfc} is called;
 
 @item iovcnt
 the number of elements in @var{iov};
 
 @item crfc
 the callback to call to free resources associated with @var{iov};
 
 @item cls
 the argument to @var{crfc};
 @end table
 
 Return @code{NULL} on error (i.e. invalid arguments, out of memory).
 @end deftypefun
 
 
 
 @c ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 
 @c ------------------------------------------------------------
 @node microhttpd-response headers
 @section Adding headers to a response
 
 
 @deftypefun enum MHD_Result MHD_add_response_header (struct MHD_Response *response, const char *header, const char *content)
 Add a header line to the response. The strings referenced by
 @var{header} and @var{content} must be zero-terminated and they are
 duplicated into memory blocks embedded in @var{response}.
 
 Notice that the strings must not hold newlines, carriage returns or tab
 chars.
 
 MHD_add_response_header() prevents applications from setting a
 ``Transfer-Encoding'' header to values other than ``identity'' or
 ``chunked'' as other transfer encodings are not supported by MHD. Note
 that usually MHD will pick the transfer encoding correctly
 automatically, but applications can use the header to force a
 particular behavior.
 
 MHD_add_response_header() also prevents applications from setting a
 ``Content-Length'' header. MHD will automatically set a correct
 ``Content-Length'' header if it is possible and allowed.
 
 Return @code{MHD_NO} on error (i.e. invalid header or content format or
 memory allocation error).
 @end deftypefun
 
 
 @deftypefun enum MHD_Result MHD_add_response_footer (struct MHD_Response *response, const char *footer, const char *content)
 Add a footer line to the response. The strings referenced by
 @var{footer} and @var{content} must be zero-terminated and they are
 duplicated into memory blocks embedded in @var{response}.
 
 Notice that the strings must not hold newlines, carriage returns or tab
 chars.  You can add response footers at any time before signalling the
 end of the response to MHD (not just before calling 'MHD_queue_response').
 Footers are useful for adding cryptographic checksums to the reply or to
 signal errors encountered during data generation.  This call was introduced
 in MHD 0.9.3.
 
 Return @code{MHD_NO} on error (i.e. invalid header or content format or
 memory allocation error).
 @end deftypefun
 
 
 
 @deftypefun enum MHD_Result MHD_del_response_header (struct MHD_Response *response, const char *header, const char *content)
 Delete a header (or footer) line from the response.  Return @code{MHD_NO} on error
 (arguments are invalid or no such header known).
 @end deftypefun
 
 
 @c ------------------------------------------------------------
 @node microhttpd-response options
 @section Setting response options
 
 
 @deftypefun enum MHD_Result MHD_set_response_options (struct MHD_Response *response, enum MHD_ResponseFlags flags, ...)
 Set special flags and options for a response.
 
 Calling this functions sets the given flags and options for the response.
 
 @table @var
 @item response
 which response should be modified;
 
 @item flags
 flags to set for the response;
 
 @end table
 
 Additional arguments are a list of options (type-value pairs,
 terminated with @code{MHD_RO_END}). It is mandatory to use
 @code{MHD_RO_END} as last argument, even when there are no
 additional arguments.
 
 Return @code{MHD_NO} on error, @code{MHD_YES} on success.
 @end deftypefun
 
 
 @c ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 
 @c ------------------------------------------------------------
 @node microhttpd-response inspect
 @section Inspecting a response object
 
 
 @deftypefun int MHD_get_response_headers (struct MHD_Response *response, MHD_KeyValueIterator iterator, void *iterator_cls)
 Get all of the headers added to a response.
 
 Invoke the @var{iterator} callback for each header in the response,
 using @var{iterator_cls} as first argument. Return number of entries
 iterated over.  @var{iterator} can be @code{NULL}: in this case the function
 just counts headers.
 
 @var{iterator} should not modify the its key and value arguments, unless
 we know what we are doing.
 @end deftypefun
 
 
 @deftypefun {const char *} MHD_get_response_header (struct MHD_Response *response, const char *key)
 Find and return a pointer to the value of a particular header from the
 response.  @var{key} must reference a zero-terminated string
 representing the header to look for. The search is case sensitive.
 Return @code{NULL} if header does not exist or @var{key} is @code{NULL}.
 
 We should not modify the value, unless we know what we are doing.
 @end deftypefun
 
 
 @c ------------------------------------------------------------
 @node microhttpd-response upgrade
 @section Creating a response for protocol upgrades
 @cindex WebSockets
 @cindex Upgrade
 @cindex HTTP2
 @cindex RFC2817
 
 With RFC 2817 a mechanism to switch protocols within HTTP was
 introduced.  Here, a client sends a request with a ``Connection:
 Upgrade'' header.  The server responds with a ``101 Switching
 Protocols'' response header, after which the two parties begin to
 speak a different (non-HTTP) protocol over the TCP connection.
 
 This mechanism is used for upgrading HTTP 1.1 connections to HTTP2 or
 HTTPS, as well as for implementing WebSockets.  Which protocol
 upgrade is performed is negotiated between server and client in
 additional headers, in particular the ``Upgrade'' header.
 
 MHD supports switching protocols using this mechanism only if the
 @code{MHD_ALLOW_SUSPEND_RESUME} flag has been set when starting
 the daemon.  If this flag has been set, applications can upgrade
 a connection by queueing a response (using the
 @code{MHD_HTTP_SWITCHING_PROTOCOLS} status code) which must
 have been created with the following function:
 
 
 @deftypefun enum MHD_Result MHD_create_response_for_upgrade (MHD_UpgradeHandler upgrade_handler, void *upgrade_handler_cls)
 Create a response suitable for switching protocols.  Returns @code{MHD_YES} on success.  @code{upgrade_handler} must not be @code{NULL}.
 
 When creating this type of response, the ``Connection: Upgrade''
 header will be set automatically for you.  MHD requires that you
 additionally set an ``Upgrade:'' header.  The ``Upgrade'' header
 must simply exist, the specific value is completely up to the
 application.
 
