111 lines
3.2 KiB
C
111 lines
3.2 KiB
C
/****************************************************************************
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* libs/libc/stdio/lib_rdflush.c
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership. The
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* ASF licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*
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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 "libc.h"
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#ifndef CONFIG_STDIO_DISABLE_BUFFERING
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/****************************************************************************
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* Public 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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int lib_rdflush(FAR FILE *stream)
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{
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/* Sanity checking */
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if (stream == NULL)
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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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/* Do nothing if there is no I/O buffer */
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if (stream->fs_bufstart == NULL)
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{
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return OK;
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}
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/* Get exclusive access to the stream */
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flockfile(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
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* that 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 +
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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
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* fseek() 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
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* user
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*/
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if (fseek(stream, -rdoffset, SEEK_CUR) < 0)
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{
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funlockfile(stream);
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return ERROR;
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}
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}
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funlockfile(stream);
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return OK;
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}
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#endif /* CONFIG_STDIO_DISABLE_BUFFERING */
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