gstreamer/gst/elements/gstfilesrc.c

/* GStreamer
 * Copyright (C) 1999,2000 Erik Walthinsen <omega@cse.ogi.edu>
 *                    2000 Wim Taymans <wtay@chello.be>
 *
 * gstfilesrc.c:
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library 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
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with this library; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */

#include <gst/gst.h>

#include "gstfilesrc.h"

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


/**********************************************************************
 * GStreamer Default File Source
 * Theory of Operation
 *
 * This source uses mmap(2) to efficiently load data from a file.
 * To do this without seriously polluting the applications' memory
 * space, it must do so in smaller chunks, say 1-4MB at a time.
 * Buffers are then subdivided from these mmap'd chunks, to directly
 * make use of the mmap.
 *
 * To handle refcounting so that the mmap can be freed at the appropriate
 * time, a buffer will be created for each mmap'd region, and all new
 * buffers will be sub-buffers of this top-level buffer.  As they are 
 * freed, the refcount goes down on the mmap'd buffer and its free()
 * function is called, which will call munmap(2) on itself.
 *
 * If a buffer happens to cross the boundaries of an mmap'd region, we
 * have to decide whether it's more efficient to copy the data into a
 * new buffer, or mmap() just that buffer.  There will have to be a
 * breakpoint size to determine which will be done.  The mmap() size
 * has a lot to do with this as well, because you end up in double-
 * jeopardy: the larger the outgoing buffer, the more data to copy when
 * it overlaps, *and* the more frequently you'll have buffers that *do*
 * overlap.
 *
 * Seeking is another tricky aspect to do efficiently.  The initial
 * implementation of this source won't make use of these features, however.
 * The issue is that if an application seeks backwards in a file, *and*
 * that region of the file is covered by an mmap that hasn't been fully
 * deallocated, we really should re-use it.  But keeping track of these
 * regions is tricky because we have to lock the structure that holds
 * them.  We need to settle on a locking primitive (GMutex seems to be
 * a really good option...), then we can do that.
 */


GstElementDetails gst_filesrc_details = {
  "File Source",
  "Source/File",
  "LGPL",
  "Read from arbitrary point in a file",
  VERSION,
  "Erik Walthinsen <omega@cse.ogi.edu>",
  "(C) 1999",
};

#define DEFAULT_BLOCKSIZE 	4*1024
#define DEFAULT_MMAPSIZE 	4*1024*1024

/* #define fs_print(format,args...) g_print(format, ## args)  */
#define fs_print(format,args...)

/* FileSrc signals and args */
enum {
  /* FILL ME */
  LAST_SIGNAL
};

enum {
  ARG_0,
  ARG_LOCATION,
  ARG_FD,
  ARG_BLOCKSIZE,
  ARG_MMAPSIZE,
  ARG_TOUCH,
};

GST_EVENT_MASK_FUNCTION (gst_filesrc_get_event_mask,
  { GST_EVENT_SEEK, GST_SEEK_METHOD_CUR | 
	  	    GST_SEEK_METHOD_SET | 
		    GST_SEEK_METHOD_END | 
		    GST_SEEK_FLAG_FLUSH },
  { GST_EVENT_FLUSH, 0 },
  { GST_EVENT_SIZE, 0 }
)

GST_PAD_QUERY_TYPE_FUNCTION (gst_filesrc_get_query_types,
  GST_PAD_QUERY_TOTAL,
  GST_PAD_QUERY_POSITION
)

GST_FORMATS_FUNCTION (gst_filesrc_get_formats,
  GST_FORMAT_BYTES
)

static void		gst_filesrc_class_init		(GstFileSrcClass *klass);
static void		gst_filesrc_init		(GstFileSrc *filesrc);
static void 		gst_filesrc_dispose 		(GObject *object);

static void		gst_filesrc_set_property	(GObject *object, guint prop_id, 
							 const GValue *value, GParamSpec *pspec);
static void		gst_filesrc_get_property	(GObject *object, guint prop_id, 
							 GValue *value, GParamSpec *pspec);

static GstBuffer *	gst_filesrc_get			(GstPad *pad);
static gboolean 	gst_filesrc_srcpad_event 	(GstPad *pad, GstEvent *event);
static gboolean 	gst_filesrc_srcpad_query 	(GstPad *pad, GstPadQueryType type,
		         				 GstFormat *format, gint64 *value);

static GstElementStateReturn	gst_filesrc_change_state	(GstElement *element);


static GstElementClass *parent_class = NULL;
/*static guint gst_filesrc_signals[LAST_SIGNAL] = { 0 };*/