 @end deftypefun
 
 The @code{upgrade_handler} argument to the above has the following type:
 
 
 @deftypefn {Function Pointer} void {*MHD_UpgradeHandler} (void *cls, struct MHD_Connection *connection, const char *extra_in, size_t extra_in_size, MHD_socket sock, struct MHD_UpgradeResponseHandle *urh)
 This function will be called once MHD has transmitted the header of the response to the connection that is being upgraded.  At this point, the application is expected to take over the socket @code{sock} and speak the non-HTTP protocol to which the connection was upgraded.  MHD will no longer use the socket; this includes handling timeouts.  The application must call @code{MHD_upgrade_action} with an upgrade action of @code{MHD_UPGRADE_ACTION_CLOSE} when it is done processing the connection to close the socket.  The application must not call @code{MHD_stop_daemon} on the respective daemon as long as it is still handling the connection.  The arguments given to the @code{upgrade_handler} have the following meaning:
 
 @table @var
 @item cls
 matches the @code{upgrade_handler_cls} that was given to @code{MHD_create_response_for_upgrade}
 @item connection
 identifies the connection that is being upgraded;
 
 @item req_cls
 last value left in `*req_cls` in the `MHD_AccessHandlerCallback`
 
 @item extra_in
 buffer of bytes MHD read ``by accident'' from the socket already.  This can happen if the client eagerly transmits more than just the HTTP request.   The application should treat these as if it had read them from the socket.
 
 @item extra_in_size
 number of bytes in @code{extra_in}
 
 @item sock
 the socket which the application can now use directly for some bi-directional communication with the client. The application can henceforth use @code{recv()} and @code{send()} or @code{read()} and @code{write()} system calls on the socket.  However, @code{ioctl()} and @code{setsockopt()} functions will not work as expected when using HTTPS.  Such operations may be supported in the future via @code{MHD_upgrade_action}.   Most importantly, the application must never call @code{close()} on this socket.  Closing the socket must be done using @code{MHD_upgrade_action}.  However, while close is forbidden, the application may call @code{shutdown()} on the socket.
 
 @item urh
 argument for calls to @code{MHD_upgrade_action}.  Applications must eventually use this function to perform the @code{close()} action on the socket.
 @end table
 
 @end deftypefn
 
 @deftypefun enum MHD_Result MHD_upgrade_action (struct MHD_UpgradeResponseHandle *urh, enum MHD_UpgradeAction action, ...)
 Perform special operations related to upgraded connections.
 
 @table @var
 @item urh
 identifies the upgraded connection to perform an action on
 
 @item action
 specifies the action to perform; further arguments to the function depend on the specifics of the action.
 @end table
 
 @end deftypefun
 
 
 @deftp {Enumeration} MHD_UpgradeAction
 Set of actions to be performed on upgraded connections.  Passed as an argument to
 @code{MHD_upgrade_action()}.
 
 @table @code
 @item MHD_UPGRADE_ACTION_CLOSE
 Closes the connection.  Must be called once the application is done with the client.  Takes no additional arguments.
 @item MHD_UPGRADE_ACTION_CORK_ON
 Enable corking on the underlying socket.
 @item MHD_UPGRADE_ACTION_CORK_OFF
 Disable corking on the underlying socket.
 
 @end table
 @end deftp
 
 
 @c ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 
 @c ------------------------------------------------------------
 @node microhttpd-flow
 @chapter Flow control.
 
 @noindent
 Sometimes it may be possible that clients upload data faster
 than an application can process it, or that an application
 needs an extended period of time to generate a response.
 If @code{MHD_USE_THREAD_PER_CONNECTION} is used, applications
 can simply deal with this by performing their logic within the
 thread and thus effectively blocking connection processing
 by MHD.  In all other modes, blocking logic must not be
 placed within the callbacks invoked by MHD as this would also
 block processing of other requests, as a single thread may be
 responsible for tens of thousands of connections.
 
 Instead, applications using thread modes other than
 @code{MHD_USE_THREAD_PER_CONNECTION} should use the
 following functions to perform flow control.
 
 @deftypefun enum MHD_Result MHD_suspend_connection (struct MHD_Connection *connection)
 Suspend handling of network data for a given connection.  This can
 be used to dequeue a connection from MHD's event loop (external
 select, internal select or thread pool; not applicable to
 thread-per-connection!) for a while.
 
 If you use this API in conjunction with a internal select or a
 thread pool, you must set the option @code{MHD_ALLOW_SUSPEND_RESUME} to
 ensure that a resumed connection is immediately processed by MHD.
 
 Suspended connections continue to count against the total number of
 connections allowed (per daemon, as well as per IP, if such limits
 are set).  Suspended connections will NOT time out; timeouts will
 restart when the connection handling is resumed.  While a
 connection is suspended, MHD will not detect disconnects by the
 client.
 
 The only safe time to suspend a connection is from the
 @code{MHD_AccessHandlerCallback} or from the respective
 @code{MHD_ContentReaderCallback} (but in this case the
 response object must not be shared among multiple
 connections).
 
 When suspending from the @code{MHD_AccessHandlerCallback}
 you MUST afterwards return @code{MHD_YES} from the access handler
 callback (as MHD_NO would imply to both close and suspend
 the connection, which is not allowed).
 
 Finally, it is an API violation to call @code{MHD_stop_daemon} while
 having suspended connections (this will at least create memory and
 socket leaks or lead to undefined behavior).  You must explicitly
 resume all connections before stopping the daemon.
 
 @table @var
 @item connection
 the connection to suspend
 @end table
 @end deftypefun
 
 @deftypefun enum MHD_Result MHD_resume_connection (struct MHD_Connection *connection)
 Resume handling of network data for suspended connection.  It is safe
 to resume a suspended connection at any time.  Calling this function
 on a connection that was not previously suspended will result in
 undefined behavior.
 
 If you are using this function in ``external'' select mode, you must
 make sure to run @code{MHD_run} afterwards (before again calling
 @code{MHD_get_fdset}), as otherwise the change may not be reflected in
 the set returned by @code{MHD_get_fdset} and you may end up with a
 connection that is stuck until the next network activity.
 
