Add RandomNumberGenerator adapter to base/rand_util.h

base/rand_util.h

-// Copyright (c) 2008 The Chromium Authors. All rights reserved.
+// Copyright (c) 2010 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 BASE_RAND_UTIL_H_
 #define BASE_RAND_UTIL_H_
 #pragma once
 
 #include "base/basictypes.h"
 
 namespace base {
 
 // Returns a random number in range [0, kuint64max]. Thread-safe.
 uint64 RandUint64();
 
 // Returns a random number between min and max (inclusive). Thread-safe.
 int RandInt(int min, int max);
 
+// Returns a random number in range [0, max).  Thread-safe.
+//
+// Note that this can be used as an adapter for std::random_shuffle():
+// Given a pre-populated |std::vector<int> myvector|, shuffle it as
+//   std::random_shuffle(myvector.begin(), myvector.end(), base::RandGenerator);
+uint64 RandGenerator(uint64 max);

[Paweł Hajdan Jr., 2010/08/30 18:09:02]

I think I'd prefer a RandomShuffle thing. The implementation seems to be small
enough to fit inline in case we need this for template reasons. However, if
Brett wouldn't like it, I'm fine with the current solution.

+
 // Returns a random double in range [0, 1). Thread-safe.
 double RandDouble();
 
 }  // namespace base
 
 #endif  // BASE_RAND_UTIL_H_