BIO_s_file(3)BIO_s_file(3)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 ); BIO_set_fp(
BIO *b,
FILE *fp,
int flags ); 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
The BIO_s_file() function returns the BIO file method. As its name
implies it is a wrapper round the stdio FILE structure and it is a
source/sink BIO.
Calls to BIO_read() and BIO_write() read and write data to the underly‐
ing stream. BIO_gets() and BIO_puts() are supported on file BIOs.
BIO_flush() on a file BIO calls the fflush() function on the wrapped
stream.
BIO_reset() attempts to change the file pointer to the start of file
using fseek(stream, 0, 0).
BIO_seek() sets the file pointer to position ofs from start of file
using fseek(stream, ofs, 0).
BIO_eof() calls feof().
Setting the BIO_CLOSE flag calls fclose() 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 the stdio function fopen(). 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 underly‐
ing stream to text mode, default is binary: this only has any effect
under Win32).
BIO_set_fp() sets the fp of a file BIO to fp. flags has the same mean‐
ing as in BIO_new_fp(), it is a macro.
BIO_get_fp() retrieves the fp of a file BIO, it is a macro.
BIO_seek() is a macro that sets the position pointer to offset bytes
from the start of file.
BIO_tell() 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.
NOTES
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 behavior will be mirrored by the corresponding BIO.
RESTRICTIONSBIO_reset() and BIO_seek() are implemented using fseek() on the under‐
lying stream. The return value for fseek() is 0 for success or -1 if an
error occurred this differs from other types of BIO which will typi‐
cally return 1 for success and a nonpositive value if an error
occurred.
RETURN VALUESBIO_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() returns the same value as the underlying fseek() function: 0
for success or -1 for failure.
BIO_tell() 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
Functions: BIO_seek(3), BIO_tell(3), BIO_reset(3), BIO_flush(3),
BIO_read(3), BIO_write(3), BIO_puts(3), BIO_gets(3), BIO_printf(3),
BIO_set_close(3), BIO_get_close(3)BIO_s_file(3)