 This function may be called from any thread, which is what makes it
 usable to hand work to threads of your own.  In ``external'' select
 mode it writes to the inter-thread communication channel that
 @code{MHD_ALLOW_SUSPEND_RESUME} sets up, and since
 @code{MHD_get_fdset} adds the reading end of that channel to the read
 set, a call from another thread interrupts a @code{select} that your
 application is blocked in.  That matters because
 @code{MHD_get_timeout} reports no timeout at all while every
 connection is suspended, so your application would otherwise block
 indefinitely.  The channel is level triggered, so a resume issued
 between @code{MHD_get_fdset} and @code{select} cannot be lost.
 
 You can check whether a connection is currently suspended using
 @code{MHD_get_connection_info} by querying for
 @code{MHD_CONNECTION_INFO_CONNECTION_SUSPENDED}.
 
 A worked example of suspending connections while worker threads
 produce the answers, driven by an external @code{select} loop, is
 given in the chapter ``Answering from another thread'' of the MHD
 tutorial.
 
 @table @var
 @item connection
 the connection to resume
 @end table
 @end deftypefun
 
 
 @c ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 
 @c ------------------------------------------------------------
 @node microhttpd-dauth
 @chapter Utilizing Authentication
 
 @noindent
 MHD support three types of client authentication.
 
 Basic authentication uses a simple authentication method based
 on BASE64 algorithm. Username and password are exchanged in clear
 between the client and the server, so this method must only be used
 for non-sensitive content or when the session is protected with https.
 When using basic authentication MHD will have access to the clear
 password, possibly allowing to create a chained authentication
 toward an external authentication server.
 
 Digest authentication uses a one-way authentication method based
 on MD5 hash algorithm. Only the hash will transit over the network,
 hence protecting the user password. The nonce will prevent replay
 attacks. This method is appropriate for general use, especially
 when https is not used to encrypt the session.
 
 Client certificate authentication uses a X.509 certificate from
 the client. This is the strongest authentication mechanism but it
 requires the use of HTTPS. Client certificate authentication can
 be used simultaneously with Basic or Digest Authentication in order
 to provide a two levels authentication (like for instance separate
 machine and user authentication).  A code example for using
 client certificates is presented in the MHD tutorial.
 
 @menu
 * microhttpd-dauth basic::      Using Basic Authentication.
 * microhttpd-dauth digest::     Using Digest Authentication.
 @end menu
 
 @c ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 
 @c ------------------------------------------------------------
 @node microhttpd-dauth basic
 @section Using Basic Authentication
 
 @deftypefun {void} MHD_free (void *ptr)
 Free the memory given at @code{ptr}.  Used to free data structures allocated by MHD. Calls @code{free(ptr)}.
 @end deftypefun
 
 @deftypefun {char *} MHD_basic_auth_get_username_password3 (struct MHD_Connection *connection)
 Get the username and password from the basic authorization header sent by the client.
 Return @code{NULL} if no Basic Authorization header set by the client or if Base64
 encoding is invalid; a pointer to the structure with username and password
 if found values set by the client.
 If returned value is not @code{NULL}, the value must be @code{MHD_free()}'ed.
 @end deftypefun
 
 @deftypefun {enum MHD_Result} MHD_queue_basic_auth_fail_response3 (struct MHD_Connection *connection, const char *realm, int prefer_utf8, struct MHD_Response *response)
 Queues a response to request basic authentication from the client.
 Return @code{MHD_YES} if successful, otherwise @code{MHD_NO}.
 
 @var{realm} must reference to a zero-terminated string representing the realm.
 
 @var{prefer_utf8} if set to @code{MHD_YES} then parameter @code{charset} with value
 @code{UTF-8} will be added to the response authentication header which indicates
 that UTF-8 encoding is preferred for username and password.
 
 @var{response} a response structure to specify what shall be presented to the
 client with a 401 HTTP status.
 @end deftypefun
 
 @c ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 
 @c ------------------------------------------------------------
 @node microhttpd-dauth digest
 @section Using Digest Authentication
 
 MHD supports MD5 (deprecated by IETF) and SHA-256 hash algorithms
 for digest authentication. The @code{MHD_DigestAuthAlgorithm} enumeration
 is used to specify which algorithm should be used.
 
 @deftp {Enumeration} MHD_DigestAuthAlgorithm
 Which digest algorithm should be used. Must be used consistently.
 
 @table @code
 @item MHD_DIGEST_ALG_AUTO
 Have MHD pick an algorithm currently considered secure.  For now defaults to SHA-256.
 
 @item MHD_DIGEST_ALG_MD5
 Force use of (deprecated, ancient, insecure) MD5.
 
 @item MHD_DIGEST_ALG_SHA256
 Force use of SHA-256.
 
 @end table
 @end deftp
 
 @deftp {Enumeration} MHD_DigestAuthResult
 The result of digest authentication of the client.
 
 @table @code
 @item MHD_DAUTH_OK
 Authentication OK.
 
 @item MHD_DAUTH_ERROR
 General error, like ``out of memory''.
 
 @item MHD_DAUTH_WRONG_HEADER
 No ``Authorization'' header or wrong format of the header.
 
 @item MHD_DAUTH_WRONG_USERNAME
 Wrong ``username''.
 
 @item MHD_DAUTH_WRONG_REALM
 Wrong ``realm''.
 
 @item MHD_DAUTH_WRONG_URI
 Wrong ``URI'' (or URI parameters).
 
 @item MHD_DAUTH_NONCE_STALE
 The ``nonce'' is too old. Suggest the client to retry with the same username and
 password to get the fresh ``nonce''.
 The validity of the ``nonce'' may not be checked.
 
 @item MHD_DAUTH_NONCE_WRONG
 The ``nonce'' is wrong. May indicate an attack attempt.
 
 @item MHD_DAUTH_RESPONSE_WRONG
 The ``response'' is wrong. May indicate an attack attempt.
 
 @end table
 @end deftp
 
 
 @deftypefun {char *} MHD_digest_auth_get_username (struct MHD_Connection *connection)
 Find and return a pointer to the username value from the request header.
 Return @code{NULL} if the value is not found or header does not exist.
 If returned value is not @code{NULL}, the value must be @code{MHD_free()}'ed.
 @end deftypefun
 
 @deftypefun enum MHD_DigestAuthResult MHD_digest_auth_check3 (struct MHD_Connection *connection, const char *realm, const char *username, const char *password, unsigned int nonce_timeout, enum MHD_DigestAuthAlgorithm algo)
 Checks if the provided values in the WWW-Authenticate header are valid
 and sound according to RFC7616. If valid return @code{MHD_DAUTH_OK}, otherwise return the error code.
 
