[M120 Migration][VD] Enable direct rendering for TVPlus

[platform/framework/web/chromium-efl.git] / base / rand_util.cc

diff --git a/base/rand_util.cc b/base/rand_util.cc
index 5881ef2..056adc2 100644 (file)
--- a/base/rand_util.cc
+++ b/base/rand_util.cc
@@ -1,4 +1,4 @@
-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Copyright 2011 The Chromium Authors
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
@@ -11,11 +11,18 @@
 #include <algorithm>
 #include <limits>
 
-#include "base/logging.h"
+#include "base/check_op.h"
 #include "base/strings/string_util.h"
+#include "base/time/time.h"
 
 namespace base {
 
+namespace {
+
+bool g_subsampling_enabled = true;
+
+}  // namespace
+
 uint64_t RandUint64() {
   uint64_t number;
   RandBytes(&number, sizeof(number));
@@ -25,7 +32,7 @@ uint64_t RandUint64() {
 int RandInt(int min, int max) {
   DCHECK_LE(min, max);
 
-  uint64_t range = static_cast<uint64_t>(max) - min + 1;
+  uint64_t range = static_cast<uint64_t>(max) - static_cast<uint64_t>(min) + 1;
   // |range| is at most UINT_MAX + 1, so the result of RandGenerator(range)
   // is at most UINT_MAX.  Hence it's safe to cast it from uint64_t to int64_t.
   int result =
@@ -39,20 +46,46 @@ double RandDouble() {
   return BitsToOpenEndedUnitInterval(base::RandUint64());
 }
 
+float RandFloat() {
+  return BitsToOpenEndedUnitIntervalF(base::RandUint64());
+}
+
+TimeDelta RandTimeDelta(TimeDelta start, TimeDelta limit) {
+  // We must have a finite, non-empty, non-reversed interval.
+  CHECK_LT(start, limit);
+  CHECK(!start.is_min());
+  CHECK(!limit.is_max());
+
+  const int64_t range = (limit - start).InMicroseconds();
+  // Because of the `CHECK_LT()` above, range > 0, so this cast is safe.
+  const uint64_t delta_us = base::RandGenerator(static_cast<uint64_t>(range));
+  // ...and because `range` fit in an `int64_t`, so will `delta_us`.
+  return start + Microseconds(static_cast<int64_t>(delta_us));
+}
+
+TimeDelta RandTimeDeltaUpTo(TimeDelta limit) {
+  return RandTimeDelta(TimeDelta(), limit);
+}
+
 double BitsToOpenEndedUnitInterval(uint64_t bits) {
   // We try to get maximum precision by masking out as many bits as will fit
   // in the target type's mantissa, and raising it to an appropriate power to
   // produce output in the range [0, 1).  For IEEE 754 doubles, the mantissa
-  // is expected to accommodate 53 bits.
-
+  // is expected to accommodate 53 bits (including the implied bit).
   static_assert(std::numeric_limits<double>::radix == 2,
                 "otherwise use scalbn");
-  static const int kBits = std::numeric_limits<double>::digits;
-  uint64_t random_bits = bits & ((UINT64_C(1) << kBits) - 1);
-  double result = ldexp(static_cast<double>(random_bits), -1 * kBits);
-  DCHECK_GE(result, 0.0);
-  DCHECK_LT(result, 1.0);
-  return result;
+  constexpr int kBits = std::numeric_limits<double>::digits;
+  return ldexp(bits & ((UINT64_C(1) << kBits) - 1u), -kBits);
+}
+
+float BitsToOpenEndedUnitIntervalF(uint64_t bits) {
+  // We try to get maximum precision by masking out as many bits as will fit
+  // in the target type's mantissa, and raising it to an appropriate power to
+  // produce output in the range [0, 1).  For IEEE 754 floats, the mantissa is
+  // expected to accommodate 12 bits (including the implied bit).
+  static_assert(std::numeric_limits<float>::radix == 2, "otherwise use scalbn");
+  constexpr int kBits = std::numeric_limits<float>::digits;
+  return ldexpf(bits & ((UINT64_C(1) << kBits) - 1u), -kBits);
 }
 
 uint64_t RandGenerator(uint64_t range) {
@@ -79,4 +112,60 @@ std::string RandBytesAsString(size_t length) {
   return result;
 }
 
+InsecureRandomGenerator::InsecureRandomGenerator() {
+  a_ = base::RandUint64();
+  b_ = base::RandUint64();
+}
+
+void InsecureRandomGenerator::ReseedForTesting(uint64_t seed) {
+  a_ = seed;
+  b_ = seed;
+}
+
+uint64_t InsecureRandomGenerator::RandUint64() {
+  // Using XorShift128+, which is simple and widely used. See
+  // https://en.wikipedia.org/wiki/Xorshift#xorshift+ for details.
+  uint64_t t = a_;
+  const uint64_t s = b_;
+
+  a_ = s;
+  t ^= t << 23;
+  t ^= t >> 17;
+  t ^= s ^ (s >> 26);
+  b_ = t;
+
+  return t + s;
+}
+
+uint32_t InsecureRandomGenerator::RandUint32() {
+  // The generator usually returns an uint64_t, truncate it.
+  //
+  // It is noted in this paper (https://arxiv.org/abs/1810.05313) that the
+  // lowest 32 bits fail some statistical tests from the Big Crush
+  // suite. Use the higher ones instead.
+  return this->RandUint64() >> 32;
+}
+
+double InsecureRandomGenerator::RandDouble() {
+  uint64_t x = RandUint64();
+  // From https://vigna.di.unimi.it/xorshift/.
+  // 53 bits of mantissa, hence the "hexadecimal exponent" 1p-53.
+  return (x >> 11) * 0x1.0p-53;
+}
+
+MetricsSubSampler::MetricsSubSampler() = default;
+bool MetricsSubSampler::ShouldSample(double probability) {
+  return !g_subsampling_enabled || generator_.RandDouble() < probability;
+}
+
+MetricsSubSampler::ScopedDisableForTesting::ScopedDisableForTesting() {
+  DCHECK(g_subsampling_enabled);
+  g_subsampling_enabled = false;
+}
+
+MetricsSubSampler::ScopedDisableForTesting::~ScopedDisableForTesting() {
+  DCHECK(!g_subsampling_enabled);
+  g_subsampling_enabled = true;
+}
+
 }  // namespace base