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/****************************************************************************
* lib/stdio/lib_libfflush.c
*
* Copyright (C) 2007-2008, 2011-2012 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.
*
****************************************************************************/
/****************************************************************************
* Compilation Switches
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <sys/types.h>
#include <stdbool.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <nuttx/fs/fs.h>
#include "lib_internal.h"
/****************************************************************************
* Definitions
****************************************************************************/
/****************************************************************************
* Private Type Declarations
****************************************************************************/
/****************************************************************************
* Private Function Prototypes
****************************************************************************/
/****************************************************************************
* Global Constant Data
****************************************************************************/
/****************************************************************************
* Global Variables
****************************************************************************/
/****************************************************************************
* Private Constant Data
****************************************************************************/
/****************************************************************************
* Private Variables
****************************************************************************/
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: lib_fflush
*
* Description:
* The function lib_fflush() forces a write of all user-space buffered data for
* the given output or update stream via the stream's underlying write
* function. The open status of the stream is unaffected.
*
* Parmeters:
* stream - the stream to flush
* bforce - flush must be complete.
*
* Return:
* A negated errno value on failure, otherwise the number of bytes remaining
* in the buffer.
*
****************************************************************************/
ssize_t lib_fflush(FAR FILE *stream, bool bforce)
{
#if CONFIG_STDIO_BUFFER_SIZE > 0
FAR const unsigned char *src;
ssize_t bytes_written;
ssize_t nbuffer;
int ret;
/* Return EBADF if the file is not opened for writing */
if (stream->fs_filedes < 0 || (stream->fs_oflags & O_WROK) == 0)
{
return -EBADF;
}
/* Make sure that we have exclusive access to the stream */
lib_take_semaphore(stream);
/* Make sure that the buffer holds valid data */
if (stream->fs_bufpos != stream->fs_bufstart)
{
/* Make sure that the buffer holds buffered write data. We do not
* support concurrent read/write buffer usage.
*/
if (stream->fs_bufread != stream->fs_bufstart)
{
/* The buffer holds read data... just return zero meaning "no bytes
* remaining in the buffer."
*/
lib_give_semaphore(stream);
return 0;
}
/* How many bytes of write data are used in the buffer now */
nbuffer = stream->fs_bufpos - stream->fs_bufstart;
/* Try to write that amount */
src = stream->fs_bufstart;
do
{
/* Perform the write */
bytes_written = write(stream->fs_filedes, src, nbuffer);
if (bytes_written < 0)
{
/* Write failed. The cause of the failure is in 'errno'.
* returned the negated errno value.
*/
lib_give_semaphore(stream);
return -get_errno();
}
/* Handle partial writes. fflush() must either return with
* an error condition or with the data successfully flushed
* from the buffer.
*/
src += bytes_written;
nbuffer -= bytes_written;
}
while (bforce && nbuffer > 0);
/* Reset the buffer position to the beginning of the buffer */
stream->fs_bufpos = stream->fs_bufstart;
/* For the case of an incomplete write, nbuffer will be non-zero
* It will hold the number of bytes that were not written.
* Move the data down in the buffer to handle this (rare) case
*/
while (nbuffer)
{
*stream->fs_bufpos++ = *src++;
--nbuffer;
}
}
/* Restore normal access to the stream and return the number of bytes
* remaining in the buffer.
*/
lib_give_semaphore(stream);
return stream->fs_bufpos - stream->fs_bufstart;
#else
/* Return no bytes remaining in the buffer */
return 0;
#endif
}
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