GType
gst_filesrc_get_type(void)
{
  static GType filesrc_type = 0;

  if (!filesrc_type) {
    static const GTypeInfo filesrc_info = {
      sizeof(GstFileSrcClass),      NULL,
      NULL,
      (GClassInitFunc)gst_filesrc_class_init,
      NULL,
      NULL,
      sizeof(GstFileSrc),
      0,
      (GInstanceInitFunc)gst_filesrc_init,
    };
    filesrc_type = g_type_register_static (GST_TYPE_ELEMENT, "GstFileSrc", &filesrc_info, 0);
  }
  return filesrc_type;
}

static void
gst_filesrc_class_init (GstFileSrcClass *klass)
{
  GObjectClass *gobject_class;
  GstElementClass *gstelement_class;

  gobject_class = (GObjectClass*)klass;
  gstelement_class = (GstElementClass*)klass;

  parent_class = g_type_class_ref (GST_TYPE_ELEMENT);

  g_object_class_install_property (G_OBJECT_CLASS (klass), ARG_FD,
    g_param_spec_int ("fd", "File-descriptor", "File-descriptor for the file being mmap()d",
                      0, G_MAXINT, 0, G_PARAM_READABLE));
  g_object_class_install_property (G_OBJECT_CLASS (klass), ARG_LOCATION,
    g_param_spec_string ("location", "File Location", "Location of the file to read",
                         NULL, G_PARAM_READWRITE));
  g_object_class_install_property (G_OBJECT_CLASS (klass), ARG_BLOCKSIZE,
    g_param_spec_ulong ("blocksize", "Block size", "Size in bytes to read per buffer",
                        1, G_MAXULONG, DEFAULT_BLOCKSIZE, G_PARAM_READWRITE));
  g_object_class_install_property (G_OBJECT_CLASS (klass), ARG_MMAPSIZE,
    g_param_spec_ulong ("mmapsize", "mmap() Block Size",
                        "Size in bytes of mmap()d regions",
                        0, G_MAXULONG, DEFAULT_MMAPSIZE, G_PARAM_READWRITE));
  g_object_class_install_property (G_OBJECT_CLASS (klass), ARG_TOUCH,
    g_param_spec_boolean ("touch", "Touch read data",
                          "Touch data to force disk read", 
			  FALSE, G_PARAM_READWRITE));

  gobject_class->dispose 	= gst_filesrc_dispose;
  gobject_class->set_property 	= gst_filesrc_set_property;
  gobject_class->get_property 	= gst_filesrc_get_property;

  gstelement_class->change_state = gst_filesrc_change_state;
}

static gint
gst_filesrc_bufcmp (gconstpointer a, gconstpointer b)
{
/*  GstBuffer *bufa = (GstBuffer *)a, *bufb = (GstBuffer *)b;*/

  /* sort first by offset, then in reverse by size */
  if (GST_BUFFER_OFFSET(a) < GST_BUFFER_OFFSET(b)) return -1;
  else if (GST_BUFFER_OFFSET(a) > GST_BUFFER_OFFSET(b)) return 1;
  else if (GST_BUFFER_SIZE(a) > GST_BUFFER_SIZE(b)) return -1;
  else if (GST_BUFFER_SIZE(a) < GST_BUFFER_SIZE(b)) return 1;
  else return 0;
}

static void
gst_filesrc_init (GstFileSrc *src)
{
  src->srcpad = gst_pad_new ("src", GST_PAD_SRC);
  gst_pad_set_get_function (src->srcpad, gst_filesrc_get);
  gst_pad_set_event_function (src->srcpad, gst_filesrc_srcpad_event);
  gst_pad_set_event_mask_function (src->srcpad, gst_filesrc_get_event_mask);
  gst_pad_set_query_function (src->srcpad, gst_filesrc_srcpad_query);
  gst_pad_set_query_type_function (src->srcpad, gst_filesrc_get_query_types);
  gst_pad_set_formats_function (src->srcpad, gst_filesrc_get_formats);
  gst_element_add_pad (GST_ELEMENT (src), src->srcpad);

  src->pagesize = getpagesize();

  src->filename = NULL;
  src->fd = 0;
  src->filelen = 0;

  src->curoffset = 0;
  src->block_size = DEFAULT_BLOCKSIZE;
  src->touch = FALSE;

  src->mapbuf = NULL;
  src->mapsize = DEFAULT_MMAPSIZE;		/* default is 4MB */

  src->map_regions = g_tree_new (gst_filesrc_bufcmp);
  src->map_regions_lock = g_mutex_new();

  src->seek_happened = FALSE;
}

static void
gst_filesrc_dispose (GObject *object)
{
  GstFileSrc *src;

  src = GST_FILESRC (object);

