/* GStreamer

 * Copyright (C) 2014 Wim Taymans <wim.taymans@gmail.com>

 *

 * gstdownloadbuffer.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., 51 Franklin St, Fifth Floor,

 * Boston, MA 02110-1301, USA.

 */

/**

 * SECTION:element-downloadbuffer

 * @title: downloadbuffer

 *

 * The downloadbuffer element provides on-disk buffering and caching of, typically,

 * a network file. temp-template should be set to a value such as

 * /tmp/gstreamer-XXXXXX and the element will allocate a random free filename and

 * buffer the data in the file.

 *

 * With max-size-bytes and max-size-time you can configure the buffering limits.

 * The downloadbuffer element will try to read-ahead these amounts of data. When

 * the amount of read-ahead data drops below low-percent of the configured max,

 * the element will start emitting BUFFERING messages until high-percent of max is

 * reached again.

 *

 * The downloadbuffer provides push and pull based scheduling on its source pad

 * and will efficiently seek in the upstream element when needed.

 *

 * The temp-location property will be used to notify the application of the

 * allocated filename.

 *

 * When the downloadbuffer has completely downloaded the media, it will

 * post an application message named  <classname>"GstCacheDownloadComplete"</classname>

 * with the following information:

 *

 * *

 *   G_TYPE_STRING

 *   <classname>"location"</classname>:

 *   the location of the completely downloaded file.

 *

 */

#ifdef HAVE_CONFIG_H

#include "config.h"

#endif

#include "gstdownloadbuffer.h"

#include <glib/gstdio.h>

#include "gst/gst-i18n-lib.h"

#include "gst/glib-compat-private.h"

#include <string.h>

#ifdef G_OS_WIN32

#include <io.h>                 /* lseek, open, close, read */

#undef lseek

#define lseek _lseeki64

#else

#include <unistd.h>

#endif

#ifdef __BIONIC__

#include <fcntl.h>

#endif

static GstStaticPadTemplate sinktemplate = GST_STATIC_PAD_TEMPLATE ("sink",

    GST_PAD_SINK,

    GST_PAD_ALWAYS,

    GST_STATIC_CAPS_ANY);

static GstStaticPadTemplate srctemplate = GST_STATIC_PAD_TEMPLATE ("src",

    GST_PAD_SRC,

    GST_PAD_ALWAYS,

    GST_STATIC_CAPS_ANY);

GST_DEBUG_CATEGORY_STATIC (downloadbuffer_debug);

#define GST_CAT_DEFAULT (downloadbuffer_debug)

enum

{

  LAST_SIGNAL

};

/* other defines */

#define DEFAULT_BUFFER_SIZE 4096

/* default property values */

#define DEFAULT_MAX_SIZE_BYTES     (2 * 1024 * 1024)    /* 2 MB */

#define DEFAULT_MAX_SIZE_TIME      2 * GST_SECOND       /* 2 seconds */

#define DEFAULT_LOW_PERCENT        10

#define DEFAULT_HIGH_PERCENT       99

#define DEFAULT_TEMP_REMOVE        TRUE

enum

{

  PROP_0,

  PROP_MAX_SIZE_BYTES,

  PROP_MAX_SIZE_TIME,

  PROP_LOW_PERCENT,

  PROP_HIGH_PERCENT,

  PROP_TEMP_TEMPLATE,

  PROP_TEMP_LOCATION,

  PROP_TEMP_REMOVE,

  PROP_LAST

};

#define GST_DOWNLOAD_BUFFER_CLEAR_LEVEL(l) G_STMT_START {         \

  l.bytes = 0;                                          \

  l.time = 0;                                           \

} G_STMT_END

#define STATUS(elem, pad, msg) \

  GST_LOG_OBJECT (elem, "(%s:%s) " msg ": %u of %u " \

                      "bytes, %" G_GUINT64_FORMAT " of %" G_GUINT64_FORMAT \

                      " ns", \

                      GST_DEBUG_PAD_NAME (pad), \

                      elem->cur_level.bytes, \

                      elem->max_level.bytes, \

                      elem->cur_level.time, \

                      elem->max_level.time)

