gnunet

gnunet_fs_service.h (96004B)

---

 /*
      This file is part of GNUnet
      Copyright (C) 2004--2013 GNUnet e.V.
 
      GNUnet is free software: you can redistribute it and/or modify it
      under the terms of the GNU Affero General Public License as published
      by the Free Software Foundation, either version 3 of the License,
      or (at your option) any later version.
 
      GNUnet is distributed in the hope that it will be useful, but
      WITHOUT ANY WARRANTY; without even the implied warranty of
      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
      Affero General Public License for more details.
 
      You should have received a copy of the GNU Affero General Public License
      along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
      SPDX-License-Identifier: AGPL3.0-or-later
  */
 /**
  * @addtogroup fs_l2  File sharing and support services/libraries
  * @{
  *
  * @author Christian Grothoff
  *
  * @file
  * API for file sharing via GNUnet
  *
  * @defgroup fs FS service
  * File sharing
  *
  * @see [Documentation](https://gnunet.org/file-sharing-service)
  *
  * @{
  */
 #ifndef GNUNET_FS_LIB_H
 #define GNUNET_FS_LIB_H
 
 
 #include "gnunet_common.h"
 #include "gnunet_util_lib.h"
 
 #ifdef __cplusplus
 extern "C"
 {
 #if 0                           /* keep Emacsens' auto-indent happy */
 }
 #endif
 #endif
 
 /**
  * Version number of the implementation.
  * History:
  *
  * 1.x.x: initial version with triple GNUNET_hash and merkle tree
  * 2.x.x: root node with mime-type, filename and version number
  * 2.1.x: combined GNUNET_EC_ContentHashKey/3HASH encoding with 25:1 super-nodes
  * 2.2.x: with directories
  * 3.0.x: with namespaces
  * 3.1.x: with namespace meta-data
  * 3.2.x: with collections
  * 4.0.x: with expiration, variable meta-data, kblocks
  * 4.1.x: with new error and configuration handling
  * 5.0.x: with location URIs
  * 6.0.0: with support for OR in KSKs
  * 6.1.x: with simplified namespace support
  * 9.0.0: CPS-style integrated API
  * 9.1.1: asynchronous directory scanning
  * 9.2.0: unified K-Block and S-block format (#2564)
  * 9.3.0: base32crockford encoded URLs
  */
 #define GNUNET_FS_VERSION 0x00090300
 
 #if GNUNET_FS_EXTRACTOR_ENABLED
 
 #include <extractor.h>
 
 #else
 
 /* definitions from extractor.h we need for the build */
 
 /**
  * Enumeration defining various sources of keywords.  See also
  * http://dublincore.org/documents/1998/09/dces/
  */
 enum EXTRACTOR_MetaType
 {
   EXTRACTOR_METATYPE_RESERVED = 0,
   EXTRACTOR_METATYPE_MIMETYPE = 1,
   EXTRACTOR_METATYPE_FILENAME = 2,
   EXTRACTOR_METATYPE_COMMENT = 3,
   EXTRACTOR_METATYPE_TITLE = 4,
   EXTRACTOR_METATYPE_BOOK_TITLE = 5,
   EXTRACTOR_METATYPE_JOURNAL_NAME = 8,
   EXTRACTOR_METATYPE_AUTHOR_NAME = 13,
   EXTRACTOR_METATYPE_PUBLICATION_DATE = 24,
   EXTRACTOR_METATYPE_URL = 29,
   EXTRACTOR_METATYPE_URI = 30,
   EXTRACTOR_METATYPE_ISRC = 31,
   EXTRACTOR_METATYPE_UNKNOWN = 45,
   EXTRACTOR_METATYPE_DESCRIPTION = 46,
   EXTRACTOR_METATYPE_KEYWORDS = 49,
   EXTRACTOR_METATYPE_SUBJECT = 52,
   EXTRACTOR_METATYPE_PACKAGE_NAME = 69,
   EXTRACTOR_METATYPE_THUMBNAIL = 114,
   EXTRACTOR_METATYPE_ALBUM = 129,
   EXTRACTOR_METATYPE_ARTIST = 130,
   EXTRACTOR_METATYPE_ORIGINAL_TITLE = 162,
   EXTRACTOR_METATYPE_GNUNET_FULL_DATA = 174,
   EXTRACTOR_METATYPE_GNUNET_ORIGINAL_FILENAME = 180,
 };
 
 /**
  * Format in which the extracted meta data is presented.
  */
 enum EXTRACTOR_MetaFormat
 {
   /**
    * Format is unknown.
    */
   EXTRACTOR_METAFORMAT_UNKNOWN = 0,
 
   /**
    * 0-terminated, UTF-8 encoded string.  "data_len"
    * is strlen(data)+1.
    */
   EXTRACTOR_METAFORMAT_UTF8 = 1,
 
   /**
    * Some kind of binary format, see given Mime type.
    */
   EXTRACTOR_METAFORMAT_BINARY = 2,
 
   /**
    * 0-terminated string.  The specific encoding is unknown.
    * "data_len" is strlen (data)+1.
    */
   EXTRACTOR_METAFORMAT_C_STRING = 3
 };
 
 
 /**
  * Type of a function that libextractor calls for each
  * meta data item found.
  *
  * @param cls closure (user-defined)
  * @param plugin_name name of the plugin that produced this value;
  *        special values can be used (e.g. '&lt;zlib&gt;' for zlib being
  *        used in the main libextractor library and yielding
  *        meta data).
  * @param type libextractor-type describing the meta data
  * @param format basic format information about @a data
  * @param data_mime_type mime-type of @a data (not of the original file);
  *        can be NULL (if mime-type is not known)
  * @param data actual meta-data found
  * @param data_len number of bytes in @a data
  * @return 0 to continue extracting, 1 to abort
  */
 typedef int (*EXTRACTOR_MetaDataProcessor) (void *cls,
                                             const char *plugin_name,
                                             enum EXTRACTOR_MetaType type,
                                             enum EXTRACTOR_MetaFormat format,
                                             const char *data_mime_type,
                                             const char *data,
                                             size_t data_len);
 
 #endif
 
 #ifndef EXTRACTOR_METATYPE_GNUNET_ORIGINAL_FILENAME
 /* hack for LE < 0.6.3 */
 #define EXTRACTOR_METATYPE_GNUNET_ORIGINAL_FILENAME 180
 #endif
 
 
 /* ******************** URI API *********************** */
 
 #define GNUNET_FS_URI_PREFIX "gnunet://fs/"
 #define GNUNET_FS_URI_KSK_INFIX "ksk/"
 #define GNUNET_FS_URI_SKS_INFIX "sks/"
 #define GNUNET_FS_URI_CHK_INFIX "chk/"
 #define GNUNET_FS_URI_LOC_INFIX "loc/"
 
 
 /**
  * How often do we signal applications that a probe for a particular
  * search result is running? (used to visualize probes).
  */
 #define GNUNET_FS_PROBE_UPDATE_FREQUENCY GNUNET_TIME_relative_multiply ( \
     GNUNET_TIME_UNIT_MILLISECONDS, 250)
 
 /**
  * A Universal Resource Identifier (URI), opaque.
  */
 struct GNUNET_FS_Uri;
 
 /**
  * @ingroup metadata
  * Meta data to associate with a file, directory or namespace.
  */
 struct GNUNET_FS_MetaData;
 
 
 /**
  * Iterator over keywords
  *
  * @param cls closure
  * @param keyword the keyword
  * @param is_mandatory is the keyword mandatory (in a search)
  * @return #GNUNET_OK to continue to iterate, #GNUNET_SYSERR to abort
  */
 typedef int
 (*GNUNET_FS_KeywordIterator) (void *cls,
                               const char *keyword,
                               int is_mandatory);
 
 
 /**
  * Get a unique key from a URI.  This is for putting URIs
  * into HashMaps.  The key may change between FS implementations.
  *
  * @param uri uri to convert to a unique key
  * @param key where to store the unique key
  * @return #GNUNET_OK on success
  */
 int
 GNUNET_FS_uri_to_key (const struct GNUNET_FS_Uri *uri,
                       struct GNUNET_HashCode *key);
 
 
 /**
  * Convert a URI to a UTF-8 String.
  *
  * @param uri uri to convert to a string
  * @return the UTF-8 string
  */
 char *
 GNUNET_FS_uri_to_string (const struct GNUNET_FS_Uri *uri);
 
 
 /**
  * Convert keyword URI to a human readable format
  * (i.e. the search query that was used in the first place)
  *
  * @param uri ksk uri to convert to a string
  * @return string with the keywords
  */
 char *
 GNUNET_FS_uri_ksk_to_string_fancy (const struct GNUNET_FS_Uri *uri);
 
 
 /**
  * Add the given keyword to the set of keywords represented by the URI.
  * Does nothing if the keyword is already present.
  *
  * @param uri ksk uri to modify
  * @param keyword keyword to add
  * @param is_mandatory is this keyword mandatory?
  */
 void
 GNUNET_FS_uri_ksk_add_keyword (struct GNUNET_FS_Uri *uri,
                                const char *keyword,
                                int is_mandatory);
 
 
 /**
  * Remove the given keyword from the set of keywords represented by the URI.
  * Does nothing if the keyword is not present.
  *
  * @param uri ksk uri to modify
  * @param keyword keyword to add
  */
 void
 GNUNET_FS_uri_ksk_remove_keyword (struct GNUNET_FS_Uri *uri,
                                   const char *keyword);
 
 
 /**
  * Convert a UTF-8 String to a URI.
  *
  * @param uri string to parse
  * @param emsg where to store the parser error message (if any)
  * @return NULL on error
  */
 struct GNUNET_FS_Uri *
 GNUNET_FS_uri_parse (const char *uri,
                      char **emsg);
 
 
 /**
  * Free URI.
  *
  * @param uri uri to free
  */
 void
 GNUNET_FS_uri_destroy (struct GNUNET_FS_Uri *uri);
 
 
 /**
  * How many keywords are ANDed in this keyword URI?
  *
  * @param uri ksk uri to get the number of keywords from
  * @return 0 if this is not a keyword URI
  */
 unsigned int
 GNUNET_FS_uri_ksk_get_keyword_count (const struct GNUNET_FS_Uri *uri);
 
 
 /**
  * Iterate over all keywords in this keyword URI.
  *
  * @param uri ksk uri to get the keywords from
  * @param iterator function to call on each keyword
  * @param iterator_cls closure for @a iterator
  * @return -1 if this is not a keyword URI, otherwise number of
  *   keywords iterated over until iterator aborted
  */
 int
 GNUNET_FS_uri_ksk_get_keywords (const struct GNUNET_FS_Uri *uri,
                                 GNUNET_FS_KeywordIterator iterator,
                                 void *iterator_cls);
 
 
 /**
  * Obtain the identity of the peer offering the data
  *
  * @param uri the location URI to inspect
  * @param peer where to store the identify of the peer (presumably) offering the content
  * @return #GNUNET_SYSERR if this is not a location URI, otherwise #GNUNET_OK
  */
 int
 GNUNET_FS_uri_loc_get_peer_identity (const struct GNUNET_FS_Uri *uri,
                                      struct GNUNET_PeerIdentity *peer);
 
 
 /**
  * Obtain the URI of the content itself.
  *
  * @param uri location URI to get the content URI from
  * @return NULL if argument is not a location URI
  */
 struct GNUNET_FS_Uri *
 GNUNET_FS_uri_loc_get_uri (const struct GNUNET_FS_Uri *uri);
 
 
 /**
  * Obtain the expiration of the LOC URI.
  *
  * @param uri location URI to get the expiration from
  * @return expiration time of the URI
  */
 struct GNUNET_TIME_Absolute
 GNUNET_FS_uri_loc_get_expiration (const struct GNUNET_FS_Uri *uri);
 
