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px4-firmware/nuttx/lib/stdio/lib_libfread.c

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/****************************************************************************
* lib/stdio/lib_libfread.c
*
* Copyright (C) 2007-2009, 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.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h> /* for CONFIG_STDIO_BUFFER_SIZE */
#include <sys/types.h>
#include <stdio.h>
#include <unistd.h>
#include <string.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
****************************************************************************/
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: lib_fread
****************************************************************************/
ssize_t lib_fread(FAR void *ptr, size_t count, FAR FILE *stream)
{
unsigned char *dest = (unsigned char*)ptr;
ssize_t bytes_read;
int ret;
/* Make sure that reading from this stream is allowed */
if (!stream || (stream->fs_oflags & O_RDOK) == 0)
{
set_errno(EBADF);
bytes_read = -1;
}
else
{
/* The stream must be stable until we complete the read */
lib_take_semaphore(stream);
#if CONFIG_NUNGET_CHARS > 0
/* First, re-read any previously ungotten characters */
while ((stream->fs_nungotten > 0) && (count > 0))
{
/* Decrement the count of ungotten bytes to get an index */
stream->fs_nungotten--;
/* Return the last ungotten byte */
*dest++ = stream->fs_ungotten[stream->fs_nungotten];
/* That's one less byte that we have to read */
count--;
}
#endif
#if CONFIG_STDIO_BUFFER_SIZE > 0
/* If the buffer is currently being used for write access, then
* flush all of the buffered write data. We do not support concurrent
* buffered read/write access.
*/
ret = lib_wrflush(stream);
if (ret < 0)
{
lib_give_semaphore(stream);
return ret;
}
/* Now get any other needed chars from the buffer or the file. */
while (count > 0)
{
/* Is there readable data in the buffer? */
while ((count > 0) && (stream->fs_bufpos < stream->fs_bufread))
{
/* Yes, copy a byte into the user buffer */
*dest++ = *stream->fs_bufpos++;
count--;
}
/* The buffer is empty OR we have already supplied the number of
* bytes requested in the read. Check if we need to read
* more from the file.
*/
if (count > 0)
{
size_t buffer_available;
/* We need to read more data into the buffer from the file */
/* Mark the buffer empty */
stream->fs_bufpos = stream->fs_bufread = stream->fs_bufstart;
/* How much space is available in the buffer? */
buffer_available = stream->fs_bufend - stream->fs_bufread;
/* Will the number of bytes that we need to read fit into
* the buffer space that is available? If the read size is
* larger than the buffer, then read some of the data
* directly into the user's buffer.
*/
if (count > buffer_available)
{
bytes_read = read(stream->fs_filedes, dest, count);
if (bytes_read < 0)
{
/* An error occurred on the read. The error code is
* in the 'errno' variable.
*/
goto errout_with_errno;
}
else if (bytes_read == 0)
{
/* We are at the end of the file. But we may already
* have buffered data. In that case, we will report
* the EOF indication later.
*/
goto shortread;
}
else
{
/* Some bytes were read. Adjust the dest pointer */
dest += bytes_read;
/* Were all of the requested bytes read? */
if (bytes_read < count)
{
/* No. We must be at the end of file. */
goto shortread;
}
else
{
/* Yes. We are done. */
count = 0;
}
}
}
else
{
/* The number of bytes required to satisfy the read
* is less than or equal to the size of the buffer
* space that we have left. Read as much as we can
* into the buffer.
*/
bytes_read = read(stream->fs_filedes, stream->fs_bufread, buffer_available);
if (bytes_read < 0)
{
/* An error occurred on the read. The error code is
* in the 'errno' variable.
*/
goto errout_with_errno;
}
else if (bytes_read == 0)
{
/* We are at the end of the file. But we may already
* have buffered data. In that case, we will report
* the EOF indication later.
*/
goto shortread;
}
else
{
/* Some bytes were read */
stream->fs_bufread += bytes_read;
}
}
}
}
#else
/* Now get any other needed chars from the file. */
while (count > 0)
{
bytes_read = read(stream->fs_filedes, dest, count);
if (bytes_read < 0)
{
/* An error occurred on the read. The error code is
* in the 'errno' variable.
*/
goto errout_with_errno;
}
else if (bytes_read == 0)
{
/* We are at the end of the file. But we may already
* have buffered data. In that case, we will report
* the EOF indication later.
*/
break;
}
else
{
dest += bytes_read;
count -= bytes_read;
}
}
#endif
/* Here after a successful (but perhaps short) read */
#if CONFIG_STDIO_BUFFER_SIZE > 0
shortread:
#endif
bytes_read = dest - (unsigned char*)ptr;
/* Set or clear the EOF indicator. If we get here because of a
* short read and the total number of* bytes read is zero, then
* we must be at the end-of-file.
*/
if (bytes_read > 0)
{
stream->fs_flags &= ~__FS_FLAG_EOF;
}
else
{
stream->fs_flags |= __FS_FLAG_EOF;
}
}
lib_give_semaphore(stream);
return bytes_read;
/* Error exits */
errout_with_errno:
lib_give_semaphore(stream);
return -get_errno();
}
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