 @var{realm} must reference to a zero-terminated string representing the realm.
 
 @var{username} must reference to a zero-terminated string representing the username,
 it is usually the returned value from MHD_digest_auth_get_username.
 
 @var{password} must reference to a zero-terminated string representing the password,
 most probably it will be the result of a lookup of the username against a local database.
 
 @var{nonce_timeout} the nonce validity duration in seconds.
 Most of the time it is sound to specify 300 seconds as its values.
 
 @var{algo} which digest algorithm should we use.
 @end deftypefun
 
 @deftypefun int MHD_digest_auth_check2 (struct MHD_Connection *connection, const char *realm, const char *username, const char *password, unsigned int nonce_timeout, enum MHD_DigestAuthAlgorithm algo)
 Checks if the provided values in the WWW-Authenticate header are valid
 and sound according to RFC2716. If valid return @code{MHD_YES}, otherwise return @code{MHD_NO}.
 
 @var{realm} must reference to a zero-terminated string representing the realm.
 
 @var{username} must reference to a zero-terminated string representing the username,
 it is usually the returned value from MHD_digest_auth_get_username.
 
 @var{password} must reference to a zero-terminated string representing the password,
 most probably it will be the result of a lookup of the username against a local database.
 
 @var{nonce_timeout} is the amount of time in seconds for a nonce to be invalid.
 Most of the time it is sound to specify 300 seconds as its values.
 
 @var{algo} which digest algorithm should we use.
 @end deftypefun
 
 
 @deftypefun int MHD_digest_auth_check (struct MHD_Connection *connection, const char *realm, const char *username, const char *password, unsigned int nonce_timeout)
 Checks if the provided values in the WWW-Authenticate header are valid
 and sound according to RFC2716. If valid return @code{MHD_YES}, otherwise return @code{MHD_NO}.
 Deprecated, use @code{MHD_digest_auth_check2} instead.
 
 
 @var{realm} must reference to a zero-terminated string representing the realm.
 
 @var{username} must reference to a zero-terminated string representing the username,
 it is usually the returned value from MHD_digest_auth_get_username.
 
 @var{password} must reference to a zero-terminated string representing the password,
 most probably it will be the result of a lookup of the username against a local database.
 
 @var{nonce_timeout} is the amount of time in seconds for a nonce to be invalid.
 Most of the time it is sound to specify 300 seconds as its values.
 @end deftypefun
 
 
 
 @deftypefun enum MHD_DigestAuthResult MHD_digest_auth_check_digest3 (struct MHD_Connection *connection, const char *realm, const char *username, const uint8_t *digest, unsigned int nonce_timeout, enum MHD_DigestAuthAlgorithm algo)
 Checks if the provided values in the WWW-Authenticate header are valid
 and sound according to RFC7616. If valid return @code{MHD_DAUTH_OK}, otherwise return the error code.
 
 @var{realm} must reference to a zero-terminated string representing the realm.
 
 @var{username} must reference to a zero-terminated string representing the username,
 it is usually the returned value from MHD_digest_auth_get_username.
 
 @var{digest} the pointer to the binary digest for the precalculated hash value ``username:realm:password'' with specified @var{algo}.
 
 @var{digest_size} the number of bytes in @var{digest} (the size must match @var{algo}!)
 
 @var{nonce_timeout} the nonce validity duration in seconds.
 Most of the time it is sound to specify 300 seconds as its values.
 
 @var{algo} digest authentication algorithm to use.
 @end deftypefun
 
 @deftypefun int MHD_digest_auth_check_digest2 (struct MHD_Connection *connection, const char *realm, const char *username, const uint8_t *digest, unsigned int nonce_timeout, enum MHD_DigestAuthAlgorithm algo)
 Checks if the provided values in the WWW-Authenticate header are valid
 and sound according to RFC2716. If valid return @code{MHD_YES}, otherwise return @code{MHD_NO}.
 
 @var{realm} must reference to a zero-terminated string representing the realm.
 
 @var{username} must reference to a zero-terminated string representing the username,
 it is usually the returned value from MHD_digest_auth_get_username.
 
 @var{digest} pointer to the binary MD5 sum for the precalculated hash value ``userame:realm:password''. The size must match the selected @var{algo}!
 
 @var{nonce_timeout} is the amount of time in seconds for a nonce to be invalid.
 Most of the time it is sound to specify 300 seconds as its values.
 
 @var{algo} digest authentication algorithm to use.
 @end deftypefun
 
 @deftypefun int MHD_digest_auth_check_digest (struct MHD_Connection *connection, const char *realm, const char *username, const unsigned char digest[MHD_MD5_DIGEST_SIZE], unsigned int nonce_timeout)
 Checks if the provided values in the WWW-Authenticate header are valid
 and sound according to RFC2716. If valid return @code{MHD_YES}, otherwise return @code{MHD_NO}.
 Deprecated, use @code{MHD_digest_auth_check_digest2} instead.
 
 @var{realm} must reference to a zero-terminated string representing the realm.
 
 @var{username} must reference to a zero-terminated string representing the username,
 it is usually the returned value from MHD_digest_auth_get_username.
 
 @var{digest} pointer to the binary MD5 sum for the precalculated hash value ``userame:realm:password'' of @code{MHD_MD5_DIGEST_SIZE} bytes.
 
 @var{nonce_timeout} is the amount of time in seconds for a nonce to be invalid.
 Most of the time it is sound to specify 300 seconds as its values.
 @end deftypefun
 
 
 @deftypefun enum MHD_Result MHD_queue_auth_fail_response2 (struct MHD_Connection *connection, const char *realm, const char *opaque, struct MHD_Response *response, int signal_stale, enum MHD_DigestAuthAlgorithm algo)
 Queues a response to request authentication from the client,
 return @code{MHD_YES} if successful, otherwise @code{MHD_NO}.
 
 @var{realm} must reference to a zero-terminated string representing the realm.
 
 @var{opaque} must reference to a zero-terminated string representing a value
 that gets passed to the client and expected to be passed again to the server
 as-is. This value can be a hexadecimal or base64 string.
 
