gstreamer/sys/shm/gstshmsink.c

/* GStreamer
 * Copyright (C) <2009> Collabora Ltd
 *  @author: Olivier Crete <olivier.crete@collabora.co.uk
 * Copyright (C) <2009> Nokia Inc
 *
 * 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-shmsink
 *
 * Send data over shared memory to the matching source.
 *
 * <refsect2>
 * <title>Example launch lines</title>
 * |[
 * gst-launch-1.0 -v videotestsrc !  shmsink socket-path=/tmp/blah shm-size=1000000
 * ]| Send video to shm buffers.
 * </refsect2>
 */
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include "gstshmsink.h"

#include <gst/gst.h>

#include <string.h>

/* signals */
enum
{
  SIGNAL_CLIENT_CONNECTED,
  SIGNAL_CLIENT_DISCONNECTED,
  LAST_SIGNAL
};

/* properties */
enum
{
  PROP_0,
  PROP_SOCKET_PATH,
  PROP_PERMS,
  PROP_SHM_SIZE,
  PROP_WAIT_FOR_CONNECTION,
  PROP_BUFFER_TIME
};

struct GstShmClient
{
  ShmClient *client;
  GstPollFD pollfd;
};

#define DEFAULT_SIZE ( 64 * 1024 * 1024 )
#define DEFAULT_WAIT_FOR_CONNECTION (TRUE)
/* Default is user read/write, group read */
#define DEFAULT_PERMS ( S_IRUSR | S_IWUSR | S_IRGRP )


GST_DEBUG_CATEGORY_STATIC (shmsink_debug);
#define GST_CAT_DEFAULT shmsink_debug

static GstStaticPadTemplate sinktemplate = GST_STATIC_PAD_TEMPLATE ("sink",
    GST_PAD_SINK,
    GST_PAD_ALWAYS,
    GST_STATIC_CAPS_ANY);

#define gst_shm_sink_parent_class parent_class
G_DEFINE_TYPE (GstShmSink, gst_shm_sink, GST_TYPE_BASE_SINK);

static void gst_shm_sink_finalize (GObject * object);
static void gst_shm_sink_set_property (GObject * object, guint prop_id,
    const GValue * value, GParamSpec * pspec);
static void gst_shm_sink_get_property (GObject * object, guint prop_id,
    GValue * value, GParamSpec * pspec);

static gboolean gst_shm_sink_start (GstBaseSink * bsink);
static gboolean gst_shm_sink_stop (GstBaseSink * bsink);
static GstFlowReturn gst_shm_sink_render (GstBaseSink * bsink, GstBuffer * buf);

static gboolean gst_shm_sink_event (GstBaseSink * bsink, GstEvent * event);
static gboolean gst_shm_sink_unlock (GstBaseSink * bsink);
static gboolean gst_shm_sink_unlock_stop (GstBaseSink * bsink);
static gboolean gst_shm_sink_propose_allocation (GstBaseSink * sink,
    GstQuery * query);

static gpointer pollthread_func (gpointer data);

static guint signals[LAST_SIGNAL] = { 0 };



/********************
 * CUSTOM ALLOCATOR *
 ********************/

#define GST_TYPE_SHM_SINK_ALLOCATOR \
  (gst_shm_sink_allocator_get_type())
#define GST_SHM_SINK_ALLOCATOR(obj) \
  (G_TYPE_CHECK_INSTANCE_CAST((obj),GST_TYPE_SHM_SINK_ALLOCATOR, \
      GstShmSinkAllocator))
#define GST_SHM_SINK_ALLOCATOR_CLASS(klass) \
  (G_TYPE_CHECK_CLASS_CAST((klass),GST_TYPE_SHM_SINK_ALLOCATOR, \
      GstShmSinkAllocatorClass))
#define GST_IS_SHM_SINK_ALLOCATOR(obj) \
  (G_TYPE_CHECK_INSTANCE_TYPE((obj),GST_TYPE_SHM_SINK_ALLOCATOR))
#define GST_IS_SHM_SINK_ALLOCATOR_CLASS(klass) \
  (G_TYPE_CHECK_CLASS_TYPE((klass),GST_TYPE_SHM_SINK_ALLOCATOR))

struct _GstShmSinkAllocator
{
  GstAllocator parent;

