IABSD.fr/src/lib/libc/stdio/fmemopen.c

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• Author : millert
  Date : 2020-08-17 16:17:39
  Hash : d35e2a8f
  Message : Fix append mode so it always writes to the end and expand regress. OK deraadt@ martijn@

• lib/libc/stdio/fmemopen.c

• /*	$OpenBSD: fmemopen.c,v 1.5 2020/08/17 16:17:39 millert Exp $	*/
  
  /*
   * Copyright (c) 2011 Martin Pieuchot <mpi@openbsd.org>
   * Copyright (c) 2009 Ted Unangst
   *
   * Permission to use, copy, modify, and distribute this software for any
   * purpose with or without fee is hereby granted, provided that the above
   * copyright notice and this permission notice appear in all copies.
   *
   * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
   * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
   * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
   * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
   * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
   * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
   * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
   */
  
  #include <errno.h>
  #include <fcntl.h>
  #include <stdio.h>
  #include <stdlib.h>
  #include <string.h>
  #include "local.h"
  
  struct state {
  	char		*string;	/* actual stream */
  	size_t		 pos;		/* current position */
  	size_t		 size;		/* allocated size */
  	size_t		 len;		/* length of the data */
  	int		 update;	/* open for update */
  	int		 append;	/* open for append */
  };
  
  static int
  fmemopen_read(void *v, char *b, int l)
  {
  	struct state	*st = v;
  	int		 i;
  
  	for (i = 0; i < l && i + st->pos < st->len; i++)
  		b[i] = st->string[st->pos + i];
  	st->pos += i;
  
  	return (i);
  }
  
  static int
  fmemopen_write(void *v, const char *b, int l)
  {
  	struct state	*st = v;
  	int		i;
  
  	if (st->append)
  		st->pos = st->len;
  
  	for (i = 0; i < l && i + st->pos < st->size; i++)
  		st->string[st->pos + i] = b[i];
  	st->pos += i;
  
  	if (st->pos >= st->len) {
  		st->len = st->pos;
  
  		if (st->len < st->size)
  			st->string[st->len] = '\0';
  		else if (!st->update)
  			st->string[st->size - 1] = '\0';
  	}
  
  	return (i);
  }
  
  static fpos_t
  fmemopen_seek(void *v, fpos_t off, int whence)
  {
  	struct state	*st = v;
  	ssize_t		 base = 0;
  
  	switch (whence) {
  	case SEEK_SET:
  		break;
  	case SEEK_CUR:
  		base = st->pos;
  		break;
  	case SEEK_END:
  		base = st->len;
  		break;
  	}
  
  	if (off > st->size - base || off < -base) {
  		errno = EOVERFLOW;
  		return (-1);
  	}
  
  	st->pos = base + off;
  
  	return (st->pos);
  }
  
  static int
  fmemopen_close(void *v)
  {
  	free(v);
  
  	return (0);
  }
  
  static int
  fmemopen_close_free(void *v)
  {
  	struct state	*st = v;
  
  	free(st->string);
  	free(st);
  
  	return (0);
  }
  
  FILE *
  fmemopen(void *buf, size_t size, const char *mode)
  {
  	struct state	*st;
  	FILE		*fp;
  	int		 flags, oflags;
  
  	if (size == 0) {
  		errno = EINVAL;
  		return (NULL);
  	}
  
  	if ((flags = __sflags(mode, &oflags)) == 0) {
  		errno = EINVAL;
  		return (NULL);
  	}
  
  	if (buf == NULL && ((oflags & O_RDWR) == 0)) {
  		errno = EINVAL;
  		return (NULL);
  	}
  
  	if ((st = malloc(sizeof(*st))) == NULL)
  		return (NULL);
  
  	if ((fp = __sfp()) == NULL) {
  		free(st);
  		return (NULL);
  	}
  
  	st->pos = 0;
  	st->len = (oflags & O_TRUNC) ? 0 : size;
  	st->size = size;
  	st->update = oflags & O_RDWR;
  	st->append = oflags & O_APPEND;
  
  	if (buf == NULL) {
  		if ((st->string = malloc(size)) == NULL) {
  			free(st);
  			fp->_flags = 0;
  			return (NULL);
  		}
  		*st->string = '\0';
  	} else {
  		st->string = (char *)buf;
  
  		if (oflags & O_TRUNC)
  			*st->string = '\0';
  
  		if (oflags & O_APPEND) {
  			char	*p;
  
  			if ((p = memchr(st->string, '\0', size)) != NULL)
  				st->pos = st->len = (p - st->string);
  			else
  				st->pos = st->len = size;
  		}
  	}
  
  	fp->_flags = (short)flags;
  	fp->_file = -1;
  	fp->_cookie = st;
  	fp->_read = (flags & __SWR) ? NULL : fmemopen_read;
  	fp->_write = (flags & __SRD) ? NULL : fmemopen_write;
  	fp->_seek = fmemopen_seek;
  	fp->_close = (buf == NULL) ? fmemopen_close_free : fmemopen_close;
  
  	return (fp);
  }
  DEF_WEAK(fmemopen);