rtp: Fix extension data support

Allocate header, payload and padding in separate memory blocks in
gst_rtp_buffer_allocate().
don't use part of the payload data as storage for the extension data but store
it in a separate memory block that can be enlarged when needed.
Rework the one and two-byte header extension to make it reserve space for the
extra extension first.
Fix RTP unit test. Don't map the complete buffer or make assumptions on the
memory layout of the underlaying implementation. We can now always add extension
data because we have a separate memory block for it.

gst-libs/gst/rtp/gstrtpbuffer.c

@@ -93,7 +93,8 @@ typedef struct _GstRTPHeader
  * Allocate enough data in @buffer to hold an RTP packet with @csrc_count CSRCs,
  * a payload length of @payload_len and padding of @pad_len.
  * @buffer must be writable and all previous memory in @buffer will be freed.
- * All other RTP header fields will be set to 0/FALSE.
+ * If @pad_len is >0, the padding bit will be set. All other RTP header fields
+ * will be set to 0/FALSE.
  */
 void
 gst_rtp_buffer_allocate_data (GstBuffer * buffer, guint payload_len,
@@ -101,23 +102,26 @@ gst_rtp_buffer_allocate_data (GstBuffer * buffer, guint payload_len,
 {
   GstMapInfo map;
   GstMemory *mem;
-  gsize len;
+  gsize hlen;
 
   g_return_if_fail (csrc_count <= 15);
   g_return_if_fail (GST_IS_BUFFER (buffer));
+  g_return_if_fail (pad_len <= 255);
   g_return_if_fail (gst_buffer_is_writable (buffer));
 
   gst_buffer_remove_all_memory (buffer);
 
-  len = GST_RTP_HEADER_LEN + csrc_count * sizeof (guint32)
+  hlen = GST_RTP_HEADER_LEN + csrc_count * sizeof (guint32);
-      + payload_len + pad_len;
 
-  mem = gst_allocator_alloc (NULL, len, NULL);
+  mem = gst_allocator_alloc (NULL, hlen, NULL);
 
   gst_memory_map (mem, &map, GST_MAP_WRITE);
   /* fill in defaults */
   GST_RTP_HEADER_VERSION (map.data) = GST_RTP_VERSION;
-  GST_RTP_HEADER_PADDING (map.data) = FALSE;
+  if (pad_len)
+    GST_RTP_HEADER_PADDING (map.data) = TRUE;
+  else
+    GST_RTP_HEADER_PADDING (map.data) = FALSE;
   GST_RTP_HEADER_EXTENSION (map.data) = FALSE;
   GST_RTP_HEADER_CSRC_COUNT (map.data) = csrc_count;
   memset (GST_RTP_HEADER_CSRC_LIST_OFFSET (map.data, 0), 0,
@@ -130,6 +134,20 @@ gst_rtp_buffer_allocate_data (GstBuffer * buffer, guint payload_len,
   gst_memory_unmap (mem, &map);
 
   gst_buffer_append_memory (buffer, mem);
+
+  if (payload_len) {
+    mem = gst_allocator_alloc (NULL, payload_len, NULL);
+    gst_buffer_append_memory (buffer, mem);
+  }
+  if (pad_len) {
+    mem = gst_allocator_alloc (NULL, pad_len, NULL);
+
+    gst_memory_map (mem, &map, GST_MAP_WRITE);
+    map.data[pad_len - 1] = pad_len;
+    gst_memory_unmap (mem, &map);
+
+    gst_buffer_append_memory (buffer, mem);
+  }
 }
 
 /**
@@ -656,6 +674,43 @@ gst_rtp_buffer_get_extension_data (GstRTPBuffer * rtp, guint16 * bits,
   return TRUE;
 }
 
