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Diffstat (limited to 'roms/edk2/CryptoPkg/Library/OpensslLib/openssl/doc/man3/BIO_read.pod')
| -rw-r--r-- | roms/edk2/CryptoPkg/Library/OpensslLib/openssl/doc/man3/BIO_read.pod | 97 |
1 files changed, 97 insertions, 0 deletions
diff --git a/roms/edk2/CryptoPkg/Library/OpensslLib/openssl/doc/man3/BIO_read.pod b/roms/edk2/CryptoPkg/Library/OpensslLib/openssl/doc/man3/BIO_read.pod new file mode 100644 index 000000000..270ab533e --- /dev/null +++ b/roms/edk2/CryptoPkg/Library/OpensslLib/openssl/doc/man3/BIO_read.pod @@ -0,0 +1,97 @@ +=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 |