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/******************************************************************************

*                                                                             *

* License Agreement                                                           *

*                                                                             *

* Copyright (c) 2004 Altera Corporation, San Jose, California, USA.           *

* All rights reserved.                                                        *

*                                                                             *

* Permission is hereby granted, free of charge, to any person obtaining a     *

* copy of this software and associated documentation files (the "Software"),  *

* to deal in the Software without restriction, including without limitation   *

* the rights to use, copy, modify, merge, publish, distribute, sublicense,    *

* and/or sell copies of the Software, and to permit persons to whom the       *

* Software is furnished to do so, subject to the following conditions:        *

*                                                                             *

* The above copyright notice and this permission notice shall be included in  *

* all copies or substantial portions of the Software.                         *

*                                                                             *

* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR  *

* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,    *

* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE *

* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER      *

* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING     *

* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER         *

* DEALINGS IN THE SOFTWARE.                                                   *

*                                                                             *

* This agreement shall be governed in all respects by the laws of the State   *

* of California and by the laws of the United States of America.              *

*                                                                             *

* Altera does not recommend, suggest or require that this reference design    *

* file be used in conjunction or combination with any other product.          *

******************************************************************************/

#include <stddef.h>

#include <stdio.h>

#include <errno.h>

#include "sys/alt_dev.h"

#include "priv/alt_file.h"

#include "alt_types.h"

#include "system.h"

/*

 * alt_get_fd() is called to allocate a new file descriptor from the file

 * descriptor pool. If a file descriptor is succesfully allocated, it is

 * configured to refer to device "dev".

 *

 * The return value is the index of the file descriptor structure (i.e.

 * the offset of the file descriptor within the file descriptor array). A

 * negative value indicates failure.

 */

int alt_get_fd (alt_dev* dev)

{

  alt_32 i;

  int rc = -EMFILE;

  /*

   * Take the alt_fd_list_lock semaphore in order to avoid races when

   * accessing the file descriptor pool.

   */

  ALT_SEM_PEND(alt_fd_list_lock, 0);

  /*

   * Search through the list of file descriptors, and allocate the first

   * free descriptor that's found.

   *

   * If a free descriptor is found, then the value of "alt_max_fd" is

   * updated accordingly. "alt_max_fd" is a 'highwater mark' which

   * indicates the highest file descriptor ever allocated. This is used to

   * improve efficency when searching the file descriptor list, and

   * therefore reduce contention on the alt_fd_list_lock semaphore.

   */

  for (i = 0; i < ALT_MAX_FD; i++)

  {

    if (!alt_fd_list[i].dev)

    {

      alt_fd_list[i].dev = dev;

      if (i > alt_max_fd)

      {

        alt_max_fd = i;

      }

      rc = i;

      goto alt_get_fd_exit;

    }

  }

 alt_get_fd_exit:

  /*

   * Release the alt_fd_list_lock semaphore now that we are done with the

   * file descriptor pool.

   */

  ALT_SEM_POST(alt_fd_list_lock);

  return rc;

}