 
 /**
  * Construct a location URI (this peer will be used for the location).
  * This function should only be called from within gnunet-service-fs,
  * as it requires the peer's private key which is generally unavailable
  * to processes directly under the user's control.  However, for
  * testing and as it logically fits under URIs, it is in this API.
  *
  * @param base_uri content offered by the sender
  * @param sign_key private key of the peer
  * @param expiration_time how long will the content be offered?
  * @return the location URI, NULL on error
  */
 struct GNUNET_FS_Uri *
 GNUNET_FS_uri_loc_create (const struct GNUNET_FS_Uri *base_uri,
                           const struct GNUNET_CRYPTO_EddsaPrivateKey *sign_key,
                           struct GNUNET_TIME_Absolute expiration_time);
 
 
 /**
  * Merge the sets of keywords from two KSK URIs.
  *
  * @param u1 first uri
  * @param u2 second uri
  * @return merged URI, NULL on error
  */
 struct GNUNET_FS_Uri *
 GNUNET_FS_uri_ksk_merge (const struct GNUNET_FS_Uri *u1,
                          const struct GNUNET_FS_Uri *u2);
 
 
 /**
  * Duplicate URI.
  *
  * @param uri the URI to duplicate
  * @return copy of the URI
  */
 struct GNUNET_FS_Uri *
 GNUNET_FS_uri_dup (const struct GNUNET_FS_Uri *uri);
 
 
 /**
  * Create an FS URI from a single user-supplied string of keywords.
  * The string is broken up at spaces into individual keywords.
  * Keywords that start with "+" are mandatory.  Double-quotes can
  * be used to prevent breaking up strings at spaces (and also
  * to specify non-mandatory keywords starting with "+").
  *
  * Keywords must contain a balanced number of double quotes and
  * double quotes can not be used in the actual keywords (for
  * example, the string '""foo bar""' will be turned into two
  * "OR"ed keywords 'foo' and 'bar', not into '"foo bar"'.
  *
  * @param keywords the keyword string
  * @param emsg where to store an error message
  * @return an FS URI for the given keywords, NULL
  *  if keywords is not legal (i.e. empty).
  */
 struct GNUNET_FS_Uri *
 GNUNET_FS_uri_ksk_create (const char *keywords,
                           char **emsg);
 
 
 /**
  * Create an FS URI from a user-supplied command line of keywords.
  * Arguments should start with "+" to indicate mandatory
  * keywords.
  *
  * @param argc number of keywords
  * @param argv keywords (double quotes are not required for
  *             keywords containing spaces; however, double
  *             quotes are required for keywords starting with
  *             "+"); there is no mechanism for having double
  *             quotes in the actual keywords (if the user
  *             did specifically specify double quotes, the
  *             caller should convert each double quote
  *             into two single quotes).
  * @return an FS URI for the given keywords, NULL
  *  if keywords is not legal (i.e. empty).
  */
 struct GNUNET_FS_Uri *
 GNUNET_FS_uri_ksk_create_from_args (unsigned int argc,
                                     const char **argv);
 
 
 /**
  * Test if two URIs are equal.
  *
  * @param u1 one of the URIs
  * @param u2 the other URI
  * @return #GNUNET_YES if the URIs are equal
  */
 int
 GNUNET_FS_uri_test_equal (const struct GNUNET_FS_Uri *u1,
                           const struct GNUNET_FS_Uri *u2);
 
 
 /**
  * Is this a namespace URI?
  *
  * @param uri the uri to check
  * @return #GNUNET_YES if this is an SKS uri
  */
 int
 GNUNET_FS_uri_test_sks (const struct GNUNET_FS_Uri *uri);
 
 
 /**
  * Create an SKS URI from a namespace ID and an identifier.
  *
  * @param ns pseudonym to use
  * @param id identifier
  * @return an FS URI for the given namespace and identifier
  */
 struct GNUNET_FS_Uri *
 GNUNET_FS_uri_sks_create (const struct GNUNET_CRYPTO_EcdsaPublicKey *ns,
                           const char *id);
 
 
 /**
  * Get the public key of a namespace from the given
  * namespace URI.
  *
  * @param uri the uri to get the namespace ID from
  * @param pseudonym where to store the public key of the namespace
  * @return #GNUNET_OK on success
  */
 int
 GNUNET_FS_uri_sks_get_namespace (const struct GNUNET_FS_Uri *uri,
                                  struct GNUNET_CRYPTO_EcdsaPublicKey *pseudonym);
 
 
 /**
  * Get the content identifier of an SKS URI.
  *
  * @param uri the sks uri
  * @return NULL on error (not a valid SKS URI)
  */
 char *
 GNUNET_FS_uri_sks_get_content_id (const struct GNUNET_FS_Uri *uri);
 
 
 /**
  * Is this a keyword URI?
  *
  * @param uri the uri
  * @return #GNUNET_YES if this is a KSK uri
  */
 int
 GNUNET_FS_uri_test_ksk (const struct GNUNET_FS_Uri *uri);
 
 
 /**
  * Is this a file (or directory) URI?
  *
  * @param uri the uri to check
  * @return #GNUNET_YES if this is a CHK uri
  */
 int
 GNUNET_FS_uri_test_chk (const struct GNUNET_FS_Uri *uri);
 
 
 /**
  * What is the size of the file that this URI
  * refers to?
  *
  * @param uri the CHK (or LOC) URI to inspect
  * @return size of the file as specified in the CHK URI
  */
 uint64_t
 GNUNET_FS_uri_chk_get_file_size (const struct GNUNET_FS_Uri *uri);
 
 
 /**
  * What is the hash of the original file's content
  * that this URI refers to?
  *
  * @param uri the CHK URI to inspect
  * @return hash of the file as specified in the CHK URI
  */
 const struct GNUNET_HashCode*
 GNUNET_FS_uri_chk_get_file_hash (const struct GNUNET_FS_Uri *uri);
 
 
 /**
  * Is this a location URI?
  *
  * @param uri the uri to check
  * @return #GNUNET_YES if this is a LOC uri
  */
 int
 GNUNET_FS_uri_test_loc (const struct GNUNET_FS_Uri *uri);
 
 
 /**
  * Construct a keyword-URI from meta-data (take all entries
  * in the meta-data and construct one large keyword URI
  * that lists all keywords that can be found in the meta-data).
  *
  * @param md metadata to use
  * @return NULL on error, otherwise a KSK URI
  */
 struct GNUNET_FS_Uri *
 GNUNET_FS_uri_ksk_create_from_meta_data (const struct GNUNET_FS_MetaData
                                          *md);
 
 
 /* ******************** command-line option parsing API *********************** */
 
 /**
  * Allow user to specify keywords.
  *
  * @param shortName short name of the option
  * @param name long name of the option
  * @param argumentHelp help text for the option argument
  * @param description long help text for the option
  * @param[out] topKeywords set to the desired value
  */
 struct GNUNET_GETOPT_CommandLineOption
 GNUNET_FS_GETOPT_KEYWORDS (char shortName,
                            const char *name,
                            const char *argumentHelp,
                            const char *description,
                            struct GNUNET_FS_Uri **topKeywords);
 
 /**
  * Allow user to specify metadata.
  *
  * @param shortName short name of the option
  * @param name long name of the option
  * @param argumentHelp help text for the option argument
  * @param description long help text for the option
  * @param[out] meta metadata set to the desired value
  */
 struct GNUNET_GETOPT_CommandLineOption
 GNUNET_FS_GETOPT_METADATA (char shortName,
                            const char *name,
                            const char *argumentHelp,
                            const char *description,
                            struct GNUNET_FS_MetaData **meta);
 
 /**
  * Command-line option parser function that allows the user to specify
  * one or more '-m' options with metadata.  Each specified entry of
  * the form "type=value" will be added to the metadata.  A pointer to
  * the metadata must be passed as the "scls" argument.
  *
  * @param ctx command line processor context
  * @param scls must be of type `struct GNUNET_FS_MetaData **`
  * @param option name of the option (typically 'k')
  * @param value command line argument given
  * @return #GNUNET_OK on success
  */
 int
 GNUNET_FS_getopt_set_metadata (struct
                                GNUNET_GETOPT_CommandLineProcessorContext *ctx,
                                void *scls,
                                const char *option,
                                const char *value);
 
 
 /* ************************* sharing API ***************** */
 
 
 /**
  * Possible status codes used in the callback for the
  * various file-sharing operations.  On each file (or search),
  * the callback is guaranteed to be called once with "START"
  * and once with STOPPED; calls with PROGRESS, ERROR or COMPLETED
  * are optional and depend on the circumstances; parent operations
  * will be STARTED before child-operations and STOPPED after
  * their respective child-operations.  START and STOP signals
  * are typically generated either due to explicit client requests
  * or because of suspend/resume operations.
  */
 enum GNUNET_FS_Status
 {
   /**
    * Notification that we have started to publish a file structure.
    */
   GNUNET_FS_STATUS_PUBLISH_START = 0,
 
   /**
    * Notification that we have resumed sharing a file structure.
    */
   GNUNET_FS_STATUS_PUBLISH_RESUME = 1,
 
   /**
    * Notification that we have suspended sharing a file structure.
    */
   GNUNET_FS_STATUS_PUBLISH_SUSPEND = 2,
 
   /**
    * Notification that we are making progress sharing a file structure.
    */
   GNUNET_FS_STATUS_PUBLISH_PROGRESS = 3,
 
   /**
    * Notification that an error was encountered  sharing a file structure.
    * The application will continue to receive resume/suspend events for
    * this structure until "GNUNET_FS_publish_stop" is called.
    */
   GNUNET_FS_STATUS_PUBLISH_ERROR = 4,
 
   /**
    * Notification that we completed sharing a file structure.
    * The application will continue to receive resume/suspend events for
    * this structure until "GNUNET_FS_publish_stop" is called.
    */
   GNUNET_FS_STATUS_PUBLISH_COMPLETED = 5,
 
   /**
    * Notification that we have stopped
    * the process of uploading a file structure; no
    * further events will be generated for this action.
    */
   GNUNET_FS_STATUS_PUBLISH_STOPPED = 6,
 
   /**
    * Notification that we have started this download.
    */
   GNUNET_FS_STATUS_DOWNLOAD_START = 7,
 
   /**
    * Notification that this download is being resumed.
    */
   GNUNET_FS_STATUS_DOWNLOAD_RESUME = 8,
 
   /**
    * Notification that this download was suspended.
    */
   GNUNET_FS_STATUS_DOWNLOAD_SUSPEND = 9,
 
   /**
    * Notification about progress with this download.
    */
   GNUNET_FS_STATUS_DOWNLOAD_PROGRESS = 10,
 
   /**
    * Notification that this download encountered an error.
    */
   GNUNET_FS_STATUS_DOWNLOAD_ERROR = 11,
 
   /**
    * Notification that this download completed.  Note that for
    * directories, completion does not imply completion of all files in
    * the directory.
    */
   GNUNET_FS_STATUS_DOWNLOAD_COMPLETED = 12,
 
   /**
    * Notification that this download was stopped
    * (final event with respect to this action).
    */
   GNUNET_FS_STATUS_DOWNLOAD_STOPPED = 13,
 
   /**
    * Notification that this download is now actively being
    * pursued (as opposed to waiting in the queue).
    */
   GNUNET_FS_STATUS_DOWNLOAD_ACTIVE = 14,
 
   /**
    * Notification that this download is no longer actively
    * being pursued (back in the queue).
    */
   GNUNET_FS_STATUS_DOWNLOAD_INACTIVE = 15,
 
   /**
    * Notification that this download is no longer part of a
    * recursive download or search but now a 'stand-alone'
    * download (and may thus need to be moved in the GUI
    * into a different category).
    */
   GNUNET_FS_STATUS_DOWNLOAD_LOST_PARENT = 16,
 
