1 /*
2  *  Copyright (c) 2012 The WebM project authors. All Rights Reserved.
3  *
4  *  Use of this source code is governed by a BSD-style license
5  *  that can be found in the LICENSE file in the root of the source
6  *  tree. An additional intellectual property rights grant can be found
7  *  in the file PATENTS.  All contributing project authors may
8  *  be found in the AUTHORS file in the root of the source tree.
9  */
10 
11 #ifndef VPX_TEST_ACM_RANDOM_H_
12 #define VPX_TEST_ACM_RANDOM_H_
13 
14 #include <assert.h>
15 
16 #include <limits>
17 
18 #include "third_party/googletest/src/include/gtest/gtest.h"
19 
20 #include "vpx/vpx_integer.h"
21 
22 namespace libvpx_test {
23 
24 class ACMRandom {
25  public:
ACMRandom()26   ACMRandom() : random_(DeterministicSeed()) {}
27 
ACMRandom(int seed)28   explicit ACMRandom(int seed) : random_(seed) {}
29 
Reset(int seed)30   void Reset(int seed) { random_.Reseed(seed); }
Rand16(void)31   uint16_t Rand16(void) {
32     const uint32_t value =
33         random_.Generate(testing::internal::Random::kMaxRange);
34     return (value >> 15) & 0xffff;
35   }
36 
Rand20Signed(void)37   int32_t Rand20Signed(void) {
38     // Use 20 bits: values between 524287 and -524288.
39     const uint32_t value = random_.Generate(1048576);
40     return static_cast<int32_t>(value) - 524288;
41   }
42 
Rand16Signed(void)43   int16_t Rand16Signed(void) {
44     // Use 16 bits: values between 32767 and -32768.
45     return static_cast<int16_t>(random_.Generate(65536));
46   }
47 
Rand13Signed(void)48   int16_t Rand13Signed(void) {
49     // Use 13 bits: values between 4095 and -4096.
50     const uint32_t value = random_.Generate(8192);
51     return static_cast<int16_t>(value) - 4096;
52   }
53 
Rand9Signed(void)54   int16_t Rand9Signed(void) {
55     // Use 9 bits: values between 255 (0x0FF) and -256 (0x100).
56     const uint32_t value = random_.Generate(512);
57     return static_cast<int16_t>(value) - 256;
58   }
59 
Rand8(void)60   uint8_t Rand8(void) {
61     const uint32_t value =
62         random_.Generate(testing::internal::Random::kMaxRange);
63     // There's a bit more entropy in the upper bits of this implementation.
64     return (value >> 23) & 0xff;
65   }
66 
Rand8Extremes(void)67   uint8_t Rand8Extremes(void) {
68     // Returns a random value near 0 or near 255, to better exercise
69     // saturation behavior.
70     const uint8_t r = Rand8();
71     return static_cast<uint8_t>((r < 128) ? r << 4 : r >> 4);
72   }
73 
RandRange(const uint32_t range)74   uint32_t RandRange(const uint32_t range) {
75     // testing::internal::Random::Generate provides values in the range
76     // testing::internal::Random::kMaxRange.
77     assert(range <= testing::internal::Random::kMaxRange);
78     return random_.Generate(range);
79   }
80 
PseudoUniform(int range)81   int PseudoUniform(int range) { return random_.Generate(range); }
82 
operator()83   int operator()(int n) { return PseudoUniform(n); }
84 
DeterministicSeed(void)85   static int DeterministicSeed(void) { return 0xbaba; }
86 
87  private:
88   testing::internal::Random random_;
89 };
90 
91 }  // namespace libvpx_test
92 
93 #endif  // VPX_TEST_ACM_RANDOM_H_
94