  GstShmSink *sink;
};

typedef struct _GstShmSinkAllocatorClass
{
  GstAllocatorClass parent;
} GstShmSinkAllocatorClass;

typedef struct _GstShmSinkMemory
{
  GstMemory mem;

  gchar *data;
  GstShmSink *sink;
  ShmBlock *block;
} GstShmSinkMemory;

GType gst_shm_sink_allocator_get_type (void);

G_DEFINE_TYPE (GstShmSinkAllocator, gst_shm_sink_allocator, GST_TYPE_ALLOCATOR);

static void
gst_shm_sink_allocator_dispose (GObject * object)
{
  GstShmSinkAllocator *self = GST_SHM_SINK_ALLOCATOR (object);

  if (self->sink)
    gst_object_unref (self->sink);
  self->sink = NULL;

  G_OBJECT_CLASS (gst_shm_sink_allocator_parent_class)->dispose (object);
}

static void
gst_shm_sink_allocator_free (GstAllocator * allocator, GstMemory * mem)
{
  GstShmSinkMemory *mymem = (GstShmSinkMemory *) mem;

  if (mymem->block) {
    GST_OBJECT_LOCK (mymem->sink);
    sp_writer_free_block (mymem->block);
    GST_OBJECT_UNLOCK (mymem->sink);
    gst_object_unref (mymem->sink);
  }
  gst_object_unref (mem->allocator);

  g_slice_free (GstShmSinkMemory, mymem);
}

static gpointer
gst_shm_sink_allocator_mem_map (GstMemory * mem, gsize maxsize,
    GstMapFlags flags)
{
  GstShmSinkMemory *mymem = (GstShmSinkMemory *) mem;

  return mymem->data;
}

static void
gst_shm_sink_allocator_mem_unmap (GstMemory * mem)
{
}

static GstMemory *
gst_shm_sink_allocator_mem_share (GstMemory * mem, gssize offset, gssize size)
{
  GstShmSinkMemory *mymem = (GstShmSinkMemory *) mem;
  GstShmSinkMemory *mysub;
  GstMemory *parent;

  /* find the real parent */
  if ((parent = mem->parent) == NULL)
    parent = mem;

  if (size == -1)
    size = mem->size - offset;

  mysub = g_slice_new0 (GstShmSinkMemory);
  /* the shared memory is always readonly */
  gst_memory_init (GST_MEMORY_CAST (mysub), GST_MINI_OBJECT_FLAGS (parent) |
      GST_MINI_OBJECT_FLAG_LOCK_READONLY, gst_object_ref (mem->allocator),
      parent, mem->maxsize, mem->align, mem->offset + offset, size);
  mysub->data = mymem->data;

  return (GstMemory *) mysub;
}

static gboolean
gst_shm_sink_allocator_mem_is_span (GstMemory * mem1, GstMemory * mem2,
    gsize * offset)
{
  GstShmSinkMemory *mymem1 = (GstShmSinkMemory *) mem1;
  GstShmSinkMemory *mymem2 = (GstShmSinkMemory *) mem2;

  if (offset) {
    GstMemory *parent;

    parent = mem1->parent;

    *offset = mem1->offset - parent->offset;
  }

  /* and memory is contiguous */
  return mymem1->data + mem1->offset + mem1->size ==
      mymem2->data + mem2->offset;
}

static void
gst_shm_sink_allocator_init (GstShmSinkAllocator * self)
{
  GstAllocator *allocator = GST_ALLOCATOR (self);

  allocator->mem_map = gst_shm_sink_allocator_mem_map;
  allocator->mem_unmap = gst_shm_sink_allocator_mem_unmap;
  allocator->mem_share = gst_shm_sink_allocator_mem_share;
  allocator->mem_is_span = gst_shm_sink_allocator_mem_is_span;
}


static GstMemory *
gst_shm_sink_allocator_alloc_locked (GstShmSinkAllocator * self, gsize size,
    GstAllocationParams * params)
{
  GstMemory *memory = NULL;
  ShmBlock *block = NULL;
  gsize maxsize = size + params->prefix + params->padding;
  gsize align = params->align;