   /**
    * First event generated when a client requests
    * a search to begin or when a namespace result
    * automatically triggers the search for updates.
    */
   GNUNET_FS_STATUS_SEARCH_START = 17,
 
   /**
    * Last event when a search is being resumed;
    * note that "GNUNET_FS_SEARCH_START" will not
    * be generated in this case.
    */
   GNUNET_FS_STATUS_SEARCH_RESUME = 18,
 
   /**
    * Event generated for each search result
    * when the respective search is resumed.
    */
   GNUNET_FS_STATUS_SEARCH_RESUME_RESULT = 19,
 
   /**
    * Last event when a search is being suspended;
    * note that "GNUNET_FS_SEARCH_STOPPED" will not
    * be generated in this case.
    */
   GNUNET_FS_STATUS_SEARCH_SUSPEND = 20,
 
   /**
    * This search has yielded a result.
    */
   GNUNET_FS_STATUS_SEARCH_RESULT = 21,
 
   /**
    * We have discovered a new namespace.
    */
   GNUNET_FS_STATUS_SEARCH_RESULT_NAMESPACE = 22,
 
   /**
    * We have additional data about the quality
    * or availability of a search result.
    */
   GNUNET_FS_STATUS_SEARCH_UPDATE = 23,
 
   /**
    * Signals a problem with this search.
    */
   GNUNET_FS_STATUS_SEARCH_ERROR = 24,
 
   /**
    * Signals that this search was paused.
    */
   GNUNET_FS_STATUS_SEARCH_PAUSED = 25,
 
   /**
    * Signals that this search was continued (unpaused).
    */
   GNUNET_FS_STATUS_SEARCH_CONTINUED = 26,
 
   /**
    * Event generated for each search result
    * when the respective search is stopped.
    */
   GNUNET_FS_STATUS_SEARCH_RESULT_STOPPED = 27,
 
   /**
    * Event generated for each search result
    * when the respective search is suspended.
    */
   GNUNET_FS_STATUS_SEARCH_RESULT_SUSPEND = 28,
 
   /**
    * Last message from a search; this signals
    * that there will be no further events associated
    * with this search.
    */
   GNUNET_FS_STATUS_SEARCH_STOPPED = 29,
 
   /**
    * Notification that we started to unindex a file.
    */
   GNUNET_FS_STATUS_UNINDEX_START = 30,
 
   /**
    * Notification that we resumed unindexing of a file.
    */
   GNUNET_FS_STATUS_UNINDEX_RESUME = 31,
 
   /**
    * Notification that we suspended unindexing a file.
    */
   GNUNET_FS_STATUS_UNINDEX_SUSPEND = 32,
 
   /**
    * Notification that we made progress unindexing a file.
    */
   GNUNET_FS_STATUS_UNINDEX_PROGRESS = 33,
 
   /**
    * Notification that we encountered an error unindexing
    * a file.
    */
   GNUNET_FS_STATUS_UNINDEX_ERROR = 34,
 
   /**
    * Notification that the unindexing of this file
    * was completed.
    */
   GNUNET_FS_STATUS_UNINDEX_COMPLETED = 35,
 
   /**
    * Notification that the unindexing of this file
    * was stopped (final event for this action).
    */
   GNUNET_FS_STATUS_UNINDEX_STOPPED = 36,
 
   /**
    * Notification that we are making progress sharing a directory.
    */
   GNUNET_FS_STATUS_PUBLISH_PROGRESS_DIRECTORY = 37
 };
 
 
 /**
  * Handle for controlling an upload.
  */
 struct GNUNET_FS_PublishContext;
 
 
 /**
  * Handle for controlling an unindexing operation.
  */
 struct GNUNET_FS_UnindexContext;
 
 
 /**
  * Handle for controlling a search.
  */
 struct GNUNET_FS_SearchContext;
 
 
 /**
  * Result from a search.  Opaque handle to refer to the search
  * (typically used when starting a download associated with the search
  * result).
  */
 struct GNUNET_FS_SearchResult;
 
 
 /**
  * Context for controlling a download.
  */
 struct GNUNET_FS_DownloadContext;
 
 
 /**
  * Handle for detail information about a file that is being published.
  * Specifies metadata, keywords, how to get the contents of the file
  * (i.e. data-buffer in memory, filename on disk) and other options.
  */
 struct GNUNET_FS_FileInformation;
 
 
 /**
  * Argument given to the progress callback with
  * information about what is going on.
  */
 struct GNUNET_FS_ProgressInfo
 {
   /**
    * Values that depend on the event type.
    */
   union
   {
     /**
      * Values for all "GNUNET_FS_STATUS_PUBLISH_*" events.
      */
     struct GNUNET_FS_PublishStatusEvent
     {
       /**
        * Context for controlling the upload.
        */
       struct GNUNET_FS_PublishContext *pc;
 
       /**
        * Information about the file that is being published.
        */
       const struct GNUNET_FS_FileInformation *fi;
 
       /**
        * Client context pointer (set the last time by the client for
        * this operation; initially NULL on START/RESUME events).
        */
       void *cctx;
 
       /**
        * Client context pointer for the parent operation
        * (if this is a file in a directory or a subdirectory).
        */
       void *pctx;
 
       /**
        * Name of the file being published; can be NULL.
        */
       const char *filename;
 
       /**
        * How large is the file overall?  For directories,
        * this is only the size of the directory itself,
        * not of the other files contained within the
        * directory.
        */
       uint64_t size;
 
       /**
        * At what time do we expect to finish the upload?
        * (will be a value in the past for completed
        * uploads).
        */
       struct GNUNET_TIME_Relative eta;
 
       /**
        * How long has this upload been actively running
        * (excludes times where the upload was suspended).
        */
       struct GNUNET_TIME_Relative duration;
 
       /**
        * How many bytes have we completed?
        */
       uint64_t completed;
 
       /**
        * What anonymity level is used for this upload?
        */
       uint32_t anonymity;
 
       /**
        * Additional values for specific events.
        */
       union
       {
         /**
          * These values are only valid for
          * #GNUNET_FS_STATUS_PUBLISH_PROGRESS events.
          */
         struct GNUNET_FS_PublishProgressEvent
         {
           /**
            * Data block we just published.
            */
           const void *data;
 
           /**
            * At what offset in the file is "data"?
            */
           uint64_t offset;
 
           /**
            * Length of the data block.
            */
           uint64_t data_len;
 
           /**
            * Depth of the given block in the tree;
            * 0 would be the lowest level (DBLOCKs).
            */
           unsigned int depth;
         } progress;
 
         /**
          * These values are only valid for
          * #GNUNET_FS_STATUS_PUBLISH_PROGRESS_DIRECTORY events.
          */
         struct GNUNET_FS_PublishProgressDirectoryEvent
         {
           /**
            * How far are we along in the overall directory?
            */
           uint64_t completed;
 
           /**
            * How big do we estimate the entire directory to be?
            */
           uint64_t total;
 
           /**
            * At what time do we expect to finish the upload of the
            * CONTENTS of the directory. (The directory itself will take
            * extra time, indicated with the "eta" member at the
            * "publish"-level of this struct.)
            */
           struct GNUNET_TIME_Relative eta;
         } progress_directory;
 
         /**
          * These values are only valid for
          * #GNUNET_FS_STATUS_PUBLISH_RESUME events.
          */
         struct GNUNET_FS_PublishResumeEvent
         {
           /**
            * Error message, NULL if no error was encountered so far.
            */
           const char *message;
 
           /**
            * URI of the file (if the download had been completed)
            */
           const struct GNUNET_FS_Uri *chk_uri;
 
           /**
            * SKS URI of the file (if the download had been completed)
            */
           const struct GNUNET_FS_Uri *sks_uri;
         } resume;
 
         /**
          * These values are only valid for
          * #GNUNET_FS_STATUS_PUBLISH_COMPLETED events.
          */
         struct GNUNET_FS_PublishCompletedEvent
         {
           /**
            * CHK URI of the file.
            */
           const struct GNUNET_FS_Uri *chk_uri;
 
           /**
            * SKS URI of the file (if the download had been completed)
            */
           const struct GNUNET_FS_Uri *sks_uri;
         } completed;
 
         /**
          * These values are only valid for
          * #GNUNET_FS_STATUS_PUBLISH_ERROR events.
          */
         struct GNUNET_FS_PublishErrorEvent
         {
           /**
            * Error message, never NULL.
            */
           const char *message;
         } error;
       } specifics;
     } publish;
 
 
     /**
      * Values for all "GNUNET_FS_STATUS_DOWNLOAD_*" events.
      */
     struct GNUNET_FS_DownloadStatusEvent
     {
       /**
        * Context for controlling the download.
        */
       struct GNUNET_FS_DownloadContext *dc;
 
       /**
        * Client context pointer (set the last time
        * by the client for this operation; initially
        * NULL on START/RESUME events).
        */
       void *cctx;
 
       /**
        * Client context pointer for the parent operation
        * (if this is a file in a directory or a subdirectory).
        */
       void *pctx;
 
       /**
        * Client context pointer for the associated search operation
        * (specifically, context pointer for the specific search
        * result, not the overall search); only set if this
        * download was started from a search result.
        */
       void *sctx;
 
       /**
        * URI used for this download.
        */
       const struct GNUNET_FS_Uri *uri;
 
       /**
        * Name of the file that we are downloading.
        */
       const char *filename;
 
       /**
        * How large is the download overall?  This
        * is NOT necessarily the size from the
        * URI since we may be doing a partial download.
        */
       uint64_t size;
 
       /**
        * At what time do we expect to finish the download?
        * (will be a value in the past for completed
        * uploads).
        */
       struct GNUNET_TIME_Relative eta;
 
       /**
        * How long has this download been active?
        */
       struct GNUNET_TIME_Relative duration;
 
       /**
        * How many bytes have we completed?
        */
       uint64_t completed;
 
       /**
        * What anonymity level is used for this download?
        */
       uint32_t anonymity;
 
       /**
        * Is the download currently active.
        */
       int is_active;
 
       /**
        * Additional values for specific events.
        */
       union
       {
         /**
          * These values are only valid for
          * #GNUNET_FS_STATUS_DOWNLOAD_PROGRESS events.
          */
         struct GNUNET_FS_DownloadProgressEvent
         {
           /**
            * Data block we just obtained, can be NULL (even if
            * data_len > 0) if we found the entire block 'intact' on
            * disk.  In this case, it is also possible for 'data_len'
            * to be larger than an individual (32k) block.
            */
           const void *data;
 
           /**
            * At what offset in the file is "data"?
            */
           uint64_t offset;
 
           /**
            * Length of the data block.
            */
           uint64_t data_len;
 
           /**
            * How much time passed between us asking for this block and
            * actually getting it? #GNUNET_TIME_UNIT_FOREVER_REL if unknown.
            */
           struct GNUNET_TIME_Relative block_download_duration;
 
           /**
            * Depth of the given block in the tree;
            * 0 would be the lowest level (DBLOCKS).
            */
           unsigned int depth;
 
           /**
            * How much respect did we offer for downloading this block? (estimate,
            * because we might have the same request pending for multiple clients,
            * and of course because a transmission may have failed at a lower
            * layer).
            */
           uint32_t respect_offered;
 
           /**
            * How often did we transmit the request? (estimate,
            * because we might have the same request pending for multiple clients,
            * and of course because a transmission may have failed at a lower
            * layer).
            */
           uint32_t num_transmissions;
         } progress;
 
         /**
          * These values are only valid for
          * #GNUNET_FS_STATUS_DOWNLOAD_START events.
          */
         struct GNUNET_FS_DownloadStartEvent
         {
           /**
            * Known metadata for the download.
            */
           const struct GNUNET_FS_MetaData *meta;
         } start;
 