  G_OBJECT_CLASS (parent_class)->dispose (object);

  g_tree_destroy (src->map_regions);
  g_mutex_free (src->map_regions_lock);
  if (src->filename)
    g_free (src->filename);
}


static void
gst_filesrc_set_property (GObject *object, guint prop_id, const GValue *value, GParamSpec *pspec)
{
  GstFileSrc *src;

  /* it's not null if we got it, but it might not be ours */
  g_return_if_fail (GST_IS_FILESRC (object));

  src = GST_FILESRC (object);

  switch (prop_id) {
    case ARG_LOCATION:
      /* the element must be stopped in order to do this */
      g_return_if_fail (GST_STATE (src) < GST_STATE_PLAYING);

      if (src->filename) g_free (src->filename);
      /* clear the filename if we get a NULL (is that possible?) */
      if (g_value_get_string (value) == NULL) {
        gst_element_set_state (GST_ELEMENT (object), GST_STATE_NULL);
        src->filename = NULL;
      /* otherwise set the new filename */
      } else {
        src->filename = g_strdup (g_value_get_string (value));
      }
      g_object_notify (G_OBJECT (src), "location");
      break;
    case ARG_BLOCKSIZE:
      src->block_size = g_value_get_ulong (value);
      g_object_notify (G_OBJECT (src), "blocksize");
      break;
    case ARG_MMAPSIZE:
      if ((src->mapsize % src->pagesize) == 0) {
        src->mapsize = g_value_get_ulong (value);
        g_object_notify (G_OBJECT (src), "mmapsize");
      } else {
        GST_INFO (0, "invalid mapsize, must a multiple of pagesize, which is %d", 
	          src->pagesize);
      }
      break;
    case ARG_TOUCH:
      src->touch = g_value_get_boolean (value);
      g_object_notify (G_OBJECT (src), "touch");
      break;
    default:
      break;
  }
}

static void
gst_filesrc_get_property (GObject *object, guint prop_id, GValue *value, GParamSpec *pspec)
{
  GstFileSrc *src;

  /* it's not null if we got it, but it might not be ours */
  g_return_if_fail (GST_IS_FILESRC (object));

  src = GST_FILESRC (object);

  switch (prop_id) {
    case ARG_LOCATION:
      g_value_set_string (value, src->filename);
      break;
    case ARG_FD:
      g_value_set_int (value, src->fd);
      break;
    case ARG_BLOCKSIZE:
      g_value_set_ulong (value, src->block_size);
      break;
    case ARG_MMAPSIZE:
      g_value_set_ulong (value, src->mapsize);
      break;
    case ARG_TOUCH:
      g_value_set_boolean (value, src->touch);
      break;
    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
      break;
  }
}

static void
gst_filesrc_free_parent_mmap (GstBuffer *buf)
{
  GstFileSrc *src = GST_FILESRC (GST_BUFFER_POOL_PRIVATE (buf));

  fs_print ("freeing mmap()d buffer at %d+%d\n", 
	    GST_BUFFER_OFFSET (buf), GST_BUFFER_SIZE (buf));

  /* remove the buffer from the list of available mmap'd regions */
  g_mutex_lock (src->map_regions_lock);
  g_tree_remove (src->map_regions, buf);
  /* check to see if the tree is empty */
  if (g_tree_nnodes (src->map_regions) == 0) {
    /* we have to free the bufferpool we don't have yet */
  }
  g_mutex_unlock (src->map_regions_lock);