  /* ensure configured alignment */
  align |= gst_memory_alignment;
  /* allocate more to compensate for alignment */
  maxsize += align;

  block = sp_writer_alloc_block (self->sink->pipe, maxsize);
  if (block) {
    GstShmSinkMemory *mymem;
    gsize aoffset, padding;

    GST_LOG_OBJECT (self,
        "Allocated block %p with %" G_GSIZE_FORMAT " bytes at %p", block, size,
        sp_writer_block_get_buf (block));

    mymem = g_slice_new0 (GstShmSinkMemory);
    memory = GST_MEMORY_CAST (mymem);
    mymem->data = sp_writer_block_get_buf (block);
    mymem->sink = gst_object_ref (self->sink);
    mymem->block = block;

    /* do alignment */
    if ((aoffset = ((guintptr) mymem->data & align))) {
      aoffset = (align + 1) - aoffset;
      mymem->data += aoffset;
      maxsize -= aoffset;
    }

    if (params->prefix && (params->flags & GST_MEMORY_FLAG_ZERO_PREFIXED))
      memset (mymem->data, 0, params->prefix);

    padding = maxsize - (params->prefix + size);
    if (padding && (params->flags & GST_MEMORY_FLAG_ZERO_PADDED))
      memset (mymem->data + params->prefix + size, 0, padding);

    gst_memory_init (memory, params->flags, g_object_ref (self), NULL,
        maxsize, align, params->prefix, size);
  }

  return memory;
}

static GstMemory *
gst_shm_sink_allocator_alloc (GstAllocator * allocator, gsize size,
    GstAllocationParams * params)
{
  GstShmSinkAllocator *self = GST_SHM_SINK_ALLOCATOR (allocator);
  GstMemory *memory = NULL;

  GST_OBJECT_LOCK (self->sink);
  memory = gst_shm_sink_allocator_alloc_locked (self, size, params);
  GST_OBJECT_UNLOCK (self->sink);

  if (!memory) {
    memory = gst_allocator_alloc (NULL, size, params);
    GST_LOG_OBJECT (self,
        "Not enough shared memory for GstMemory of %" G_GSIZE_FORMAT
        "bytes, allocating using standard allocator", size);
  }

  return memory;
}


static void
gst_shm_sink_allocator_class_init (GstShmSinkAllocatorClass * klass)
{
  GstAllocatorClass *allocator_class = GST_ALLOCATOR_CLASS (klass);
  GObjectClass *object_class = G_OBJECT_CLASS (klass);

  allocator_class->alloc = gst_shm_sink_allocator_alloc;
  allocator_class->free = gst_shm_sink_allocator_free;
  object_class->dispose = gst_shm_sink_allocator_dispose;
}

static GstShmSinkAllocator *
gst_shm_sink_allocator_new (GstShmSink * sink)
{
  GstShmSinkAllocator *self = g_object_new (GST_TYPE_SHM_SINK_ALLOCATOR, NULL);

  self->sink = gst_object_ref (sink);

  return self;
}


/***************
 * MAIN OBJECT *
 ***************/

static void
gst_shm_sink_init (GstShmSink * self)
{
  g_cond_init (&self->cond);
  self->size = DEFAULT_SIZE;
  self->wait_for_connection = DEFAULT_WAIT_FOR_CONNECTION;
  self->perms = DEFAULT_PERMS;

  gst_allocation_params_init (&self->params);
}

static void
gst_shm_sink_class_init (GstShmSinkClass * klass)
{
  GObjectClass *gobject_class;
  GstElementClass *gstelement_class;
  GstBaseSinkClass *gstbasesink_class;

