372 lines
10 KiB
C
372 lines
10 KiB
C
/* Copyright (C) 2007 Eric Blake
|
|
* Permission to use, copy, modify, and distribute this software
|
|
* is freely granted, provided that this notice is preserved.
|
|
*/
|
|
|
|
/*
|
|
FUNCTION
|
|
<<fmemopen>>---open a stream around a fixed-length string
|
|
|
|
INDEX
|
|
fmemopen
|
|
|
|
ANSI_SYNOPSIS
|
|
#include <stdio.h>
|
|
FILE *fmemopen(void *restrict <[buf]>, size_t <[size]>,
|
|
const char *restrict <[mode]>);
|
|
|
|
DESCRIPTION
|
|
<<fmemopen>> creates a seekable <<FILE>> stream that wraps a
|
|
fixed-length buffer of <[size]> bytes starting at <[buf]>. The stream
|
|
is opened with <[mode]> treated as in <<fopen>>, where append mode
|
|
starts writing at the first NUL byte. If <[buf]> is NULL, then
|
|
<[size]> bytes are automatically provided as if by <<malloc>>, with
|
|
the initial size of 0, and <[mode]> must contain <<+>> so that data
|
|
can be read after it is written.
|
|
|
|
The stream maintains a current position, which moves according to
|
|
bytes read or written, and which can be one past the end of the array.
|
|
The stream also maintains a current file size, which is never greater
|
|
than <[size]>. If <[mode]> starts with <<r>>, the position starts at
|
|
<<0>>, and file size starts at <[size]> if <[buf]> was provided. If
|
|
<[mode]> starts with <<w>>, the position and file size start at <<0>>,
|
|
and if <[buf]> was provided, the first byte is set to NUL. If
|
|
<[mode]> starts with <<a>>, the position and file size start at the
|
|
location of the first NUL byte, or else <[size]> if <[buf]> was
|
|
provided.
|
|
|
|
When reading, NUL bytes have no significance, and reads cannot exceed
|
|
the current file size. When writing, the file size can increase up to
|
|
<[size]> as needed, and NUL bytes may be embedded in the stream (see
|
|
<<open_memstream>> for an alternative that automatically enlarges the
|
|
buffer). When the stream is flushed or closed after a write that
|
|
changed the file size, a NUL byte is written at the current position
|
|
if there is still room; if the stream is not also open for reading, a
|
|
NUL byte is additionally written at the last byte of <[buf]> when the
|
|
stream has exceeded <[size]>, so that a write-only <[buf]> is always
|
|
NUL-terminated when the stream is flushed or closed (and the initial
|
|
<[size]> should take this into account). It is not possible to seek
|
|
outside the bounds of <[size]>. A NUL byte written during a flush is
|
|
restored to its previous value when seeking elsewhere in the string.
|
|
|
|
RETURNS
|
|
The return value is an open FILE pointer on success. On error,
|
|
<<NULL>> is returned, and <<errno>> will be set to EINVAL if <[size]>
|
|
is zero or <[mode]> is invalid, ENOMEM if <[buf]> was NULL and memory
|
|
could not be allocated, or EMFILE if too many streams are already
|
|
open.
|
|
|
|
PORTABILITY
|
|
This function is being added to POSIX 200x, but is not in POSIX 2001.
|
|
|
|
Supporting OS subroutines required: <<sbrk>>.
|
|
*/
|
|
|
|
#include <stdio.h>
|
|
#include <errno.h>
|
|
#include <string.h>
|
|
#include <sys/lock.h>
|
|
#include "local.h"
|
|
|
|
/* Describe details of an open memstream. */
|
|
typedef struct fmemcookie {
|
|
void *storage; /* storage to free on close */
|
|
char *buf; /* buffer start */
|
|
size_t pos; /* current position */
|
|
size_t eof; /* current file size */
|
|
size_t max; /* maximum file size */
|
|
char append; /* nonzero if appending */
|
|
char writeonly; /* 1 if write-only */
|
|
char saved; /* saved character that lived at pos before write-only NUL */
|
|
} fmemcookie;
|
|
|
|
/* Read up to non-zero N bytes into BUF from stream described by
|
|
COOKIE; return number of bytes read (0 on EOF). */
|
|
static _READ_WRITE_RETURN_TYPE
|
|
_DEFUN(fmemreader, (ptr, cookie, buf, n),
|
|
struct _reent *ptr _AND
|
|
void *cookie _AND
|
|
char *buf _AND
|
|
int n)
|
|
{
|
|
fmemcookie *c = (fmemcookie *) cookie;
|
|
/* Can't read beyond current size, but EOF condition is not an error. */
|
|
if (c->pos > c->eof)
|
|
return 0;
|
|
if (n >= c->eof - c->pos)
|
|
n = c->eof - c->pos;
|
|
memcpy (buf, c->buf + c->pos, n);
|
|
c->pos += n;
|
|
return n;
|
|
}
|
|
|
|
