mirror of
https://github.com/openssl/openssl.git
synced 2024-12-21 06:09:35 +08:00
130 lines
5.1 KiB
Plaintext
130 lines
5.1 KiB
Plaintext
=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 I<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 2000-2023 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
|