/****************************************************************************
 * lib/stdio/lib_ungetc.c
 *
 *   Copyright (C) 2007, 2008, 2011 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 <stdio.h>
#include <fcntl.h>
#include <errno.h>
#include <nuttx/fs/fs.h>
#include "lib_internal.h"

/****************************************************************************
 * Definitions
 ****************************************************************************/

/****************************************************************************
 * Private Type Declarations
 ****************************************************************************/

/****************************************************************************
 * Private Function Prototypes
 ****************************************************************************/

/****************************************************************************
 * Global Function Prototypes
 ****************************************************************************/

/**************************************************************************
 * Global Constant Data
 **************************************************************************/

/****************************************************************************
 * Global Variables
 ****************************************************************************/

/**************************************************************************
 * Private Constant Data
 **************************************************************************/

/****************************************************************************
 * Private Variables
 **************************************************************************/

/****************************************************************************
 * Public Functions
 **************************************************************************/

/****************************************************************************
 * Name: ungetc
 **************************************************************************/

int ungetc(int c, FAR FILE *stream)
{
#if CONFIG_NUNGET_CHARS > 0
  int nungotten;
#endif

  /* Stream must be open for read access */

  if ((stream && stream->fs_filedes < 0) ||
      ((stream->fs_oflags & O_RDOK) == 0))
    {
      set_errno(EBADF);
      return EOF;
    }

#if CONFIG_NUNGET_CHARS > 0
  nungotten = stream->fs_nungotten;
  if (stream->fs_nungotten < CONFIG_NUNGET_CHARS)
    {
      stream->fs_ungotten[nungotten] = c;
      stream->fs_nungotten = nungotten + 1;
      return c;
    }
  else
#endif
    {
      set_errno(ENOMEM);
      return EOF;
    }
}