Smarter algorithm for extending 8-bit frame IDs to 32-bit frame IDs.

media/cast/net/frame_id_wrap_helper_test.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <gtest/gtest.h>
+#include "media/cast/cast_defines.h"
 #include "media/cast/net/cast_transport_defines.h"
 
 namespace media {
 namespace cast {
 
 class FrameIdWrapHelperTest : public ::testing::Test {
  protected:
   FrameIdWrapHelperTest() {}
   virtual ~FrameIdWrapHelperTest() {}
 
@@ skipping 23 matching lines @@
   }
   EXPECT_EQ(254u, new_frame_id);
   new_frame_id = frame_id_wrap_helper_.MapTo32bitsFrameId(0u);
   EXPECT_EQ(256u, new_frame_id);
   new_frame_id = frame_id_wrap_helper_.MapTo32bitsFrameId(255u);
   EXPECT_EQ(255u, new_frame_id);
   new_frame_id = frame_id_wrap_helper_.MapTo32bitsFrameId(1u);
   EXPECT_EQ(257u, new_frame_id);
 }
 
+TEST_F(FrameIdWrapHelperTest, Windowed) {
+  srand(0);

[miu, 2014/08/13 18:38:57]

For the normal, consecutive case, consider adding:

  for (uint32 frame_id = 0; frame_id < 100000; ++frame_id) {
    EXPECT_EQ(...);
  }

and also test wrap-around case:

  for (uint32 frame_id = 0xfffff000; frame_id < 0x00000fff; ++frame_id) {
    EXPECT_EQ(...);
  }

+  const int window_size = 64;
+  uint32 window_base = 0;
+  for (int i = 0; i < 100000; i++) {
+    int offset = rand() % window_size;
+    uint32 frame_id = window_base + offset;
+    uint32 mapped_frame_id =
+        frame_id_wrap_helper_.MapTo32bitsFrameId(frame_id & 0xff);
+    EXPECT_EQ(frame_id, mapped_frame_id);
+    if (frame_id != mapped_frame_id) {
+      break;
+    }
+    window_base += rand() % window_size;
+  }
+}
+
 }  // namespace cast
 }  // namespace media