#ifdef MADV_DONTNEED
  /* madvise to tell the kernel what to do with it */
  madvise (GST_BUFFER_DATA (buf), GST_BUFFER_SIZE (buf), MADV_DONTNEED);
#endif
  /* now unmap the memory */
  munmap (GST_BUFFER_DATA (buf), GST_BUFFER_MAXSIZE (buf));
  GST_DEBUG (0, "unmapped region %08llx+%08llx at %p", 
		  GST_BUFFER_OFFSET (buf), GST_BUFFER_MAXSIZE (buf), 
		  GST_BUFFER_DATA (buf));

  GST_BUFFER_DATA (buf) = NULL;

  gst_buffer_default_free (buf);
}

static GstBuffer *
gst_filesrc_map_region (GstFileSrc *src, off_t offset, size_t size)
{
  GstBuffer *buf;
  gint retval;
  void *mmapregion;

  g_return_val_if_fail (offset >= 0, NULL);

  fs_print  ("mapping region %08llx+%08x from file into memory\n",offset,size);
  mmapregion = mmap (NULL, size, PROT_READ, MAP_SHARED, src->fd, offset);

  if (mmapregion == NULL) {
    gst_element_error (GST_ELEMENT (src), "couldn't map file");
    return NULL;
  }
  else if (mmapregion == MAP_FAILED) {
    gst_element_error (GST_ELEMENT (src), "mmap (0x%x, %d, 0x%llx) : %s",
 	     size, src->fd, offset, strerror (errno));
    return NULL;
  }
  GST_DEBUG (0, "mapped region %08llx+%08x from file into memory at %p", 
		  offset, size, mmapregion);

  /* time to allocate a new mapbuf */
  buf = gst_buffer_new ();
  /* mmap() the data into this new buffer */
  GST_BUFFER_DATA (buf) = mmapregion;

#ifdef MADV_SEQUENTIAL
  /* madvise to tell the kernel what to do with it */
  retval = madvise (GST_BUFFER_DATA (buf), GST_BUFFER_SIZE (buf), MADV_SEQUENTIAL);
#endif
  /* fill in the rest of the fields */
  GST_BUFFER_FLAG_SET (buf, GST_BUFFER_READONLY);
  GST_BUFFER_FLAG_SET (buf, GST_BUFFER_ORIGINAL);
  GST_BUFFER_SIZE (buf) = size;
  GST_BUFFER_MAXSIZE (buf) = size;
  GST_BUFFER_OFFSET (buf) = offset;
  GST_BUFFER_TIMESTAMP (buf) = GST_CLOCK_TIME_NONE;
  GST_BUFFER_POOL_PRIVATE (buf) = src;
  GST_BUFFER_FREE_FUNC (buf) = (GstDataFreeFunction) gst_filesrc_free_parent_mmap;

  g_mutex_lock (src->map_regions_lock);
  g_tree_insert (src->map_regions,buf,buf);
  g_mutex_unlock (src->map_regions_lock);

  return buf;
}

static GstBuffer *
gst_filesrc_map_small_region (GstFileSrc *src, off_t offset, size_t size)
{
  size_t mapsize;
  off_t mod, mapbase;
  GstBuffer *map;

/*  printf("attempting to map a small buffer at %d+%d\n",offset,size); */

  /* if the offset starts at a non-page boundary, we have to special case */
  if ((mod = offset % src->pagesize)) {
    GstBuffer *ret;

    mapbase = offset - mod;
    mapsize = ((size + mod + src->pagesize - 1) / src->pagesize) * src->pagesize;
/*    printf("not on page boundaries, resizing map to %d+%d\n",mapbase,mapsize);*/
    map = gst_filesrc_map_region(src, mapbase, mapsize);
    if (map == NULL)
      return NULL;

    ret = gst_buffer_create_sub (map, offset - mapbase, size);

    gst_buffer_unref (map);

    return ret;
  }

  return gst_filesrc_map_region(src,offset,size);
}

typedef struct {
  off_t offset;
  off_t size;
} GstFileSrcRegion;

/* This allows us to search for a potential mmap region. */
static gint
gst_filesrc_search_region_match (gpointer a, gpointer b)
{
  GstFileSrcRegion *r = (GstFileSrcRegion *)b;

