adapter: add support for 0 sized buffers

Add support for 0 sized buffers. This is interesting in combination with the
timestamp functions.

Fixes #629553

2 files changed, 112 insertions, 31 deletions

diff --git a/libs/gst/base/gstadapter.c b/libs/gst/base/gstadapter.c
index 33574981bf..e956948e28 100644
--- a/libs/gst/base/gstadapter.c
+++ b/libs/gst/base/gstadapter.c
@@ -271,10 +271,13 @@ copy_into_unchecked (GstAdapter * adapter, guint8 * dest, guint skip,
   while (size > 0) {
     g = g_slist_next (g);
     buf = g->data;
-    csize = MIN (GST_BUFFER_SIZE (buf), size);
-    memcpy (dest, GST_BUFFER_DATA (buf), csize);
-    size -= csize;
-    dest += csize;
+    bsize = GST_BUFFER_SIZE (buf);
+    if (G_LIKELY (bsize > 0)) {
+      csize = MIN (bsize, size);
+      memcpy (dest, GST_BUFFER_DATA (buf), csize);
+      size -= csize;
+      dest += csize;
+    }
   }
 }
 
@@ -285,8 +288,6 @@ copy_into_unchecked (GstAdapter * adapter, guint8 * dest, guint skip,
  *
  * Adds the data from @buf to the data stored inside @adapter and takes
  * ownership of the buffer.
- * Empty buffers will be automatically dereferenced and not stored in the
- * @adapter.
  */
 void
 gst_adapter_push (GstAdapter * adapter, GstBuffer * buf)
@@ -297,27 +298,19 @@ gst_adapter_push (GstAdapter * adapter, GstBuffer * buf)
   g_return_if_fail (GST_IS_BUFFER (buf));
 
   size = GST_BUFFER_SIZE (buf);
+  adapter->size += size;
 
-  if (G_UNLIKELY (size == 0)) {
-    /* we can't have empty buffers, several parts in this file rely on it, this
-     * has some problems for the timestamp tracking. */
-    GST_LOG_OBJECT (adapter, "discarding empty buffer");
-    gst_buffer_unref (buf);
+  /* Note: merging buffers at this point is premature. */
+  if (G_UNLIKELY (adapter->buflist == NULL)) {
+    GST_LOG_OBJECT (adapter, "pushing first %u bytes", size);
+    adapter->buflist = adapter->buflist_end = g_slist_append (NULL, buf);
+    update_timestamp (adapter, buf);
   } else {
-    adapter->size += size;
-
-    /* Note: merging buffers at this point is premature. */
-    if (G_UNLIKELY (adapter->buflist == NULL)) {
-      GST_LOG_OBJECT (adapter, "pushing first %u bytes", size);
-      adapter->buflist = adapter->buflist_end = g_slist_append (NULL, buf);
-      update_timestamp (adapter, buf);
-    } else {
-      /* Otherwise append to the end, and advance our end pointer */
-      GST_LOG_OBJECT (adapter, "pushing %u bytes at end, size now %u", size,
-          adapter->size);
-      adapter->buflist_end = g_slist_append (adapter->buflist_end, buf);
-      adapter->buflist_end = g_slist_next (adapter->buflist_end);
-    }
+    /* Otherwise append to the end, and advance our end pointer */
+    GST_LOG_OBJECT (adapter, "pushing %u bytes at end, size now %u", size,
+        adapter->size);
+    adapter->buflist_end = g_slist_append (adapter->buflist_end, buf);
+    adapter->buflist_end = g_slist_next (adapter->buflist_end);
   }
 }
 
@@ -711,22 +704,29 @@ gst_adapter_available (GstAdapter * adapter)
 guint
 gst_adapter_available_fast (GstAdapter * adapter)
 {
-  GstBuffer *first;
+  GstBuffer *cur;
   guint size;
+  GSList *g;
 
   g_return_val_if_fail (GST_IS_ADAPTER (adapter), 0);
 
-  /* no buffers, we have no data */
-  if (!adapter->buflist)
+  /* no data */
+  if (adapter->size == 0)
     return 0;
 
   /* some stuff we already assembled */
   if (adapter->assembled_len)
     return adapter->assembled_len;
 
-  /* take the first buffer and its size */
-  first = GST_BUFFER_CAST (adapter->buflist->data);
-  size = GST_BUFFER_SIZE (first);
+  /* take the first non-zero buffer */
+  g = adapter->buflist;
+  while (TRUE) {
+    cur = g->data;
+    size = GST_BUFFER_SIZE (cur);
+    if (size != 0)
+      break;
+    g = g_slist_next (g);
+  }
 