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

  gobject_class->finalize = gst_shm_sink_finalize;
  gobject_class->set_property = gst_shm_sink_set_property;
  gobject_class->get_property = gst_shm_sink_get_property;

  gstbasesink_class->start = GST_DEBUG_FUNCPTR (gst_shm_sink_start);
  gstbasesink_class->stop = GST_DEBUG_FUNCPTR (gst_shm_sink_stop);
  gstbasesink_class->render = GST_DEBUG_FUNCPTR (gst_shm_sink_render);
  gstbasesink_class->event = GST_DEBUG_FUNCPTR (gst_shm_sink_event);
  gstbasesink_class->unlock = GST_DEBUG_FUNCPTR (gst_shm_sink_unlock);
  gstbasesink_class->unlock_stop = GST_DEBUG_FUNCPTR (gst_shm_sink_unlock_stop);
  gstbasesink_class->propose_allocation =
      GST_DEBUG_FUNCPTR (gst_shm_sink_propose_allocation);

  g_object_class_install_property (gobject_class, PROP_SOCKET_PATH,
      g_param_spec_string ("socket-path",
          "Path to the control socket",
          "The path to the control socket used to control the shared memory "
          "transport. This may be modified during the NULL->READY transition",
          NULL, G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));

  g_object_class_install_property (gobject_class, PROP_PERMS,
      g_param_spec_uint ("perms",
          "Permissions on the shm area",
          "Permissions to set on the shm area",
          0, 07777, DEFAULT_PERMS, G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));

  g_object_class_install_property (gobject_class, PROP_SHM_SIZE,
      g_param_spec_uint ("shm-size",
          "Size of the shm area",
          "Size of the shared memory area",
          0, G_MAXUINT, DEFAULT_SIZE,
          G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));

  g_object_class_install_property (gobject_class, PROP_WAIT_FOR_CONNECTION,
      g_param_spec_boolean ("wait-for-connection",
          "Wait for a connection until rendering",
          "Block the stream until the shm pipe is connected",
          DEFAULT_WAIT_FOR_CONNECTION,
          G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));

  g_object_class_install_property (gobject_class, PROP_BUFFER_TIME,
      g_param_spec_int64 ("buffer-time",
          "Buffer Time of the shm buffer",
          "Maximum Size of the shm buffer in nanoseconds (-1 to disable)",
          -1, G_MAXINT64, -1,
          G_PARAM_CONSTRUCT | G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));

  signals[SIGNAL_CLIENT_CONNECTED] = g_signal_new ("client-connected",
      GST_TYPE_SHM_SINK, G_SIGNAL_RUN_LAST, 0, NULL, NULL,
      g_cclosure_marshal_VOID__INT, G_TYPE_NONE, 1, G_TYPE_INT);

  signals[SIGNAL_CLIENT_DISCONNECTED] = g_signal_new ("client-disconnected",
      GST_TYPE_SHM_SINK, G_SIGNAL_RUN_LAST, 0, NULL, NULL,
      g_cclosure_marshal_VOID__INT, G_TYPE_NONE, 1, G_TYPE_INT);

  gst_element_class_add_pad_template (gstelement_class,
      gst_static_pad_template_get (&sinktemplate));

  gst_element_class_set_static_metadata (gstelement_class,
      "Shared Memory Sink",
      "Sink",
      "Send data over shared memory to the matching source",
      "Olivier Crete <olivier.crete@collabora.co.uk>");

  GST_DEBUG_CATEGORY_INIT (shmsink_debug, "shmsink", 0, "Shared Memory Sink");
}

static void
gst_shm_sink_finalize (GObject * object)
{
  GstShmSink *self = GST_SHM_SINK (object);

  g_cond_clear (&self->cond);
  g_free (self->socket_path);

  G_OBJECT_CLASS (parent_class)->finalize (object);
}

/*
 * Set the value of a property for the server sink.
 */
static void
gst_shm_sink_set_property (GObject * object, guint prop_id,
    const GValue * value, GParamSpec * pspec)
{
  GstShmSink *self = GST_SHM_SINK (object);
  int ret = 0;