 @var{response} a response structure to specify what shall be presented to the
 client with a 401 HTTP status.
 
 @var{signal_stale} a value that signals "stale=true" in the response header to
 indicate the invalidity of the nonce and no need to ask for authentication
 parameters and only a new nonce gets generated. @code{MHD_YES} to generate a new
 nonce, @code{MHD_NO} to ask for authentication parameters.
 
 @var{algo} which digest algorithm should we use.  The same algorithm
 must then be selected when checking digests received from clients!
 
 @end deftypefun
 
 
 @deftypefun enum MHD_Result MHD_queue_auth_fail_response (struct MHD_Connection *connection, const char *realm, const char *opaque, struct MHD_Response *response, int signal_stale)
 Queues a response to request authentication from the client,
 return @code{MHD_YES} if successful, otherwise @code{MHD_NO}.
 
 @var{realm} must reference to a zero-terminated string representing the realm.
 
 @var{opaque} must reference to a zero-terminated string representing a value
 that gets passed to the client and expected to be passed again to the server
 as-is. This value can be a hexadecimal or base64 string.
 
 @var{response} a response structure to specify what shall be presented to the
 client with a 401 HTTP status.
 
 @var{signal_stale} a value that signals "stale=true" in the response header to
 indicate the invalidity of the nonce and no need to ask for authentication
 parameters and only a new nonce gets generated. @code{MHD_YES} to generate a new
 nonce, @code{MHD_NO} to ask for authentication parameters.
 @end deftypefun
 
 Example: handling digest authentication requests and responses.
 
 @example
 #define PAGE "<html><head><title>libmicrohttpd demo</title></head><body>Access granted</body></html>"
 #define DENIED "<html><head><title>libmicrohttpd demo</title></head><body>Access denied</body></html>"
 #define OPAQUE "11733b200778ce33060f31c9af70a870ba96ddd4"
 
 static int
 ahc_echo (void *cls,
           struct MHD_Connection *connection,
           const char *url,
           const char *method,
           const char *version,
           const char *upload_data, size_t *upload_data_size, void **ptr)
 @{
   struct MHD_Response *response;
   char *username;
   const char *password = "testpass";
   const char *realm = "test@@example.com";
   int ret;
   static int already_called_marker;
 
   if (&already_called_marker != *req_cls)
     @{ /* Called for the first time, request not fully read yet */
       *req_cls = &already_called_marker;
       /* Wait for complete request */
       return MHD_YES;
     @}
 
   username = MHD_digest_auth_get_username (connection);
   if (username == NULL)
     @{
       response = MHD_create_response_from_buffer(strlen (DENIED),
 					         DENIED,
 					         MHD_RESPMEM_PERSISTENT);
       ret = MHD_queue_auth_fail_response2 (connection,
                                            realm,
 					   OPAQUE,
 					   response,
 					   MHD_NO,
                                            MHD_DIGEST_ALG_SHA256);
       MHD_destroy_response(response);
       return ret;
     @}
   ret = MHD_digest_auth_check2 (connection,
                                 realm,
 			        username,
 			        password,
 			        300,
                                 MHD_DIGEST_ALG_SHA256);
   MHD_free(username);
   if ( (ret == MHD_INVALID_NONCE) ||
        (ret == MHD_NO) )
     @{
       response = MHD_create_response_from_buffer(strlen (DENIED),
 					         DENIED,
 					         MHD_RESPMEM_PERSISTENT);
       if (NULL == response)
 	return MHD_NO;
       ret = MHD_queue_auth_fail_response2 (connection,
                                            realm,
 					   OPAQUE,
 					   response,
 					   (ret == MHD_INVALID_NONCE) ? MHD_YES : MHD_NO,
                                            MHD_DIGEST_ALG_SHA256);
       MHD_destroy_response(response);
       return ret;
     @}
   response = MHD_create_response_from_buffer (strlen(PAGE),
                                               PAGE,
  					      MHD_RESPMEM_PERSISTENT);
   ret = MHD_queue_response (connection,
                             MHD_HTTP_OK,
                             response);
   MHD_destroy_response(response);
   return ret;
 @}
 @end example
 
 @c ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 
 @c ------------------------------------------------------------
 @node microhttpd-post
 @chapter Adding a @code{POST} processor
 @cindex POST method
 
 @menu
 * microhttpd-post api::         Programming interface for the
                                 @code{POST} processor.
 @end menu
 
 
 @noindent
 MHD provides the post processor API to make it easier for applications to
 parse the data of a client's @code{POST} request: the
 @code{MHD_AccessHandlerCallback} will be invoked multiple times to
 process data as it arrives; at each invocation a new chunk of data must
 be processed. The arguments @var{upload_data} and @var{upload_data_size}
 are used to reference the chunk of data.
 
 When @code{MHD_AccessHandlerCallback} is invoked for a new request:
 its @code{*@var{req_cls}} argument is set to @code{NULL}. When @code{POST}
 data comes in the upload buffer it is @strong{mandatory} to use the
 @var{req_cls} to store a reference to per-request data.  The fact
 that the pointer was initially @code{NULL} can be used to detect that
 this is a new request.
 
 One method to detect that a new request was started is
 to set @code{*req_cls} to an unused integer:
 
 @example
 int
 access_handler (void *cls,
                 struct MHD_Connection * connection,
                 const char *url,
                 const char *method, const char *version,
                 const char *upload_data, size_t *upload_data_size,
                 void **req_cls)
 @{
   static int old_connection_marker;
   int new_connection = (NULL == *req_cls);
 
   if (new_connection)
     @{
       /* new connection with POST */
       *req_cls = &old_connection_marker;
     @}
 
   ...
 @}
 @end example
 
 @noindent
 In contrast to the previous example, for @code{POST} requests in particular,
 it is more common to use the value of @code{*req_cls} to keep track of
 actual state used during processing, such as the post processor (or a
 struct containing a post processor):
 
 @example
 int
 access_handler (void *cls,
                 struct MHD_Connection * connection,
                 const char *url,
                 const char *method, const char *version,
                 const char *upload_data, size_t *upload_data_size,
                 void **req_cls)
 @{
   struct MHD_PostProcessor * pp = *req_cls;
 
   if (pp == NULL)
     @{
       pp = MHD_create_post_processor(connection, ...);
       *req_cls = pp;
       return MHD_YES;
     @}
   if (*upload_data_size)
     @{
       MHD_post_process(pp, upload_data, *upload_data_size);
       *upload_data_size = 0;
       return MHD_YES;
     @}
   else
     @{
       MHD_destroy_post_processor(pp);
       return MHD_queue_response(...);
     @}
 @}
 @end example
 
 Note that the callback from @code{MHD_OPTION_NOTIFY_COMPLETED}
 should be used to destroy the post processor.  This cannot be
 done inside of the access handler since the connection may not
 always terminate normally.
 
