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/*
* SPDX-License-Identifier: BSD-3-Clause
*
* Copyright © 2022 Keith Packard
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following
* disclaimer in the documentation and/or other materials provided
* with the distribution.
*
* 3. Neither the name of the copyright holder nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
* OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "stdio_private.h"
#define __MALL 0x01
#define __MAPP 0x02
struct __file_mem {
struct __file_ext xfile;
char *buf;
size_t size; /* Current size. */
size_t bufsize; /* Upper limit on size. */
size_t pos;
uint8_t mflags;
};
static int
__fmem_put(char c, FILE *f)
{
struct __file_mem *mf = (struct __file_mem *)f;
size_t pos = mf->mflags & __MAPP ? mf->size : mf->pos;
if ((f->flags & __SWR) == 0) {
return _FDEV_ERR;
} else if (pos < mf->bufsize) {
mf->buf[pos++] = c;
if (pos > mf->size) {
mf->size = pos;
/* When a stream open for update (the mode argument includes '+') or
* for writing only is successfully written and the write advances
* the current buffer end position, a null byte shall be written at
* the new buffer end position if it fits. */
if (mf->size < mf->bufsize) {
mf->buf[mf->size] = '\0';
}
}
mf->pos = pos;
return (unsigned char)c;
} else {
return _FDEV_EOF;
}
}
static int
__fmem_get(FILE *f)
{
struct __file_mem *mf = (struct __file_mem *)f;
if ((f->flags & __SRD) == 0) {
return _FDEV_ERR;
} else if (mf->pos < mf->size) {
return (unsigned char)mf->buf[mf->pos++];
} else {
return _FDEV_EOF;
}
}
static int
__fmem_flush(FILE *f)
{
struct __file_mem *mf = (struct __file_mem *)f;
if ((f->flags & __SWR) && mf->pos < mf->bufsize) {
mf->buf[mf->pos] = '\0';
if (mf->pos > mf->size) {
mf->size = mf->pos;
}
}
return 0;
}
static off_t
__fmem_seek(FILE *f, off_t pos, int whence)
{
struct __file_mem *mf = (struct __file_mem *)f;
switch (whence) {
case SEEK_SET:
break;
case SEEK_CUR:
pos += mf->pos;
break;
case SEEK_END:
pos += mf->size;
break;
}
_Static_assert(sizeof(off_t) >= sizeof(size_t), "must avoid truncation");
if (pos < 0 || (off_t)mf->bufsize < pos)
return EOF;
mf->pos = pos;
return pos;
}
static int
__fmem_close(FILE *f)
{
struct __file_mem *mf = (struct __file_mem *)f;
if (mf->mflags & __MALL)
free(mf->buf);
else
__fmem_flush(f);
free(f);
return 0;
}
FILE *
fmemopen(void *buf, size_t size, const char *mode)
{
int stdio_flags;
int open_flags;
uint8_t mflags = 0;
size_t initial_pos = 0;
size_t initial_size;
struct __file_mem *mf;
stdio_flags = __stdio_flags(mode, &open_flags);
if (stdio_flags == 0 || size == 0) {
errno = EINVAL;
return NULL;
}
/* Allocate file structure and necessary buffers */
mf = calloc(1, sizeof(struct __file_mem));
if (mf == NULL)
return NULL;
if (buf == NULL) {
/* POSIX says return EINVAL if: The buf argument is a null pointer and
* the mode argument does not include a '+' character. */
if ((stdio_flags & (__SRD | __SWR)) != (__SRD | __SWR)) {
free(mf);
errno = EINVAL;
return NULL;
}
buf = malloc(size);
if (!buf) {
free(mf);
errno = ENOMEM;
return NULL;
}
*((char *)buf) = '\0';
mflags |= __MALL;
}
if (open_flags & O_CREAT) {
if (open_flags & O_APPEND) {
/* For append the position is set to the first NUL byte or the end. */
initial_pos = (mflags & __MALL) ? 0 : strnlen(buf, size);
initial_size = initial_pos;
mflags |= __MAPP;
} else {
initial_size = 0;
/* w+ mode truncates the buffer, writing NUL */
if ((open_flags & O_ACCMODE) == O_RDWR)
*((char *)buf) = '\0';
}
} else {
initial_size = size;
}
*mf = (struct __file_mem) {
.xfile = FDEV_SETUP_EXT(__fmem_put, __fmem_get, __fmem_flush, __fmem_close, __fmem_seek,
NULL, stdio_flags),
.buf = buf,
.size = initial_size,
.bufsize = size,
.pos = initial_pos,
.mflags = mflags,
};
return (FILE *)mf;
}