BIO_ctrl 3 2001-04-11 0.9.9-dev OpenSSL

NAME

BIO_ctrl, BIO_callback_ctrl, BIO_ptr_ctrl, BIO_int_ctrl, BIO_reset, BIO_seek, BIO_tell, BIO_flush, BIO_eof, BIO_set_close, BIO_get_close, BIO_pending, BIO_wpending, BIO_ctrl_pending, BIO_ctrl_wpending, BIO_get_info_callback, BIO_set_info_callback - BIO control operations

LIBRARY

libcrypto, -lcrypto

SYNOPSIS


 #include 




 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);

DESCRIPTION

_B_I_O___c_t_r_l_(_), _B_I_O___c_a_l_l_b_a_c_k___c_t_r_l_(_), _B_I_O___p_t_r___c_t_r_l_(_) and _B_I_O___i_n_t___c_t_r_l_(_) are BIO "control" operations taking arguments of various types. These functions are not normally called directly, various macros are used instead. The standard macros are described below, macros specific to a particular type of BIO are described in the specific BIOs manual page as well as any special features of the standard calls.

_B_I_O___r_e_s_e_t_(_) 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.

_B_I_O___s_e_e_k_(_) resets a file related BIO's (that is file descriptor and FILE BIOs) file position pointer to ooffss bytes from start of file.

_B_I_O___t_e_l_l_(_) returns the current file position of a file related BIO.

_B_I_O___f_l_u_s_h_(_) normally writes out any internally buffered data, in some cases it is used to signal EOF and that no more data will be written.

_B_I_O___e_o_f_(_) returns 1 if the BIO has read EOF, the precise meaning of "EOF" varies according to the BIO type.

_B_I_O___s_e_t___c_l_o_s_e_(_) sets the BIO bb close flag to ffllaagg. ffllaagg 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.

_B_I_O___g_e_t___c_l_o_s_e_(_) returns the BIOs close flag.

_B_I_O___p_e_n_d_i_n_g_(_), _B_I_O___c_t_r_l___p_e_n_d_i_n_g_(_), _B_I_O___w_p_e_n_d_i_n_g_(_) and _B_I_O___c_t_r_l___w_p_e_n_d_i_n_g_(_) return the number of pending characters in the BIOs read and write buffers. Not all BIOs support these calls. _B_I_O___c_t_r_l___p_e_n_d_i_n_g_(_) and _B_I_O___c_t_r_l___w_p_e_n_d_i_n_g_(_) return a size_t type and are functions, _B_I_O___p_e_n_d_i_n_g_(_) and _B_I_O___w_p_e_n_d_i_n_g_(_) are macros which call _B_I_O___c_t_r_l_(_).

RETURN VALUES

_B_I_O___r_e_s_e_t_(_) normally returns 1 for success and 0 or -1 for failure. File BIOs are an exception, they return 0 for success and -1 for failure.

_B_I_O___s_e_e_k_(_) and _B_I_O___t_e_l_l_(_) both return the current file position on success and -1 for failure, except file BIOs which for _B_I_O___s_e_e_k_(_) always return 0 for success and -1 for failure.

_B_I_O___f_l_u_s_h_(_) returns 1 for success and 0 or -1 for failure.

_B_I_O___e_o_f_(_) returns 1 if EOF has been reached 0 otherwise.

_B_I_O___s_e_t___c_l_o_s_e_(_) always returns 1.

_B_I_O___g_e_t___c_l_o_s_e_(_) returns the close flag value: BIO_CLOSE or BIO_NOCLOSE.

_B_I_O___p_e_n_d_i_n_g_(_), _B_I_O___c_t_r_l___p_e_n_d_i_n_g_(_), _B_I_O___w_p_e_n_d_i_n_g_(_) and _B_I_O___c_t_r_l___w_p_e_n_d_i_n_g_(_) return the amount of pending data.

NOTES

_B_I_O___f_l_u_s_h_(_), because it can write data may return 0 or -1 indicating that the call should be retried later in a similar manner to _B_I_O___w_r_i_t_e_(_). The _B_I_O___s_h_o_u_l_d___r_e_t_r_y_(_) call should be used and appropriate action taken is the call fails.

The return values of _B_I_O___p_e_n_d_i_n_g_(_) and _B_I_O___w_p_e_n_d_i_n_g_(_) 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 _B_I_O___c_t_r_l_(_) 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 _B_I_O___s_e_e_k_(_), 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 _B_I_O___c_t_r_l_(_) operation.

BUGS

Some of the return values are ambiguous and care should be taken. In particular a return value of 0 can be returned if an operation is not supported, if an error occurred, if EOF has not been reached and in the case of _B_I_O___s_e_e_k_(_) on a file BIO for a successful operation.

SEE ALSO

TBA