 
 @c ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 
 @c ------------------------------------------------------------
 @node microhttpd-post api
 @section Programming interface for the @code{POST} processor
 @cindex POST method
 
 @deftypefun {struct MHD_PostProcessor *} MHD_create_post_processor (struct MHD_Connection *connection, size_t buffer_size, MHD_PostDataIterator iterator, void *iterator_cls)
 Create a PostProcessor.  A PostProcessor can be used to (incrementally)
 parse the data portion of a @code{POST} request.
 
 @table @var
 @item connection
 the connection on which the @code{POST} is happening (used to determine
 the @code{POST} format);
 
 @item buffer_size
 maximum number of bytes to use for internal buffering (used only for the
 parsing, specifically the parsing of the keys).  A tiny value (256-1024)
 should be sufficient; do @strong{NOT} use a value smaller than 256;
 for good performance, use 32k or 64k (i.e. 65536).
 
 @item iterator
 iterator to be called with the parsed data; must @strong{NOT} be
 @code{NULL};
 
 @item iterator_cls
 custom value to be used as first argument to @var{iterator}.
 @end table
 
 Return @code{NULL} on error (out of memory, unsupported encoding), otherwise
 a PP handle.
 @end deftypefun
 
 
 @deftypefun enum MHD_Result MHD_post_process (struct MHD_PostProcessor *pp, const char *post_data, size_t post_data_len)
 Parse and process @code{POST} data.  Call this function when @code{POST}
 data is available (usually during an @code{MHD_AccessHandlerCallback})
 with the @var{upload_data} and @var{upload_data_size}.  Whenever
 possible, this will then cause calls to the
 @code{MHD_IncrementalKeyValueIterator}.
 
 @table @var
 @item pp
 the post processor;
 
 @item post_data
 @var{post_data_len} bytes of @code{POST} data;
 
 @item post_data_len
 length of @var{post_data}.
 @end table
 
 Return @code{MHD_YES} on success, @code{MHD_NO} on error
 (out-of-memory, iterator aborted, parse error).
 @end deftypefun
 
 
 @deftypefun enum MHD_Result MHD_destroy_post_processor (struct MHD_PostProcessor *pp)
 Release PostProcessor resources.  After this function is being called,
 the PostProcessor is guaranteed to no longer call its iterator.  There
 is no special call to the iterator to indicate the end of the post processing
 stream.  After destroying the PostProcessor, the programmer should
 perform any necessary work to complete the processing of the iterator.
 
 Return @code{MHD_YES} if processing completed nicely, @code{MHD_NO}
 if there were spurious characters or formatting problems with
 the post request.  It is common to ignore the return value
 of this function.
 
 
 @end deftypefun
 
 
 
 @c ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 
 @c ------------------------------------------------------------
 @node microhttpd-info
 @chapter Obtaining and modifying status information.
 
 
 @menu
 * microhttpd-info daemon::      State information about an MHD daemon
 * microhttpd-info conn::        State information about a connection
 * microhttpd-option conn::      Modify per-connection options
 @end menu
 
 
 @c ------------------------------------------------------------
 @node microhttpd-info daemon
 @section Obtaining state information about an MHD daemon
 
 @deftypefun {const union MHD_DaemonInfo *} MHD_get_daemon_info (struct MHD_Daemon *daemon, enum MHD_DaemonInfoType infoType, ...)
 Obtain information about the given daemon.  This function
 is currently not fully implemented.
 
 @table @var
 @item daemon
 the daemon about which information is desired;
 
 @item infoType
 type of information that is desired
 
 @item ...
 additional arguments about the desired information (depending on
 infoType)
 @end table
 
 Returns a union with the respective member (depending on
 infoType) set to the desired information), or @code{NULL}
 in case the desired information is not available or
 applicable.
 @end deftypefun
 
 
 @deftp {Enumeration} MHD_DaemonInfoType
 Values of this enum are used to specify what
 information about a daemon is desired.
 @table @code
 @item MHD_DAEMON_INFO_KEY_SIZE
 Request information about the key size for a particular cipher
 algorithm.  The cipher algorithm should be passed as an extra argument
 (of type 'enum MHD_GNUTLS_CipherAlgorithm').  No longer supported,
 using this value will cause @code{MHD_get_daemon_info} to return NULL.
 
 @item MHD_DAEMON_INFO_MAC_KEY_SIZE
 Request information about the key size for a particular cipher
 algorithm.  The cipher algorithm should be passed as an extra argument
 (of type 'enum MHD_GNUTLS_HashAlgorithm').  No longer supported,
 using this value will cause @code{MHD_get_daemon_info} to return NULL.
 
 @item MHD_DAEMON_INFO_LISTEN_FD
 @cindex listen
 Request the file-descriptor number that MHD is using to listen to the
 server socket.  This can be useful if no port
 was specified and a client needs to learn what port
 is actually being used by MHD.
 No extra arguments should be passed.
 
 @item MHD_DAEMON_INFO_EPOLL_FD
 @cindex epoll
 Request the file-descriptor number that MHD is using for epoll.  If
 the build is not supporting epoll, NULL is returned; if we are using a
 thread pool or this daemon was not started with
 @code{MHD_USE_EPOLL}, (a pointer to) -1 is returned.  If we are
 using @code{MHD_USE_INTERNAL_POLLING_THREAD} or are in 'external' select mode, the
 internal epoll FD is returned.  This function must be used in external
 select mode with epoll to obtain the FD to call epoll on.  No extra
 arguments should be passed.
 
