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 control operations 9 10=head1 SYNOPSIS 11 12 #include <openssl/bio.h> 13 14 long BIO_ctrl(BIO *bp,int cmd,long larg,void *parg); 15 long BIO_callback_ctrl(BIO *b, int cmd, void (*fp)(struct bio_st *, int, const char *, int, long, long)); 16 char * BIO_ptr_ctrl(BIO *bp,int cmd,long larg); 17 long BIO_int_ctrl(BIO *bp,int cmd,long larg,int iarg); 18 19 int BIO_reset(BIO *b); 20 int BIO_seek(BIO *b, int ofs); 21 int BIO_tell(BIO *b); 22 int BIO_flush(BIO *b); 23 int BIO_eof(BIO *b); 24 int BIO_set_close(BIO *b,long flag); 25 int BIO_get_close(BIO *b); 26 int BIO_pending(BIO *b); 27 int BIO_wpending(BIO *b); 28 size_t BIO_ctrl_pending(BIO *b); 29 size_t BIO_ctrl_wpending(BIO *b); 30 31 int BIO_get_info_callback(BIO *b,bio_info_cb **cbp); 32 int BIO_set_info_callback(BIO *b,bio_info_cb *cb); 33 34 typedef void bio_info_cb(BIO *b, int oper, const char *ptr, int arg1, long arg2, long arg3); 35 36=head1 DESCRIPTION 37 38BIO_ctrl(), BIO_callback_ctrl(), BIO_ptr_ctrl() and BIO_int_ctrl() 39are BIO "control" operations taking arguments of various types. 40These functions are not normally called directly, various macros 41are used instead. The standard macros are described below, macros 42specific to a particular type of BIO are described in the specific 43BIOs manual page as well as any special features of the standard 44calls. 45 46BIO_reset() typically resets a BIO to some initial state, in the case 47of file related BIOs for example it rewinds the file pointer to the 48start of the file. 49 50BIO_seek() resets a file related BIO's (that is file descriptor and 51FILE BIOs) file position pointer to B<ofs> bytes from start of file. 52 53BIO_tell() returns the current file position of a file related BIO. 54 55BIO_flush() normally writes out any internally buffered data, in some 56cases it is used to signal EOF and that no more data will be written. 57 58BIO_eof() returns 1 if the BIO has read EOF, the precise meaning of 59"EOF" varies according to the BIO type. 60 61BIO_set_close() sets the BIO B<b> close flag to B<flag>. B<flag> can 62take the value BIO_CLOSE or BIO_NOCLOSE. Typically BIO_CLOSE is used 63in a source/sink BIO to indicate that the underlying I/O stream should 64be closed when the BIO is freed. 65 66BIO_get_close() returns the BIOs close flag. 67 68BIO_pending(), BIO_ctrl_pending(), BIO_wpending() and BIO_ctrl_wpending() 69return the number of pending characters in the BIOs read and write buffers. 70Not all BIOs support these calls. BIO_ctrl_pending() and BIO_ctrl_wpending() 71return a size_t type and are functions, BIO_pending() and BIO_wpending() are 72macros which call BIO_ctrl(). 73 74=head1 RETURN VALUES 75 76BIO_reset() normally returns 1 for success and 0 or -1 for failure. File 77BIOs are an exception, they return 0 for success and -1 for failure. 78 79BIO_seek() and BIO_tell() both return the current file position on success 80and -1 for failure, except file BIOs which for BIO_seek() always return 0 81for success and -1 for failure. 82 83BIO_flush() returns 1 for success and 0 or -1 for failure. 84 85BIO_eof() returns 1 if EOF has been reached 0 otherwise. 86 87BIO_set_close() always returns 1. 88 89BIO_get_close() returns the close flag value: BIO_CLOSE or BIO_NOCLOSE. 90 91BIO_pending(), BIO_ctrl_pending(), BIO_wpending() and BIO_ctrl_wpending() 92return the amount of pending data. 93 94=head1 NOTES 95 96BIO_flush(), because it can write data may return 0 or -1 indicating 97that the call should be retried later in a similar manner to BIO_write(). 98The BIO_should_retry() call should be used and appropriate action taken 99is the call fails. 100 101The return values of BIO_pending() and BIO_wpending() may not reliably 102determine the amount of pending data in all cases. For example in the 103case of a file BIO some data may be available in the FILE structures 104internal buffers but it is not possible to determine this in a 105portably way. For other types of BIO they may not be supported. 106 107Filter BIOs if they do not internally handle a particular BIO_ctrl() 108operation usually pass the operation to the next BIO in the chain. 109This often means there is no need to locate the required BIO for 110a particular operation, it can be called on a chain and it will 111be automatically passed to the relevant BIO. However this can cause 112unexpected results: for example no current filter BIOs implement 113BIO_seek(), but this may still succeed if the chain ends in a FILE 114or file descriptor BIO. 115 116Source/sink BIOs return an 0 if they do not recognize the BIO_ctrl() 117operation. 118 119=head1 BUGS 120 121Some of the return values are ambiguous and care should be taken. In 122particular a return value of 0 can be returned if an operation is not 123supported, if an error occurred, if EOF has not been reached and in 124the case of BIO_seek() on a file BIO for a successful operation. 125 126=head1 SEE ALSO 127 128TBA 129