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/****************************************************************************
* libc/stdio/lib_ftell.c
*
* Copyright (C) 2008, 2011, 2013 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.
*
****************************************************************************/
/****************************************************************************
* Compilation Switches
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <sys/types.h>
#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include "lib_internal.h"
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
/****************************************************************************
* Private Type Declarations
****************************************************************************/
/****************************************************************************
* Private Function Prototypes
****************************************************************************/
/****************************************************************************
* Global Constant Data
****************************************************************************/
/****************************************************************************
* Global Variables
****************************************************************************/
/****************************************************************************
* Private Constant Data
****************************************************************************/
/****************************************************************************
* Private Variables
****************************************************************************/
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: lib_getrdoffset
*
* Description:
* It is insufficient to simply use the file offset; we must also account
* for the data offset in the any buffered data. This function calculates
* that offset.
*
* Returned Value:
* The file position offset due to buffered data.
*
****************************************************************************/
#if CONFIG_STDIO_BUFFER_SIZE > 0
static off_t lib_getrdoffset(FAR FILE *stream)
{
off_t rdoffset = 0;
lib_take_semaphore(stream);
if (stream->fs_bufread != stream->fs_bufstart)
{
#if CONFIG_NUNGET_CHARS > 0
rdoffset = stream->fs_bufread - stream->fs_bufpos + stream->fs_nungotten;
#else
rdoffset = stream->fs_bufread - stream->fs_bufpos;
#endif
}
lib_give_semaphore(stream);
return rdoffset;
}
#else
# define lib_getrdoffset(stream) (0)
#endif
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: ftell
*
* Description:
* ftell() returns the current value of the file position indicator for the
* stream pointed to by stream.
*
* Returned Value:
* Zero on success; -1 on failure with errno set appropriately.
*
****************************************************************************/
long ftell(FAR FILE *stream)
{
off_t position;
/* Verify that we were provided with a stream */
if (!stream)
{
set_errno(EBADF);
return ERROR;
}
/* Perform the lseek to the current position. This will not move the
* file pointer, but will return its current setting
*/
position = lseek(stream->fs_fd, 0, SEEK_CUR);
if (position != (off_t)-1)
{
return (long)(position - lib_getrdoffset(stream));
}
else
{
return ERROR;
}
}
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