         /**
          * These values are only valid for
          * #GNUNET_FS_STATUS_DOWNLOAD_RESUME events.
          */
         struct GNUNET_FS_DownloadResumeEvent
         {
           /**
            * Known metadata for the download.
            */
           const struct GNUNET_FS_MetaData *meta;
 
           /**
            * Error message, NULL if we have not encountered any error yet.
            */
           const char *message;
         } resume;
 
         /**
          * These values are only valid for
          * #GNUNET_FS_STATUS_DOWNLOAD_ERROR events.
          */
         struct GNUNET_FS_DownloadErrorEvent
         {
           /**
            * Error message.
            */
           const char *message;
         } error;
       } specifics;
     } download;
 
     /**
      * Values for all "GNUNET_FS_STATUS_SEARCH_*" events.
      */
     struct GNUNET_FS_SearchStatusEvent
     {
       /**
        * Context for controlling the search, NULL for
        * searches that were not explicitly triggered
        * by the client (i.e., searches for updates in
        * namespaces).
        */
       struct GNUNET_FS_SearchContext *sc;
 
       /**
        * Client context pointer (set the last time by the client for
        * this operation; initially NULL on START/RESUME events).  Note
        * that this value can only be set on START/RESUME; returning
        * non-NULL on RESULT/RESUME_RESULT will actually update the
        * private context for "UPDATE" events.
        */
       void *cctx;
 
       /**
        * Client parent-context pointer; NULL for top-level searches,
        * refers to the client context of the associated search result
        * for automatically triggered searches for updates in
        * namespaces.  In this case, 'presult' refers to that search
        * result.
        */
       void *pctx;
 
       /**
        * What query is used for this search
        * (list of keywords or SKS identifier).
        */
       const struct GNUNET_FS_Uri *query;
 
       /**
        * How long has this search been actively running
        * (excludes times where the search was paused or
        * suspended).
        */
       struct GNUNET_TIME_Relative duration;
 
       /**
        * What anonymity level is used for this search?
        */
       uint32_t anonymity;
 
       /**
        * Additional values for specific events.
        */
       union
       {
         /**
          * These values are only valid for
          * #GNUNET_FS_STATUS_SEARCH_RESULT events.
          */
         struct GNUNET_FS_SearchResultEvent
         {
           /**
            * Metadata for the search result.
            */
           const struct GNUNET_FS_MetaData *meta;
 
           /**
            * URI for the search result.
            */
           const struct GNUNET_FS_Uri *uri;
 
           /**
            * Handle to the result (for starting downloads).
            */
           struct GNUNET_FS_SearchResult *result;
 
           /**
            * Applicability rank (the larger, the better the result
            * fits the search criteria).
            */
           uint32_t applicability_rank;
         } result;
 
         /**
          * These values are only valid for
          * #GNUNET_FS_STATUS_SEARCH_RESUME_RESULT events.
          */
         struct GNUNET_FS_SearchResumeResultEvent
         {
           /**
            * Metadata for the search result.
            */
           const struct GNUNET_FS_MetaData *meta;
 
           /**
            * URI for the search result.
            */
           const struct GNUNET_FS_Uri *uri;
 
           /**
            * Handle to the result (for starting downloads).
            */
           struct GNUNET_FS_SearchResult *result;
 
           /**
            * Current availability rank (negative:
            * unavailable, positive: available)
            */
           int32_t availability_rank;
 
           /**
            * On how many total queries is the given
            * availability_rank based?
            */
           uint32_t availability_certainty;
 
           /**
            * Updated applicability rank (the larger,
            * the better the result fits the search
            * criteria).
            */
           uint32_t applicability_rank;
         } resume_result;
 
         /**
          * These values are only valid for
          * #GNUNET_FS_STATUS_SEARCH_UPDATE events.
          */
         struct GNUNET_FS_SearchUpdateEvent
         {
           /**
            * Private context set for for this result
            * during the "RESULT" event.
            */
           void *cctx;
 
           /**
            * Metadata for the search result.
            */
           const struct GNUNET_FS_MetaData *meta;
 
           /**
            * URI for the search result.
            */
           const struct GNUNET_FS_Uri *uri;
 
           /**
            * Current availability rank (negative:
            * unavailable, positive: available)
            */
           int32_t availability_rank;
 
           /**
            * On how many total queries is the given
            * availability_rank based?
            */
           uint32_t availability_certainty;
 
           /**
            * Updated applicability rank (the larger,
            * the better the result fits the search
            * criteria).
            */
           uint32_t applicability_rank;
 
           /**
            * How long has the current probe been active?
            */
           struct GNUNET_TIME_Relative current_probe_time;
         } update;
 
         /**
          * These values are only valid for
          * #GNUNET_FS_STATUS_SEARCH_RESULT_SUSPEND events.
          * These events are automatically triggered for
          * each search result before the
          * #GNUNET_FS_STATUS_SEARCH_SUSPEND event.  This
          * happens primarily to give the client a chance
          * to clean up the "cctx" (if needed).
          */
         struct GNUNET_FS_SearchSuspendResultEvent
         {
           /**
            * Private context set for for this result
            * during the "RESULT" event.
            */
           void *cctx;
 
           /**
            * Metadata for the search result.
            */
           const struct GNUNET_FS_MetaData *meta;
 
           /**
            * URI for the search result.
            */
           const struct GNUNET_FS_Uri *uri;
         } result_suspend;
 
         /**
          * These values are only valid for
          * #GNUNET_FS_STATUS_SEARCH_RESULT_STOPPED events.
          * These events are automatically triggered for
          * each search result before the
          * #GNUNET_FS_STATUS_SEARCH_STOPPED event.  This
          * happens primarily to give the client a chance
          * to clean up the "cctx" (if needed).
          */
         struct GNUNET_FS_SearchStoppedResultEvent
         {
           /**
            * Private context set for for this result
            * during the "RESULT" event.
            */
           void *cctx;
 
           /**
            * Metadata for the search result.
            */
           const struct GNUNET_FS_MetaData *meta;
 
           /**
            * URI for the search result.
            */
           const struct GNUNET_FS_Uri *uri;
         } result_stopped;
 
         /**
          * These values are only valid for
          * #GNUNET_FS_STATUS_SEARCH_RESUME events.
          */
         struct GNUNET_GS_SearchResumeEvent
         {
           /**
            * Error message, NULL if we have not encountered any error yet.
            */
           const char *message;
 
           /**
            * Is this search currently paused?
            */
           int is_paused;
         } resume;
 
         /**
          * These values are only valid for
          * #GNUNET_FS_STATUS_SEARCH_ERROR events.
          */
         struct GNUNET_FS_SearchErrorEvent
         {
           /**
            * Error message.
            */
           const char *message;
         } error;
 
         /**
          * Values for #GNUNET_FS_STATUS_SEARCH_RESULT_NAMESPACE events.
          */
         struct GNUNET_GS_SearchResultNamespaceEvent
         {
           /**
            * Short, human-readable name of the namespace.
            */
           const char *name;
 
           /**
            * Root identifier for the namespace, can be NULL.
            */
           const char *root;
 
           /**
            * Metadata for the namespace.
            */
           const struct GNUNET_FS_MetaData *meta;
 
           /**
            * Public key of the namespace.
            */
           struct GNUNET_CRYPTO_EcdsaPublicKey pseudonym;
         } ns;
       } specifics;
     } search;
 
     /**
      * Values for all "GNUNET_FS_STATUS_UNINDEX_*" events.
      */
     struct GNUNET_FS_UnindexEvent
     {
       /**
        * Context for controlling the unindexing.
        */
       struct GNUNET_FS_UnindexContext *uc;
 
       /**
        * Client context pointer (set the last time
        * by the client for this operation; initially
        * NULL on START/RESUME events).
        */
       void *cctx;
 
       /**
        * Name of the file that is being unindexed.
        */
       const char *filename;
 
       /**
        * How large is the file overall?
        */
       uint64_t size;
 
       /**
        * At what time do we expect to finish unindexing?
        * (will be a value in the past for completed
        * unindexing operations).
        */
       struct GNUNET_TIME_Relative eta;
 
       /**
        * How long has this upload been actively running
        * (excludes times where the upload was suspended).
        */
       struct GNUNET_TIME_Relative duration;
 
       /**
        * How many bytes have we completed?
        */
       uint64_t completed;
 
       /**
        * Additional values for specific events.
        */
       union
       {
         /**
          * These values are only valid for
          * #GNUNET_FS_STATUS_UNINDEX_PROGRESS events.
          */
         struct GNUNET_FS_UnindexProgressEvent
         {
           /**
            * Data block we just unindexed.
            */
           const void *data;
 
           /**
            * At what offset in the file is "data"?
            */
           uint64_t offset;
 
           /**
            * Length of the data block.
            */
           uint64_t data_len;
 
           /**
            * Depth of the given block in the tree;
            * 0 would be the lowest level (DBLOCKS).
            */
           unsigned int depth;
         } progress;
 
         /**
          * These values are only valid for
          * #GNUNET_FS_STATUS_UNINDEX_RESUME events.
          */
         struct GNUNET_FS_UnindexResumeEvent
         {
           /**
            * Error message, NULL if we have not encountered any error yet.
            */
           const char *message;
         } resume;
 
         /**
          * These values are only valid for
          * #GNUNET_FS_STATUS_UNINDEX_ERROR events.
          */
         struct GNUNET_FS_UnindexErrorEvent
         {
           /**
            * Error message.
            */
           const char *message;
         } error;
       } specifics;
     } unindex;
   } value;
 
   /**
    * Specific status code (determines the event type).
    */
   enum GNUNET_FS_Status status;
 
   /**
    * File-sharing handle that generated the event.
    */
   struct GNUNET_FS_Handle *fsh;
 };
 
 
 /**
  * Notification of FS to a client about the progress of an
  * operation.  Callbacks of this type will be used for uploads,
  * downloads and searches.  Some of the arguments depend a bit
  * in their meaning on the context in which the callback is used.
  *
  * @param cls closure
  * @param info details about the event, specifying the event type
  *        and various bits about the event
  * @return client-context (for the next progress call
  *         for this operation; should be set to NULL for
  *         SUSPEND and STOPPED events).  The value returned
  *         will be passed to future callbacks in the respective
  *         field in the `struct GNUNET_FS_ProgressInfo`.
  */
 typedef void *
 (*GNUNET_FS_ProgressCallback) (void *cls,
                                const struct GNUNET_FS_ProgressInfo *info);
 
 
 /**
  * General (global) option flags for file-sharing.
  */
 enum GNUNET_FS_Flags
 {
   /**
    * No special flags set.
    */
   GNUNET_FS_FLAGS_NONE = 0,
 
   /**
    * Is persistence of operations desired?
    * (will create SUSPEND/RESUME events).
    */
   GNUNET_FS_FLAGS_PERSISTENCE = 1,
 
   /**
    * Should we automatically trigger probes for search results
    * to determine availability?
    * (will create #GNUNET_FS_STATUS_SEARCH_UPDATE events).
    */
   GNUNET_FS_FLAGS_DO_PROBES = 2
 };
 
 
 /**
  * Options specified in the VARARGs portion of GNUNET_FS_start.
  */
 enum GNUNET_FS_OPTIONS
 {
   /**
    * Last option in the VARARG list.
    */
   GNUNET_FS_OPTIONS_END = 0,
 
   /**
    * Select the desired amount of parallelism (this option should be
    * followed by an "unsigned int" giving the desired maximum number
    * of parallel downloads).
    */
   GNUNET_FS_OPTIONS_DOWNLOAD_PARALLELISM = 1,
 
   /**
    * Maximum number of requests that should be pending at a given
    * point in time (individual downloads may go above this, but
    * if we are above this threshold, we should not activate any
    * additional downloads.
    */
   GNUNET_FS_OPTIONS_REQUEST_PARALLELISM = 2
 };
 