#define GST_DOWNLOAD_BUFFER_MUTEX_LOCK(q) G_STMT_START {                          \

  g_mutex_lock (&q->qlock);                                              \

} G_STMT_END

#define GST_DOWNLOAD_BUFFER_MUTEX_LOCK_CHECK(q,res,label) G_STMT_START {         \

  GST_DOWNLOAD_BUFFER_MUTEX_LOCK (q);                                            \

  if (res != GST_FLOW_OK)                                               \

    goto label;                                                         \

} G_STMT_END

#define GST_DOWNLOAD_BUFFER_MUTEX_UNLOCK(q) G_STMT_START {                        \

  g_mutex_unlock (&q->qlock);                                            \

} G_STMT_END

#define GST_DOWNLOAD_BUFFER_WAIT_ADD_CHECK(q, res, o, label) G_STMT_START {       \

  STATUS (q, q->srcpad, "wait for ADD");                            \

  q->waiting_add = TRUE;                                                \

  q->waiting_offset = o;                                                \

  g_cond_wait (&q->item_add, &q->qlock);                                \

  q->waiting_add = FALSE;                                               \

  if (res != GST_FLOW_OK) {                                             \

    STATUS (q, q->srcpad, "received ADD wakeup");                   \

    goto label;                                                         \

  }                                                                     \

  STATUS (q, q->srcpad, "received ADD");                            \

} G_STMT_END

#define GST_DOWNLOAD_BUFFER_SIGNAL_ADD(q, o) G_STMT_START {                       \

  if (q->waiting_add && q->waiting_offset <= o) {                       \

    STATUS (q, q->sinkpad, "signal ADD");                               \

    g_cond_signal (&q->item_add);                                       \

  }                                                                     \

} G_STMT_END

#define _do_init \

    GST_DEBUG_CATEGORY_INIT (downloadbuffer_debug, "downloadbuffer", 0, \

        "downloadbuffer element");

#define gst_download_buffer_parent_class parent_class

G_DEFINE_TYPE_WITH_CODE (GstDownloadBuffer, gst_download_buffer,

    GST_TYPE_ELEMENT, _do_init);

static GstMessage *update_buffering (GstDownloadBuffer * dlbuf);

static void gst_download_buffer_finalize (GObject * object);

static void gst_download_buffer_set_property (GObject * object,

    guint prop_id, const GValue * value, GParamSpec * pspec);

static void gst_download_buffer_get_property (GObject * object,

    guint prop_id, GValue * value, GParamSpec * pspec);

static GstFlowReturn gst_download_buffer_chain (GstPad * pad,

    GstObject * parent, GstBuffer * buffer);

static void gst_download_buffer_loop (GstPad * pad);

static gboolean gst_download_buffer_handle_sink_event (GstPad * pad,

    GstObject * parent, GstEvent * event);

static gboolean gst_download_buffer_handle_sink_query (GstPad * pad,

    GstObject * parent, GstQuery * query);

static gboolean gst_download_buffer_handle_src_event (GstPad * pad,

    GstObject * parent, GstEvent * event);

static gboolean gst_download_buffer_handle_src_query (GstPad * pad,

    GstObject * parent, GstQuery * query);

static gboolean gst_download_buffer_handle_query (GstElement * element,

    GstQuery * query);

static GstFlowReturn gst_download_buffer_get_range (GstPad * pad,

    GstObject * parent, guint64 offset, guint length, GstBuffer ** buffer);

static gboolean gst_download_buffer_src_activate_mode (GstPad * pad,

    GstObject * parent, GstPadMode mode, gboolean active);

static gboolean gst_download_buffer_sink_activate_mode (GstPad * pad,

    GstObject * parent, GstPadMode mode, gboolean active);

static GstStateChangeReturn gst_download_buffer_change_state (GstElement *

    element, GstStateChange transition);

/* static guint gst_download_buffer_signals[LAST_SIGNAL] = { 0 }; */

static void

gst_download_buffer_class_init (GstDownloadBufferClass * klass)

{

  GObjectClass *gobject_class = G_OBJECT_CLASS (klass);

  GstElementClass *gstelement_class = GST_ELEMENT_CLASS (klass);

  gobject_class->set_property = gst_download_buffer_set_property;

  gobject_class->get_property = gst_download_buffer_get_property;