+/* ensure header, payload and padding are in separate buffers */
+static void
+ensure_buffers (GstRTPBuffer * rtp)
+{
+  guint i, pos;
+  gsize offset;
+  gboolean changed = FALSE;
+
+  /* make sure payload is mapped */
+  gst_rtp_buffer_get_payload (rtp);
+
+  for (i = 0, pos = 0; i < 4; i++) {
+    if (rtp->size[i]) {
+      offset = rtp->map[i].data - (guint8 *) rtp->data[i];
+
+      if (offset != 0 || rtp->map[i].size != rtp->size[i]) {
+        GstMemory *mem;
+
+        /* make copy */
+        mem = gst_memory_copy (rtp->map[i].memory, offset, rtp->size[i]);
+
+        /* insert new memory */
+        gst_buffer_insert_memory (rtp->buffer, pos, mem);
+
+        changed = TRUE;
+      }
+      pos++;
+    }
+  }
+
+  if (changed) {
+    gst_rtp_buffer_unmap (rtp);
+    gst_buffer_remove_memory_range (rtp->buffer, pos, -1);
+    gst_rtp_buffer_map (rtp->buffer, GST_MAP_READWRITE, rtp);
+  }
+}
+
 /**
  * gst_rtp_buffer_set_extension_data:
  * @rtp: the RTP packet
@@ -664,8 +719,8 @@ gst_rtp_buffer_get_extension_data (GstRTPBuffer * rtp, guint16 * bits,
  * the extension, excluding the extension header ( therefore zero is a valid length)
  *
  * Set the extension bit of the rtp buffer and fill in the @bits and @length of the
- * extension header. It will refuse to set the extension data if the buffer is not
+ * extension header. If the existing extension data is not large enough, it will
- * large enough.
+ * be made larger.
  *
  * Returns: True if done.
  */
@@ -675,16 +730,43 @@ gst_rtp_buffer_set_extension_data (GstRTPBuffer * rtp, guint16 bits,
 {
   guint32 min_size = 0;
   guint8 *data;
+  GstMemory *mem = NULL;
 
-  /* FIXME, we should allocate and map the extension data */
+  ensure_buffers (rtp);
-  data = rtp->data[0];
 
-  /* check if the buffer is big enough to hold the extension */
+  /* this is the size of the extension data we need */
   min_size = 4 + length * sizeof (guint32);
-  if (G_UNLIKELY (min_size > rtp->size[1]))
+
-    goto too_small;
+  /* we should allocate and map the extension data */
+  if (rtp->data[1] == NULL || min_size > rtp->size[1]) {
+    GstMapInfo map;
+
+    /* we don't have (enough) extension data, make some */
+    mem = gst_allocator_alloc (NULL, min_size, NULL);
+
+    if (rtp->data[1]) {
+      /* copy old data */
+      gst_memory_map (mem, &map, GST_MAP_WRITE);
+      memcpy (map.data, rtp->data[1], rtp->size[1]);
+      gst_memory_unmap (mem, &map);
+
+      /* unmap old */
+      gst_buffer_unmap (rtp->buffer, &rtp->map[1]);
+      gst_buffer_replace_memory (rtp->buffer, 1, mem);
+    } else {
+      /* we didn't have extension data, add */
+      gst_buffer_insert_memory (rtp->buffer, 1, mem);
+    }
+
+    /* map new */
+    gst_memory_map (mem, &rtp->map[1], GST_MAP_READWRITE);
+    gst_memory_ref (mem);
+    rtp->data[1] = rtp->map[1].data;
+    rtp->size[1] = rtp->map[1].size;
+  }
 
   /* now we can set the extension bit */
+  data = rtp->data[0];
   GST_RTP_HEADER_EXTENSION (data) = TRUE;
 
   data = rtp->data[1];
@@ -692,15 +774,6 @@ gst_rtp_buffer_set_extension_data (GstRTPBuffer * rtp, guint16 bits,
   GST_WRITE_UINT16_BE (data + 2, length);
 
   return TRUE;
-
-  /* ERRORS */
-too_small:
-  {
-    g_warning
-        ("rtp buffer too small: need more than %d bytes but only have %"
-        G_GSIZE_FORMAT " bytes", min_size, rtp->size[1]);
-    return FALSE;
-  }
 }
 