  switch (prop_id) {
    case PROP_SOCKET_PATH:
      GST_OBJECT_LOCK (object);
      g_free (self->socket_path);
      self->socket_path = g_value_dup_string (value);
      GST_OBJECT_UNLOCK (object);
      break;
    case PROP_PERMS:
      GST_OBJECT_LOCK (object);
      self->perms = g_value_get_uint (value);
      if (self->pipe)
        ret = sp_writer_setperms_shm (self->pipe, self->perms);
      GST_OBJECT_UNLOCK (object);
      if (ret < 0)
        GST_WARNING_OBJECT (object, "Could not set permissions on pipe: %s",
            strerror (ret));
      break;
    case PROP_SHM_SIZE:
      GST_OBJECT_LOCK (object);
      if (self->pipe) {
        if (sp_writer_resize (self->pipe, g_value_get_uint (value)) < 0) {
          /* Swap allocators, so we can know immediately if the memory is
           * ours */
          gst_object_unref (self->allocator);
          self->allocator = gst_shm_sink_allocator_new (self);

          GST_DEBUG_OBJECT (self, "Resized shared memory area from %u to "
              "%u bytes", self->size, g_value_get_uint (value));
        } else {
          GST_WARNING_OBJECT (self, "Could not resize shared memory area from"
              "%u to %u bytes", self->size, g_value_get_uint (value));
        }
      }
      self->size = g_value_get_uint (value);
      GST_OBJECT_UNLOCK (object);
      break;
    case PROP_WAIT_FOR_CONNECTION:
      GST_OBJECT_LOCK (object);
      self->wait_for_connection = g_value_get_boolean (value);
      GST_OBJECT_UNLOCK (object);
      g_cond_broadcast (&self->cond);
      break;
    case PROP_BUFFER_TIME:
      GST_OBJECT_LOCK (object);
      self->buffer_time = g_value_get_int64 (value);
      GST_OBJECT_UNLOCK (object);
      g_cond_broadcast (&self->cond);
      break;
    default:
      break;
  }
}

static void
gst_shm_sink_get_property (GObject * object, guint prop_id,
    GValue * value, GParamSpec * pspec)
{
  GstShmSink *self = GST_SHM_SINK (object);

  GST_OBJECT_LOCK (object);

  switch (prop_id) {
    case PROP_SOCKET_PATH:
      g_value_set_string (value, self->socket_path);
      break;
    case PROP_PERMS:
      g_value_set_uint (value, self->perms);
      break;
    case PROP_SHM_SIZE:
      g_value_set_uint (value, self->size);
      break;
    case PROP_WAIT_FOR_CONNECTION:
      g_value_set_boolean (value, self->wait_for_connection);
      break;
    case PROP_BUFFER_TIME:
      g_value_set_int64 (value, self->buffer_time);
      break;
    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
      break;
  }

  GST_OBJECT_UNLOCK (object);
}



static gboolean
gst_shm_sink_start (GstBaseSink * bsink)
{
  GstShmSink *self = GST_SHM_SINK (bsink);
  GError *err = NULL;

  self->stop = FALSE;

  if (!self->socket_path) {
    GST_ELEMENT_ERROR (self, RESOURCE, OPEN_READ_WRITE,
        ("Could not open socket."), (NULL));
    return FALSE;
  }

  GST_DEBUG_OBJECT (self, "Creating new socket at %s"
      " with shared memory of %d bytes", self->socket_path, self->size);

  self->pipe = sp_writer_create (self->socket_path, self->size, self->perms);

  if (!self->pipe) {
    GST_ELEMENT_ERROR (self, RESOURCE, OPEN_READ_WRITE,
        ("Could not open socket."), (NULL));
    return FALSE;
  }

  sp_set_data (self->pipe, self);
  g_free (self->socket_path);
  self->socket_path = g_strdup (sp_writer_get_path (self->pipe));

  GST_DEBUG ("Created socket at %s", self->socket_path);

  self->poll = gst_poll_new (TRUE);
  gst_poll_fd_init (&self->serverpollfd);
  self->serverpollfd.fd = sp_get_fd (self->pipe);
  gst_poll_add_fd (self->poll, &self->serverpollfd);
  gst_poll_fd_ctl_read (self->poll, &self->serverpollfd, TRUE);

  self->pollthread =
      g_thread_try_new ("gst-shmsink-poll-thread", pollthread_func, self, &err);

  if (!self->pollthread)
    goto thread_error;

  self->allocator = gst_shm_sink_allocator_new (self);

  return TRUE;

thread_error:

  sp_writer_close (self->pipe, NULL, NULL);
  self->pipe = NULL;
  gst_poll_free (self->poll);

