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/****************************************************************************
* libc/stdio/lib_rdflush.c
*
* Copyright (C) 2008, 2011 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 <errno.h>
#include "lib_internal.h"
/****************************************************************************
* Definitions
****************************************************************************/
/****************************************************************************
* Private Type Declarations
****************************************************************************/
/****************************************************************************
* Private Function Prototypes
****************************************************************************/
/****************************************************************************
* Global Constant Data
****************************************************************************/
/****************************************************************************
* Global Variables
****************************************************************************/
/****************************************************************************
* Private Constant Data
****************************************************************************/
/****************************************************************************
* Private Variables
****************************************************************************/
/****************************************************************************
* Global Functions
****************************************************************************/
/****************************************************************************
* Name: lib_rdflush
*
* Description:
* Flush read data from the I/O buffer and adjust the file pointer to
* account for the unread data
*
****************************************************************************/
#if CONFIG_STDIO_BUFFER_SIZE > 0
int lib_rdflush(FAR FILE *stream)
{
if (!stream)
{
set_errno(EBADF);
return ERROR;
}
/* Get exclusive access to the stream */
lib_take_semaphore(stream);
/* If the buffer is currently being used for read access, then discard all
* of the read-ahead data. We do not support concurrent buffered read/write
* access.
*/
if (stream->fs_bufread != stream->fs_bufstart)
{
/* Now adjust the stream pointer to account for the read-ahead data that
* was not actually read by the user.
*/
#if CONFIG_NUNGET_CHARS > 0
off_t rdoffset = stream->fs_bufread - stream->fs_bufpos + stream->fs_nungotten;
#else
off_t rdoffset = stream->fs_bufread - stream->fs_bufpos;
#endif
/* Mark the buffer as empty (do this before calling fseek() because fseek()
* also calls this function).
*/
stream->fs_bufpos = stream->fs_bufread = stream->fs_bufstart;
#if CONFIG_NUNGET_CHARS > 0
stream->fs_nungotten = 0;
#endif
/* Then seek to the position corresponding to the last data read by the user */
if (fseek(stream, -rdoffset, SEEK_CUR) < 0)
{
lib_give_semaphore(stream);
return ERROR;
}
}
lib_give_semaphore(stream);
return OK;
}
#endif /* CONFIG_STDIO_BUFFER_SIZE */
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