  /* properties */

  g_object_class_install_property (gobject_class, PROP_MAX_SIZE_BYTES,

      g_param_spec_uint ("max-size-bytes", "Max. size (kB)",

          "Max. amount of data to buffer (bytes, 0=disable)",

          0, G_MAXUINT, DEFAULT_MAX_SIZE_BYTES,

          G_PARAM_READWRITE | GST_PARAM_MUTABLE_PLAYING |

          G_PARAM_STATIC_STRINGS));

  g_object_class_install_property (gobject_class, PROP_MAX_SIZE_TIME,

      g_param_spec_uint64 ("max-size-time", "Max. size (ns)",

          "Max. amount of data to buffer (in ns, 0=disable)", 0, G_MAXUINT64,

          DEFAULT_MAX_SIZE_TIME, G_PARAM_READWRITE | GST_PARAM_MUTABLE_PLAYING |

          G_PARAM_STATIC_STRINGS));

  g_object_class_install_property (gobject_class, PROP_LOW_PERCENT,

      g_param_spec_int ("low-percent", "Low percent",

          "Low threshold for buffering to start. Only used if use-buffering is True",

          0, 100, DEFAULT_LOW_PERCENT,

          G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));

  g_object_class_install_property (gobject_class, PROP_HIGH_PERCENT,

      g_param_spec_int ("high-percent", "High percent",

          "High threshold for buffering to finish. Only used if use-buffering is True",

          0, 100, DEFAULT_HIGH_PERCENT,

          G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));

  g_object_class_install_property (gobject_class, PROP_TEMP_TEMPLATE,

      g_param_spec_string ("temp-template", "Temporary File Template",

          "File template to store temporary files in, should contain directory "

          "and XXXXXX. (NULL == disabled)",

          NULL, G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));

  g_object_class_install_property (gobject_class, PROP_TEMP_LOCATION,

      g_param_spec_string ("temp-location", "Temporary File Location",

          "Location to store temporary files in (Only read this property, "

          "use temp-template to configure the name template)",

          NULL, G_PARAM_READABLE | G_PARAM_STATIC_STRINGS));

  /**

   * GstDownloadBuffer:temp-remove

   *

   * When temp-template is set, remove the temporary file when going to READY.

   */

  g_object_class_install_property (gobject_class, PROP_TEMP_REMOVE,

      g_param_spec_boolean ("temp-remove", "Remove the Temporary File",

          "Remove the temp-location after use",

          DEFAULT_TEMP_REMOVE, G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));

  /* set several parent class virtual functions */

  gobject_class->finalize = gst_download_buffer_finalize;

  gst_element_class_add_static_pad_template (gstelement_class, &srctemplate);

  gst_element_class_add_static_pad_template (gstelement_class, &sinktemplate);

  gst_element_class_set_static_metadata (gstelement_class, "DownloadBuffer",

      "Generic", "Download Buffer element",

      "Wim Taymans <wim.taymans@gmail.com>");

  gstelement_class->change_state =

      GST_DEBUG_FUNCPTR (gst_download_buffer_change_state);

  gstelement_class->query =

      GST_DEBUG_FUNCPTR (gst_download_buffer_handle_query);

}

static void

gst_download_buffer_init (GstDownloadBuffer * dlbuf)

{

  dlbuf->sinkpad = gst_pad_new_from_static_template (&sinktemplate, "sink");

  gst_pad_set_chain_function (dlbuf->sinkpad,

      GST_DEBUG_FUNCPTR (gst_download_buffer_chain));

  gst_pad_set_activatemode_function (dlbuf->sinkpad,

      GST_DEBUG_FUNCPTR (gst_download_buffer_sink_activate_mode));

  gst_pad_set_event_function (dlbuf->sinkpad,

      GST_DEBUG_FUNCPTR (gst_download_buffer_handle_sink_event));

  gst_pad_set_query_function (dlbuf->sinkpad,

      GST_DEBUG_FUNCPTR (gst_download_buffer_handle_sink_query));