  GST_ELEMENT_ERROR (self, CORE, THREAD, ("Could not start thread"),
      ("%s", err->message));
  g_error_free (err);
  return FALSE;
}


static gboolean
gst_shm_sink_stop (GstBaseSink * bsink)
{
  GstShmSink *self = GST_SHM_SINK (bsink);

  self->stop = TRUE;
  gst_poll_set_flushing (self->poll, TRUE);

  if (self->allocator)
    gst_object_unref (self->allocator);
  self->allocator = NULL;

  g_thread_join (self->pollthread);
  self->pollthread = NULL;

  GST_DEBUG_OBJECT (self, "Stopping");

  while (self->clients) {
    struct GstShmClient *client = self->clients->data;
    self->clients = g_list_remove (self->clients, client);
    sp_writer_close_client (self->pipe, client->client,
        (sp_buffer_free_callback) gst_buffer_unref, NULL);
    g_signal_emit (self, signals[SIGNAL_CLIENT_DISCONNECTED], 0,
        client->pollfd.fd);
    g_slice_free (struct GstShmClient, client);
  }

  gst_poll_free (self->poll);
  self->poll = NULL;

  sp_writer_close (self->pipe, NULL, NULL);
  self->pipe = NULL;

  return TRUE;
}

static gboolean
gst_shm_sink_can_render (GstShmSink * self, GstClockTime time)
{
  ShmBuffer *b;

  if (time == GST_CLOCK_TIME_NONE || self->buffer_time == GST_CLOCK_TIME_NONE)
    return TRUE;

  b = sp_writer_get_pending_buffers (self->pipe);
  for (; b != NULL; b = sp_writer_get_next_buffer (b)) {
    GstBuffer *buf = sp_writer_buf_get_tag (b);
    if (GST_CLOCK_DIFF (time, GST_BUFFER_PTS (buf)) > self->buffer_time)
      return FALSE;
  }

  return TRUE;
}

static GstFlowReturn
gst_shm_sink_render (GstBaseSink * bsink, GstBuffer * buf)
{
  GstShmSink *self = GST_SHM_SINK (bsink);
  int rv = 0;
  GstMapInfo map;
  gboolean need_new_memory = FALSE;
  GstFlowReturn ret = GST_FLOW_OK;
  GstMemory *memory = NULL;
  GstBuffer *sendbuf = NULL;

  GST_OBJECT_LOCK (self);
  while (self->wait_for_connection && !self->clients) {
    g_cond_wait (&self->cond, GST_OBJECT_GET_LOCK (self));
    if (self->unlock)
      goto flushing;
  }

  while (!gst_shm_sink_can_render (self, GST_BUFFER_TIMESTAMP (buf))) {
    g_cond_wait (&self->cond, GST_OBJECT_GET_LOCK (self));
    if (self->unlock)
      goto flushing;
  }


  if (gst_buffer_n_memory (buf) > 1) {
    GST_LOG_OBJECT (self, "Buffer %p has %d GstMemory, we only support a single"
        " one, need to do a memcpy", buf, gst_buffer_n_memory (buf));
    need_new_memory = TRUE;
  } else {
    memory = gst_buffer_peek_memory (buf, 0);

    if (memory->allocator != GST_ALLOCATOR (self->allocator)) {
      need_new_memory = TRUE;
      GST_LOG_OBJECT (self, "Memory in buffer %p was not allocated by "
          "%" GST_PTR_FORMAT ", will memcpy", buf, memory->allocator);
    }
  }

  if (need_new_memory) {
    if (gst_buffer_get_size (buf) > sp_writer_get_max_buf_size (self->pipe)) {
      gsize area_size = sp_writer_get_max_buf_size (self->pipe);
      GST_OBJECT_UNLOCK (self);
      GST_ELEMENT_ERROR (self, RESOURCE, NO_SPACE_LEFT,
          ("Shared memory area is too small"),
          ("Shared memory area of size %" G_GSIZE_FORMAT " is smaller than"
              "buffer of size %" G_GSIZE_FORMAT, area_size,
              gst_buffer_get_size (buf)));
      return GST_FLOW_ERROR;
    }