 
 /**
  * Settings for publishing a block (which may of course also
  * apply to an entire directory or file).
  */
 struct GNUNET_FS_BlockOptions
 {
   /**
    * At what time should the block expire?  Data blocks (DBLOCKS and
    * IBLOCKS) may still be used even if they are expired (however,
    * they'd be removed quickly from the datastore if we are short on
    * space), all other types of blocks will no longer be returned
    * after they expire.
    */
   struct GNUNET_TIME_Absolute expiration_time;
 
   /**
    * At which anonymity level should the block be shared?
    * (0: no anonymity, 1: normal GAP, >1: with cover traffic).
    */
   uint32_t anonymity_level;
 
   /**
    * How important is it for us to store the block?  If we run
    * out of space, the highest-priority, non-expired blocks will
    * be kept.
    */
   uint32_t content_priority;
 
   /**
    * How often should we try to migrate the block to other peers?
    * Only used if "CONTENT_PUSHING" is set to YES, in which case we
    * first push each block to other peers according to their
    * replication levels.  Once each block has been pushed that many
    * times to other peers, blocks are chosen for migration at random.
    * Naturally, there is no guarantee that the other peers will keep
    * these blocks for any period of time (since they won't have any
    * priority or might be too busy to even store the block in the
    * first place).
    */
   uint32_t replication_level;
 };
 
 
 /**
  * Handle to the file-sharing service.
  */
 struct GNUNET_FS_Handle;
 
 
 /**
  * Setup a connection to the file-sharing service.
  *
  * @param cfg configuration to use
  * @param client_name unique identifier for this client
  * @param upcb function to call to notify about FS actions
  * @param upcb_cls closure for @a upcb
  * @param flags specific attributes for fs-operations
  * @param ... list of optional options, terminated with #GNUNET_FS_OPTIONS_END
  * @return NULL on error
  */
 struct GNUNET_FS_Handle *
 GNUNET_FS_start (const struct GNUNET_CONFIGURATION_Handle *cfg,
                  const char *client_name,
                  GNUNET_FS_ProgressCallback upcb,
                  void *upcb_cls,
                  enum GNUNET_FS_Flags flags,
                  ...);
 
 
 /**
  * Close our connection with the file-sharing service.
  * The callback given to #GNUNET_FS_start() will no longer be
  * called after this function returns.
  * This function MUST NOT be called from within the
  * callback itself.
  *
  * @param h handle that was returned from #GNUNET_FS_start()
  */
 void
 GNUNET_FS_stop (struct GNUNET_FS_Handle *h);
 
 
 /**
  * Function called on entries in a `struct GNUNET_FS_FileInformation` iteration.
  *
  * @param cls closure
  * @param fi the entry in the publish-structure
  * @param length length of the file or directory
  * @param meta metadata for the file or directory (can be modified)
  * @param uri pointer to the keywords that will be used for this entry (can be modified)
  * @param bo block options (can be modified)
  * @param do_index should we index (can be modified)
  * @param client_info pointer to client context set upon creation (can be modified)
  * @return #GNUNET_OK to continue, #GNUNET_NO to remove
  *         this entry from the directory, #GNUNET_SYSERR
  *         to abort the iteration
  */
 typedef int
 (*GNUNET_FS_FileInformationProcessor) (void *cls,
                                        struct GNUNET_FS_FileInformation *fi,
                                        uint64_t length,
                                        struct GNUNET_FS_MetaData *meta,
                                        struct GNUNET_FS_Uri **uri,
                                        struct GNUNET_FS_BlockOptions *bo,
                                        int *do_index,
                                        void **client_info);
 
 
 /**
  * Obtain the name under which this file information
  * structure is stored on disk.  Only works for top-level
  * file information structures.
  *
  * @param s structure to get the filename for
  * @return NULL on error, otherwise filename that can be used
  *         to read this fi-struct from disk.
  */
 const char *
 GNUNET_FS_file_information_get_id (struct GNUNET_FS_FileInformation *s);
 
 
 /**
  * Obtain the filename from the file information structure.
  *
  * @param s structure to get the filename for
  * @return "filename" field of the structure (can be NULL)
  */
 const char *
 GNUNET_FS_file_information_get_filename (const struct
                                          GNUNET_FS_FileInformation *s);
 
 
 /**
  * Set the filename in the file information structure.
  * If filename was already set, frees it before setting the new one.
  * Makes a copy of the argument.
  *
  * @param s structure to get the filename for
  * @param filename filename to set
  */
 void
 GNUNET_FS_file_information_set_filename (struct GNUNET_FS_FileInformation *s,
                                          const char *filename);
 
 
 /**
  * Create an entry for a file in a publish-structure.
  *
  * @param h handle to the file sharing subsystem
  * @param client_info initial client-info value for this entry
  * @param filename name of the file or directory to publish
  * @param keywords under which keywords should this file be available
  *         directly; can be NULL
  * @param meta metadata for the file
  * @param do_index #GNUNET_YES for index, #GNUNET_NO for insertion,
  *                #GNUNET_SYSERR for simulation
  * @param bo block options
  * @return publish structure entry for the file
  */
 struct GNUNET_FS_FileInformation *
 GNUNET_FS_file_information_create_from_file (struct GNUNET_FS_Handle *h,
                                              void *client_info,
                                              const char *filename,
                                              const struct
                                              GNUNET_FS_Uri *keywords,
                                              const struct
                                              GNUNET_FS_MetaData *meta,
                                              int do_index,
                                              const struct
                                              GNUNET_FS_BlockOptions *bo);
 
 
 /**
  * Create an entry for a file in a publish-structure.
  *
  * @param h handle to the file sharing subsystem
  * @param client_info initial client-info value for this entry
  * @param length length of the file
  * @param data data for the file (should not be used afterwards by
  *        the caller; callee will "free")
  * @param keywords under which keywords should this file be available
  *         directly; can be NULL
  * @param meta metadata for the file
  * @param do_index #GNUNET_YES for index, #GNUNET_NO for insertion,
  *                #GNUNET_SYSERR for simulation
  * @param bo block options
  * @return publish structure entry for the file
  */
 struct GNUNET_FS_FileInformation *
 GNUNET_FS_file_information_create_from_data (struct GNUNET_FS_Handle *h,
                                              void *client_info,
                                              uint64_t length,
                                              void *data,
                                              const struct
                                              GNUNET_FS_Uri *keywords,
                                              const struct
                                              GNUNET_FS_MetaData *meta,
                                              int do_index,
                                              const struct
                                              GNUNET_FS_BlockOptions *bo);
 
 
 /**
  * Function that provides data.
  *
  * @param cls closure
  * @param offset offset to read from; it is possible
  *            that the caller might need to go backwards
  *            a bit at times; set to UINT64_MAX to tell
  *            the reader that we won't be reading for a while
  *            (used to close the file descriptor but NOT fully
  *             clean up the reader's state); in this case,
  *            a value of '0' for max should be ignored
  * @param max maximum number of bytes that should be
  *            copied to buf; readers are not allowed
  *            to provide less data unless there is an error;
  *            a value of "0" will be used at the end to allow
  *            the reader to clean up its internal state
  * @param buf where the reader should write the data
  * @param emsg location for the reader to store an error message
  * @return number of bytes written, usually @a max, 0 on error
  */
 typedef size_t
 (*GNUNET_FS_DataReader) (void *cls,
                          uint64_t offset,
                          size_t max,
                          void *buf,
                          char **emsg);
 
 
 /**
  * Create an entry for a file in a publish-structure.
  *
  * @param h handle to the file sharing subsystem
  * @param client_info initial client-info value for this entry
  * @param length length of the file
  * @param reader function that can be used to obtain the data for the file
  * @param reader_cls closure for @a reader
  * @param keywords under which keywords should this file be available
  *         directly; can be NULL
  * @param meta metadata for the file
  * @param do_index #GNUNET_YES for index, #GNUNET_NO for insertion,
  *                #GNUNET_SYSERR for simulation
  * @param bo block options
  * @return publish structure entry for the file
  */
 struct GNUNET_FS_FileInformation *
 GNUNET_FS_file_information_create_from_reader (struct GNUNET_FS_Handle *h,
                                                void *client_info,
                                                uint64_t length,
                                                GNUNET_FS_DataReader reader,
                                                void *reader_cls,
                                                const struct GNUNET_FS_Uri
                                                *keywords,
                                                const struct
                                                GNUNET_FS_MetaData *meta,
                                                int do_index,
                                                const struct
                                                GNUNET_FS_BlockOptions *bo);
 
 
 /**
  * Create an entry for an empty directory in a publish-structure.
  *
  * @param h handle to the file sharing subsystem
  * @param client_info initial client-info value for this entry
  * @param keywords under which keywords should this directory be available
  *         directly; can be NULL
  * @param meta metadata for the directory
  * @param bo block options
  * @param filename name of the directory; can be NULL
  * @return publish structure entry for the directory , NULL on error
  */
 struct GNUNET_FS_FileInformation *
 GNUNET_FS_file_information_create_empty_directory (struct GNUNET_FS_Handle *h,
                                                    void *client_info,
                                                    const struct GNUNET_FS_Uri
                                                    *keywords,
                                                    const struct
                                                    GNUNET_FS_MetaData
                                                    *meta,
                                                    const struct
                                                    GNUNET_FS_BlockOptions *bo,
                                                    const char *filename);
 
 
 /**
  * Test if a given entry represents a directory.
  *
  * @param ent check if this FI represents a directory
  * @return #GNUNET_YES if so, #GNUNET_NO if not
  */
 int
 GNUNET_FS_file_information_is_directory (const struct GNUNET_FS_FileInformation
                                          *ent);
 
 
 /**
  * Add an entry to a directory in a publish-structure.  Clients
  * should never modify publish structures that were passed to
  * #GNUNET_FS_publish_start() already.
  *
  * @param dir the directory
  * @param ent the entry to add; the entry must not have been
  *            added to any other directory at this point and
  *            must not include @a dir in its structure
  * @return #GNUNET_OK on success, #GNUNET_SYSERR on error
  */
 int
 GNUNET_FS_file_information_add (struct GNUNET_FS_FileInformation *dir,
                                 struct GNUNET_FS_FileInformation *ent);
 
 
 /**
  * Inspect a file or directory in a publish-structure.  Clients
  * should never modify publish structures that were passed to
  * #GNUNET_FS_publish_start already.  When called on a directory,
  * this function will FIRST call @a proc with information about
  * the directory itself and then for each of the files in the
  * directory (but not for files in subdirectories).  When called
  * on a file, @a proc will be called exactly once (with information
  * about the specific file).
  *
  * @param dir the directory
  * @param proc function to call on each entry
  * @param proc_cls closure for @a proc
  */
 void
 GNUNET_FS_file_information_inspect (struct GNUNET_FS_FileInformation *dir,
                                     GNUNET_FS_FileInformationProcessor proc,
                                     void *proc_cls);
 
 
 /**
  * Destroy publish-structure.  Clients should never destroy publish
  * structures that were passed to #GNUNET_FS_publish_start already.
  *
  * @param fi structure to destroy
  * @param cleaner function to call on each entry in the structure
  *        (useful to clean up client_info); can be NULL; return
  *        values are ignored
  * @param cleaner_cls closure for @a cleaner
  */
 void
 GNUNET_FS_file_information_destroy (struct GNUNET_FS_FileInformation *fi,
                                     GNUNET_FS_FileInformationProcessor cleaner,
                                     void *cleaner_cls);
 
 
 /**
  * Options for publishing.  Compatible options
  * can be OR'ed together.
  */
 enum GNUNET_FS_PublishOptions
 {
   /**
    * No options (use defaults for everything).
    */
   GNUNET_FS_PUBLISH_OPTION_NONE = 0,
 
   /**
    * Simulate publishing.  With this option, no data will be stored
    * in the datastore.  Useful for computing URIs from files.
    */
   GNUNET_FS_PUBLISH_OPTION_SIMULATE_ONLY = 1
 };
 
