NAME
BIO_s_file,
BIO_new_file, BIO_new_fp,
BIO_set_fp, BIO_get_fp,
BIO_read_filename,
BIO_write_filename,
BIO_append_filename,
BIO_rw_filename —
FILE BIO
SYNOPSIS
#include
<openssl/bio.h>
BIO_METHOD *
BIO_s_file(void);
BIO *
BIO_new_file(const char
*filename, const char *mode);
BIO *
BIO_new_fp(FILE *stream,
int flags);
long
BIO_set_fp(BIO *b,
FILE *fp, int flags);
long
BIO_get_fp(BIO *b,
FILE **fpp);
int
BIO_read_filename(BIO *b,
char *name);
int
BIO_write_filename(BIO *b,
char *name);
int
BIO_append_filename(BIO *b,
char *name);
int
BIO_rw_filename(BIO *b,
char *name);
DESCRIPTION
BIO_s_file()
returns the BIO file method. As its name implies, it is a wrapper around the
stdio FILE structure and it is a source/sink BIO.
Calls to BIO_read(3) and BIO_write(3) read and write data to the underlying stream. BIO_gets(3) and BIO_puts(3) are supported on file BIOs.
BIO_flush(3) on a file BIO calls the fflush(3) function on the wrapped stream.
BIO_reset(3) attempts to change the file pointer to the start
of file using
fseek(stream,
0, 0).
BIO_seek(3) sets the file pointer to position
ofs from the start of the file using
fseek(stream,
ofs, 0).
BIO_eof(3) calls feof(3).
Setting the BIO_CLOSE flag calls
fclose(3) on the stream when the BIO is freed.
BIO_new_file()
creates a new file BIO with mode mode. The meaning of
mode is the same as for the stdio function
fopen(3). The BIO_CLOSE flag is set on the
returned BIO.
BIO_new_fp()
creates a file BIO wrapping stream. Flags can be:
BIO_CLOSE, BIO_NOCLOSE (the
close flag), BIO_FP_TEXT (sets the underlying stream
to text mode, default is binary: this only has any effect under Win32).
BIO_set_fp()
set the file pointer of a file BIO to fp.
flags has the same meaning as in
BIO_new_fp(). BIO_set_fp()
is a macro.
BIO_get_fp()
retrieves the file pointer of a file BIO, it is a macro.
BIO_seek(3) is a macro that sets the position pointer to offset bytes from the start of file.
BIO_tell(3) returns the value of the position pointer.
BIO_read_filename(),
BIO_write_filename(),
BIO_append_filename(),
and
BIO_rw_filename()
set the file BIO b to use file
name for reading, writing, append or read write
respectively.
When wrapping stdout, stdin, or stderr, the underlying stream
should not normally be closed, so the BIO_NOCLOSE
flag should be set.
Because the file BIO calls the underlying stdio functions, any quirks in stdio behaviour will be mirrored by the corresponding BIO.
On Windows,
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.
RETURN VALUES
BIO_s_file() returns the file BIO
method.
BIO_new_file() and
BIO_new_fp() return a file BIO or
NULL if an error occurred.
BIO_set_fp() and
BIO_get_fp() return 1 for success or 0 for failure
(although the current implementation never returns 0).
BIO_seek(3) returns the same value as the underlying fseek(3) function: 0 for success or -1 for failure.
BIO_tell(3) returns the current file position.
BIO_read_filename(),
BIO_write_filename(),
BIO_append_filename(), and
BIO_rw_filename() return 1 for success or 0 for
failure.
EXAMPLES
File BIO "hello world":
BIO *bio_out; bio_out = BIO_new_fp(stdout, BIO_NOCLOSE); BIO_printf(bio_out, "Hello World\n");
Alternative technique:
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\n");
Write to a file:
BIO *out;
out = BIO_new_file("filename.txt", "w");
if(!out) /* Error occurred */
BIO_printf(out, "Hello World\n");
BIO_free(out);
Alternative technique:
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\n"); BIO_free(out);
SEE ALSO
BUGS
BIO_reset(3) and BIO_seek(3) are implemented using fseek(3) on the underlying stream. The return value for 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.