  GST_PAD_SET_PROXY_CAPS (dlbuf->sinkpad);

  gst_element_add_pad (GST_ELEMENT (dlbuf), dlbuf->sinkpad);

  dlbuf->srcpad = gst_pad_new_from_static_template (&srctemplate, "src");

  gst_pad_set_activatemode_function (dlbuf->srcpad,

      GST_DEBUG_FUNCPTR (gst_download_buffer_src_activate_mode));

  gst_pad_set_getrange_function (dlbuf->srcpad,

      GST_DEBUG_FUNCPTR (gst_download_buffer_get_range));

  gst_pad_set_event_function (dlbuf->srcpad,

      GST_DEBUG_FUNCPTR (gst_download_buffer_handle_src_event));

  gst_pad_set_query_function (dlbuf->srcpad,

      GST_DEBUG_FUNCPTR (gst_download_buffer_handle_src_query));

  GST_PAD_SET_PROXY_CAPS (dlbuf->srcpad);

  gst_element_add_pad (GST_ELEMENT (dlbuf), dlbuf->srcpad);

  /* levels */

  GST_DOWNLOAD_BUFFER_CLEAR_LEVEL (dlbuf->cur_level);

  dlbuf->max_level.bytes = DEFAULT_MAX_SIZE_BYTES;

  dlbuf->max_level.time = DEFAULT_MAX_SIZE_TIME;

  dlbuf->low_percent = DEFAULT_LOW_PERCENT;

  dlbuf->high_percent = DEFAULT_HIGH_PERCENT;

  dlbuf->srcresult = GST_FLOW_FLUSHING;

  dlbuf->sinkresult = GST_FLOW_FLUSHING;

  dlbuf->in_timer = g_timer_new ();

  dlbuf->out_timer = g_timer_new ();

  g_mutex_init (&dlbuf->qlock);

  dlbuf->waiting_add = FALSE;

  g_cond_init (&dlbuf->item_add);

  /* tempfile related */

  dlbuf->temp_template = NULL;

  dlbuf->temp_location = NULL;

  dlbuf->temp_remove = DEFAULT_TEMP_REMOVE;

}

/* called only once, as opposed to dispose */

static void

gst_download_buffer_finalize (GObject * object)

{

  GstDownloadBuffer *dlbuf = GST_DOWNLOAD_BUFFER (object);

  g_mutex_clear (&dlbuf->qlock);

  g_cond_clear (&dlbuf->item_add);

  g_timer_destroy (dlbuf->in_timer);

  g_timer_destroy (dlbuf->out_timer);

  /* temp_file path cleanup  */

  g_free (dlbuf->temp_template);

  g_free (dlbuf->temp_location);

  G_OBJECT_CLASS (parent_class)->finalize (object);

}

static void

reset_positions (GstDownloadBuffer * dlbuf)

{

  dlbuf->write_pos = 0;

  dlbuf->read_pos = 0;

  dlbuf->filling = TRUE;

  dlbuf->buffering_percent = 0;

  dlbuf->is_buffering = TRUE;

  dlbuf->seeking = FALSE;

  GST_DOWNLOAD_BUFFER_CLEAR_LEVEL (dlbuf->cur_level);

}

static void

reset_rate_timer (GstDownloadBuffer * dlbuf)

{

  dlbuf->bytes_in = 0;

  dlbuf->bytes_out = 0;

  dlbuf->byte_in_rate = 0.0;

  dlbuf->byte_in_period = 0;

  dlbuf->byte_out_rate = 0.0;

  dlbuf->last_in_elapsed = 0.0;

  dlbuf->last_out_elapsed = 0.0;

  dlbuf->in_timer_started = FALSE;

  dlbuf->out_timer_started = FALSE;

}

/* the interval in seconds to recalculate the rate */

#define RATE_INTERVAL    0.2

/* Tuning for rate estimation. We use a large window for the input rate because

 * it should be stable when connected to a network. The output rate is less

 * stable (the elements preroll, queues behind a demuxer fill, ...) and should

 * therefore adapt more quickly.