 
 /**
  * Publish a file or directory.
  *
  * @param h handle to the file sharing subsystem
  * @param fi information about the file or directory structure to publish
  * @param ns namespace to publish the file in, NULL for no namespace
  * @param nid identifier to use for the published content in the namespace
  *        (can be NULL, must be NULL if namespace is NULL)
  * @param nuid update-identifier that will be used for future updates
  *        (can be NULL, must be NULL if namespace or nid is NULL)
  * @param options options for the publication
  * @return context that can be used to control the publish operation
  */
 struct GNUNET_FS_PublishContext *
 GNUNET_FS_publish_start (struct GNUNET_FS_Handle *h,
                          struct GNUNET_FS_FileInformation *fi,
                          const struct GNUNET_CRYPTO_EcdsaPrivateKey *ns,
                          const char *nid,
                          const char *nuid,
                          enum GNUNET_FS_PublishOptions options);
 
 
 /**
  * Stop a publication.  Will abort incomplete publications (but
  * not remove blocks that have already been published) or
  * simply clean up the state for completed publications.
  * Must NOT be called from within the event callback!
  *
  * @param pc context for the publication to stop
  */
 void
 GNUNET_FS_publish_stop (struct GNUNET_FS_PublishContext *pc);
 
 
 /**
  * Signature of a function called as the continuation of a KBlock or
  * SBlock publication.
  *
  * @param cls closure
  * @param uri URI under which the block is now available, NULL on error
  * @param emsg error message, NULL on success
  */
 typedef void
 (*GNUNET_FS_PublishContinuation) (void *cls,
                                   const struct GNUNET_FS_Uri *uri,
                                   const char *emsg);
 
 
 /**
  * Handle to cancel publish KSK operation.
  */
 struct GNUNET_FS_PublishKskContext;
 
 
 /**
  * Publish a KBlock on GNUnet.
  *
  * @param h handle to the file sharing subsystem
  * @param ksk_uri keywords to use
  * @param meta metadata to use
  * @param uri URI to refer to in the KBlock
  * @param bo block options
  * @param options publication options
  * @param cont continuation
  * @param cont_cls closure for @a cont
  * @return NULL on error (@a cont will still be called)
  */
 struct GNUNET_FS_PublishKskContext *
 GNUNET_FS_publish_ksk (struct GNUNET_FS_Handle *h,
                        const struct GNUNET_FS_Uri *ksk_uri,
                        const struct GNUNET_FS_MetaData *meta,
                        const struct GNUNET_FS_Uri *uri,
                        const struct GNUNET_FS_BlockOptions *bo,
                        enum GNUNET_FS_PublishOptions options,
                        GNUNET_FS_PublishContinuation cont, void *cont_cls);
 
 
 /**
  * Abort the KSK publishing operation.
  *
  * @param pkc context of the operation to abort.
  */
 void
 GNUNET_FS_publish_ksk_cancel (struct GNUNET_FS_PublishKskContext *pkc);
 
 
 /**
  * Handle to cancel publish SKS operation.
  */
 struct GNUNET_FS_PublishSksContext;
 
 
 /**
  * Publish an SBlock on GNUnet.
  *
  * @param h handle to the file sharing subsystem
  * @param ns namespace to publish in
  * @param identifier identifier to use
  * @param update update identifier to use
  * @param meta metadata to use
  * @param uri URI to refer to in the SBlock
  * @param bo block options
  * @param options publication options
  * @param cont continuation
  * @param cont_cls closure for @a cont
  * @return NULL on error (@a cont will still be called)
  */
 struct GNUNET_FS_PublishSksContext *
 GNUNET_FS_publish_sks (struct GNUNET_FS_Handle *h,
                        const struct GNUNET_CRYPTO_EcdsaPrivateKey *ns,
                        const char *identifier,
                        const char *update,
                        const struct GNUNET_FS_MetaData *meta,
                        const struct GNUNET_FS_Uri *uri,
                        const struct GNUNET_FS_BlockOptions *bo,
                        enum GNUNET_FS_PublishOptions options,
                        GNUNET_FS_PublishContinuation cont, void *cont_cls);
 
 
 /**
  * Abort the SKS publishing operation.
  *
  * @param psc context of the operation to abort.
  */
 void
 GNUNET_FS_publish_sks_cancel (struct GNUNET_FS_PublishSksContext *psc);
 
 
 /**
  * Type of a function called by #GNUNET_FS_get_indexed_files.
  *
  * @param cls closure
  * @param filename the name of the file, NULL for end of list
  * @param file_id hash of the contents of the indexed file
  * @return #GNUNET_OK to continue iteration, #GNUNET_SYSERR to abort
  */
 typedef int
 (*GNUNET_FS_IndexedFileProcessor) (void *cls,
                                    const char *filename,
                                    const struct GNUNET_HashCode *file_id);
 
 
 /**
  * Handle to cancel 'GNUNET_FS_get_indexed_files'.
  */
 struct GNUNET_FS_GetIndexedContext;
 
 
 /**
  * Iterate over all indexed files.
  *
  * @param h handle to the file sharing subsystem
  * @param iterator function to call on each indexed file
  * @param iterator_cls closure for @a iterator
  * @return NULL on error (@a iterator is not called)
  */
 struct GNUNET_FS_GetIndexedContext *
 GNUNET_FS_get_indexed_files (struct GNUNET_FS_Handle *h,
                              GNUNET_FS_IndexedFileProcessor iterator,
                              void *iterator_cls);
 
 
 /**
  * Cancel iteration over all indexed files.
  *
  * @param gic operation to cancel
  */
 void
 GNUNET_FS_get_indexed_files_cancel (struct GNUNET_FS_GetIndexedContext *gic);
 
 
 /**
  * Unindex a file.
  *
  * @param h handle to the file sharing subsystem
  * @param filename file to unindex
  * @param cctx initial value for the client context
  * @return NULL on error, otherwise handle
  */
 struct GNUNET_FS_UnindexContext *
 GNUNET_FS_unindex_start (struct GNUNET_FS_Handle *h,
                          const char *filename,
                          void *cctx);
 
 
 /**
  * Clean up after completion of an unindex operation.
  *
  * @param uc handle
  */
 void
 GNUNET_FS_unindex_stop (struct GNUNET_FS_UnindexContext *uc);
 
 
 /**
  * Function called on updateable identifiers.
  *
  * @param cls closure
  * @param last_id last identifier
  * @param last_uri uri used for the content published under the @a last_id
  * @param last_meta metadata associated with @a last_uri
  * @param next_id identifier that should be used for updates
  */
 typedef void (*GNUNET_FS_IdentifierProcessor) (void *cls,
                                                const char *last_id,
                                                const struct
                                                GNUNET_FS_Uri *last_uri,
                                                const struct
                                                GNUNET_FS_MetaData *
                                                last_meta,
                                                const char *next_id);
 
 
 /**
  * List all of the identifiers in the namespace for which we could
  * produce an update.  Namespace updates form a graph where each node
  * has a name.  Each node can have any number of URI/meta-data entries
  * which can each be linked to other nodes.  Cycles are possible.
  *
  * Calling this function with @a next_id NULL will cause the library to
  * call @a ip with a root for each strongly connected component of the
  * graph (a root being a node from which all other nodes in the Scc
  * are reachable).
  *
  * Calling this function with @a next_id being the name of a node will
  * cause the library to call @a ip with all children of the node.  Note
  * that cycles within an SCC are possible (including self-loops).
  *
  * @param h fs handle to use
  * @param ns namespace to inspect for updateable content
  * @param next_id ID to look for; use NULL to look for SCC roots
  * @param ip function to call on each updateable identifier
  * @param ip_cls closure for @a ip
  */
 void
 GNUNET_FS_namespace_list_updateable (struct GNUNET_FS_Handle *h,
                                      const struct
                                      GNUNET_CRYPTO_EcdsaPrivateKey *ns,
                                      const char *next_id,
                                      GNUNET_FS_IdentifierProcessor ip,
                                      void *ip_cls);
 
 
 /**
  * Options for searching.  Compatible options
  * can be OR'ed together.
  */
 enum GNUNET_FS_SearchOptions
 {
   /**
    * No options (use defaults for everything).
    */
   GNUNET_FS_SEARCH_OPTION_NONE = 0,
 
   /**
    * Only search the local host, do not search remote systems (no P2P)
    */
   GNUNET_FS_SEARCH_OPTION_LOOPBACK_ONLY = 1
 };
 
 
 /**
  * Start search for content.
  *
  * @param h handle to the file sharing subsystem
  * @param uri specifies the search parameters; can be
  *        a KSK URI or an SKS URI.
  * @param anonymity desired level of anonymity
  * @param options options for the search
  * @param cctx initial value for the client context
  * @return context that can be used to control the search
  */
 struct GNUNET_FS_SearchContext *
 GNUNET_FS_search_start (struct GNUNET_FS_Handle *h,
                         const struct GNUNET_FS_Uri *uri, uint32_t anonymity,
                         enum GNUNET_FS_SearchOptions options, void *cctx);
 
 
 /**
  * Pause search.
  *
  * @param sc context for the search that should be paused
  */
 void
 GNUNET_FS_search_pause (struct GNUNET_FS_SearchContext *sc);
 
 
 /**
  * Continue paused search.
  *
  * @param sc context for the search that should be resumed
  */
 void
 GNUNET_FS_search_continue (struct GNUNET_FS_SearchContext *sc);
 
 
 /**
  * Stop search for content.
  *
  * @param sc context for the search that should be stopped
  */
 void
 GNUNET_FS_search_stop (struct GNUNET_FS_SearchContext *sc);
 
 
 /**
  * Start download probes for the given search result.
  *
  * @param h file-sharing handle to use for the operation
  * @param uri URI to probe
  * @param meta meta data associated with the URI
  * @param client_info client info pointer to use for associated events
  * @param anonymity anonymity level to use for the probes
  * @return the search result handle to access the probe activity
  */
 struct GNUNET_FS_SearchResult *
 GNUNET_FS_probe (struct GNUNET_FS_Handle *h,
                  const struct GNUNET_FS_Uri *uri,
                  const struct GNUNET_FS_MetaData *meta,
                  void *client_info,
                  uint32_t anonymity);
 
 
 /**
  * Stop probe activity.  Must ONLY be used on values
  * returned from #GNUNET_FS_probe.
  *
  * @param sr search result to stop probing for (freed)
  * @return the value of the 'client_info' pointer
  */
 void *
 GNUNET_FS_probe_stop (struct GNUNET_FS_SearchResult *sr);
 
 
 /**
  * Options for downloading.  Compatible options
  * can be OR'ed together.
  */
 enum GNUNET_FS_DownloadOptions
 {
   /**
    * No options (use defaults for everything).
    */
   GNUNET_FS_DOWNLOAD_OPTION_NONE = 0,
 
   /**
    * Only download from the local host, do not access remote systems (no P2P)
    */
   GNUNET_FS_DOWNLOAD_OPTION_LOOPBACK_ONLY = 1,
 
   /**
    * Do a recursive download (that is, automatically trigger the
    * download of files in directories).
    */
   GNUNET_FS_DOWNLOAD_OPTION_RECURSIVE = 2,
 
   /**
    * Do not append temporary data to
    * the target file (for the IBlocks).
    */
   GNUNET_FS_DOWNLOAD_NO_TEMPORARIES = 4,
 
   /**
    * Internal option used to flag this download as a 'probe' for a
    * search result.  Impacts the priority with which the download is
    * run and causes signalling callbacks to be done differently.
    * Also, probe downloads are not serialized on suspension.  Normal
    * clients should not use this!
    */
   GNUNET_FS_DOWNLOAD_IS_PROBE = (UINT32_C(1) << 31)
 };
 
