Simple LRU class

media/blink/test_random.h

+// Copyright 2015 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_BLINK_TEST_RANDOM_H_
+#define MEDIA_BLINK_TEST_RANDOM_H_
+
+// Vastly simplified ACM random class meant to only be used for testing.
+// This class is meant to generate predictable sequences of pseudorandom

[xhwang, 2015/11/10 19:55:13]

Please also mention the "platform independent" part, which is why we can't just
use C rand().

Also, this "platform independent" feature seems generically useful. Shall we try
to add it to rand_util.h?

+// numbers, unlike the classes in base/rand_util.h which are meant to generate
+// unpredictable sequences.
+// See
+// https://code.google.com/p/szl/source/browse/trunk/src/utilities/acmrandom.h
+// for more information.
+
+namespace media {
+
+class TestRandom {
+ public:
+  explicit TestRandom(uint32_t seed) {
+    seed_ = seed & 0x7fffffff;  // make this a non-negative number
+    if (seed_ == 0 || seed_ == M) {
+      seed_ = 1;
+    }
+  }
+
+  int32_t Rand() {
+    static const uint64 A = 16807;  // bits 14, 8, 7, 5, 2, 1, 0
+    seed_ = static_cast<int32_t>((seed_ * A) % M);
+    CHECK_GT(seed_, 0);
+    return seed_;
+  }
+
+ private:
+  static const uint64 M = 2147483647L;  // 2^32-1
+  int32_t seed_;
+};
+
+}  // namespace media
+
+#endif  // MEDIA_BLINK_TEST_RANDOM_H_