rtpbuffer: optimise payload mapping for buffers with one memory

Micro-optimisation: if the buffer consist of just one memory, we
know we have already mapped that memory to read the headers, so
no need to map it another time to get to the payload data, we
can just set up the payload data details right there and then
and avoid another map call in gst_rtp_buffer_get_payload().
Adds up when receiving RTP-payloaded raw video which can easily
be thousands of packets per frame.

diff --git a/gst-libs/gst/rtp/gstrtpbuffer.c b/gst-libs/gst/rtp/gstrtpbuffer.c
index f479637..fe160ab 100644 (file)
--- a/gst-libs/gst/rtp/gstrtpbuffer.c
+++ b/gst-libs/gst/rtp/gstrtpbuffer.c
@@ -323,12 +323,14 @@ gst_rtp_buffer_map (GstBuffer * buffer, GstMapFlags flags, GstRTPBuffer * rtp)
   guint size;
   gsize bufsize, skip;
   guint idx, length;
+  guint n_mem;
 
   g_return_val_if_fail (GST_IS_BUFFER (buffer), FALSE);
   g_return_val_if_fail (rtp != NULL, FALSE);
   g_return_val_if_fail (rtp->buffer == NULL, FALSE);
 
-  if (gst_buffer_n_memory (buffer) < 1)
+  n_mem = gst_buffer_n_memory (buffer);
+  if (n_mem < 1)
     goto no_memory;
 
   /* map first memory, this should be the header */
@@ -423,10 +425,19 @@ gst_rtp_buffer_map (GstBuffer * buffer, GstMapFlags flags, GstRTPBuffer * rtp)
     goto wrong_padding;
 
   rtp->buffer = buffer;
-  /* we have not yet mapped the payload */
-  rtp->data[2] = NULL;
-  rtp->size[2] = 0;
-  rtp->state = 0;
+
+  if (n_mem == 1) {
+    /* we have mapped the buffer already, so might just as well fill in the
+     * payload pointer and size and avoid another buffer map/unmap later */
+    rtp->data[2] = rtp->map[0].data + header_len;
+    rtp->size[2] = bufsize - header_len - padding;
+  } else {
+    /* we have not yet mapped the payload */
+    rtp->data[2] = NULL;
+    rtp->size[2] = 0;
+  }
+
+  /* rtp->state = 0; *//* unused */
 
   return TRUE;
 
@@ -469,7 +480,7 @@ dump_packet:
     GST_MEMDUMP ("buffer", data, size);
 
     for (i = 0; i < G_N_ELEMENTS (rtp->map); ++i) {
-      if (rtp->data[i] != NULL)
+      if (rtp->map[i].memory != NULL)
         gst_buffer_unmap (buffer, &rtp->map[i]);
     }
     return FALSE;
@@ -491,8 +502,12 @@ gst_rtp_buffer_unmap (GstRTPBuffer * rtp)
   g_return_if_fail (rtp->buffer != NULL);
 
   for (i = 0; i < 4; i++) {
-    if (rtp->data[i])
+    if (rtp->map[i].memory != NULL) {
       gst_buffer_unmap (rtp->buffer, &rtp->map[i]);
+      rtp->map[i].memory = NULL;
+    }
+    rtp->data[i] = NULL;
+    rtp->size[i] = 0;
   }
   rtp->buffer = NULL;
 }