#include <openssl/bio.h> long BIO_ctrl(BIO *bp,int cmd,long larg,void *parg); long BIO_callback_ctrl(BIO *b, int cmd, void (*fp)(struct bio_st *, int, const char *, int, long, long)); char * BIO_ptr_ctrl(BIO *bp,int cmd,long larg); long BIO_int_ctrl(BIO *bp,int cmd,long larg,int iarg); int BIO_reset(BIO *b); int BIO_seek(BIO *b, int ofs); int BIO_tell(BIO *b); int BIO_flush(BIO *b); int BIO_eof(BIO *b); int BIO_set_close(BIO *b,long flag); int BIO_get_close(BIO *b); int BIO_pending(BIO *b); int BIO_wpending(BIO *b); size_t BIO_ctrl_pending(BIO *b); size_t BIO_ctrl_wpending(BIO *b); int BIO_get_info_callback(BIO *b,bio_info_cb **cbp); int BIO_set_info_callback(BIO *b,bio_info_cb *cb); typedef void bio_info_cb(BIO *b, int oper, const char *ptr, int arg1, long arg2, long arg3);
BIO_reset() typically resets a BIO to some initial state, in the case of file related BIOs for example it rewinds the file pointer to the start of the file.
BIO_seek() resets a file related BIO's (that is file descriptor and FILE BIOs) file position pointer to ofs bytes from start of file.
BIO_tell() returns the current file position of a file related BIO.
BIO_flush() normally writes out any internally buffered data, in some cases it is used to signal EOF and that no more data will be written.
BIO_eof() returns 1 if the BIO has read EOF, the precise meaning of ``EOF'' varies according to the BIO type.
BIO_set_close() sets the BIO b close flag to flag. flag can take the value BIO_CLOSE or BIO_NOCLOSE. Typically BIO_CLOSE is used in a source/sink BIO to indicate that the underlying I/O stream should be closed when the BIO is freed.
BIO_get_close() returns the BIOs close flag.
BIO_pending(), BIO_ctrl_pending(), BIO_wpending() and BIO_ctrl_wpending() return the number of pending characters in the BIOs read and write buffers. Not all BIOs support these calls. BIO_ctrl_pending() and BIO_ctrl_wpending() return a size_t type and are functions, BIO_pending() and BIO_wpending() are macros which call BIO_ctrl().
BIO_seek() and BIO_tell() both return the current file position on success and -1 for failure, except file BIOs which for BIO_seek() always return 0 for success and -1 for failure.
BIO_flush() returns 1 for success and 0 or -1 for failure.
BIO_eof() returns 1 if EOF has been reached 0 otherwise.
BIO_set_close() always returns 1.
BIO_get_close() returns the close flag value: BIO_CLOSE or BIO_NOCLOSE.
BIO_pending(), BIO_ctrl_pending(), BIO_wpending() and BIO_ctrl_wpending() return the amount of pending data.
The return values of BIO_pending() and BIO_wpending() may not reliably determine the amount of pending data in all cases. For example in the case of a file BIO some data may be available in the FILE structures internal buffers but it is not possible to determine this in a portably way. For other types of BIO they may not be supported.
Filter BIOs if they do not internally handle a particular BIO_ctrl() operation usually pass the operation to the next BIO in the chain. This often means there is no need to locate the required BIO for a particular operation, it can be called on a chain and it will be automatically passed to the relevant BIO. However this can cause unexpected results: for example no current filter BIOs implement BIO_seek(), but this may still succeed if the chain ends in a FILE or file descriptor BIO.
Source/sink BIOs return an 0 if they do not recognize the BIO_ctrl() operation.