Initial commit of sync engine code to browser/sync....

chrome/browser/sync/util/dbgq.h

+// Copyright (c) 2009 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 CHROME_BROWSER_SYNC_UTIL_DBGQ_H_
+#define CHROME_BROWSER_SYNC_UTIL_DBGQ_H_
+
+#include "base/basictypes.h"  // for COMPILE_ASSERT
+
+// A circular queue that is designed to be easily inspectable in a debugger. It
+// puts the elements into the array in reverse, so you can just look at the i_
+// pointer for a recent history.
+template <typename T, size_t size>
+class DebugQueue {
+  COMPILE_ASSERT(size > 0, DebugQueue_size_must_be_greater_than_zero);
+ public:
+  DebugQueue() : i_(array_) { }
+  void Push(const T& t) {
+    i_ = (array_ == i_ ? array_ + size - 1 : i_ - 1);
+    *i_ = t;
+  }
+ protected:
+  T* i_;  // Points to the newest element in the queue.
+  T array_[size];
+};
+
+#endif  // CHROME_BROWSER_SYNC_UTIL_DBGQ_H_