test/acm_random.h

/*
 * Copyright (c) 2016, Alliance for Open Media. All rights reserved
 *
 * This source code is subject to the terms of the BSD 2 Clause License and
 * the Alliance for Open Media Patent License 1.0. If the BSD 2 Clause License
 * was not distributed with this source code in the LICENSE file, you can
 * obtain it at www.aomedia.org/license/software. If the Alliance for Open
 * Media Patent License 1.0 was not distributed with this source code in the
 * PATENTS file, you can obtain it at www.aomedia.org/license/patent.
 */

#ifndef AOM_TEST_ACM_RANDOM_H_
#define AOM_TEST_ACM_RANDOM_H_

#include "third_party/googletest/src/googletest/include/gtest/gtest.h"

#include "aom/aom_integer.h"

namespace libaom_test {

class ACMRandom {
 public:
  ACMRandom() : random_(DeterministicSeed()) {}

  explicit ACMRandom(int seed) : random_(seed) {}

  void Reset(int seed) { random_.Reseed(seed); }

  // Generates a random 31-bit unsigned integer from [0, 2^31).
  uint32_t Rand31() {
    return random_.Generate(testing::internal::Random::kMaxRange);
  }

  uint16_t Rand16() {
    const uint32_t value =
        random_.Generate(testing::internal::Random::kMaxRange);
    // There's a bit more entropy in the upper bits of this implementation.
    return (value >> 15) & 0xffff;
  }

  int16_t Rand16Signed() { return static_cast<int16_t>(Rand16()); }

  int16_t Rand15() {
    const uint32_t value =
        random_.Generate(testing::internal::Random::kMaxRange);
    // There's a bit more entropy in the upper bits of this implementation.
    return (value >> 16) & 0x7fff;
  }

  int16_t Rand15Signed() {
    // Use 15 bits: values between 16383 (0x3FFF) and -16384 (0xC000).
    return static_cast<int16_t>(Rand15()) - (1 << 14);
  }

  uint16_t Rand12() {
    const uint32_t value =
        random_.Generate(testing::internal::Random::kMaxRange);
    // There's a bit more entropy in the upper bits of this implementation.
    return (value >> 19) & 0xfff;
  }

  int16_t Rand9Signed() {
    // Use 9 bits: values between 255 (0x0FF) and -256 (0x100).
    const uint32_t value = random_.Generate(512);
    return static_cast<int16_t>(value) - 256;
  }

  uint8_t Rand8() {
    const uint32_t value =
        random_.Generate(testing::internal::Random::kMaxRange);
    // There's a bit more entropy in the upper bits of this implementation.
    return (value >> 23) & 0xff;
  }

  uint8_t Rand8Extremes() {
    // Returns a random value near 0 or near 255, to better exercise
    // saturation behavior.
    const uint8_t r = Rand8();
    return static_cast<uint8_t>((r < 128) ? r << 4 : r >> 4);
  }

  int PseudoUniform(int range) { return random_.Generate(range); }

  int operator()(int n) { return PseudoUniform(n); }

  static int DeterministicSeed() { return 0xbaba; }

 private:
  testing::internal::Random random_;
};

}  // namespace libaom_test

#endif  // AOM_TEST_ACM_RANDOM_H_