 * However, initial input rate may be subject to a burst, and should therefore

 * initially also adapt more quickly to changes, and only later on give higher

 * weight to previous values. */

#define AVG_IN(avg,val,w1,w2)  ((avg) * (w1) + (val) * (w2)) / ((w1) + (w2))

#define AVG_OUT(avg,val) ((avg) * 3.0 + (val)) / 4.0

static void

update_levels (GstDownloadBuffer * dlbuf, guint bytes)

{

  dlbuf->cur_level.bytes = bytes;

  if (dlbuf->byte_in_rate > 0.0) {

    dlbuf->cur_level.time =

        dlbuf->cur_level.bytes / dlbuf->byte_in_rate * GST_SECOND;

  }

  GST_DEBUG ("levels: bytes %u/%u, time %" GST_TIME_FORMAT "/%" GST_TIME_FORMAT,

      dlbuf->cur_level.bytes, dlbuf->max_level.bytes,

      GST_TIME_ARGS (dlbuf->cur_level.time),

      GST_TIME_ARGS (dlbuf->max_level.time));

}

static void

update_in_rates (GstDownloadBuffer * dlbuf)

{

  gdouble elapsed, period;

  gdouble byte_in_rate;

  if (!dlbuf->in_timer_started) {

    dlbuf->in_timer_started = TRUE;

    g_timer_start (dlbuf->in_timer);

    return;

  }

  elapsed = g_timer_elapsed (dlbuf->in_timer, NULL);

  /* recalc after each interval. */

  if (dlbuf->last_in_elapsed + RATE_INTERVAL < elapsed) {

    period = elapsed - dlbuf->last_in_elapsed;

    GST_DEBUG_OBJECT (dlbuf,

        "rates: period %f, in %" G_GUINT64_FORMAT ", global period %f",

        period, dlbuf->bytes_in, dlbuf->byte_in_period);

    byte_in_rate = dlbuf->bytes_in / period;

    if (dlbuf->byte_in_rate == 0.0)

      dlbuf->byte_in_rate = byte_in_rate;

    else

      dlbuf->byte_in_rate = AVG_IN (dlbuf->byte_in_rate, byte_in_rate,

          (double) dlbuf->byte_in_period, period);

    /* another data point, cap at 16 for long time running average */

    if (dlbuf->byte_in_period < 16 * RATE_INTERVAL)

      dlbuf->byte_in_period += period;

    /* reset the values to calculate rate over the next interval */

    dlbuf->last_in_elapsed = elapsed;

    dlbuf->bytes_in = 0;

    GST_DEBUG_OBJECT (dlbuf, "rates: in %f", dlbuf->byte_in_rate);

  }

}

static void

update_out_rates (GstDownloadBuffer * dlbuf)

{

  gdouble elapsed, period;

  gdouble byte_out_rate;

  if (!dlbuf->out_timer_started) {

    dlbuf->out_timer_started = TRUE;

    g_timer_start (dlbuf->out_timer);

    return;

  }

  elapsed = g_timer_elapsed (dlbuf->out_timer, NULL);

  /* recalc after each interval. */

  if (dlbuf->last_out_elapsed + RATE_INTERVAL < elapsed) {

    period = elapsed - dlbuf->last_out_elapsed;

    GST_DEBUG_OBJECT (dlbuf,

        "rates: period %f, out %" G_GUINT64_FORMAT, period, dlbuf->bytes_out);

    byte_out_rate = dlbuf->bytes_out / period;

    if (dlbuf->byte_out_rate == 0.0)

      dlbuf->byte_out_rate = byte_out_rate;

    else

      dlbuf->byte_out_rate = AVG_OUT (dlbuf->byte_out_rate, byte_out_rate);

    /* reset the values to calculate rate over the next interval */

    dlbuf->last_out_elapsed = elapsed;

    dlbuf->bytes_out = 0;

    GST_DEBUG_OBJECT (dlbuf, "rates: out %f", dlbuf->byte_out_rate);

  }

}

static gboolean

get_buffering_percent (GstDownloadBuffer * dlbuf, gboolean * is_buffering,

    gint * percent)

{

  gint perc;

  if (dlbuf->high_percent <= 0) {

    if (percent)

      *percent = 100;

    if (is_buffering)

      *is_buffering = FALSE;

    return FALSE;

  }

  /* Ensure the variables used to calculate buffering state are up-to-date. */

  update_in_rates (dlbuf);

  update_out_rates (dlbuf);