 @item MHD_DAEMON_INFO_CURRENT_CONNECTIONS
 @cindex connection, limiting number of connections
 Request the number of current connections handled by the daemon.  No
 extra arguments should be passed and a pointer to a @code{union
 MHD_DaemonInfo} value is returned, with the @code{num_connections}
 member of type @code{unsigned int} set to the number of active
 connections.
 
 Note that in multi-threaded or internal-select mode, the real number of current
 connections may already be different when @code{MHD_get_daemon_info} returns.
 The number of current connections can be used (even in multi-threaded and
 internal-select mode) after @code{MHD_quiesce_daemon} to detect whether all
 connections have been handled.
 
 @end table
 @end deftp
 
 
 
 @c ------------------------------------------------------------
 @node microhttpd-info conn
 @section Obtaining state information about a connection
 
 
 @deftypefun {const union MHD_ConnectionInfo *} MHD_get_connection_info (struct MHD_Connection *connection, enum MHD_ConnectionInfoType infoType, ...)
 Obtain information about the given connection.
 
 @table @var
 @item connection
 the connection about which information is desired;
 
 @item infoType
 type of information that is desired
 
 @item ...
 additional arguments about the desired information (depending on
 infoType)
 @end table
 
 Returns a union with the respective member (depending on
 infoType) set to the desired information), or @code{NULL}
 in case the desired information is not available or
 applicable.
 @end deftypefun
 
 @deftp {Enumeration} MHD_ConnectionInfoType
 Values of this enum are used to specify what information about a
 connection is desired.
 
 @table @code
 
 @item MHD_CONNECTION_INFO_CIPHER_ALGO
 What cipher algorithm is being used (HTTPS connections only).
 @code{NULL} is returned for non-HTTPS connections.
 
 Takes no extra arguments.
 
 @item MHD_CONNECTION_INFO_PROTOCOL,
 Allows finding out the TLS/SSL protocol used
 (HTTPS connections only).
 @code{NULL} is returned for non-HTTPS connections.
 
 Takes no extra arguments.
 
 @item MHD_CONNECTION_INFO_CLIENT_ADDRESS
 Returns information about the address of the client.  Returns
 essentially a @code{struct sockaddr **} (since the API returns
 a @code{union MHD_ConnectionInfo *} and that union contains
 a @code{struct sockaddr *}).
 
 Takes no extra arguments.
 
 @item MHD_CONNECTION_INFO_GNUTLS_SESSION,
 Takes no extra arguments.  Allows access to the underlying GNUtls session,
 including access to the underlying GNUtls client certificate
 (HTTPS connections only).  Takes no extra arguments.
 @code{NULL} is returned for non-HTTPS connections.
 
 Takes no extra arguments.
 
 @item MHD_CONNECTION_INFO_GNUTLS_CLIENT_CERT,
 Dysfunctional (never implemented, deprecated).  Use
 MHD_CONNECTION_INFO_GNUTLS_SESSION to get the @code{gnutls_session_t}
 and then call @code{gnutls_certificate_get_peers()}.
 
 @item MHD_CONNECTION_INFO_DAEMON
 Returns information about @code{struct MHD_Daemon} which manages
 this connection.
 
 Takes no extra arguments.
 
 @item MHD_CONNECTION_INFO_CONNECTION_FD
 Returns the file descriptor (usually a TCP socket) associated with
 this connection (in the ``connect-fd'' member of the returned struct).
 Note that manipulating the descriptor directly can have problematic
 consequences (as in, break HTTP).  Applications might use this access
 to manipulate TCP options, for example to set the ``TCP-NODELAY''
 option for COMET-like applications.  Note that MHD will set TCP-CORK
 after sending the HTTP header and clear it after finishing the footers
 automatically (if the platform supports it).  As the connection
 callbacks are invoked in between, those might be used to set different
 values for TCP-CORK and TCP-NODELAY in the meantime.
 
 Takes no extra arguments.
 
 @item MHD_CONNECTION_INFO_CONNECTION_SUSPENDED
 Returns pointer to an integer that is @code{MHD_YES} if the connection
 is currently suspended (and thus can be safely resumed) and
 @code{MHD_NO} otherwise.
 
 Takes no extra arguments.
 
 @item MHD_CONNECTION_INFO_SOCKET_CONTEXT
 Returns the client-specific pointer to a @code{void *} that was
 (possibly) set during a @code{MHD_NotifyConnectionCallback} when the
 socket was first accepted.  Note that this is NOT the same as the
 @code{req_cls} argument of the @code{MHD_AccessHandlerCallback}.  The
 @code{req_cls} is fresh for each HTTP request, while the
 @code{socket_context} is fresh for each socket.
 
 Takes no extra arguments.
 
 @item MHD_CONNECTION_INFO_CONNECTION_TIMEOUT
 Returns pointer to an @code{unsigned int} that is the current timeout
 used for the connection (in seconds, 0 for no timeout).  Note that
 while suspended connections will not timeout, the timeout value
 returned for suspended connections will be the timeout that the
 connection will use after it is resumed, and thus might not be zero.
 
 Takes no extra arguments.
 
 @item MHD_CONNECTION_INFO_REQUEST_HEADER_SIZE
 @cindex performance
 Returns pointer to an @code{size_t} that represents the size of the
 HTTP header received from the client. Only valid after the first callback
 to the access handler.
 
 Takes no extra arguments.
 
 @item MHD_CONNECTION_INFO_HTTP_STATUS
 Returns the HTTP status code of the response that was
 queued. Returns NULL if no response was queued yet.
 
 Takes no extra arguments.
 
 @end table
 @end deftp
 
 
 
 @c ------------------------------------------------------------
 @node microhttpd-option conn
 @section Setting custom options for an individual connection
 @cindex timeout
 
 
 
 @deftypefun {int} MHD_set_connection_option (struct MHD_Connection *daemon, enum MHD_CONNECTION_OPTION option, ...)
 Set a custom option for the given connection.
 
 @table @var
 @item connection
 the connection for which an option should be set or modified;
 
 @item option
 option to set
 
 @item ...
 additional arguments for the option (depending on option)
 @end table
 
 Returns @code{MHD_YES} on success, @code{MHD_NO} for errors
 (i.e. option argument invalid or option unknown).
 @end deftypefun
 
 
 @deftp {Enumeration} MHD_CONNECTION_OPTION
 Values of this enum are used to specify which option for a
 connection should be changed.
 
