.\" $OpenBSD: BIO_ctrl.3,v 1.16 2022/08/18 18:42:13 tb Exp $ .\" OpenSSL b055fceb Thu Oct 20 09:56:18 2016 +0100 .\" .\" This file was written by Dr. Stephen Henson . .\" Copyright (c) 2000, 2016 The OpenSSL Project. All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in .\" the documentation and/or other materials provided with the .\" distribution. .\" .\" 3. All advertising materials mentioning features or use of this .\" software must display the following acknowledgment: .\" "This product includes software developed by the OpenSSL Project .\" for use in the OpenSSL Toolkit. 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IN NO EVENT SHALL THE OpenSSL PROJECT OR .\" ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, .\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; .\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, .\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED .\" OF THE POSSIBILITY OF SUCH DAMAGE. .\" .Dd $Mdocdate: August 18 2022 $ .Dt BIO_CTRL 3 .Os .Sh NAME .Nm BIO_ctrl , .Nm BIO_callback_ctrl , .Nm BIO_ptr_ctrl , .Nm BIO_int_ctrl , .Nm BIO_reset , .Nm BIO_seek , .Nm BIO_tell , .Nm BIO_flush , .Nm BIO_eof , .Nm BIO_set_close , .Nm BIO_get_close , .Nm BIO_pending , .Nm BIO_wpending , .Nm BIO_ctrl_pending , .Nm BIO_ctrl_wpending , .Nm BIO_get_info_callback , .Nm BIO_set_info_callback , .Nm BIO_info_cb .Nd BIO control operations .Sh SYNOPSIS .In openssl/bio.h .Ft long .Fo BIO_ctrl .Fa "BIO *bp" .Fa "int cmd" .Fa "long larg" .Fa "void *parg" .Fc .Ft long .Fo BIO_callback_ctrl .Fa "BIO *b" .Fa "int cmd" .Fa "BIO_info_cb cb" .Fc .Ft char * .Fo BIO_ptr_ctrl .Fa "BIO *bp" .Fa "int cmd" .Fa "long larg" .Fc .Ft long .Fo BIO_int_ctrl .Fa "BIO *bp" .Fa "int cmd" .Fa "long larg" .Fa "int iarg" .Fc .Ft int .Fo BIO_reset .Fa "BIO *b" .Fc .Ft int .Fo BIO_seek .Fa "BIO *b" .Fa "int ofs" .Fc .Ft int .Fo BIO_tell .Fa "BIO *b" .Fc .Ft int .Fo BIO_flush .Fa "BIO *b" .Fc .Ft int .Fo BIO_eof .Fa "BIO *b" .Fc .Ft int .Fo BIO_set_close .Fa "BIO *b" .Fa "long flag" .Fc .Ft int .Fo BIO_get_close .Fa "BIO *b" .Fc .Ft int .Fo BIO_pending .Fa "BIO *b" .Fc .Ft int .Fo BIO_wpending .Fa "BIO *b" .Fc .Ft size_t .Fo BIO_ctrl_pending .Fa "BIO *b" .Fc .Ft size_t .Fo BIO_ctrl_wpending .Fa "BIO *b" .Fc .Ft int .Fo BIO_get_info_callback .Fa "BIO *b" .Fa "BIO_info_cb **cbp" .Fc .Ft int .Fo BIO_set_info_callback .Fa "BIO *b" .Fa "BIO_info_cb *cb" .Fc .Ft typedef int .Fo BIO_info_cb .Fa "BIO *b" .Fa "int state" .Fa "int res" .Fc .Sh DESCRIPTION .Fn BIO_ctrl , .Fn BIO_callback_ctrl , .Fn BIO_ptr_ctrl , and .Fn BIO_int_ctrl 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 BIO's manual page as well as any special features of the standard calls. .Pp .Fn 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. .Pp .Fn BIO_seek resets a file related BIO's (that is file descriptor and FILE BIOs) file position pointer to .Fa ofs bytes from start of file. .Pp .Fn BIO_tell returns the current file position of a file related BIO. .Pp .Fn 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. .Pp .Fn BIO_eof returns 1 if the BIO has read EOF. The precise meaning of "EOF" varies according to the BIO type. .Pp .Fn BIO_set_close sets the BIO .Fa b close flag to .Fa flag . .Fa flag can take the value .Dv BIO_CLOSE or .Dv BIO_NOCLOSE . Typically .Dv 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. .Pp .Fn BIO_get_close returns the BIO's close flag. .Pp .Fn BIO_pending , .Fn BIO_ctrl_pending , .Fn BIO_wpending , and .Fn BIO_ctrl_wpending return the number of pending characters in the BIO's read and write buffers. Not all BIOs support these calls. .Fn BIO_ctrl_pending and .Fn BIO_ctrl_wpending return a .Vt size_t type and are functions. .Fn BIO_pending and .Fn BIO_wpending are macros which call .Fn BIO_ctrl . .Sh RETURN VALUES .Fn BIO_reset normally returns 1 for success and 0 or -1 for failure. File BIOs are an exception, returning 0 for success and -1 for failure. .Pp .Fn BIO_seek and .Fn BIO_tell both return the current file position on success and -1 for failure, except file BIOs which for .Fn BIO_seek always return 0 for success and -1 for failure. .Pp .Fn BIO_flush returns 1 for success and 0 or -1 for failure. .Pp .Fn BIO_eof returns 1 if EOF has been reached or 0 otherwise. .Pp .Fn BIO_set_close always returns 1. .Pp .Fn BIO_get_close returns the close flag value .Dv BIO_CLOSE or .Dv BIO_NOCLOSE . .Pp .Fn BIO_pending , .Fn BIO_ctrl_pending , .Fn BIO_wpending , and .Fn BIO_ctrl_wpending return the amount of pending data. .Sh NOTES Because it can write data, .Fn BIO_flush may return 0 or -1 indicating that the call should be retried later in a similar manner to .Xr BIO_write 3 . The .Xr BIO_should_retry 3 call should be used and appropriate action taken if the call fails. .Pp The return values of .Fn BIO_pending and .Fn 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 .Vt FILE structure's internal buffers but it is not possible to determine this in a portable way. For other types of BIO they may not be supported. .Pp If they do not internally handle a particular .Fn BIO_ctrl operation, filter BIOs 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 .Fn BIO_seek , but this may still succeed if the chain ends in a FILE or file descriptor BIO. .Pp Source/sink BIOs return a 0 if they do not recognize the .Fn BIO_ctrl operation. .Sh SEE ALSO .Xr BIO_meth_new 3 , .Xr BIO_new 3 .Sh HISTORY .Fn BIO_ctrl , .Fn BIO_reset , .Fn BIO_flush , .Fn BIO_eof , .Fn BIO_set_close , .Fn BIO_get_close , and .Fn BIO_pending first appeared in SSLeay 0.6.0. .Fn BIO_wpending first appeared in SSLeay 0.8.1. .Fn BIO_ptr_ctrl , .Fn BIO_int_ctrl , .Fn BIO_get_info_callback and .Fn BIO_set_info_callback first appeared in SSLeay 0.9.0. All these functions have been available since .Ox 2.4 . .Pp .Fn BIO_seek and .Fn BIO_tell first appeared in SSLeay 0.9.1. .Fn BIO_ctrl_pending and .Fn BIO_ctrl_wpending first appeared in OpenSSL 0.9.4. These functions have been available since .Ox 2.6 . .Pp .Fn BIO_callback_ctrl first appeared in OpenSSL 0.9.5 and has been available since .Ox 2.7 . .Sh 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 .Fn BIO_seek on a file BIO for a successful operation.