  /* figure out the percent we are filled, we take the max of all formats. */

  if (dlbuf->max_level.bytes > 0) {

    if (dlbuf->cur_level.bytes >= dlbuf->max_level.bytes)

      perc = 100;

    else

      perc = dlbuf->cur_level.bytes * 100 / dlbuf->max_level.bytes;

  } else

    perc = 0;

  if (dlbuf->max_level.time > 0) {

    if (dlbuf->cur_level.time >= dlbuf->max_level.time)

      perc = 100;

    else

      perc = MAX (perc, dlbuf->cur_level.time * 100 / dlbuf->max_level.time);

  } else

    perc = MAX (0, perc);

  if (is_buffering)

    *is_buffering = dlbuf->is_buffering;

  /* scale to high percent so that it becomes the 100% mark */

  perc = perc * 100 / dlbuf->high_percent;

  /* clip */

  if (perc > 100)

    perc = 100;

  if (percent)

    *percent = perc;

  GST_DEBUG_OBJECT (dlbuf, "buffering %d, percent %d", dlbuf->is_buffering,

      perc);

  return TRUE;

}

static void

get_buffering_stats (GstDownloadBuffer * dlbuf, gint percent,

    GstBufferingMode * mode, gint * avg_in, gint * avg_out,

    gint64 * buffering_left)

{

  if (mode)

    *mode = GST_BUFFERING_DOWNLOAD;

  if (avg_in)

    *avg_in = dlbuf->byte_in_rate;

  if (avg_out)

    *avg_out = dlbuf->byte_out_rate;

  if (buffering_left) {

    guint64 max, cur;

    *buffering_left = (percent == 100 ? 0 : -1);

    max = dlbuf->max_level.time;

    cur = dlbuf->cur_level.time;

    if (percent != 100 && max > cur)

      *buffering_left = (max - cur) / 1000000;

  }

}

static GstMessage *

update_buffering (GstDownloadBuffer * dlbuf)

{

  gint percent;

  gboolean post = FALSE;

  GstMessage *message = NULL;

  if (!get_buffering_percent (dlbuf, NULL, &percent))

    return NULL;

  if (dlbuf->is_buffering) {

    post = TRUE;

    /* if we were buffering see if we reached the high watermark */

    if (percent >= dlbuf->high_percent)

      dlbuf->is_buffering = FALSE;

  } else {

    /* we were not buffering, check if we need to start buffering if we drop

     * below the low threshold */

    if (percent < dlbuf->low_percent) {

      dlbuf->is_buffering = TRUE;

      post = TRUE;

    }

  }

  if (post) {

    if (percent == dlbuf->buffering_percent)

      post = FALSE;

    else

      dlbuf->buffering_percent = percent;

  }

  if (post) {

    GstBufferingMode mode;

    gint avg_in, avg_out;

    gint64 buffering_left;

    get_buffering_stats (dlbuf, percent, &mode, &avg_in, &avg_out,

        &buffering_left);

    message = gst_message_new_buffering (GST_OBJECT_CAST (dlbuf),

        (gint) percent);

    gst_message_set_buffering_stats (message, mode,

        avg_in, avg_out, buffering_left);

  }

  return message;

}

static gboolean

perform_seek_to_offset (GstDownloadBuffer * dlbuf, guint64 offset)

{

  GstEvent *event;

  gboolean res;

  if (dlbuf->seeking)

    return TRUE;

  /* until we receive the FLUSH_STOP from this seek, we skip data */

  dlbuf->seeking = TRUE;

  dlbuf->write_pos = offset;

  dlbuf->filling = FALSE;

  GST_DOWNLOAD_BUFFER_MUTEX_UNLOCK (dlbuf);

  GST_DEBUG_OBJECT (dlbuf, "Seeking to %" G_GUINT64_FORMAT, offset);

  event =

      gst_event_new_seek (1.0, GST_FORMAT_BYTES,

      GST_SEEK_FLAG_FLUSH | GST_SEEK_FLAG_ACCURATE, GST_SEEK_TYPE_SET, offset,

      GST_SEEK_TYPE_NONE, -1);

  res = gst_pad_push_event (dlbuf->sinkpad, event);

  GST_DOWNLOAD_BUFFER_MUTEX_LOCK (dlbuf);

  return res;

