4e3973b457
After the recent reworking, not everything matched up, and some comments didn't catch up to the outl-->dlen and inl-->dlen renames that happened during the development of the recent patches. Try to make parameter names consistent across header, implementation, and manual pages. Also remove some trailing whitespace that was inadvertently introduced. Reviewed-by: Matt Caswell <matt@openssl.org> Reviewed-by: Richard Levitte <levitte@openssl.org> (Merged from https://github.com/openssl/openssl/pull/1798)
91 lines
3.4 KiB
Text
91 lines
3.4 KiB
Text
=pod
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=head1 NAME
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BIO_read_ex, BIO_write_ex, BIO_read, BIO_write, BIO_gets, BIO_puts
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- BIO I/O functions
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=head1 SYNOPSIS
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#include <openssl/bio.h>
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int BIO_read_ex(BIO *b, void *data, size_t dlen, size_t *readbytes);
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int BIO_write_ex(BIO *b, const void *data, size_t dlen, size_t *written);
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int BIO_read(BIO *b, void *data, int dlen);
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int BIO_gets(BIO *b, char *buf, int size);
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int BIO_write(BIO *b, const void *data, int dlen);
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int BIO_puts(BIO *b, const char *buf);
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=head1 DESCRIPTION
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BIO_read_ex() attempts to read B<dlen> bytes from BIO B<b> and places the data
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in B<data>. If any bytes were successfully read then the number of bytes read is
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stored in B<*readbytes>.
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BIO_write_ex() attempts to write B<dlen> bytes from B<data> to BIO B<b>. If
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successful then the number of bytes written is stored in B<*written>.
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BIO_read() attempts to read B<len> bytes from BIO B<b> and places
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the data in B<buf>.
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BIO_gets() performs the BIOs "gets" operation and places the data
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in B<buf>. Usually this operation will attempt to read a line of data
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from the BIO of maximum length B<size-1>. There are exceptions to this,
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however; for example, BIO_gets() on a digest BIO will calculate and
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return the digest and other BIOs may not support BIO_gets() at all.
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The returned string is always NUL-terminated.
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BIO_write() attempts to write B<len> bytes from B<buf> to BIO B<b>.
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BIO_puts() attempts to write a NUL-terminated string B<buf> to BIO B<b>.
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=head1 RETURN VALUES
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BIO_read_ex() and BIO_write_ex() return 1 if data was successfully read or
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written, and 0 otherwise.
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All other functions return either the amount of data successfully read or
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written (if the return value is positive) or that no data was successfully
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read or written if the result is 0 or -1. If the return value is -2 then
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the operation is not implemented in the specific BIO type. The trailing
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NUL is not included in the length returned by BIO_gets().
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=head1 NOTES
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A 0 or -1 return is not necessarily an indication of an error. In
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particular when the source/sink is non-blocking or of a certain type
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it may merely be an indication that no data is currently available and that
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the application should retry the operation later.
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One technique sometimes used with blocking sockets is to use a system call
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(such as select(), poll() or equivalent) to determine when data is available
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and then call read() to read the data. The equivalent with BIOs (that is call
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select() on the underlying I/O structure and then call BIO_read() to
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read the data) should B<not> be used because a single call to BIO_read()
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can cause several reads (and writes in the case of SSL BIOs) on the underlying
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I/O structure and may block as a result. Instead select() (or equivalent)
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should be combined with non blocking I/O so successive reads will request
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a retry instead of blocking.
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See L<BIO_should_retry(3)> for details of how to
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determine the cause of a retry and other I/O issues.
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If the BIO_gets() function is not supported by a BIO then it possible to
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work around this by adding a buffering BIO L<BIO_f_buffer(3)>
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to the chain.
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=head1 SEE ALSO
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L<BIO_should_retry(3)>
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=head1 COPYRIGHT
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Copyright 2000-2016 The OpenSSL Project Authors. All Rights Reserved.
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Licensed under the OpenSSL license (the "License"). You may not use
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this file except in compliance with the License. You can obtain a copy
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in the file LICENSE in the source distribution or at
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L<https://www.openssl.org/source/license.html>.
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=cut
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