 /**
@@ -1311,6 +1384,7 @@ gst_rtp_buffer_add_extension_onebyte_header (GstRTPBuffer * rtp, guint8 id,
   guint8 *pdata = 0;
   guint wordlen;
   gboolean has_bit;
+  guint extlen, offset = 0;
 
   g_return_val_if_fail (id > 0 && id < 15, FALSE);
   g_return_val_if_fail (size >= 1 && size <= 16, FALSE);
@@ -1320,51 +1394,30 @@ gst_rtp_buffer_add_extension_onebyte_header (GstRTPBuffer * rtp, guint8 id,
       (gpointer) & pdata, &wordlen);
 
   if (has_bit) {
-    gulong offset = 0;
-    guint8 *nextext;
-    guint extlen;
-
     if (bits != 0xBEDE)
       return FALSE;
 
     offset = get_onebyte_header_end_offset (pdata, wordlen);
     if (offset == 0)
       return FALSE;
-
-    nextext = pdata + offset;
-    offset = nextext - rtp->map[0].data;
-
-    /* Don't add extra header if there isn't enough space */
-    if (rtp->map[0].size < offset + size + 1)
-      return FALSE;
-
-    nextext[0] = (id << 4) | (0x0F & (size - 1));
-    memcpy (nextext + 1, data, size);
-
-    extlen = nextext - pdata + size + 1;
-    if (extlen % 4) {
-      wordlen = extlen / 4 + 1;
-      memset (nextext + size + 1, 0, 4 - extlen % 4);
-    } else {
-      wordlen = extlen / 4;
-    }
-
-    gst_rtp_buffer_set_extension_data (rtp, 0xBEDE, wordlen);
-  } else {
-    wordlen = (size + 1) / 4 + (((size + 1) % 4) ? 1 : 0);
-
-    gst_rtp_buffer_set_extension_data (rtp, 0xBEDE, wordlen);
-
-    gst_rtp_buffer_get_extension_data (rtp, &bits,
-        (gpointer) & pdata, &wordlen);
-
-    pdata[0] = (id << 4) | (0x0F & (size - 1));
-    memcpy (pdata + 1, data, size);
-
-    if ((size + 1) % 4)
-      memset (pdata + size + 1, 0, 4 - ((size + 1) % 4));
   }
 
+  /* the required size of the new extension data */
+  extlen = offset + size + 1;
+  /* calculate amount of words */
+  wordlen = extlen / 4 + ((extlen % 4) ? 1 : 0);
+
+  gst_rtp_buffer_set_extension_data (rtp, 0xBEDE, wordlen);
+  gst_rtp_buffer_get_extension_data (rtp, &bits, (gpointer) & pdata, &wordlen);
+
+  pdata += offset;
+
+  pdata[0] = (id << 4) | (0x0F & (size - 1));
+  memcpy (pdata + 1, data, size);
+
+  if (extlen % 4)
+    memset (pdata + 1 + size, 0, 4 - (extlen % 4));
+
   return TRUE;
 }
 
@@ -1430,6 +1483,8 @@ gst_rtp_buffer_add_extension_twobytes_header (GstRTPBuffer * rtp,
   guint8 *pdata = 0;
   guint wordlen;
   gboolean has_bit;
+  gulong offset = 0;
+  guint extlen;
 
   g_return_val_if_fail ((appbits & 0xF0) == 0, FALSE);
   g_return_val_if_fail (size < 256, FALSE);
@@ -1439,52 +1494,30 @@ gst_rtp_buffer_add_extension_twobytes_header (GstRTPBuffer * rtp,
       (gpointer) & pdata, &wordlen);
 
