_cdio_stdio.c

linux下的MPEG1

/*
    $Id: _cdio_stdio.c,v 1.2 2004/04/11 12:20:31 miguelfreitas Exp $

    Copyright (C) 2000 Herbert Valerio Riedel <[e-mail]>
    Copyright (C) 2003, 2004 Rocky Bernstein <[e-mail]>

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*/

#ifdef HAVE_CONFIG_H
# include "config.h"
#endif

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h> 
#include <sys/stat.h>
#include <errno.h>

#include <cdio/logging.h>
#include <cdio/util.h>
#include "_cdio_stream.h"
#include "_cdio_stdio.h"

static const char _rcsid[] = "$Id: _cdio_stdio.c,v 1.2 2004/04/11 12:20:31 miguelfreitas Exp $";

#define CDIO_STDIO_BUFSIZE (128*1024)

typedef struct {
  char *pathname;
  FILE *fd;
  char *fd_buf;
  off_t st_size; /* used only for source */
} _UserData;

static int
_stdio_open (void *user_data) 
{
  _UserData *const ud = user_data;
  
  if ((ud->fd = fopen (ud->pathname, "rb")))
    {
      ud->fd_buf = _cdio_malloc (CDIO_STDIO_BUFSIZE);
      setvbuf (ud->fd, ud->fd_buf, _IOFBF, CDIO_STDIO_BUFSIZE);
    }

  return (ud->fd == NULL);
}

static int
_stdio_close(void *user_data)
{
  _UserData *const ud = user_data;

  if (fclose (ud->fd))
    cdio_error ("fclose (): %s", strerror (errno));
 
  ud->fd = NULL;

  free (ud->fd_buf);
  ud->fd_buf = NULL;

  return 0;
}

static void
_stdio_free(void *user_data)
{
  _UserData *const ud = user_data;

  if (ud->pathname)
    free(ud->pathname);

  if (ud->fd) /* should be NULL anyway... */
    _stdio_close(user_data); 

  free(ud);
}

/*! 
  Like fseek(3) and in fact may be the same.
  
  This  function sets the file position indicator for the stream
  pointed to by stream.  The new position, measured in bytes, is obtained
  by  adding offset bytes to the position specified by whence.  If whence
  is set to SEEK_SET, SEEK_CUR, or SEEK_END, the offset  is  relative  to
  the  start of the file, the current position indicator, or end-of-file,
  respectively.  A successful call to the fseek function clears the end-
  of-file indicator for the stream and undoes any effects of the
  ungetc(3) function on the same stream.
  
  RETURN VALUE
  Upon successful completion, return 0,
  Otherwise, -1 is returned and the global variable errno is set to indi-
  cate the error.
*/
static long
_stdio_seek(void *user_data, long offset, int whence)
{
  _UserData *const ud = user_data;

  if ( (offset=fseek (ud->fd, offset, whence)) ) {
    cdio_error ("fseek (): %s", strerror (errno));
  }

  return offset;
}

static long int
_stdio_stat(void *user_data)
{
  const _UserData *const ud = user_data;

  return ud->st_size;
}

/*!
  Like fread(3) and in fact is about the same.
  
  DESCRIPTION:
  The function fread reads nmemb elements of data, each size bytes long,
  from the stream pointed to by stream, storing them at the location
  given by ptr.
  
  RETURN VALUE:
  return the number of items successfully read or written (i.e.,
  not the number of characters).  If an error occurs, or the
  end-of-file is reached, the return value is a short item count
  (or zero).
  
  We do not distinguish between end-of-file and error, and callers
  must use feof(3) and ferror(3) to determine which occurred.
  */
static long
_stdio_read(void *user_data, void *buf, long int count)
{
  _UserData *const ud = user_data;
  long read;

  read = fread(buf, 1, count, ud->fd);

  if (read != count)
    { /* fixme -- ferror/feof */
      if (feof (ud->fd))
        {
          cdio_debug ("fread (): EOF encountered");
          clearerr (ud->fd);
        }
      else if (ferror (ud->fd))
        {
          cdio_error ("fread (): %s", strerror (errno));
          clearerr (ud->fd);
        }
      else
        cdio_debug ("fread (): short read and no EOF?!?");
    }

  return read;
}

/*!
  Deallocate resources assocaited with obj. After this obj is unusable.
*/
void
cdio_stdio_destroy(CdioDataSource *obj)
{
  cdio_stream_destroy(obj);
}

CdioDataSource*
cdio_stdio_new(const char pathname[])
{
  CdioDataSource *new_obj = NULL;
  cdio_stream_io_functions funcs = { 0, };
  _UserData *ud = NULL;
  struct stat statbuf;
  
  if (stat (pathname, &statbuf) == -1) 
    {
      cdio_warn ("could not retrieve file info for `%s': %s", 
                 pathname, strerror (errno));
      return NULL;
    }

  ud = _cdio_malloc (sizeof (_UserData));

  ud->pathname = strdup(pathname);
  ud->st_size  = statbuf.st_size; /* let's hope it doesn't change... */

  funcs.open   = _stdio_open;
  funcs.seek   = _stdio_seek;
  funcs.stat   = _stdio_stat;
  funcs.read   = _stdio_read;
  funcs.close  = _stdio_close;
  funcs.free   = _stdio_free;

  new_obj = cdio_stream_new(ud, &funcs);

  return new_obj;
}


/* 
 * Local variables:
 *  c-file-style: "gnu"
 *  tab-width: 8
 *  indent-tabs-mode: nil
 * End:
 */