Cast:Moving netwrok sender related code to a designated folder

media/cast/net/cast_net_defines.h

+// Copyright 2013 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.
+
+#ifndef MEDIA_CAST_NET_CAST_NET_DEFINES_H_
+#define MEDIA_CAST_NET_CAST_NET_DEFINES_H_
+
+#include "base/basictypes.h"
+
+namespace media {
+namespace cast {
+
+class FrameIdWrapHelper {
+ public:
+  FrameIdWrapHelper()
+      : first_(true),
+        frame_id_wrap_count_(0),
+        range_(kLowRange) {}
+
+  uint32 MapTo32bitsFrameId(const uint8 over_the_wire_frame_id) {
+    if (first_) {
+      first_ = false;
+      if (over_the_wire_frame_id == 0xff) {
+        // Special case for startup.
+        return kStartFrameId;
+      }
+    }
+
+    uint32 wrap_count = frame_id_wrap_count_;
+    switch (range_) {
+      case kLowRange:
+        if (over_the_wire_frame_id > kLowRangeThreshold &&
+            over_the_wire_frame_id < kHighRangeThreshold) {
+          range_ = kMiddleRange;
+        }
+        if (over_the_wire_frame_id > kHighRangeThreshold) {
+          // Wrap count was incremented in High->Low transition, but this frame
+          // is 'old', actually from before the wrap count got incremented.
+          --wrap_count;
+        }
+        break;
+      case kMiddleRange:
+        if (over_the_wire_frame_id > kHighRangeThreshold) {
+          range_ = kHighRange;
+        }
+        break;
+      case kHighRange:
+        if (over_the_wire_frame_id < kLowRangeThreshold) {
+          // Wrap-around detected.
+          range_ = kLowRange;
+          ++frame_id_wrap_count_;
+          // Frame triggering wrap-around so wrap count should be incremented as
+          // as well to match |frame_id_wrap_count_|.
+          ++wrap_count;
+        }
+        break;
+    }
+    return (wrap_count << 8) + over_the_wire_frame_id;
+  }
+
+ private:
+  enum Range {
+    kLowRange,
+    kMiddleRange,
+    kHighRange,
+  };
+
+  static const uint8 kLowRangeThreshold = 0x0f;
+  static const uint8 kHighRangeThreshold = 0xf0;
+  static const uint32 kStartFrameId = GG_UINT32_C(0xffffffff);
+
+  bool first_;
+  uint32 frame_id_wrap_count_;
+  Range range_;
+};
+
+
+}  // namespace cast
+}  // namespace media
+
+#endif  // MEDIA_CAST_NET_CAST_NET_DEFINES_H_