   if (has_bit) {
-    gulong offset = 0;
-    guint8 *nextext;
-    guint extlen;
-
     if (bits != ((0x100 << 4) | (appbits & 0x0f)))
       return FALSE;
 
     offset = get_twobytes_header_end_offset (pdata, wordlen);
-
+    if (offset == 0)
-    nextext = pdata + offset;
-
-    offset = nextext - rtp->map[0].data;
-
-    /* Don't add extra header if there isn't enough space */
-    if (rtp->map[0].size < offset + size + 2)
       return FALSE;
-
-    nextext[0] = id;
-    nextext[1] = size;
-    memcpy (nextext + 2, data, size);
-
-    extlen = nextext - pdata + size + 2;
-    if (extlen % 4) {
-      wordlen = extlen / 4 + 1;
-      memset (nextext + size + 2, 0, 4 - extlen % 4);
-    } else {
-      wordlen = extlen / 4;
-    }
-
-    gst_rtp_buffer_set_extension_data (rtp, (0x100 << 4) | (appbits & 0x0F),
-        wordlen);
-  } else {
-    wordlen = (size + 2) / 4 + (((size + 2) % 4) ? 1 : 0);
-
-    gst_rtp_buffer_set_extension_data (rtp, (0x100 << 4) | (appbits & 0x0F),
-        wordlen);
-
-    gst_rtp_buffer_get_extension_data (rtp, &bits,
-        (gpointer) & pdata, &wordlen);
-
-    pdata[0] = id;
-    pdata[1] = size;
-    memcpy (pdata + 2, data, size);
-    if ((size + 2) % 4)
-      memset (pdata + size + 2, 0, 4 - ((size + 2) % 4));
   }
 
+  /* the required size of the new extension data */
+  extlen = offset + size + 2;
+  /* calculate amount of words */
+  wordlen = extlen / 4 + ((extlen % 4) ? 1 : 0);
+
+  gst_rtp_buffer_set_extension_data (rtp, (0x100 << 4) | (appbits & 0x0F),
+      wordlen);
+  gst_rtp_buffer_get_extension_data (rtp, &bits, (gpointer) & pdata, &wordlen);
+
+  pdata += offset;
+
+  pdata[0] = id;
+  pdata[1] = size;
+  memcpy (pdata + 2, data, size);
+  if (extlen % 4)
+    memset (pdata + 2 + size, 0, 4 - (extlen % 4));
+
   return TRUE;
 }

tests/check/libs/rtp.c

@@ -50,12 +50,12 @@ GST_START_TEST (test_rtp_buffer)
 
   /* check defaults */
   fail_unless_equals_int (gst_rtp_buffer_get_version (&rtp), 2);
-  fail_unless (gst_rtp_buffer_get_padding (&rtp) == FALSE);
+  fail_unless (gst_rtp_buffer_get_padding (&rtp) == TRUE);
   fail_unless (gst_rtp_buffer_get_extension (&rtp) == FALSE);
   fail_unless_equals_int (gst_rtp_buffer_get_csrc_count (&rtp), 0);
   fail_unless (gst_rtp_buffer_get_marker (&rtp) == FALSE);
   fail_unless (gst_rtp_buffer_get_payload_type (&rtp) == 0);
-  fail_unless_equals_int (GST_READ_UINT16_BE (data), 0x8000);
+  fail_unless_equals_int (GST_READ_UINT16_BE (data), 0xa000);
 
   /* check version in bitfield */
   gst_rtp_buffer_set_version (&rtp, 3);
@@ -224,7 +224,6 @@ GST_END_TEST;
 GST_START_TEST (test_rtp_buffer_set_extension_data)
 {
   GstBuffer *buf;
-  GstMapInfo map;
   guint8 *data;
   guint16 bits;
   guint size;
@@ -235,33 +234,19 @@ GST_START_TEST (test_rtp_buffer_set_extension_data)
 
