path: root/lib/libcrypto/man/BIO_s_file.3

.\"	$OpenBSD: BIO_s_file.3,v 1.2 2016/11/06 15:52:50 jmc Exp $
.\"
.Dd $Mdocdate: November 6 2016 $
.Dt BIO_S_FILE 3
.Os
.Sh NAME
.Nm BIO_s_file ,
.Nm BIO_new_file ,
.Nm BIO_new_fp ,
.Nm BIO_set_fp ,
.Nm BIO_get_fp ,
.Nm BIO_read_filename ,
.Nm BIO_write_filename ,
.Nm BIO_append_filename ,
.Nm BIO_rw_filename
.Nd FILE bio
.Sh SYNOPSIS
.In openssl/bio.h
.Ft BIO_METHOD *
.Fo BIO_s_file
.Fa void
.Fc
.Ft BIO *
.Fo BIO_new_file
.Fa "const char *filename"
.Fa "const char *mode"
.Fc
.Ft BIO *
.Fo BIO_new_fp
.Fa "FILE *stream"
.Fa "int flags"
.Fc
.Ft long
.Fo BIO_set_fp
.Fa "BIO *b"
.Fa "FILE *fp"
.Fa "int flags"
.Fc
.Ft long
.Fo BIO_get_fp
.Fa "BIO *b"
.Fa "FILE **fpp"
.Fc
.Ft int
.Fo BIO_read_filename
.Fa "BIO *b"
.Fa "char *name"
.Fc
.Ft int
.Fo BIO_write_filename
.Fa "BIO *b"
.Fa "char *name"
.Fc
.Ft int
.Fo BIO_append_filename
.Fa "BIO *b"
.Fa "char *name"
.Fc
.Ft int
.Fo BIO_rw_filename
.Fa "BIO *b"
.Fa "char *name"
.Fc
.Sh DESCRIPTION
.Fn BIO_s_file
returns the BIO file method.
As its name implies, it is a wrapper around the stdio
.Vt FILE
structure and it is a source/sink BIO.
.Pp
Calls to
.Xr BIO_read 3
and
.Xr BIO_write 3
read and write data to the underlying stream.
.Xr BIO_gets 3
and
.Xr BIO_puts 3
are supported on file BIOs.
.Pp
.Xr BIO_flush 3
on a file BIO calls the
.Xr fflush 3
function on the wrapped stream.
.Pp
.Xr BIO_reset 3
attempts to change the file pointer to the start of file using
.Fn fseek stream 0 0 .
.Pp
.Xr BIO_seek 3
sets the file pointer to position
.Fa ofs
from the start of the file using
.Fn fseek stream ofs 0 .
.Pp
.Xr BIO_eof 3
calls
.Xr feof 3 .
.Pp
Setting the
.Dv BIO_CLOSE
flag calls
.Xr fclose 3
on the stream when the BIO is freed.
.Pp
.Fn BIO_new_file
creates a new file BIO with mode
.Fa mode .
The meaning of
.Fa mode
is the same as for the stdio function
.Xr fopen 3 .
The
.Dv BIO_CLOSE
flag is set on the returned BIO.
.Pp
.Fn BIO_new_fp
creates a file BIO wrapping
.Fa stream .
Flags can be:
.Dv BIO_CLOSE , BIO_NOCLOSE Pq the close flag ,
.Dv BIO_FP_TEXT
(sets the underlying stream to text mode, default is binary:
this only has any effect under Win32).
.Pp
.Fn BIO_set_fp
set the file pointer of a file BIO to
.Fa fp .
.Fa flags
has the same meaning as in
.Fn BIO_new_fp .
.Fn BIO_set_fp
is a macro.
.Pp
.Fn BIO_get_fp
retrieves the file pointer of a file BIO, it is a macro.
.Pp
.Xr BIO_seek 3
is a macro that sets the position pointer to
.Fa offset
bytes from the start of file.
.Pp
.Xr BIO_tell 3
returns the value of the position pointer.
.Pp
.Fn BIO_read_filename ,
.Fn BIO_write_filename ,
.Fn BIO_append_filename ,
and
.Fn BIO_rw_filename
set the file BIO
.Fa b
to use file
.Fa name
for reading, writing, append or read write respectively.
.Sh NOTES
When wrapping stdout, stdin, or stderr, the underlying stream
should not normally be closed, so the
.Dv BIO_NOCLOSE
flag should be set.
.Pp
Because the file BIO calls the underlying stdio functions, any quirks
in stdio behaviour will be mirrored by the corresponding BIO.
.Pp
On Windows,
.Fn BIO_new_files
reserves for the filename argument to be UTF-8 encoded.
In other words, if you have to make it work in a multi-lingual
environment, encode file names in UTF-8.
.Sh RETURN VALUES
.Fn BIO_s_file
returns the file BIO method.
.Pp
.Fn BIO_new_file
and
.Fn BIO_new_fp
return a file BIO or
.Dv NULL
if an error occurred.
.Pp
.Fn BIO_set_fp
and
.Fn BIO_get_fp
return 1 for success or 0 for failure (although the current
implementation never returns 0).
.Pp
.Xr BIO_seek 3
returns the same value as the underlying
.Xr fseek 3
function: 0 for success or -1 for failure.
.Pp
.Xr BIO_tell 3
returns the current file position.
.Pp
.Fn BIO_read_filename ,
.Fn BIO_write_filename ,
.Fn BIO_append_filename ,
and
.Fn BIO_rw_filename
return 1 for success or 0 for failure.
.Sh EXAMPLES
File BIO "hello world":
.Bd -literal -offset indent
BIO *bio_out;
bio_out = BIO_new_fp(stdout, BIO_NOCLOSE);
BIO_printf(bio_out, "Hello World\en");
.Ed
.Pp
Alternative technique:
.Bd -literal -offset indent
BIO *bio_out;
bio_out = BIO_new(BIO_s_file());
if(bio_out == NULL) /* Error ... */
if(!BIO_set_fp(bio_out, stdout, BIO_NOCLOSE)) /* Error ... */
BIO_printf(bio_out, "Hello World\en");
.Ed
.Pp
Write to a file:
.Bd -literal -offset indent
BIO *out;
out = BIO_new_file("filename.txt", "w");
if(!out) /* Error occurred */
BIO_printf(out, "Hello World\en");
BIO_free(out);
.Ed
.Pp
Alternative technique:
.Bd -literal -offset indent
BIO *out;
out = BIO_new(BIO_s_file());
if(out == NULL) /* Error ... */
if(!BIO_write_filename(out, "filename.txt")) /* Error ... */
BIO_printf(out, "Hello World\en");
BIO_free(out);
.Ed
.Sh SEE ALSO
.Xr BIO_read 3 ,
.Xr BIO_seek 3
.Sh BUGS
.Xr BIO_reset 3
and
.Xr BIO_seek 3
are implemented using
.Xr fseek 3
on the underlying stream.
The return value for
.Xr fseek 3
is 0 for success or -1 if an error occurred.
This differs from other types of BIO which will typically return
1 for success and a non positive value if an error occurred.