/* Write up to non-zero N bytes of BUF into the stream described by COOKIE,
|
|
returning the number of bytes written or EOF on failure. */
|
|
static _READ_WRITE_RETURN_TYPE
|
|
_DEFUN(fmemwriter, (ptr, cookie, buf, n),
|
|
struct _reent *ptr _AND
|
|
void *cookie _AND
|
|
const char *buf _AND
|
|
int n)
|
|
{
|
|
fmemcookie *c = (fmemcookie *) cookie;
|
|
int adjust = 0; /* true if at EOF, but still need to write NUL. */
|
|
|
|
/* Append always seeks to eof; otherwise, if we have previously done
|
|
a seek beyond eof, ensure all intermediate bytes are NUL. */
|
|
if (c->append)
|
|
c->pos = c->eof;
|
|
else if (c->pos > c->eof)
|
|
memset (c->buf + c->eof, '\0', c->pos - c->eof);
|
|
/* Do not write beyond EOF; saving room for NUL on write-only stream. */
|
|
if (c->pos + n > c->max - c->writeonly)
|
|
{
|
|
adjust = c->writeonly;
|
|
n = c->max - c->pos;
|
|
}
|
|
/* Now n is the number of bytes being modified, and adjust is 1 if
|
|
the last byte is NUL instead of from buf. Write a NUL if
|
|
write-only; or if read-write, eof changed, and there is still
|
|
room. When we are within the file contents, remember what we
|
|
overwrite so we can restore it if we seek elsewhere later. */
|
|
if (c->pos + n > c->eof)
|
|
{
|
|
c->eof = c->pos + n;
|
|
if (c->eof - adjust < c->max)
|
|
c->saved = c->buf[c->eof - adjust] = '\0';
|
|
}
|
|
else if (c->writeonly)
|
|
{
|
|
if (n)
|
|
{
|
|
c->saved = c->buf[c->pos + n - adjust];
|
|
c->buf[c->pos + n - adjust] = '\0';
|
|
}
|
|
else
|
|
adjust = 0;
|
|
}
|
|
c->pos += n;
|
|
if (n - adjust)
|
|
memcpy (c->buf + c->pos - n, buf, n - adjust);
|
|
else
|
|
{
|
|
ptr->_errno = ENOSPC;
|
|
return EOF;
|
|
}
|
|
return n;
|
|
}
|
|
|
|
/* Seek to position POS relative to WHENCE within stream described by
|
|
COOKIE; return resulting position or fail with EOF. */
|
|
static _fpos_t
|
|
_DEFUN(fmemseeker, (ptr, cookie, pos, whence),
|
|
struct _reent *ptr _AND
|
|
void *cookie _AND
|
|
_fpos_t pos _AND
|
|
int whence)
|
|
{
|
|
fmemcookie *c = (fmemcookie *) cookie;
|
|
#ifndef __LARGE64_FILES
|
|
off_t offset = (off_t) pos;
|
|
#else /* __LARGE64_FILES */
|
|
_off64_t offset = (_off64_t) pos;
|
|
#endif /* __LARGE64_FILES */
|
|
|
|
if (whence == SEEK_CUR)
|
|
offset += c->pos;
|
|
else if (whence == SEEK_END)
|
|
offset += c->eof;
|
|
if (offset < 0)
|
|
{
|
|
ptr->_errno = EINVAL;
|
|
offset = -1;
|
|
}
|
|
else if (offset > c->max)
|
|
{
|
|
ptr->_errno = ENOSPC;
|
|
offset = -1;
|
|
}
|
|
#ifdef __LARGE64_FILES
|
|
else if ((_fpos_t) offset != offset)
|
|
{
|
|
ptr->_errno = EOVERFLOW;
|
|
offset = -1;
|
|
}
|
|
#endif /* __LARGE64_FILES */
|
|
else
|
|
{
|
|
if (c->writeonly && c->pos < c->eof)
|
|
{
|
|
c->buf[c->pos] = c->saved;
|
|
c->saved = '\0';
|
|
}
|
|
c->pos = offset;
|
|
if (c->writeonly && c->pos < c->eof)
|
|
{
|
|
c->saved = c->buf[c->pos];
|
|
c->buf[c->pos] = '\0';
|
|
}
|
|
}
|
|
return (_fpos_t) offset;
|
|
}
|
|
|
|
/* Seek to position POS relative to WHENCE within stream described by
|
|
COOKIE; return resulting position or fail with EOF. */
|
|
#ifdef __LARGE64_FILES
|
|
static _fpos64_t
|
|
_DEFUN(fmemseeker64, (ptr, cookie, pos, whence),
|
|
struct _reent *ptr _AND
|
|
void *cookie _AND
|
|
_fpos64_t pos _AND
|
|
int whence)
|
|
{
|
|
_off64_t offset = (_off64_t) pos;
|
|
fmemcookie *c = (fmemcookie *) cookie;
|
|
if (whence == SEEK_CUR)
|
|
offset += c->pos;
|
|
else if (whence == SEEK_END)
|
|
offset += c->eof;
|
|
if (offset < 0)
|
|
{
|
|
ptr->_errno = EINVAL;
|
|
offset = -1;
|
|
}
|
|
else if (offset > c->max)
|
|
{
|
|
ptr->_errno = ENOSPC;
|
|
offset = -1;
|
|
}
|
|
else
|
|
{
|
|
if (c->writeonly && c->pos < c->eof)
|
|
{
|
|
c->buf[c->pos] = c->saved;
|
|
c->saved = '\0';
|
|
}
|
|
c->pos = offset;
|
|
if (c->writeonly && c->pos < c->eof)
|
|
{
|
|
c->saved = c->buf[c->pos];
|
|
c->buf[c->pos] = '\0';
|
|
}
|
|
}
|
|
return (_fpos64_t) offset;
|
|
}
|
|
#endif /* __LARGE64_FILES */
|
|
|
|
/* Reclaim resources used by stream described by COOKIE. */
|
|
static int
|
|
_DEFUN(fmemcloser, (ptr, cookie),
|
|
struct _reent *ptr _AND
|
|
void *cookie)
|
|
{
|
|
fmemcookie *c = (fmemcookie *) cookie;
|
|
_free_r (ptr, c->storage);
|
|
return 0;
|
|
}
|
|
|
|
/* Open a memstream around buffer BUF of SIZE bytes, using MODE.
