145 lines
5.3 KiB
C
145 lines
5.3 KiB
C
/****************************************************************************
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* lib/stdio/lib_rdflush.c
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*
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* Copyright (C) 2008, 2011 Gregory Nutt. All rights reserved.
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* Author: Gregory Nutt <gnutt@nuttx.org>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* 3. Neither the name NuttX nor the names of its contributors may be
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* used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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****************************************************************************/
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/****************************************************************************
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* Compilation Switches
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <sys/types.h>
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#include <stdio.h>
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#include <unistd.h>
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#include <errno.h>
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#include "lib_internal.h"
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/****************************************************************************
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* Definitions
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****************************************************************************/
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/****************************************************************************
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* Private Type Declarations
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****************************************************************************/
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/****************************************************************************
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* Private Function Prototypes
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****************************************************************************/
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/****************************************************************************
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* Global Constant Data
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****************************************************************************/
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/****************************************************************************
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* Global Variables
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****************************************************************************/
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/****************************************************************************
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* Private Constant Data
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****************************************************************************/
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/****************************************************************************
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* Private Variables
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****************************************************************************/
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/****************************************************************************
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* Global Functions
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****************************************************************************/
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/****************************************************************************
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* Name: lib_rdflush
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*
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* Description:
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* Flush read data from the I/O buffer and adjust the file pointer to
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* account for the unread data
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*
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****************************************************************************/
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#if CONFIG_STDIO_BUFFER_SIZE > 0
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int lib_rdflush(FAR FILE *stream)
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{
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if (!stream)
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{
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set_errno(EBADF);
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return ERROR;
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}
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/* Get exclusive access to the stream */
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lib_take_semaphore(stream);
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/* If the buffer is currently being used for read access, then discard all
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* of the read-ahead data. We do not support concurrent buffered read/write
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* access.
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*/
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if (stream->fs_bufread != stream->fs_bufstart)
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{
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/* Now adjust the stream pointer to account for the read-ahead data that
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* was not actually read by the user.
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*/
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#if CONFIG_NUNGET_CHARS > 0
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off_t rdoffset = stream->fs_bufread - stream->fs_bufpos + stream->fs_nungotten;
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#else
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off_t rdoffset = stream->fs_bufread - stream->fs_bufpos;
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#endif
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/* Mark the buffer as empty (do this before calling fseek() because fseek()
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* also calls this function).
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*/
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stream->fs_bufpos = stream->fs_bufread = stream->fs_bufstart;
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#if CONFIG_NUNGET_CHARS > 0
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stream->fs_nungotten = 0;
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#endif
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/* Then seek to the position corresponding to the last data read by the user */
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if (fseek(stream, -rdoffset, SEEK_CUR) < 0)
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{
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lib_give_semaphore(stream);
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return ERROR;
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}
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}
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lib_give_semaphore(stream);
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return OK;
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}
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#endif /* CONFIG_STDIO_BUFFER_SIZE */
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