 @table @code
 
 @item MHD_CONNECTION_OPTION_TIMEOUT
 Set a custom timeout for the given connection.   Specified
 as the number of seconds, given as an @code{unsigned int}.  Use
 zero for no timeout.
 
 @end table
 @end deftp
 
 
 
 @c ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 
 @c ------------------------------------------------------------
 @node microhttpd-util
 @chapter Utility functions.
 
 
 @menu
 * microhttpd-util feature::     Test supported MHD features
 * microhttpd-util unescape::    Unescape strings
 @end menu
 
 
 @c ------------------------------------------------------------
 @node microhttpd-util feature
 @section Testing for supported MHD features
 
 
 @deftp {Enumeration} MHD_FEATURE
 Values of this enum are used to specify what
 information about a daemon is desired.
 @table @code
 @item MHD_FEATURE_MESSAGES
 Get whether messages are supported. If supported then in debug
 mode messages can be printed to stderr or to external logger.
 
 @item MHD_FEATURE_SSL
 Get whether HTTPS is supported.  If supported then flag
 MHD_USE_SSL and options MHD_OPTION_HTTPS_MEM_KEY,
 MHD_OPTION_HTTPS_MEM_CERT, MHD_OPTION_HTTPS_MEM_TRUST,
 MHD_OPTION_HTTPS_MEM_DHPARAMS, MHD_OPTION_HTTPS_CRED_TYPE,
 MHD_OPTION_HTTPS_PRIORITIES can be used.
 
 @item MHD_FEATURE_HTTPS_CERT_CALLBACK
 Get whether option #MHD_OPTION_HTTPS_CERT_CALLBACK is
 supported.
 
 @item MHD_FEATURE_IPv6
 Get whether IPv6 is supported. If supported then flag
 MHD_USE_IPv6 can be used.
 
 @item MHD_FEATURE_IPv6_ONLY
 Get whether IPv6 without IPv4 is supported. If not supported
 then IPv4 is always enabled in IPv6 sockets and
 flag MHD_USE_DUAL_STACK if always used when MHD_USE_IPv6 is
 specified.
 
 @item MHD_FEATURE_POLL
 Get whether @code{poll()} is supported. If supported then flag
 MHD_USE_POLL can be used.
 
 @item MHD_FEATURE_EPOLL
 Get whether @code{epoll()} is supported. If supported then Flags
 MHD_USE_EPOLL and
 MHD_USE_EPOLL_INTERNAL_THREAD can be used.
 
 @item MHD_FEATURE_SHUTDOWN_LISTEN_SOCKET
 Get whether shutdown on listen socket to signal other
 threads is supported. If not supported flag
 MHD_USE_ITC is automatically forced.
 
 @item MHD_FEATURE_SOCKETPAIR
 Get whether a @code{socketpair()} is used internally instead of
 a @code{pipe()} to signal other threads.
 
 @item MHD_FEATURE_TCP_FASTOPEN
 Get whether TCP Fast Open is supported. If supported then
 flag MHD_USE_TCP_FASTOPEN and option
 MHD_OPTION_TCP_FASTOPEN_QUEUE_SIZE can be used.
 
 @item MHD_FEATURE_BASIC_AUTH
 Get whether HTTP Basic authorization is supported. If supported
 then functions @code{MHD_basic_auth_get_username_password()} and
 @code{MHD_queue_basic_auth_fail_response()} can be used.
 
 @item MHD_FEATURE_DIGEST_AUTH
 Get whether HTTP Digest authorization is supported. If
 supported then options MHD_OPTION_DIGEST_AUTH_RANDOM,
 MHD_OPTION_NONCE_NC_SIZE and functions @code{MHD_digest_auth_check()},
 can be used.
 
 @item MHD_FEATURE_POSTPROCESSOR
 Get whether postprocessor is supported. If supported then
 functions @code{MHD_create_post_processor()},
 @code{MHD_post_process()}, @code{MHD_destroy_post_processor()}
 can be used.
 
 @item MHD_FEATURE_SENDFILE
 Get whether @code{sendfile()} is supported.
 
 @end table
 @end deftp
 
 
 
 @deftypefun {int} MHD_is_feature_supported (enum MHD_FEATURE feature)
 Get information about supported MHD features.  Indicate that MHD was
 compiled with or without support for particular feature. Some features
 require additional support by the kernel.  However, kernel support is not
 checked by this function.
 
 @table @var
 @item feature
 type of requested information
 @end table
 
 Returns @code{MHD_YES} if the feature is supported,
 and @code{MHD_NO} if not.
 @end deftypefun
 
 
 @c ------------------------------------------------------------
 @node microhttpd-util unescape
 @section Unescape strings
 
 @deftypefun {size_t} MHD_http_unescape (char *val)
 Process escape sequences ('%HH') Updates val in place; the result
 should be UTF-8 encoded and cannot be larger than the input.  The
 result must also still be 0-terminated.
 
 @table @var
 @item val
 value to unescape (modified in the process), must be
 a 0-terminated UTF-8 string.
 @end table
 
 Returns length of the resulting val (@code{strlen(val)} may be
 shorter afterwards due to elimination of escape sequences).
 
 @end deftypefun
 
 
 
 
 
 @c ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 
 
 @c **********************************************************
 @c *******************  Appendices  *************************
 @c **********************************************************
 
 @node GNU-LGPL
 @unnumbered GNU-LGPL
 @cindex license
 @include lgpl.texi
 
 @node eCos License
 @unnumbered eCos License
 @cindex license
 @include ecos.texi
 
 @node GNU-GPL
 @unnumbered GNU General Public License
 @cindex license
 @include gpl-2.0.texi
 
 @node GNU-FDL
 @unnumbered GNU-FDL
 @cindex license
 @include fdl-1.3.texi
 
 @node Concept Index
 @unnumbered Concept Index
 
 @printindex cp
 
 @node Function and Data Index
 @unnumbered Function and Data Index
 
 @printindex fn
 
 @node Type Index
 @unnumbered Type Index
 
 @printindex tp
 
 @bye