Adds a modified copy of talk/base to webrtc/base. It is the first step in migrating talk/base to webrtc/base.

BUG=N/A
R=andrew@webrtc.org, wu@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/12199004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@6107 4adac7df-926f-26a2-2b94-8c16560cd09d

webrtc/base/ratelimiter.h

@@ -0,0 +1,63 @@
+/*
+ *  Copyright 2012 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef WEBRTC_BASE_RATELIMITER_H_
+#define WEBRTC_BASE_RATELIMITER_H_
+
+#include <stdlib.h>
+#include "webrtc/base/basictypes.h"
+
+namespace rtc {
+
+// Limits the rate of use to a certain maximum quantity per period of
+// time.  Use, for example, for simple bandwidth throttling.
+//
+// It's implemented like a diet plan: You have so many calories per
+// day.  If you hit the limit, you can't eat any more until the next
+// day.
+class RateLimiter {
+ public:
+  // For example, 100kb per second.
+  RateLimiter(size_t max, double period)
+      : max_per_period_(max),
+        period_length_(period),
+        used_in_period_(0),
+        period_start_(0.0),
+        period_end_(period) {
+  }
+  virtual ~RateLimiter() {}
+
+  // Returns true if if the desired quantity is available in the
+  // current period (< (max - used)).  Once the given time passes the
+  // end of the period, used is set to zero and more use is available.
+  bool CanUse(size_t desired, double time);
+  // Increment the quantity used this period.  If past the end of a
+  // period, a new period is started.
+  void Use(size_t used, double time);
+
+  size_t used_in_period() const {
+    return used_in_period_;
+  }
+
+  size_t max_per_period() const {
+    return max_per_period_;
+  }
+
+ private:
+  size_t max_per_period_;
+  double period_length_;
+  size_t used_in_period_;
+  double period_start_;
+  double period_end_;
+};
+
+}  // namespace rtc
+
+#endif  // WEBRTC_BASE_RATELIMITER_H_