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nuttx/libc/stdio/lib_fopen.c
Gregory Nutt e3b12cbaa9 Add x qualifier to fopen to support exlusive open
2014-01-07 17:18:38 -06:00

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/****************************************************************************
* libc/stdio/lib_fopen.c
*
* Copyright (C) 2007-2012 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <gnutt@nuttx.org>
*
* 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 NuttX 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 OWNER 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.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>
#include <assert.h>
#include <errno.h>
#include "lib_internal.h"
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
/* Open mode flags */
#define MODE_R (1 << 0) /* Bit 0: "r{b|x|+}" open for reading */
#define MODE_W (1 << 1) /* Bit 1: "w{b|x|+}" open for writing, truncating,
* or creating file */
#define MODE_A (1 << 2) /* Bit 2: "a{b|x|+}" open for writing, appending
* the to file */
#define MODE_PLUS (1 << 3) /* Bit 3: "{r|w|a|b|x}+" open for update (reading
* and writing) */
#define MODE_B (1 << 4) /* Bit 4: "{r|w|a|x|+}b" Binary mode */
#define MODE_X (1 << 5) /* Bit 5: "{r|w|a|b|+}x" Open exclusive mode */
#define MODE_NONE 0 /* No access mode determined */
#define MODE_MASK (MODE_R | MODE_W | MODE_A)
/****************************************************************************
* Private Types
****************************************************************************/
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: lib_mode2oflags
****************************************************************************/
static int lib_mode2oflags(FAR const char *mode)
{
unsigned int state;
int oflags;
/* Verify that a mode string was provided. */
DEBUGASSERT(mode);
/* Parse the mode string to determine the corresponding open flags */
state = MODE_NONE;
oflags = 0;
for (; *mode; mode++)
{
switch (*mode)
{
/* Open for read access ("r{b|x|+}") */
case 'r' :
if (state == MODE_NONE)
{
/* Open for read access */
oflags = O_RDOK;
state = MODE_R;
}
else
{
goto errout;
}
break;
/* Open for write access ("w{b|x|+}") */
case 'w' :
if (state == MODE_NONE)
{
/* Open for write access, truncating any existing file */
oflags = (O_WROK | O_CREAT | O_TRUNC);
state = MODE_W;
}
else
{
goto errout;
}
break;
/* Open for write/append access ("a{b|x|+}") */
case 'a' :
if (state == MODE_NONE)
{
/* Write to the end of the file */
oflags = O_WROK|O_CREAT|O_APPEND;
state = MODE_A;
}
else
{
goto errout;
}
break;
/* Open for update access ("{r|w|a|b|x}+") */
case '+' :
switch (state & MODE_MASK)
{
case MODE_R:
{
/* Retain any binary and exclusive mode selections */
oflags &= (O_BINARY | O_EXCL);
/* Open for read/write access */
oflags |= O_RDWR;
state |= MODE_PLUS;
}
break;
case MODE_W:
{
/* Retain any binary and exclusive mode selections */
oflags &= (O_BINARY | O_EXCL);
/* Open for write read/access, truncating any existing file */
oflags |= (O_RDWR | O_CREAT | O_TRUNC);
state |= MODE_PLUS;
}
break;
case MODE_A:
{
/* Retain any binary and exclusive mode selections */
oflags &= (O_BINARY | O_EXCL);
/* Read from the beginning of the file; write to the end */
oflags |= (O_RDWR | O_CREAT | O_APPEND);
state |= MODE_PLUS;
}
break;
default:
goto errout;
break;
}
break;
/* Open for binary access ("{r|w|a|x|+}b") */
case 'b' :
if ((state & MODE_MASK) != MODE_NONE)
{
/* The file is opened in binary mode */
oflags |= O_BINARY;
state |= MODE_B;
}
else
{
goto errout;
}
break;
/* Open for exclusive access ("{r|w|a|b|+}x") */
case 'X' :
if ((state & MODE_MASK) != MODE_NONE)
{
/* The file is opened in exclusive mode */
oflags |= O_EXCL;
state |= MODE_X;
}
else
{
goto errout;
}
break;
/* Unrecognized or unsupported mode */
default:
goto errout;
break;
}
}
return oflags;
/* Both fopen and fdopen should fail with errno == EINVAL if the mode
* string is invalid.
*/
errout:
set_errno(EINVAL);
return ERROR;
}
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: fdopen
****************************************************************************/
FAR FILE *fdopen(int fd, FAR const char *mode)
{
FAR FILE *ret = NULL;
int oflags;
/* Map the open mode string to open flags */
oflags = lib_mode2oflags(mode);
if (oflags >= 0)
{
ret = fs_fdopen(fd, oflags, NULL);
}
return ret;
}
/****************************************************************************
* Name: fopen
****************************************************************************/
FAR FILE *fopen(FAR const char *path, FAR const char *mode)
{
FAR FILE *ret = NULL;
int oflags;
int fd;
/* Map the open mode string to open flags */
oflags = lib_mode2oflags(mode);
if (oflags < 0)
{
return NULL;
}
/* Open the file */
fd = open(path, oflags, 0666);
/* If the open was successful, then fdopen() the fil using the file
* desciptor returned by open. If open failed, then just return the
* NULL stream -- open() has already set the errno.
*/
if (fd >= 0)
{
ret = fs_fdopen(fd, oflags, NULL);
if (!ret)
{
/* Don't forget to close the file descriptor if any other
* failures are reported by fdopen().
*/
(void)close(fd);
}
}
return ret;
}
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