}

/* get the threshold for when we decide to seek rather than wait */

static guint64

get_seek_threshold (GstDownloadBuffer * dlbuf)

{

  guint64 threshold;

  /* FIXME, find a good threshold based on the incoming rate. */

  threshold = 1024 * 512;

  return threshold;

}

/* called with DOWNLOAD_BUFFER_MUTEX */

static void

gst_download_buffer_update_upstream_size (GstDownloadBuffer * dlbuf)

{

  gint64 upstream_size = 0;

  if (gst_pad_peer_query_duration (dlbuf->sinkpad, GST_FORMAT_BYTES,

          &upstream_size)) {

    GST_INFO_OBJECT (dlbuf, "upstream size: %" G_GINT64_FORMAT, upstream_size);

    dlbuf->upstream_size = upstream_size;

  }

}

/* called with DOWNLOAD_BUFFER_MUTEX */

static GstFlowReturn

gst_download_buffer_wait_for_data (GstDownloadBuffer * dlbuf, guint64 offset,

    guint length)

{

  gsize start, stop;

  guint64 wanted;

  gboolean started;

  GST_DEBUG_OBJECT (dlbuf, "wait for %" G_GUINT64_FORMAT ", length %u",

      offset, length);

  wanted = offset + length;

  /* pause the timer while we wait. The fact that we are waiting does not mean

   * the byterate on the output pad is lower */

  if ((started = dlbuf->out_timer_started))

    g_timer_stop (dlbuf->out_timer);

  /* check range before us */

  if (gst_sparse_file_get_range_before (dlbuf->file, offset, &start, &stop)) {

    GST_DEBUG_OBJECT (dlbuf,

        "range before %" G_GSIZE_FORMAT " - %" G_GSIZE_FORMAT, start, stop);

    if (start <= offset && offset < stop) {

      GST_DEBUG_OBJECT (dlbuf, "we have the offset");

      /* we have the range, continue it */

      offset = stop;

    } else {

      guint64 threshold, dist;

      /* there is a range before us, check how far away it is */

      threshold = get_seek_threshold (dlbuf);

      dist = offset - stop;

      if (dist <= threshold) {

        GST_DEBUG_OBJECT (dlbuf, "not too far");

        /* not far away, continue it */

        offset = stop;

      }

    }

  }

  if (dlbuf->write_pos != offset)

    perform_seek_to_offset (dlbuf, offset);

  dlbuf->filling = TRUE;

  if (dlbuf->write_pos > dlbuf->read_pos)

    update_levels (dlbuf, dlbuf->write_pos - dlbuf->read_pos);

  else

    update_levels (dlbuf, 0);

  /* now wait for more data */

  GST_DEBUG_OBJECT (dlbuf, "waiting for more data");

  GST_DOWNLOAD_BUFFER_WAIT_ADD_CHECK (dlbuf, dlbuf->srcresult, wanted,

      out_flushing);

  GST_DEBUG_OBJECT (dlbuf, "got more data");

  /* and continue if we were running before */

  if (started)

    g_timer_continue (dlbuf->out_timer);

  return GST_FLOW_OK;

out_flushing:

  {

    GST_DEBUG_OBJECT (dlbuf, "we are flushing");

    return GST_FLOW_FLUSHING;

  }

}

/* called with DOWNLOAD_BUFFER_MUTEX */

static gboolean

check_upstream_size (GstDownloadBuffer * dlbuf, gsize offset, guint * length)

{

  gsize stop = offset + *length;

  /* catch any reads beyond the size of the file here to make sure cache

   * doesn't send seek events beyond the size of the file upstream, since

   * that would confuse elements such as souphttpsrc and/or http servers.