 
 /**
  * Download parts of a file.  Note that this will store
  * the blocks at the respective offset in the given file.  Also, the
  * download is still using the blocking of the underlying FS
  * encoding.  As a result, the download may *write* outside of the
  * given boundaries (if offset and length do not match the 32k FS
  * block boundaries).
  *
  * The given range can be used to focus a download towards a
  * particular portion of the file (optimization), not to strictly
  * limit the download to exactly those bytes.
  *
  * @param h handle to the file sharing subsystem
  * @param uri the URI of the file (determines what to download); CHK or LOC URI
  * @param meta known metadata for the file (can be NULL)
  * @param filename where to store the file, maybe NULL (then no file is
  *        created on disk and data must be grabbed from the callbacks)
  * @param tempname where to store temporary file data, not used if filename is non-NULL;
  *        can be NULL (in which case we will pick a name if needed); the temporary file
  *        may already exist, in which case we will try to use the data that is there and
  *        if it is not what is desired, will overwrite it
  * @param offset at what offset should we start the download (typically 0)
  * @param length how many bytes should be downloaded starting at offset
  * @param anonymity anonymity level to use for the download
  * @param options various download options
  * @param cctx initial value for the client context for this download
  * @param parent parent download to associate this download with (use NULL
  *        for top-level downloads; useful for manually-triggered recursive downloads)
  * @return context that can be used to control this download
  */
 struct GNUNET_FS_DownloadContext *
 GNUNET_FS_download_start (struct GNUNET_FS_Handle *h,
                           const struct GNUNET_FS_Uri *uri,
                           const struct GNUNET_FS_MetaData *meta,
                           const char *filename, const char *tempname,
                           uint64_t offset, uint64_t length, uint32_t anonymity,
                           enum GNUNET_FS_DownloadOptions options, void *cctx,
                           struct GNUNET_FS_DownloadContext *parent);
 
 
 /**
  * Download parts of a file based on a search result.  The download
  * will be associated with the search result (and the association
  * will be preserved when serializing/deserializing the state).
  * If the search is stopped, the download will not be aborted but
  * be 'promoted' to a stand-alone download.
  *
  * As with the other download function, this will store
  * the blocks at the respective offset in the given file.  Also, the
  * download is still using the blocking of the underlying FS
  * encoding.  As a result, the download may *write* outside of the
  * given boundaries (if offset and length do not match the 32k FS
  * block boundaries).
  *
  * The given range can be used to focus a download towards a
  * particular portion of the file (optimization), not to strictly
  * limit the download to exactly those bytes.
  *
  * @param h handle to the file sharing subsystem
  * @param sr the search result to use for the download (determines uri and
  *        meta data and associations)
  * @param filename where to store the file, maybe NULL (then no file is
  *        created on disk and data must be grabbed from the callbacks)
  * @param tempname where to store temporary file data, not used if filename is non-NULL;
  *        can be NULL (in which case we will pick a name if needed); the temporary file
  *        may already exist, in which case we will try to use the data that is there and
  *        if it is not what is desired, will overwrite it
  * @param offset at what offset should we start the download (typically 0)
  * @param length how many bytes should be downloaded starting at offset
  * @param anonymity anonymity level to use for the download
  * @param options various download options
  * @param cctx initial value for the client context for this download
  * @return context that can be used to control this download
  */
 struct GNUNET_FS_DownloadContext *
 GNUNET_FS_download_start_from_search (struct GNUNET_FS_Handle *h,
                                       struct GNUNET_FS_SearchResult *sr,
                                       const char *filename,
                                       const char *tempname, uint64_t offset,
                                       uint64_t length, uint32_t anonymity,
                                       enum GNUNET_FS_DownloadOptions options,
                                       void *cctx);
 
 
 /**
  * Stop a download (aborts if download is incomplete).
  *
  * @param dc handle for the download
  * @param do_delete delete files of incomplete downloads
  */
 void
 GNUNET_FS_download_stop (struct GNUNET_FS_DownloadContext *dc, int do_delete);
 
 
 /**
  * Suspend a download.
  *
  * @param dc handle for the download
  */
 void
 GNUNET_FS_download_suspend (struct GNUNET_FS_DownloadContext *dc);
 
 
 /**
  * Resume a suspended download.
  *
  * @param dc handle for the download
  */
 void
 GNUNET_FS_download_resume (struct GNUNET_FS_DownloadContext *dc);
 
 
 /* ******************** Directory API *********************** */
 
 
 #define GNUNET_FS_DIRECTORY_MIME  "application/gnunet-directory"
 #define GNUNET_FS_DIRECTORY_MAGIC "\211GND\r\n\032\n"
 #define GNUNET_FS_DIRECTORY_EXT   ".gnd"
 
 /**
  * Does the meta-data claim that this is a directory?
  * Checks if the mime-type is that of a GNUnet directory.
  *
  * @return #GNUNET_YES if it is, #GNUNET_NO if it is not, #GNUNET_SYSERR if
  *  we have no mime-type information (treat as #GNUNET_NO)
  */
 int
 GNUNET_FS_meta_data_test_for_directory (const struct GNUNET_FS_MetaData
                                         *md);
 
 
 /**
  * Set the MIMETYPE information for the given
  * metadata to "application/gnunet-directory".
  *
  * @param md metadata to add mimetype to
  */
 void
 GNUNET_FS_meta_data_make_directory (struct GNUNET_FS_MetaData *md);
 
 
 /**
  * Suggest a filename based on given metadata.
  *
  * @param md given meta data
  * @return NULL if meta data is useless for suggesting a filename
  */
 char *
 GNUNET_FS_meta_data_suggest_filename (const struct
                                       GNUNET_FS_MetaData *md);
 
 
 /**
  * Function used to process entries in a directory.
  *
  * @param cls closure
  * @param filename name of the file in the directory
  * @param uri URI of the file
  * @param metadata metadata for the file; metadata for
  *        the directory if everything else is NULL/zero
  * @param length length of the available data for the file
  *           (of type size_t since data must certainly fit
  *            into memory; if files are larger than size_t
  *            permits, then they will certainly not be
  *            embedded with the directory itself).
  * @param data data available for the file (length bytes)
  */
 typedef void (*GNUNET_FS_DirectoryEntryProcessor) (void *cls,
                                                    const char *filename,
                                                    const struct GNUNET_FS_Uri *
                                                    uri,
                                                    const struct
                                                    GNUNET_FS_MetaData *
                                                    meta, size_t length,
                                                    const void *data);
 
 
 /**
  * Iterate over all entries in a directory.  Note that directories
  * are structured such that it is possible to iterate over the
  * individual blocks as well as over the entire directory.  Thus
  * a client can call this function on the buffer in the
  * GNUNET_FS_ProgressCallback.  Also, directories can optionally
  * include the contents of (small) files embedded in the directory
  * itself; for those files, the processor may be given the
  * contents of the file directly by this function.
  *
  * @param size number of bytes in data
  * @param data pointer to the beginning of the directory
  * @param offset offset of data in the directory
  * @param dep function to call on each entry
  * @param dep_cls closure for @a dep
  * @return #GNUNET_OK if this could be a block in a directory,
  *         #GNUNET_NO if this could be part of a directory (but not 100% OK)
  *         #GNUNET_SYSERR if 'data' does not represent a directory
  */
 int
 GNUNET_FS_directory_list_contents (size_t size, const void *data,
                                    uint64_t offset,
                                    GNUNET_FS_DirectoryEntryProcessor dep,
                                    void *dep_cls);
 
 
 /**
  * Opaque handle to a directory builder.
  */
 struct GNUNET_FS_DirectoryBuilder;
 
 
 /**
  * Create a directory builder.
  *
  * @param mdir metadata for the directory
  */
 struct GNUNET_FS_DirectoryBuilder *
 GNUNET_FS_directory_builder_create (const struct GNUNET_FS_MetaData
                                     *mdir);
 
 
 /**
  * Add an entry to a directory.
  *
  * @param bld directory to extend
  * @param uri uri of the entry (must not be a KSK)
  * @param md metadata of the entry
  * @param data raw data of the entry, can be NULL, otherwise
  *        data must point to exactly the number of bytes specified
  *        by the uri
  */
 void
 GNUNET_FS_directory_builder_add (struct GNUNET_FS_DirectoryBuilder *bld,
                                  const struct GNUNET_FS_Uri *uri,
                                  const struct GNUNET_FS_MetaData *md,
                                  const void *data);
 
 
 /**
  * Finish building the directory.  Frees the
  * builder context and returns the directory
  * in-memory.
  *
  * @param bld directory to finish
  * @param rsize set to the number of bytes needed
  * @param rdata set to the encoded directory
  * @return #GNUNET_OK on success
  */
 int
 GNUNET_FS_directory_builder_finish (struct GNUNET_FS_DirectoryBuilder *bld,
                                     size_t *rsize, void **rdata);
 
 
 /* ******************** DirScanner API *********************** */
 
 /**
  * Progress reasons of the directory scanner.
  */
 enum GNUNET_FS_DirScannerProgressUpdateReason
 {
   /**
    * We've started processing a file or directory.
    */
   GNUNET_FS_DIRSCANNER_FILE_START = 0,
 
   /**
    * We're having trouble accessing a file (soft-error); it will
    * be ignored.
    */
   GNUNET_FS_DIRSCANNER_FILE_IGNORED,
 
   /**
    * We've found all files (in the pre-pass).
    */
   GNUNET_FS_DIRSCANNER_ALL_COUNTED,
 
   /**
    * We've finished extracting meta data from a file.
    */
   GNUNET_FS_DIRSCANNER_EXTRACT_FINISHED,
 
   /**
    * Last call to the progress function: we have finished scanning
    * the directory.
    */
   GNUNET_FS_DIRSCANNER_FINISHED,
 
   /**
    * There was an internal error.  Application should abort the scan.
    */
   GNUNET_FS_DIRSCANNER_INTERNAL_ERROR
 };
 
 
 /**
  * Function called over time as the directory scanner makes
  * progress on the job at hand.
  *
  * @param cls closure
  * @param filename which file we are making progress on
  * @param is_directory #GNUNET_YES if this is a directory,
  *                     #GNUNET_NO if this is a file
  *                     #GNUNET_SYSERR if it is neither (or unknown)
  * @param reason kind of progress we are making
  */
 typedef void (*GNUNET_FS_DirScannerProgressCallback) (void *cls,
                                                       const char *filename,
                                                       int is_directory,
                                                       enum
                                                       GNUNET_FS_DirScannerProgressUpdateReason
                                                       reason);
 
 
 /**
  * A node of a directory tree (produced by dirscanner)
  */
 struct GNUNET_FS_ShareTreeItem
 {
   /**
    * This is a doubly-linked list
    */
   struct GNUNET_FS_ShareTreeItem *prev;
 
   /**
    * This is a doubly-linked list
    */
   struct GNUNET_FS_ShareTreeItem *next;
 
   /**
    * This is a doubly-linked tree
    * NULL for top-level entries.
    */
   struct GNUNET_FS_ShareTreeItem *parent;
 
   /**
    * This is a doubly-linked tree
    * NULL for files and empty directories
    */
   struct GNUNET_FS_ShareTreeItem *children_head;
 
   /**
    * This is a doubly-linked tree
    * NULL for files and empty directories
    */
   struct GNUNET_FS_ShareTreeItem *children_tail;
 
   /**
    * Metadata for this file or directory
    */
   struct GNUNET_FS_MetaData *meta;
 
   /**
    * Keywords for this file or directory (derived from metadata).
    */
   struct GNUNET_FS_Uri *ksk_uri;
 
   /**
    * Name of the file/directory
    */
   char *filename;
 
   /**
    * Base name of the file/directory.
    */
   char *short_filename;
 
   /**
    * #GNUNET_YES if this is a directory
    */
   int is_directory;
 };
 
