doc/man3/BIO_read.pod - third_party/openssl - Git at Google

 =pod

 =head1 NAME

 BIO_read_ex, BIO_write_ex, BIO_read, BIO_write,
 BIO_gets, BIO_get_line, 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_get_line(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 I<dlen> bytes from BIO I<b> and places the data
 in I<data>. If any bytes were successfully read then the number of bytes read is
 stored in I<*readbytes>.

 BIO_write_ex() attempts to write I<dlen> bytes from I<data> to BIO I<b>.
 If successful then the number of bytes written is stored in I<*written>
 unless I<written> is NULL.

 BIO_read() attempts to read I<len> bytes from BIO I<b> and places
 the data in I<buf>.

 BIO_gets() performs the BIOs "gets" operation and places the data
 in I<buf>. Usually this operation will attempt to read a line of data
 from the BIO of maximum length I<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.
 On binary input there may be NUL characters within the string;
 in this case the return value (if nonnegative) may give an incorrect length.

 BIO_get_line() attempts to read from BIO <b> a line of data up to the next '\n'
 or the maximum length I<size-1> is reached and places the data in I<buf>.
 The returned string is always NUL-terminated and the '\n' is preserved
 if present in the input data.
 On binary input there may be NUL characters within the string;
 in this case the return value (if nonnegative) gives the actual length read.
 For implementing this, unfortunately the data needs to be read byte-by-byte.

 BIO_write() attempts to write I<len> bytes from I<buf> to BIO I<b>.

 BIO_puts() attempts to write a NUL-terminated string I<buf> to BIO I<b>.

 =head1 RETURN VALUES

 BIO_read_ex() returns 1 if data was successfully read, and 0 otherwise.

 BIO_write_ex() returns 1 if no error was encountered writing data, 0 otherwise.
 Requesting to write 0 bytes is not considered an error.

 BIO_write() returns -2 if the "write" operation is not implemented by the BIO
 or -1 on other errors.
 Otherwise it returns the number of bytes written.
 This may be 0 if the BIO I<b> is NULL or I<dlen <= 0>.

 BIO_gets() returns -2 if the "gets" operation is not implemented by the BIO
 or -1 on other errors.
 Otherwise it typically returns the amount of data read,
 but depending on the implementation it may return only the length up to
 the first NUL character contained in the data read.
 In any case the trailing NUL that is added after the data read
 is not included in the length returned.

 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.

 =head1 NOTES

 A 0 or -1 return is not necessarily an indication of an error. In
 particular when the source/sink is nonblocking 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 "gets" method is not supported by a BIO then BIO_get_line() can be used.
 It is also possible to make BIO_gets() usable even if the "gets" method is not
 supported 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 did not
 keep the '\n' at the end of the line in the buffer.

 BIO_get_line() was added in OpenSSL 3.0.

 BIO_write_ex() returns 1 if the size of the data to write is 0 and the
 I<written> parameter of the function can be NULL since OpenSSL 3.0.

 =head1 COPYRIGHT

 Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved.

 Licensed under the Apache License 2.0 (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
	=pod

	=head1 NAME

	BIO_read_ex, BIO_write_ex, BIO_read, BIO_write,
	BIO_gets, BIO_get_line, 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_get_line(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 I<dlen> bytes from BIO I<b> and places the data
	in I<data>. If any bytes were successfully read then the number of bytes read is
	stored in I<*readbytes>.

	BIO_write_ex() attempts to write I<dlen> bytes from I<data> to BIO I<b>.
	If successful then the number of bytes written is stored in I<*written>
	unless I<written> is NULL.

	BIO_read() attempts to read I<len> bytes from BIO I<b> and places
	the data in I<buf>.

	BIO_gets() performs the BIOs "gets" operation and places the data
	in I<buf>. Usually this operation will attempt to read a line of data
	from the BIO of maximum length I<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.
	On binary input there may be NUL characters within the string;
	in this case the return value (if nonnegative) may give an incorrect length.

	BIO_get_line() attempts to read from BIO <b> a line of data up to the next '\n'
	or the maximum length I<size-1> is reached and places the data in I<buf>.
	The returned string is always NUL-terminated and the '\n' is preserved
	if present in the input data.
	On binary input there may be NUL characters within the string;
	in this case the return value (if nonnegative) gives the actual length read.
	For implementing this, unfortunately the data needs to be read byte-by-byte.

	BIO_write() attempts to write I<len> bytes from I<buf> to BIO I<b>.

	BIO_puts() attempts to write a NUL-terminated string I<buf> to BIO I<b>.

	=head1 RETURN VALUES

	BIO_read_ex() returns 1 if data was successfully read, and 0 otherwise.

	BIO_write_ex() returns 1 if no error was encountered writing data, 0 otherwise.
	Requesting to write 0 bytes is not considered an error.

	BIO_write() returns -2 if the "write" operation is not implemented by the BIO
	or -1 on other errors.
	Otherwise it returns the number of bytes written.
	This may be 0 if the BIO I<b> is NULL or I<dlen <= 0>.

	BIO_gets() returns -2 if the "gets" operation is not implemented by the BIO
	or -1 on other errors.
	Otherwise it typically returns the amount of data read,
	but depending on the implementation it may return only the length up to
	the first NUL character contained in the data read.
	In any case the trailing NUL that is added after the data read
	is not included in the length returned.

	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.

	=head1 NOTES

	A 0 or -1 return is not necessarily an indication of an error. In
	particular when the source/sink is nonblocking 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 "gets" method is not supported by a BIO then BIO_get_line() can be used.
	It is also possible to make BIO_gets() usable even if the "gets" method is not
	supported 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 did not
	keep the '\n' at the end of the line in the buffer.

	BIO_get_line() was added in OpenSSL 3.0.

	BIO_write_ex() returns 1 if the size of the data to write is 0 and the
	I<written> parameter of the function can be NULL since OpenSSL 3.0.

	=head1 COPYRIGHT

	Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved.

	Licensed under the Apache License 2.0 (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