  /* trying to walk b down the tree, current node is a */
  if (r->offset < GST_BUFFER_OFFSET(a)) return -1;
  else if (r->offset >= (GST_BUFFER_OFFSET(a) + GST_BUFFER_SIZE(a))) return 1;
  else if ((r->offset + r->size) <= (GST_BUFFER_OFFSET(a) + GST_BUFFER_SIZE(a))) return 0;

  return -2;
}

/**
 * gst_filesrc_get:
 * @pad: #GstPad to push a buffer from
 *
 * Push a new buffer from the filesrc at the current offset.
 */
static GstBuffer *
gst_filesrc_get (GstPad *pad)
{
  GstFileSrc *src;
  GstBuffer *buf = NULL, *map;
  size_t readsize;
  off_t readend,mapstart,mapend;
  GstFileSrcRegion region;
  int i;

  g_return_val_if_fail (pad != NULL, NULL);
  src = GST_FILESRC (gst_pad_get_parent (pad));
  g_return_val_if_fail (GST_FLAG_IS_SET (src, GST_FILESRC_OPEN), NULL);

  /* check for seek */
  if (src->seek_happened) {
    GstEvent *event;

    src->seek_happened = FALSE;
    GST_DEBUG (GST_CAT_EVENT, "filesrc sending discont");
    event = gst_event_new_discontinuous (FALSE, GST_FORMAT_BYTES, src->curoffset, NULL);
    GST_EVENT_DISCONT_NEW_MEDIA (event) = FALSE;
    src->need_flush = FALSE;
    return GST_BUFFER (event);
  }
  /* check for flush */
  if (src->need_flush) {
    src->need_flush = FALSE;
    GST_DEBUG (GST_CAT_EVENT, "filesrc sending flush");
    return GST_BUFFER (gst_event_new_flush ());
  }

  /* check for EOF */
  if (src->curoffset == src->filelen) {
    GST_DEBUG (0, "filesrc eos %lld %lld", src->curoffset, src->filelen);
    gst_element_set_eos (GST_ELEMENT (src));
    return GST_BUFFER (gst_event_new (GST_EVENT_EOS));
  }

  /* calculate end pointers so we don't have to do so repeatedly later */
  readsize = src->block_size;
  readend = src->curoffset + src->block_size;		/* note this is the byte *after* the read */
  mapstart = GST_BUFFER_OFFSET(src->mapbuf);
  mapend = mapstart + GST_BUFFER_SIZE(src->mapbuf);	/* note this is the byte *after* the map */

  /* check to see if we're going to overflow the end of the file */
  if (readend > src->filelen) {
    readsize = src->filelen - src->curoffset;
    readend = src->curoffset + readsize;
  }

  GST_DEBUG (0, "attempting to read %08x, %08llx, %08llx, %08llx", 
		  readsize, readend, mapstart, mapend);

  /* if the start is past the mapstart */
  if (src->curoffset >= mapstart) {
    /* if the end is before the mapend, the buffer is in current mmap region... */
    /* ('cause by definition if readend is in the buffer, so's readstart) */
    if (readend <= mapend) {
      fs_print ("read buf %llu+%d lives in current mapbuf %lld+%d, creating subbuffer of mapbuf\n",
             src->curoffset, readsize, mapstart, GST_BUFFER_SIZE(src->mapbuf));
      buf = gst_buffer_create_sub (src->mapbuf, src->curoffset - GST_BUFFER_OFFSET(src->mapbuf),
                                   readsize);

    /* if the start actually is within the current mmap region, map an overlap buffer */
    } else if (src->curoffset < mapend) {
      fs_print ("read buf %llu+%d starts in mapbuf %d+%d but ends outside, creating new mmap\n",
             src->curoffset,readsize,GST_BUFFER_OFFSET(src->mapbuf),GST_BUFFER_SIZE(src->mapbuf));
      buf = gst_filesrc_map_small_region (src, src->curoffset, readsize);
      if (buf == NULL)
        return NULL;
    }

    /* the only other option is that buffer is totally outside, which means we search for it */

  /* now we can assume that the start is *before* the current mmap region */
  /* if the readend is past mapstart, we have two options */
  } else if (readend >= mapstart) {
    /* either the read buffer overlaps the start of the mmap region */
    /* or the read buffer fully contains the current mmap region    */
    /* either way, it's really not relevant, we just create a new region anyway*/
    fs_print ("read buf %llu+%d starts before mapbuf %d+%d, but overlaps it\n",
             src->curoffset,readsize,GST_BUFFER_OFFSET(src->mapbuf),GST_BUFFER_SIZE(src->mapbuf));
    buf = gst_filesrc_map_small_region (src, src->curoffset, readsize);
    if (buf == NULL)
      return NULL;
  }