 
 /**
  * Opaque handle to an asynchronous directory scanning activity.
  */
 struct GNUNET_FS_DirScanner;
 
 
 /**
  * Start a directory scanner.
  *
  * @param filename name of the directory to scan
  * @param disable_extractor #GNUNET_YES to not run libextractor on files (only
  *        build a tree)
  * @param ex if not NULL, must be a list of extra plugins for extractor
  * @param cb the callback to call when there are scanning progress messages
  * @param cb_cls closure for @a cb
  * @return directory scanner object to be used for controlling the scanner
  */
 struct GNUNET_FS_DirScanner *
 GNUNET_FS_directory_scan_start (const char *filename,
                                 int disable_extractor,
                                 const char *ex,
                                 GNUNET_FS_DirScannerProgressCallback cb,
                                 void *cb_cls);
 
 
 /**
  * Abort the scan. Must not be called from within the progress_callback
  * function.
  *
  * @param ds directory scanner structure
  */
 void
 GNUNET_FS_directory_scan_abort (struct GNUNET_FS_DirScanner *ds);
 
 
 /**
  * Obtain the result of the scan after the scan has signalled
  * completion.  Must not be called prior to completion.  The @a ds is
  * freed as part of this call.
  *
  * @param ds directory scanner structure
  * @return the results of the scan (a directory tree)
  */
 struct GNUNET_FS_ShareTreeItem *
 GNUNET_FS_directory_scan_get_result (struct GNUNET_FS_DirScanner *ds);
 
 
 /**
  * Process a share item tree, moving frequent keywords up and
  * copying frequent metadata up.
  *
  * @param toplevel toplevel directory in the tree, returned by the scanner
  */
 void
 GNUNET_FS_share_tree_trim (struct GNUNET_FS_ShareTreeItem *toplevel);
 
 
 /**
  * Release memory of a share item tree.
  *
  * @param toplevel toplevel of the tree to be freed
  */
 void
 GNUNET_FS_share_tree_free (struct GNUNET_FS_ShareTreeItem *toplevel);
 
 /**
  * Meta data processing
  * @defgroup metadata  Metadata
  * GNU libextractor key-value pairs
  */
 
 
 /* ****************** metadata ******************* */
 
 
 /**
  * @ingroup metadata
  * Create a fresh meta data container.
  *
  * @return empty meta-data container
  */
 struct GNUNET_FS_MetaData *
 GNUNET_FS_meta_data_create (void);
 
 
 /**
  * @ingroup metadata
  * Duplicate a MetaData token.
  *
  * @param md what to duplicate
  * @return duplicate meta-data container
  */
 struct GNUNET_FS_MetaData *
 GNUNET_FS_meta_data_duplicate (
   const struct GNUNET_FS_MetaData *md);
 
 
 /**
  * @ingroup metadata
  * Free meta data.
  *
  * @param md what to free
  */
 void
 GNUNET_FS_meta_data_destroy (struct GNUNET_FS_MetaData *md);
 
 
 /**
  * @ingroup metadata
  * Test if two MDs are equal. We consider them equal if
  * the meta types, formats and content match (we do not
  * include the mime types and plugins names in this
  * consideration).
  *
  * @param md1 first value to check
  * @param md2 other value to check
  * @return #GNUNET_YES if they are equal
  */
 int
 GNUNET_FS_meta_data_test_equal (
   const struct GNUNET_FS_MetaData *md1,
   const struct GNUNET_FS_MetaData *md2);
 
 
 /**
  * @ingroup metadata
  * Extend metadata.
  *
  * @param md metadata to extend
  * @param plugin_name name of the plugin that produced this value;
  *        special values can be used (e.g. '&lt;zlib&gt;' for zlib being
  *        used in the main libextractor library and yielding
  *        meta data).
  * @param type libextractor-type describing the meta data
  * @param format basic format information about data
  * @param data_mime_type mime-type of data (not of the original file);
  *        can be NULL (if mime-type is not known)
  * @param data actual meta-data found
  * @param data_size number of bytes in data
  * @return #GNUNET_OK on success, #GNUNET_SYSERR if this entry already exists
  *         data_mime_type and plugin_name are not considered for "exists" checks
  */
 int
 GNUNET_FS_meta_data_insert (struct GNUNET_FS_MetaData *md,
                                    const char *plugin_name,
                                    enum EXTRACTOR_MetaType type,
                                    enum EXTRACTOR_MetaFormat format,
                                    const char *data_mime_type,
                                    const char *data,
                                    size_t data_size);
 
 
 /**
  * @ingroup metadata
  * Extend metadata.  Merges the meta data from the second argument
  * into the first, discarding duplicate key-value pairs.
  *
  * @param md metadata to extend
  * @param in metadata to merge
  */
 void
 GNUNET_FS_meta_data_merge (struct GNUNET_FS_MetaData *md,
                                   const struct GNUNET_FS_MetaData *in);
 
 
 /**
  * @ingroup metadata
  * Remove an item.
  *
  * @param md metadata to manipulate
  * @param type type of the item to remove
  * @param data specific value to remove, NULL to remove all
  *        entries of the given type
  * @param data_size number of bytes in data
  * @return #GNUNET_OK on success, #GNUNET_SYSERR if the item does not exist in md
  */
 int
 GNUNET_FS_meta_data_delete (struct GNUNET_FS_MetaData *md,
                                    enum EXTRACTOR_MetaType type,
                                    const char *data,
                                    size_t data_size);
 
 
 /**
  * @ingroup metadata
  * Remove all items in the container.
  *
  * @param md metadata to manipulate
  */
 void
 GNUNET_FS_meta_data_clear (struct GNUNET_FS_MetaData *md);
 
 
 /**
  * @ingroup metadata
  * Add the current time as the publication date
  * to the meta-data.
  *
  * @param md metadata to modify
  */
 void
 GNUNET_FS_meta_data_add_publication_date (
   struct GNUNET_FS_MetaData *md);
 
 
 /**
  * @ingroup metadata
  * Iterate over MD entries.
  *
  * @param md metadata to inspect
  * @param iter function to call on each entry, return 0 to continue to iterate
  *             and 1 to abort iteration in this function (GNU libextractor API!)
  * @param iter_cls closure for @a iter
  * @return number of entries
  */
 int
 GNUNET_FS_meta_data_iterate (const struct GNUNET_FS_MetaData *md,
                                     EXTRACTOR_MetaDataProcessor iter,
                                     void *iter_cls);
 
 
 /**
  * @ingroup metadata
  * Get the first MD entry of the given type.  Caller
  * is responsible for freeing the return value.
  * Also, only meta data items that are strings (0-terminated)
  * are returned by this function.
  *
  * @param md metadata to inspect
  * @param type type to look for
  * @return NULL if no entry was found
  */
 char *
 GNUNET_FS_meta_data_get_by_type (
   const struct GNUNET_FS_MetaData *md,
   enum EXTRACTOR_MetaType type);
 
 
 /**
  * @ingroup metadata
  * Get the first matching MD entry of the given types. Caller is
  * responsible for freeing the return value.  Also, only meta data
  * items that are strings (0-terminated) are returned by this
  * function.
  *
  * @param md metadata to inspect
  * @param ... -1-terminated list of types
  * @return NULL if we do not have any such entry,
  *  otherwise client is responsible for freeing the value!
  */
 char *
 GNUNET_FS_meta_data_get_first_by_types (
   const struct GNUNET_FS_MetaData *md,
   ...);
 
 /**
  * @ingroup metadata
  * Get a thumbnail from the meta-data (if present).  Only matches meta
  * data with mime type "image" and binary format.
  *
  * @param md metadata to inspect
  * @param thumb will be set to the thumbnail data.  Must be
  *        freed by the caller!
  * @return number of bytes in thumbnail, 0 if not available
  */
 size_t
 GNUNET_FS_meta_data_get_thumbnail (
   const struct GNUNET_FS_MetaData *md,
   unsigned char **thumb);
 
 
 /**
  * @ingroup metadata
  * Options for metadata serialization.
  */
 enum GNUNET_FS_MetaDataSerializationOptions
 {
   /**
    * @ingroup metadata
    * Serialize all of the data.
    */
   GNUNET_FS_META_DATA_SERIALIZE_FULL = 0,
 
   /**
    * @ingroup metadata
    * If not enough space is available, it is acceptable
    * to only serialize some of the metadata.
    */
   GNUNET_FS_META_DATA_SERIALIZE_PART = 1,
 
   /**
    * @ingroup metadata
    * Speed is of the essence, do not allow compression.
    */
   GNUNET_FS_META_DATA_SERIALIZE_NO_COMPRESS = 2
 };
 
 
 /**
  * @ingroup metadata
  * Serialize meta-data to target.
  *
  * @param md metadata to serialize
  * @param target where to write the serialized metadata;
  *         *target can be NULL, in which case memory is allocated
  * @param max maximum number of bytes available
  * @param opt is it ok to just write SOME of the
  *        meta-data to match the size constraint,
  *        possibly discarding some data?
  * @return number of bytes written on success,
  *         -1 on error (typically: not enough
  *         space)
  */
 ssize_t
 GNUNET_FS_meta_data_serialize (
   const struct GNUNET_FS_MetaData *md,
   char **target,
   size_t max,
   enum GNUNET_FS_MetaDataSerializationOptions opt);
 
 
 /**
  * @ingroup metadata
  * Get the size of the full meta-data in serialized form.
  *
  * @param md metadata to inspect
  * @return number of bytes needed for serialization, -1 on error
  */
 ssize_t
 GNUNET_FS_meta_data_get_serialized_size (
   const struct GNUNET_FS_MetaData *md);
 
 
 /**
  * @ingroup metadata
  * Deserialize meta-data.  Initializes md.
  *
  * @param input serialized meta-data.
  * @param size number of bytes available
  * @return MD on success, NULL on error (e.g.
  *         bad format)
  */
 struct GNUNET_FS_MetaData *
 GNUNET_FS_meta_data_deserialize (const char *input, size_t size);
 
 /**
  * Write a metadata container.
  *
  * @param h the IO handle to write to
  * @param what what is being written (for error message creation)
  * @param m metadata to write
  * @return #GNUNET_OK on success, #GNUNET_SYSERR on error
  */
 enum GNUNET_GenericReturnValue
 GNUNET_FS_write_meta_data (struct GNUNET_BIO_WriteHandle *h,
                             const char *what,
                             const struct GNUNET_FS_MetaData *m);
 
 /**
  * Create the specification to read a metadata container.
  *
  * @param what describes what is being read (for error message creation)
  * @param result the buffer to store a pointer to the (allocated) metadata
  * @return the read spec
  */
 struct GNUNET_BIO_ReadSpec
 GNUNET_FS_read_spec_meta_data (const char *what,
                                 struct GNUNET_FS_MetaData **result);
 
 
 
 /**
  * Create the specification to write a metadata container.
  *
  * @param what what is being written (for error message creation)
  * @param m metadata to write
  * @return the write spec
  */
 struct GNUNET_BIO_WriteSpec
 GNUNET_FS_write_spec_meta_data (const char *what,
                                  const struct GNUNET_FS_MetaData *m);
 
 /**
  * Read a metadata container.
  *
  * @param h handle to an open file
  * @param what describes what is being read (for error message creation)
  * @param result the buffer to store a pointer to the (allocated) metadata
  * @return #GNUNET_OK on success, #GNUNET_SYSERR on failure
  */
 enum GNUNET_GenericReturnValue
 GNUNET_FS_read_meta_data (struct GNUNET_BIO_ReadHandle *h,
                            const char *what,
                            struct GNUNET_FS_MetaData **result);
 
 
 #if 0                           /* keep Emacsens' auto-indent happy */
 {
 #endif
 #ifdef __cplusplus
 }
 #endif
 
 #endif
 
 /** @} */  /* end of group */
 
 /** @} */ /* end of group addition */