    while ((memory =
            gst_shm_sink_allocator_alloc_locked (self->allocator,
                gst_buffer_get_size (buf), &self->params)) == NULL) {
      g_cond_wait (&self->cond, GST_OBJECT_GET_LOCK (self));
      if (self->unlock)
        goto flushing;
    }

    while (self->wait_for_connection && !self->clients) {
      g_cond_wait (&self->cond, GST_OBJECT_GET_LOCK (self));
      if (self->unlock) {
        GST_OBJECT_UNLOCK (self);
        gst_memory_unref (memory);
        return GST_FLOW_FLUSHING;
      }
    }

    gst_memory_map (memory, &map, GST_MAP_WRITE);
    gst_buffer_extract (buf, 0, map.data, map.size);
    gst_memory_unmap (memory, &map);

    sendbuf = gst_buffer_new ();
    gst_buffer_copy_into (sendbuf, buf, GST_BUFFER_COPY_METADATA, 0, -1);
    gst_buffer_append_memory (sendbuf, memory);
  } else {
    sendbuf = gst_buffer_ref (buf);
  }

  gst_buffer_map (sendbuf, &map, GST_MAP_READ);
  /* Make the memory readonly as of now as we've sent it to the other side
   * We know it's not mapped for writing anywhere as we just mapped it for
   * reading
   */

  rv = sp_writer_send_buf (self->pipe, (char *) map.data, map.size, sendbuf);

  gst_buffer_unmap (sendbuf, &map);

  GST_OBJECT_UNLOCK (self);

  if (rv == 0) {
    GST_DEBUG_OBJECT (self, "No clients connected, unreffing buffer");
    gst_buffer_unref (sendbuf);
  } else if (rv == -1) {
    GST_ELEMENT_ERROR (self, STREAM, FAILED, ("Invalid allocated buffer"),
        ("The shmpipe library rejects our buffer, this is a bug"));
    ret = GST_FLOW_ERROR;
  }

  /* If we allocated our own memory, then unmap it */

  return ret;

flushing:
  GST_OBJECT_UNLOCK (self);
  return GST_FLOW_FLUSHING;
}

static void
free_buffer_locked (GstBuffer * buffer, void *data)
{
  GSList **list = data;

  g_assert (buffer != NULL);

  *list = g_slist_prepend (*list, buffer);
}

static gpointer
pollthread_func (gpointer data)
{
  GstShmSink *self = GST_SHM_SINK (data);
  GList *item;
  GstClockTime timeout = GST_CLOCK_TIME_NONE;

  while (!self->stop) {

    if (gst_poll_wait (self->poll, timeout) < 0)
      return NULL;

    timeout = GST_CLOCK_TIME_NONE;

    if (self->stop)
      return NULL;

    if (gst_poll_fd_has_closed (self->poll, &self->serverpollfd)) {
      GST_ELEMENT_ERROR (self, RESOURCE, READ, ("Failed read from shmsink"),
          ("Control socket has closed"));
      return NULL;
    }

    if (gst_poll_fd_has_error (self->poll, &self->serverpollfd)) {
      GST_ELEMENT_ERROR (self, RESOURCE, READ, ("Failed to read from shmsink"),
          ("Control socket has error"));
      return NULL;
    }

    if (gst_poll_fd_can_read (self->poll, &self->serverpollfd)) {
      ShmClient *client;
      struct GstShmClient *gclient;