  /* then deal with the case where the read buffer is totally outside */
  if (buf == NULL) {
    /* first check to see if there's a map that covers the right region already */
    fs_print ("searching for mapbuf to cover %llu+%d\n",src->curoffset,readsize);
    region.offset = src->curoffset;
    region.size = readsize;
    map = g_tree_search (src->map_regions,
			 (GCompareFunc) gst_filesrc_search_region_match,
			 (gpointer)&region);

    /* if we found an exact match, subbuffer it */
    if (map != NULL) {
      fs_print ("found mapbuf at %d+%d, creating subbuffer\n",GST_BUFFER_OFFSET(map),GST_BUFFER_SIZE(map));
      buf = gst_buffer_create_sub (map, src->curoffset - GST_BUFFER_OFFSET(map), readsize);

    /* otherwise we need to create something out of thin air */
    } else {
      /* if the read buffer crosses a mmap region boundary, create a one-off region */
      if ((src->curoffset / src->mapsize) != (readend / src->mapsize)) {
        fs_print ("read buf %llu+%d crosses a %d-byte boundary, creating a one-off\n",
               src->curoffset,readsize,src->mapsize);
        buf = gst_filesrc_map_small_region (src, src->curoffset, readsize);
	if (buf == NULL)
          return NULL;

      /* otherwise we will create a new mmap region and set it to the default */
      } else {
	size_t mapsize;

        off_t nextmap = src->curoffset - (src->curoffset % src->mapsize);
        fs_print ("read buf %llu+%d in new mapbuf at %llu+%d, mapping and subbuffering\n",
               src->curoffset, readsize, nextmap, src->mapsize);
        /* first, we're done with the old mapbuf */
        gst_buffer_unref(src->mapbuf);
	mapsize = src->mapsize;

	/* double the mapsize as long as the readsize is smaller */
	while (readsize - (src->curoffset - nextmap) > mapsize) {
          fs_print ("readsize smaller then mapsize %08x %d\n", readsize, mapsize);
          mapsize <<=1;
	}
        /* create a new one */
        src->mapbuf = gst_filesrc_map_region (src, nextmap, mapsize);
	if (src->mapbuf == NULL)
          return NULL;

        /* subbuffer it */
        buf = gst_buffer_create_sub (src->mapbuf, src->curoffset - nextmap, readsize);
      }
    }
  }

  /* if we need to touch the buffer (to bring it into memory), do so */
  if (src->touch) {
    volatile guchar *p = GST_BUFFER_DATA (buf), c;

    for (i=0; i < GST_BUFFER_SIZE (buf); i += src->pagesize)
      c = p[i];
  }

  /* we're done, return the buffer */
  src->curoffset += GST_BUFFER_SIZE(buf);
  return buf;
}

/* open the file and mmap it, necessary to go to READY state */
static gboolean 
gst_filesrc_open_file (GstFileSrc *src)
{
  g_return_val_if_fail (!GST_FLAG_IS_SET (src ,GST_FILESRC_OPEN), FALSE);

  GST_DEBUG(0, "opening file %s",src->filename);

  /* open the file */
  src->fd = open (src->filename, O_RDONLY);
  if (src->fd < 0) {
    gst_element_error (GST_ELEMENT (src), "opening file \"%s\" (%s)", 
    		       src->filename, strerror (errno), NULL);
    return FALSE;
  } else {
    /* check if it is a regular file, otherwise bail out */
    struct stat stat_results;

    fstat(src->fd, &stat_results);

    if (!S_ISREG(stat_results.st_mode)) {
      gst_element_error (GST_ELEMENT (src), "opening file \"%s\" failed. it isn't a regular file", 
      					src->filename, NULL);
      close(src->fd);
      return FALSE;
    }
		
    /* find the file length */
    src->filelen = lseek (src->fd, 0, SEEK_END);
    lseek (src->fd, 0, SEEK_SET);

    /* allocate the first mmap'd region */
    src->mapbuf = gst_filesrc_map_region (src, 0, src->mapsize);
    if (src->mapbuf == NULL)
      return FALSE;

    src->curoffset = 0;

    GST_FLAG_SET (src, GST_FILESRC_OPEN);
  }
  return TRUE;
}

/* unmap and close the file */
static void
gst_filesrc_close_file (GstFileSrc *src)
{
  g_return_if_fail (GST_FLAG_IS_SET (src, GST_FILESRC_OPEN));

