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+=pod
+
+=head1 NAME
+
+BIO_read_ex, BIO_write_ex, BIO_read, BIO_write, BIO_gets, BIO_puts
+- BIO I/O functions
+
+=head1 SYNOPSIS
+
+ #include <openssl/bio.h>
+
+ int BIO_read_ex(BIO *b, void *data, size_t dlen, size_t *readbytes);
+ int BIO_write_ex(BIO *b, const void *data, size_t dlen, size_t *written);
+
+ int BIO_read(BIO *b, void *data, int dlen);
+ int BIO_gets(BIO *b, char *buf, int size);
+ int BIO_write(BIO *b, const void *data, int dlen);
+ int BIO_puts(BIO *b, const char *buf);
+
+=head1 DESCRIPTION
+
+BIO_read_ex() attempts to read B<dlen> bytes from BIO B<b> and places the data
+in B<data>. If any bytes were successfully read then the number of bytes read is
+stored in B<*readbytes>.
+
+BIO_write_ex() attempts to write B<dlen> bytes from B<data> to BIO B<b>. If
+successful then the number of bytes written is stored in B<*written>.
+
+BIO_read() attempts to read B<len> bytes from BIO B<b> and places
+the data in B<buf>.
+
+BIO_gets() performs the BIOs "gets" operation and places the data
+in B<buf>. Usually this operation will attempt to read a line of data
+from the BIO of maximum length B<size-1>. There are exceptions to this,
+however; for example, BIO_gets() on a digest BIO will calculate and
+return the digest and other BIOs may not support BIO_gets() at all.
+The returned string is always NUL-terminated and the '\n' is preserved
+if present in the input data.
+
+BIO_write() attempts to write B<len> bytes from B<buf> to BIO B<b>.
+
+BIO_puts() attempts to write a NUL-terminated string B<buf> to BIO B<b>.
+
+=head1 RETURN VALUES
+
+BIO_read_ex() and BIO_write_ex() return 1 if data was successfully read or
+written, and 0 otherwise.
+
+All other functions return either the amount of data successfully read or
+written (if the return value is positive) or that no data was successfully
+read or written if the result is 0 or -1. If the return value is -2 then
+the operation is not implemented in the specific BIO type. The trailing
+NUL is not included in the length returned by BIO_gets().
+
+=head1 NOTES
+
+A 0 or -1 return is not necessarily an indication of an error. In
+particular when the source/sink is non-blocking or of a certain type
+it may merely be an indication that no data is currently available and that
+the application should retry the operation later.
+
+One technique sometimes used with blocking sockets is to use a system call
+(such as select(), poll() or equivalent) to determine when data is available
+and then call read() to read the data. The equivalent with BIOs (that is call
+select() on the underlying I/O structure and then call BIO_read() to
+read the data) should B<not> be used because a single call to BIO_read()
+can cause several reads (and writes in the case of SSL BIOs) on the underlying
+I/O structure and may block as a result. Instead select() (or equivalent)
+should be combined with non blocking I/O so successive reads will request
+a retry instead of blocking.
+
+See L<BIO_should_retry(3)> for details of how to
+determine the cause of a retry and other I/O issues.
+
+If the BIO_gets() function is not supported by a BIO then it possible to
+work around this by adding a buffering BIO L<BIO_f_buffer(3)>
+to the chain.
+
+=head1 SEE ALSO
+
+L<BIO_should_retry(3)>
+
+=head1 HISTORY
+
+BIO_gets() on 1.1.0 and older when called on BIO_fd() based BIO does not
+keep the '\n' at the end of the line in the buffer.
+
+=head1 COPYRIGHT
+
+Copyright 2000-2016 The OpenSSL Project Authors. All Rights Reserved.
+
+Licensed under the OpenSSL license (the "License"). You may not use
+this file except in compliance with the License. You can obtain a copy
+in the file LICENSE in the source distribution or at
+L<https://www.openssl.org/source/license.html>.
+
+=cut