      GST_OBJECT_LOCK (self);
      client = sp_writer_accept_client (self->pipe);
      GST_OBJECT_UNLOCK (self);

      if (!client) {
        GST_ELEMENT_ERROR (self, RESOURCE, READ,
            ("Failed to read from shmsink"),
            ("Control socket returns wrong data"));
        return NULL;
      }

      gclient = g_slice_new (struct GstShmClient);
      gclient->client = client;
      gst_poll_fd_init (&gclient->pollfd);
      gclient->pollfd.fd = sp_writer_get_client_fd (client);
      gst_poll_add_fd (self->poll, &gclient->pollfd);
      gst_poll_fd_ctl_read (self->poll, &gclient->pollfd, TRUE);
      self->clients = g_list_prepend (self->clients, gclient);
      g_signal_emit (self, signals[SIGNAL_CLIENT_CONNECTED], 0,
          gclient->pollfd.fd);
      /* we need to call gst_poll_wait before calling gst_poll_* status
         functions on that new descriptor, so restart the loop, so _wait
         will have been called on all elements of self->poll, whether
         they have just been added or not. */
      timeout = 0;
      continue;
    }

  again:
    for (item = self->clients; item; item = item->next) {
      struct GstShmClient *gclient = item->data;

      if (gst_poll_fd_has_closed (self->poll, &gclient->pollfd)) {
        GST_WARNING_OBJECT (self, "One client is gone, closing");
        goto close_client;
      }

      if (gst_poll_fd_has_error (self->poll, &gclient->pollfd)) {
        GST_WARNING_OBJECT (self, "One client fd has error, closing");
        goto close_client;
      }

      if (gst_poll_fd_can_read (self->poll, &gclient->pollfd)) {
        int rv;
        gpointer tag = NULL;

        GST_OBJECT_LOCK (self);
        rv = sp_writer_recv (self->pipe, gclient->client, &tag);
        GST_OBJECT_UNLOCK (self);

        if (rv < 0) {
          GST_WARNING_OBJECT (self, "One client has read error,"
              " closing (retval: %d errno: %d)", rv, errno);
          goto close_client;
        }

        g_assert (rv == 0 || tag == NULL);

        if (rv == 0)
          gst_buffer_unref (tag);
      }
      continue;
    close_client:
      {
        GSList *list = NULL;
        GST_OBJECT_LOCK (self);
        sp_writer_close_client (self->pipe, gclient->client,
            (sp_buffer_free_callback) free_buffer_locked, (void **) &list);
        GST_OBJECT_UNLOCK (self);
        g_slist_free_full (list, (GDestroyNotify) gst_buffer_unref);
      }

      gst_poll_remove_fd (self->poll, &gclient->pollfd);
      self->clients = g_list_remove (self->clients, gclient);

      g_signal_emit (self, signals[SIGNAL_CLIENT_DISCONNECTED], 0,
          gclient->pollfd.fd);
      g_slice_free (struct GstShmClient, gclient);

      goto again;
    }

    g_cond_broadcast (&self->cond);
  }

  return NULL;
}

static gboolean
gst_shm_sink_event (GstBaseSink * bsink, GstEvent * event)
{
  GstShmSink *self = GST_SHM_SINK (bsink);

  switch (GST_EVENT_TYPE (event)) {
    case GST_EVENT_EOS:
      GST_OBJECT_LOCK (self);
      while (self->wait_for_connection && sp_writer_pending_writes (self->pipe)
          && !self->unlock)
        g_cond_wait (&self->cond, GST_OBJECT_GET_LOCK (self));
      GST_OBJECT_UNLOCK (self);
      break;
    default:
      break;
  }

  return GST_BASE_SINK_CLASS (parent_class)->event (bsink, event);
}


static gboolean
gst_shm_sink_unlock (GstBaseSink * bsink)
{
  GstShmSink *self = GST_SHM_SINK (bsink);

  GST_OBJECT_LOCK (self);
  self->unlock = TRUE;
  GST_OBJECT_UNLOCK (self);

  g_cond_broadcast (&self->cond);
  return TRUE;
}

static gboolean
gst_shm_sink_unlock_stop (GstBaseSink * bsink)
{
  GstShmSink *self = GST_SHM_SINK (bsink);

  GST_OBJECT_LOCK (self);
  self->unlock = FALSE;
  GST_OBJECT_UNLOCK (self);

  return TRUE;
}

static gboolean
gst_shm_sink_propose_allocation (GstBaseSink * sink, GstQuery * query)
{
  GstShmSink *self = GST_SHM_SINK (sink);

  if (self->allocator)
    gst_query_add_allocation_param (query, GST_ALLOCATOR (self->allocator),
        NULL);

  return TRUE;
}