   /* check GstRTPHeader structure alignment and packing */
   buf = gst_rtp_buffer_new_allocate (4, 0, 0);
-  gst_buffer_map (buf, &map, GST_MAP_READWRITE);
-  data = map.data;
 
   gst_rtp_buffer_map (buf, GST_MAP_READWRITE, &rtp);
 
-  /* should be impossible to set the extension data */
-  ASSERT_WARNING (fail_unless (gst_rtp_buffer_set_extension_data (&rtp, 0,
-              4) == FALSE));
-  fail_unless (gst_rtp_buffer_get_extension (&rtp) == FALSE);
-
   /* should be possible to set the extension data */
-  fail_unless (gst_rtp_buffer_set_extension_data (&rtp, 270, 0) == TRUE);
+  fail_unless (gst_rtp_buffer_set_extension_data (&rtp, 270, 4) == TRUE);
   fail_unless (gst_rtp_buffer_get_extension (&rtp) == TRUE);
   gst_rtp_buffer_get_extension_data (&rtp, &bits, &pointer, &size);
   fail_unless (bits == 270);
-  fail_unless (size == 0);
+  fail_unless (size == 4);
-  fail_unless (pointer == data + 16);
-  pointer = gst_rtp_buffer_get_payload (&rtp);
-  fail_unless (pointer == data + 16);
-
-  gst_buffer_unmap (buf, &map);
   gst_rtp_buffer_unmap (&rtp);
   gst_buffer_unref (buf);
 
   buf = gst_rtp_buffer_new_allocate (20, 0, 0);
-  gst_buffer_map (buf, &map, GST_MAP_READWRITE);
-  data = map.data;
   gst_rtp_buffer_map (buf, GST_MAP_READWRITE, &rtp);
 
   fail_unless (gst_rtp_buffer_get_extension (&rtp) == FALSE);
@@ -270,18 +255,12 @@ GST_START_TEST (test_rtp_buffer_set_extension_data)
   gst_rtp_buffer_get_extension_data (&rtp, &bits, &pointer, &size);
   fail_unless (bits == 333);
   fail_unless (size == 2);
-  fail_unless (pointer == data + 16);
-  pointer = gst_rtp_buffer_get_payload (&rtp);
-  fail_unless (pointer == data + 24);
 
-  gst_buffer_unmap (buf, &map);
   gst_rtp_buffer_unmap (&rtp);
   gst_buffer_unref (buf);
 
   /* Test header extensions with a one byte header */
   buf = gst_rtp_buffer_new_allocate (20, 0, 0);
-  gst_buffer_map (buf, &map, GST_MAP_READWRITE);
-  data = map.data;
   gst_rtp_buffer_map (buf, GST_MAP_READWRITE, &rtp);
 
   fail_unless (gst_rtp_buffer_get_extension (&rtp) == FALSE);
@@ -339,14 +318,11 @@ GST_START_TEST (test_rtp_buffer_set_extension_data)
   fail_unless (size == 2);
   fail_unless (memcmp (pointer, misc_data, 2) == 0);
 
-  gst_buffer_unmap (buf, &map);
   gst_rtp_buffer_unmap (&rtp);
   gst_buffer_unref (buf);
 
   /* Test header extensions with a two bytes header */
   buf = gst_rtp_buffer_new_allocate (20, 0, 0);
-  gst_buffer_map (buf, &map, GST_MAP_READWRITE);
-  data = map.data;
   gst_rtp_buffer_map (buf, GST_MAP_READWRITE, &rtp);
 
   fail_unless (gst_rtp_buffer_get_extension (&rtp) == FALSE);
@@ -405,7 +381,6 @@ GST_START_TEST (test_rtp_buffer_set_extension_data)
   fail_unless (size == 2);
   fail_unless (memcmp (pointer, misc_data, 2) == 0);
 
-  gst_buffer_unmap (buf, &map);
   gst_rtp_buffer_unmap (&rtp);
   gst_buffer_unref (buf);
 }