NAME
fmemopen —
open a stream that points to the given
buffer
SYNOPSIS
#include
<stdio.h>
FILE *
fmemopen(void
*buffer, size_t
size, const char
*mode);
DESCRIPTION
The
fmemopen()
function associates a stream with the given buffer and
size. The buffer can be either
NULL, or must be of the given
size. If the buffer is
NULL, a buffer of the given
size will be dynamically allocated using
malloc(3) and released when
fclose(3) is called.
The mode argument has the same meaning as in fopen(3).
The stream treats the buffer as it would treat a file tracking the
current position to perform I/O operations. For example, in the beginning
the stream points to the beginning of the buffer, unless ‘a’
was specified in the mode argument, and then it points
to the first NUL byte. If a
NULL buffer was specified,
then the stream will always point at the first byte of the
buffer.
The stream also keeps track of the size of the buffer. The size is initialized depending on the mode:
Read or write operations advance the buffer, but not to exceed the
given size of the buffer. Trying
to read beyond the size of the
buffer results in EOF
returned. NUL bytes are read normally. Trying to
write beyond the size of the
buffer has no effect.
When a stream open for writing is either flushed or closed, a
NUL byte is written at the current position or at
the end of the current size as kept internally.
RETURN VALUES
Upon successful completion, fmemopen()
returns a FILE pointer. Otherwise,
NULL is returned and the global variable
errno is set to indicate the error.
ERRORS
- [
EINVAL] - The size was
0; or the mode argument is invalid; or the buffer argument isNULLand the mode argument does not specify a ‘+’.
The fmemopen() function may also fail and
set errno for any of the errors specified for the
routine malloc(3).
SEE ALSO
STANDARDS
The function fmemopen() conform to
IEEE Std 1003.1-2008 (“POSIX.1”).
HISTORY
The fmemopen() function first appeared in
OpenBSD 5.4.