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nuttx/libs/libc/stdio/lib_setvbuf.c

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/****************************************************************************
* libs/libc/stdio/lib_setvbuf.c
*
* Copyright (C) 2017 Gregory Nutt. All rights reserved.
* Author: Alan Carvalho de Assis <acassis@gmail.com>
* 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 will 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>
#include <sys/types.h>
#include <stdbool.h>
#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <nuttx/fs/fs.h>
#include "libc.h"
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: setvbuf
*
* Description:
* The setvbuf() function may be used after the stream pointed to by
* stream is associated with an open file but before any other operation
* (other than an unsuccessful call to setvbuf()) is performed on the
* stream. The argument type determines how stream will be buffered, as
* follows:
*
* _IOFBF - Will cause input/output to be fully buffered.
* _IOLBF - Will cause input/output to be line buffered.
* _IONBF - Will cause input/output to be unbuffered.
*
* If buf is not a null pointer, the array it points to may be used instead
* of a buffer allocated by setvbuf() and the argument size specifies the size
* of the array; otherwise, size may determine the size of a buffer allocated
* by the setvbuf() function. The contents of the array at any time are
* unspecified.
*
* Input Parameters:
* stream - the stream to flush
* buffer - the user allocate buffer. If NULL, will allocates a buffer of
* specified size
* mode - specifies a mode for file buffering
* size - size of buffer
*
* Returned Value:
* Upon successful completion, setvbuf() will return 0. Otherwise, it will
* return a non-zero value if an invalid value is given for type or if the
* request cannot be honored, [CX] and may set errno to indicate the error
*
****************************************************************************/
int setvbuf(FAR FILE *stream, FAR char *buffer, int mode, size_t size)
{
#ifndef CONFIG_STDIO_DISABLE_BUFFERING
FAR unsigned char *newbuf = NULL;
uint8_t flags;
int errcode;
/* Verify arguments */
/* Make sure that a valid mode was provided */
if (mode != _IOFBF && mode != _IOLBF && mode != _IONBF)
{
errcode = EINVAL;
goto errout;
}
/* If a buffer pointer is provided, then it must have a non-zero size */
if (buffer != NULL && size == 0)
{
errcode = EINVAL;
goto errout;
}
/* My assumption is that if size is zero for modes {_IOFBF, _IOLBF} the
* caller is only attempting to change the buffering mode. In this case,
* the existing buffer should be re-used (if there is one). If there is no
* existing buffer, then I suppose we should allocate one of the default
* size?
*/
if ((mode == _IOFBF || mode == _IOLBF) && size == 0 &&
stream->fs_bufstart == NULL)
{
size = BUFSIZ;
}
/* A non-zero size (or a non-NULL buffer) with mode = _IONBF makes no
* sense but is, apparently, permissible. We simply force the buffer to
* NULL and size to zero in this case without complaining.
*/
else if (mode == _IONBF)
{
buffer = NULL;
size = 0;
}
/* Make sure that we have exclusive access to the stream */
lib_take_semaphore(stream);
/* setvbuf() may only be called AFTER the stream has been opened and
* BEFORE any operations have been performed on the stream.
*/
/* Return EBADF if the file is not open */
if (stream->fs_fd < 0)
{
errcode = EBADF;
goto errout_with_semaphore;
}
/* Return EBUSY if operations have already been performed on the buffer.
* Here we really only verify that there is no valid data in the existing
* buffer.
*
* REVIST: There could be race conditions here, could there not?
*/
if (stream->fs_bufpos != stream->fs_bufstart)
{
errcode = EBUSY;
goto errout_with_semaphore;
}
/* Initialize by clearing related flags. We try to avoid any permanent
* changes to the stream structure until we know that we will be
* successful.
*/
flags = stream->fs_flags & ~(__FS_FLAG_LBF | __FS_FLAG_UBF);
/* Allocate a new buffer if one is needed or reuse the existing buffer it
* is appropriate to do so.
*/
switch (mode)
{
case _IOLBF:
flags |= __FS_FLAG_LBF;
/* Fall through */
case _IOFBF:
/* Use the existing buffer if size == 0 */
if (size > 0)
{
/* A new buffer is needed. Did the caller provide the buffer
* memory?
*/
if (buffer != NULL)
{
newbuf = (FAR unsigned char *)buffer;
/* Indicate that we have an I/O buffer managed by the caller of
* setvbuf.
*/
flags |= __FS_FLAG_UBF;
}
else
{
newbuf = (FAR unsigned char *)lib_malloc(size);
if (newbuf == NULL)
{
errcode = ENOMEM;
goto errout_with_semaphore;
}
}
}
else
{
/* Re-use the existing buffer and retain some existing flags.
* This supports changing the buffering mode without changing
* the buffer.
*/
DEBUGASSERT(stream->fs_bufstart != NULL);
flags |= stream->fs_flags & __FS_FLAG_UBF;
goto reuse_buffer;
}
break;
case _IONBF:
/* No buffer needed... We must be performing unbuffered I/O */
newbuf = NULL;
break;
default:
DEBUGPANIC();
}
/* Do not release the previous buffer if it was allocated by the user
* on a previous call to setvbuf().
*/
if (stream->fs_bufstart != NULL &&
(stream->fs_flags & __FS_FLAG_UBF) == 0)
{
lib_free(stream->fs_bufstart);
}
/* Set the new buffer information */
stream->fs_bufstart = newbuf;
stream->fs_bufpos = newbuf;
stream->fs_bufread = newbuf;
stream->fs_bufend = newbuf + size;
/* Update the stream flags and return success */
reuse_buffer:
stream->fs_flags = flags;
lib_give_semaphore(stream);
return OK;
errout_with_semaphore:
lib_give_semaphore(stream);
errout:
set_errno(errcode);
return ERROR;
#else
/* Return that setvbuf() is not supported */
set_errno(ENOSYS);
return ERROR;
#endif
}
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