  /* close the file */
  close (src->fd);

  /* zero out a lot of our state */
  src->fd = 0;
  src->filelen = 0;
  src->curoffset = 0;

  if (src->mapbuf) {
    gst_buffer_unref (src->mapbuf);
    src->mapbuf = NULL;
  }

  GST_FLAG_UNSET (src, GST_FILESRC_OPEN);
}


static GstElementStateReturn
gst_filesrc_change_state (GstElement *element)
{
  GstFileSrc *src = GST_FILESRC(element);

  switch (GST_STATE_TRANSITION (element)) {
    case GST_STATE_NULL_TO_READY:
      break;
    case GST_STATE_READY_TO_NULL:
      break;
    case GST_STATE_READY_TO_PAUSED:
      if (!GST_FLAG_IS_SET (element, GST_FILESRC_OPEN)) {
        if (!gst_filesrc_open_file (GST_FILESRC (element)))
          return GST_STATE_FAILURE;
      }
      break;
    case GST_STATE_PAUSED_TO_READY:
      if (GST_FLAG_IS_SET (element, GST_FILESRC_OPEN))
        gst_filesrc_close_file (GST_FILESRC (element));
      src->seek_happened = TRUE;
      break;
    default:
      break;
  }

  if (GST_ELEMENT_CLASS (parent_class)->change_state)
    return GST_ELEMENT_CLASS (parent_class)->change_state (element);

  return GST_STATE_SUCCESS;
}

static gboolean
gst_filesrc_srcpad_query (GstPad *pad, GstPadQueryType type,
		          GstFormat *format, gint64 *value)
{
  GstFileSrc *src = GST_FILESRC (GST_PAD_PARENT (pad));

  switch (type) {
    case GST_PAD_QUERY_TOTAL:
      if (*format != GST_FORMAT_BYTES) {
	return FALSE;
      }
      *value = src->filelen;
      break;
    case GST_PAD_QUERY_POSITION:
      if (*format != GST_FORMAT_BYTES) {
	return FALSE;
      }
      *value = src->curoffset;
      break;
    default:
      return FALSE;
      break;
  }
  return TRUE;
}

static gboolean
gst_filesrc_srcpad_event (GstPad *pad, GstEvent *event)
{
  GstFileSrc *src = GST_FILESRC (GST_PAD_PARENT (pad));

  GST_DEBUG(0, "event %d", GST_EVENT_TYPE (event));

  switch (GST_EVENT_TYPE (event)) {
    case GST_EVENT_SEEK:
    {
      guint64 offset;

      if (GST_EVENT_SEEK_FORMAT (event) != GST_FORMAT_BYTES) {
	goto error;
      }

      offset = GST_EVENT_SEEK_OFFSET (event);

      switch (GST_EVENT_SEEK_METHOD (event)) {
        case GST_SEEK_METHOD_SET:
          if (offset > src->filelen) 
	    goto error;
          src->curoffset = offset;
          GST_DEBUG(0, "seek set pending to %lld", src->curoffset);
	  break;
        case GST_SEEK_METHOD_CUR:
          if (offset + src->curoffset > src->filelen) 
	    goto error;
          src->curoffset += offset;
          GST_DEBUG(0, "seek cur pending to %lld", src->curoffset);
	  break;
        case GST_SEEK_METHOD_END:
          if (ABS (offset) > src->filelen) 
	    goto error;
          src->curoffset = src->filelen - ABS (offset);
          GST_DEBUG(0, "seek end pending to %lld", src->curoffset);
	  break;
	default:
          goto error;
	  break;
      }
      src->seek_happened = TRUE;
      src->need_flush = GST_EVENT_SEEK_FLAGS(event) & GST_SEEK_FLAG_FLUSH;
      break;
    }
    case GST_EVENT_SIZE:
      if (GST_EVENT_SIZE_FORMAT (event) != GST_FORMAT_BYTES) {
	goto error;
      }
      src->block_size = GST_EVENT_SIZE_VALUE (event);
      g_object_notify (G_OBJECT (src), "blocksize");  
      break;
    case GST_EVENT_FLUSH:
      src->need_flush = TRUE;
      break;
    default:
      goto error;
      break;
  }
  gst_event_unref (event);
  return TRUE;

error:
  gst_event_unref (event);
  return FALSE;
}