|
|
Return the new stream, or fail with NULL. */
|
|
FILE *
|
|
_DEFUN(_fmemopen_r, (ptr, buf, size, mode),
|
|
struct _reent *ptr _AND
|
|
void *buf _AND
|
|
size_t size _AND
|
|
const char *mode)
|
|
{
|
|
FILE *fp;
|
|
fmemcookie *c;
|
|
int flags;
|
|
int dummy;
|
|
|
|
if ((flags = __sflags (ptr, mode, &dummy)) == 0)
|
|
return NULL;
|
|
if (!size || !(buf || flags & __SAPP))
|
|
{
|
|
ptr->_errno = EINVAL;
|
|
return NULL;
|
|
}
|
|
if ((fp = __sfp (ptr)) == NULL)
|
|
return NULL;
|
|
if ((c = (fmemcookie *) _malloc_r (ptr, sizeof *c + (buf ? 0 : size)))
|
|
== NULL)
|
|
{
|
|
__sfp_lock_acquire ();
|
|
fp->_flags = 0; /* release */
|
|
#ifndef __SINGLE_THREAD__
|
|
__lock_close_recursive (fp->_lock);
|
|
#endif
|
|
__sfp_lock_release ();
|
|
return NULL;
|
|
}
|
|
|
|
c->storage = c;
|
|
c->max = size;
|
|
/* 9 modes to worry about. */
|
|
/* w/a, buf or no buf: Guarantee a NUL after any file writes. */
|
|
c->writeonly = (flags & __SWR) != 0;
|
|
c->saved = '\0';
|
|
if (!buf)
|
|
{
|
|
/* r+/w+/a+, and no buf: file starts empty. */
|
|
c->buf = (char *) (c + 1);
|
|
*(char *) buf = '\0';
|
|
c->pos = c->eof = 0;
|
|
c->append = (flags & __SAPP) != 0;
|
|
}
|
|
else
|
|
{
|
|
c->buf = (char *) buf;
|
|
switch (*mode)
|
|
{
|
|
case 'a':
|
|
/* a/a+ and buf: position and size at first NUL. */
|
|
buf = memchr (c->buf, '\0', size);
|
|
c->eof = c->pos = buf ? (char *) buf - c->buf : size;
|
|
if (!buf && c->writeonly)
|
|
/* a: guarantee a NUL within size even if no writes. */
|
|
c->buf[size - 1] = '\0';
|
|
c->append = 1;
|
|
break;
|
|
case 'r':
|
|
/* r/r+ and buf: read at beginning, full size available. */
|
|
c->pos = c->append = 0;
|
|
c->eof = size;
|
|
break;
|
|
case 'w':
|
|
/* w/w+ and buf: write at beginning, truncate to empty. */
|
|
c->pos = c->append = c->eof = 0;
|
|
*c->buf = '\0';
|
|
break;
|
|
default:
|
|
abort ();
|
|
}
|
|
}
|
|
|
|
_flockfile (fp);
|
|
fp->_file = -1;
|
|
fp->_flags = flags;
|
|
fp->_cookie = c;
|
|
fp->_read = flags & (__SRD | __SRW) ? fmemreader : NULL;
|
|
fp->_write = flags & (__SWR | __SRW) ? fmemwriter : NULL;
|
|
fp->_seek = fmemseeker;
|
|
#ifdef __LARGE64_FILES
|
|
fp->_seek64 = fmemseeker64;
|
|
fp->_flags |= __SL64;
|
|
#endif
|
|
fp->_close = fmemcloser;
|
|
_funlockfile (fp);
|
|
return fp;
|
|
}
|
|
|
|
#ifndef _REENT_ONLY
|
|
FILE *
|
|
_DEFUN(fmemopen, (buf, size, mode),
|
|
void *buf _AND
|
|
size_t size _AND
|
|
const char *mode)
|
|
{
|
|
return _fmemopen_r (_REENT, buf, size, mode);
|
|
}
|
|
#endif /* !_REENT_ONLY */
|