1=pod 2 3=head1 NAME 4 5BIO_ctrl, BIO_callback_ctrl, BIO_ptr_ctrl, BIO_int_ctrl, BIO_reset, 6BIO_seek, BIO_tell, BIO_flush, BIO_eof, BIO_set_close, BIO_get_close, 7BIO_pending, BIO_wpending, BIO_ctrl_pending, BIO_ctrl_wpending, 8BIO_get_info_callback, BIO_set_info_callback, BIO_info_cb 9- BIO control operations 10 11=head1 SYNOPSIS 12 13 #include <openssl/bio.h> 14 15 typedef int BIO_info_cb(BIO *b, int state, int res); 16 17 long BIO_ctrl(BIO *bp, int cmd, long larg, void *parg); 18 long BIO_callback_ctrl(BIO *b, int cmd, BIO_info_cb *cb); 19 char *BIO_ptr_ctrl(BIO *bp, int cmd, long larg); 20 long BIO_int_ctrl(BIO *bp, int cmd, long larg, int iarg); 21 22 int BIO_reset(BIO *b); 23 int BIO_seek(BIO *b, int ofs); 24 int BIO_tell(BIO *b); 25 int BIO_flush(BIO *b); 26 int BIO_eof(BIO *b); 27 int BIO_set_close(BIO *b, long flag); 28 int BIO_get_close(BIO *b); 29 int BIO_pending(BIO *b); 30 int BIO_wpending(BIO *b); 31 size_t BIO_ctrl_pending(BIO *b); 32 size_t BIO_ctrl_wpending(BIO *b); 33 34 int BIO_get_info_callback(BIO *b, BIO_info_cb **cbp); 35 int BIO_set_info_callback(BIO *b, BIO_info_cb *cb); 36 37=head1 DESCRIPTION 38 39BIO_ctrl(), BIO_callback_ctrl(), BIO_ptr_ctrl() and BIO_int_ctrl() 40are BIO "control" operations taking arguments of various types. 41These functions are not normally called directly, various macros 42are used instead. The standard macros are described below, macros 43specific to a particular type of BIO are described in the specific 44BIOs manual page as well as any special features of the standard 45calls. 46 47BIO_reset() typically resets a BIO to some initial state, in the case 48of file related BIOs for example it rewinds the file pointer to the 49start of the file. 50 51BIO_seek() resets a file related BIO's (that is file descriptor and 52FILE BIOs) file position pointer to B<ofs> bytes from start of file. 53 54BIO_tell() returns the current file position of a file related BIO. 55 56BIO_flush() normally writes out any internally buffered data, in some 57cases it is used to signal EOF and that no more data will be written. 58 59BIO_eof() returns 1 if the BIO has read EOF, the precise meaning of 60"EOF" varies according to the BIO type. 61 62BIO_set_close() sets the BIO B<b> close flag to B<flag>. B<flag> can 63take the value BIO_CLOSE or BIO_NOCLOSE. Typically BIO_CLOSE is used 64in a source/sink BIO to indicate that the underlying I/O stream should 65be closed when the BIO is freed. 66 67BIO_get_close() returns the BIOs close flag. 68 69BIO_pending(), BIO_ctrl_pending(), BIO_wpending() and BIO_ctrl_wpending() 70return the number of pending characters in the BIOs read and write buffers. 71Not all BIOs support these calls. BIO_ctrl_pending() and BIO_ctrl_wpending() 72return a size_t type and are functions, BIO_pending() and BIO_wpending() are 73macros which call BIO_ctrl(). 74 75=head1 RETURN VALUES 76 77BIO_reset() normally returns 1 for success and 0 or -1 for failure. File 78BIOs are an exception, they return 0 for success and -1 for failure. 79 80BIO_seek() and BIO_tell() both return the current file position on success 81and -1 for failure, except file BIOs which for BIO_seek() always return 0 82for success and -1 for failure. 83 84BIO_flush() returns 1 for success and 0 or -1 for failure. 85 86BIO_eof() returns 1 if EOF has been reached 0 otherwise. 87 88BIO_set_close() always returns 1. 89 90BIO_get_close() returns the close flag value: BIO_CLOSE or BIO_NOCLOSE. 91 92BIO_pending(), BIO_ctrl_pending(), BIO_wpending() and BIO_ctrl_wpending() 93return the amount of pending data. 94 95=head1 NOTES 96 97BIO_flush(), because it can write data may return 0 or -1 indicating 98that the call should be retried later in a similar manner to BIO_write_ex(). 99The BIO_should_retry() call should be used and appropriate action taken 100is the call fails. 101 102The return values of BIO_pending() and BIO_wpending() may not reliably 103determine the amount of pending data in all cases. For example in the 104case of a file BIO some data may be available in the FILE structures 105internal buffers but it is not possible to determine this in a 106portably way. For other types of BIO they may not be supported. 107 108Filter BIOs if they do not internally handle a particular BIO_ctrl() 109operation usually pass the operation to the next BIO in the chain. 110This often means there is no need to locate the required BIO for 111a particular operation, it can be called on a chain and it will 112be automatically passed to the relevant BIO. However this can cause 113unexpected results: for example no current filter BIOs implement 114BIO_seek(), but this may still succeed if the chain ends in a FILE 115or file descriptor BIO. 116 117Source/sink BIOs return an 0 if they do not recognize the BIO_ctrl() 118operation. 119 120=head1 BUGS 121 122Some of the return values are ambiguous and care should be taken. In 123particular a return value of 0 can be returned if an operation is not 124supported, if an error occurred, if EOF has not been reached and in 125the case of BIO_seek() on a file BIO for a successful operation. 126 127=head1 COPYRIGHT 128 129Copyright 2000-2016 The OpenSSL Project Authors. All Rights Reserved. 130 131Licensed under the OpenSSL license (the "License"). You may not use 132this file except in compliance with the License. You can obtain a copy 133in the file LICENSE in the source distribution or at 134L<https://www.openssl.org/source/license.html>. 135 136=cut 137