   * Demuxers often just loop until EOS at the end of the file to figure out

   * when they've read all the end-headers or index chunks. */

  if (G_UNLIKELY (dlbuf->upstream_size == -1 || stop >= dlbuf->upstream_size)) {

    gst_download_buffer_update_upstream_size (dlbuf);

  }

  if (dlbuf->upstream_size != -1) {

    if (offset >= dlbuf->upstream_size)

      return FALSE;

    if (G_UNLIKELY (stop > dlbuf->upstream_size)) {

      *length = dlbuf->upstream_size - offset;

      GST_DEBUG_OBJECT (dlbuf, "adjusting length downto %u", *length);

    }

  }

  return TRUE;

}

/* called with DOWNLOAD_BUFFER_MUTEX */

static GstFlowReturn

gst_download_buffer_read_buffer (GstDownloadBuffer * dlbuf, guint64 offset,

    guint length, GstBuffer ** buffer)

{

  GstBuffer *buf;

  GstMapInfo info;

  GstFlowReturn ret = GST_FLOW_OK;

  gsize res, remaining;

  GError *error = NULL;

  length = (length == -1) ? DEFAULT_BUFFER_SIZE : length;

  offset = (offset == -1) ? dlbuf->read_pos : offset;

  if (!check_upstream_size (dlbuf, offset, &length))

    goto hit_eos;

  /* allocate the output buffer of the requested size */

  if (*buffer == NULL)

    buf = gst_buffer_new_allocate (NULL, length, NULL);

  else

    buf = *buffer;

  if (!gst_buffer_map (buf, &info, GST_MAP_WRITE))

    goto map_failed;

  GST_DEBUG_OBJECT (dlbuf, "Reading %u bytes from %" G_GUINT64_FORMAT, length,

      offset);

  dlbuf->read_pos = offset;

  do {

    res =

        gst_sparse_file_read (dlbuf->file, offset, info.data, length,

        &remaining, &error);

    if (G_UNLIKELY (res == 0)) {

      switch (error->code) {

        case GST_SPARSE_FILE_IO_ERROR_WOULD_BLOCK:

          /* we don't have the requested data in the file, decide what to

           * do next. */

          ret = gst_download_buffer_wait_for_data (dlbuf, offset, length);

          if (ret != GST_FLOW_OK)

            goto out_flushing;

          break;

        default:

          goto read_error;

      }

      g_clear_error (&error);

    }

  } while (res == 0);

  gst_buffer_unmap (buf, &info;;

  gst_buffer_resize (buf, 0, res);

  dlbuf->bytes_out += res;

  dlbuf->read_pos += res;

  GST_DEBUG_OBJECT (dlbuf,

      "Read %" G_GSIZE_FORMAT " bytes, remaining %" G_GSIZE_FORMAT, res,

      remaining);

  if (dlbuf->read_pos + remaining == dlbuf->upstream_size)

    update_levels (dlbuf, dlbuf->max_level.bytes);

  else

    update_levels (dlbuf, remaining);

  GST_BUFFER_OFFSET (buf) = offset;

  GST_BUFFER_OFFSET_END (buf) = offset + res;

  *buffer = buf;

  return ret;

  /* ERRORS */

hit_eos:

  {

    GST_DEBUG_OBJECT (dlbuf, "EOS hit");

    return GST_FLOW_EOS;

  }

map_failed:

  {

    GST_ELEMENT_ERROR (dlbuf, RESOURCE, BUSY,

        (_("Failed to map buffer.")), ("failed to map buffer in WRITE mode"));

    if (*buffer == NULL)

      gst_buffer_unref (buf);

    return GST_FLOW_ERROR;

  }

out_flushing:

  {

    GST_DEBUG_OBJECT (dlbuf, "we are flushing");

    g_clear_error (&error);

    gst_buffer_unmap (buf, &info;;

    if (*buffer == NULL)

      gst_buffer_unref (buf);

    return GST_FLOW_FLUSHING;

  }

read_error:

  {

    GST_DEBUG_OBJECT (dlbuf, "we have a read error: %s", error->message);

    g_clear_error (&error);

    gst_buffer_unmap (buf, &info;;

    if (*buffer == NULL)

      gst_buffer_unref (buf);

    return ret;

  }

}

/* must be called with MUTEX_LOCK. Will briefly release the lock when notifying

 * the temp filename. */

static gboolean

gst_download_buffer_open_temp_location_file (GstDownloadBuffer * dlbuf)

{

  gint fd = -1;

  gchar *name = NULL;

  if (dlbuf->file)

    goto already_opened;

  GST_DEBUG_OBJECT (dlbuf, "opening temp file %s", dlbuf->temp_template);

  /* If temp_template was set, allocate a filename and open that file */