   /* we can quickly get the (remaining) data of the first buffer */
   return size - adapter->skip;
diff --git a/tests/check/libs/adapter.c b/tests/check/libs/adapter.c
index e5a371ead8..0c3ebd3b5e 100644
--- a/tests/check/libs/adapter.c
+++ b/tests/check/libs/adapter.c
@@ -335,6 +335,8 @@ GST_START_TEST (test_timestamp)
   guint avail;
   GstClockTime timestamp;
   guint64 dist;
+  guint8 *data;
+  const guint8 *cdata;
 
   adapter = gst_adapter_new ();
   fail_unless (adapter != NULL);
@@ -448,6 +450,85 @@ GST_START_TEST (test_timestamp)
   fail_unless (timestamp == GST_CLOCK_TIME_NONE);
   fail_unless (dist == 0);
 
+  /* push an empty buffer with timestamp in the adapter */
+  buffer = gst_buffer_new ();
+  GST_BUFFER_TIMESTAMP (buffer) = 2 * GST_SECOND;
+  gst_adapter_push (adapter, buffer);
+  avail = gst_adapter_available (adapter);
+  fail_unless (avail == 0);
+  timestamp = gst_adapter_prev_timestamp (adapter, &dist);
+  fail_unless (timestamp == 2 * GST_SECOND);
+  fail_unless (dist == 0);
+
+  /* push another empty buffer */
+  buffer = gst_buffer_new ();
+  GST_BUFFER_TIMESTAMP (buffer) = 3 * GST_SECOND;
+  gst_adapter_push (adapter, buffer);
+  avail = gst_adapter_available (adapter);
+  fail_unless (avail == 0);
+  timestamp = gst_adapter_prev_timestamp (adapter, &dist);
+  fail_unless (timestamp == 2 * GST_SECOND);
+  fail_unless (dist == 0);
+
+  /* push a buffer with timestamp in the adapter */
+  buffer = gst_buffer_new_and_alloc (100);
+  GST_BUFFER_TIMESTAMP (buffer) = 4 * GST_SECOND;
+  gst_adapter_push (adapter, buffer);
+  avail = gst_adapter_available (adapter);
+  fail_unless (avail == 100);
+  timestamp = gst_adapter_prev_timestamp (adapter, &dist);
+  fail_unless (timestamp == 2 * GST_SECOND);
+  fail_unless (dist == 0);
+
+  gst_adapter_flush (adapter, 1);
+  avail = gst_adapter_available (adapter);
+  fail_unless (avail == 99);
+  timestamp = gst_adapter_prev_timestamp (adapter, &dist);
+  fail_unless (timestamp == 4 * GST_SECOND);
+  fail_unless (dist == 1);
+
+  /* push an empty buffer with timestamp in the adapter */
+  buffer = gst_buffer_new ();
+  GST_BUFFER_TIMESTAMP (buffer) = 5 * GST_SECOND;
+  gst_adapter_push (adapter, buffer);
+  avail = gst_adapter_available (adapter);
+  fail_unless (avail == 99);
+  timestamp = gst_adapter_prev_timestamp (adapter, &dist);
+  fail_unless (timestamp == 4 * GST_SECOND);
+  fail_unless (dist == 1);
+
+  /* push buffer without timestamp */
+  buffer = gst_buffer_new_and_alloc (100);
+  gst_adapter_push (adapter, buffer);
+  avail = gst_adapter_available (adapter);
+  fail_unless (avail == 199);
+  timestamp = gst_adapter_prev_timestamp (adapter, &dist);
+  fail_unless (timestamp == 4 * GST_SECOND);
+  fail_unless (dist == 1);
+
+  /* remove first buffer, timestamp of empty buffer is visible */
+  buffer = gst_adapter_take_buffer (adapter, 99);
+  fail_unless (buffer != NULL);
+  fail_unless (GST_BUFFER_SIZE (buffer) == 99);
+  gst_buffer_unref (buffer);
+  avail = gst_adapter_available (adapter);
+  fail_unless (avail == 100);
+  timestamp = gst_adapter_prev_timestamp (adapter, &dist);
+  fail_unless (timestamp == 5 * GST_SECOND);
+  fail_unless (dist == 0);
+
+  /* remove empty buffer, timestamp still visible */
+  cdata = gst_adapter_peek (adapter, 50);
+  fail_unless (cdata != NULL);
+  data = gst_adapter_take (adapter, 50);
+  fail_unless (data != NULL);
+  g_free (data);
+  avail = gst_adapter_available (adapter);
+  fail_unless (avail == 50);
+  timestamp = gst_adapter_prev_timestamp (adapter, &dist);
+  fail_unless (timestamp == 5 * GST_SECOND);
+  fail_unless (dist == 50);
+
   g_object_unref (adapter);
 }