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Issue 25468003: Always use timeGetTime() for TimeTicks::Now() on Windows. (Closed) Base URL: https://v8.googlecode.com/svn/branches/bleeding_edge
Patch Set: REBASE Created 7 years, 2 months ago
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1 // Copyright 2013 the V8 project authors. All rights reserved. 1 // Copyright 2013 the V8 project authors. All rights reserved.
2 // Redistribution and use in source and binary forms, with or without 2 // Redistribution and use in source and binary forms, with or without
3 // modification, are permitted provided that the following conditions are 3 // modification, are permitted provided that the following conditions are
4 // met: 4 // met:
5 // 5 //
6 // * Redistributions of source code must retain the above copyright 6 // * Redistributions of source code must retain the above copyright
7 // notice, this list of conditions and the following disclaimer. 7 // notice, this list of conditions and the following disclaimer.
8 // * Redistributions in binary form must reproduce the above 8 // * Redistributions in binary form must reproduce the above
9 // copyright notice, this list of conditions and the following 9 // copyright notice, this list of conditions and the following
10 // disclaimer in the documentation and/or other materials provided 10 // disclaimer in the documentation and/or other materials provided
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92 92
93 // We cannot assume that random() or rand() were seeded 93 // We cannot assume that random() or rand() were seeded
94 // properly, so instead of relying on random() or rand(), 94 // properly, so instead of relying on random() or rand(),
95 // we just seed our PRNG using timing data as fallback. 95 // we just seed our PRNG using timing data as fallback.
96 // This is weak entropy, but it's sufficient, because 96 // This is weak entropy, but it's sufficient, because
97 // it is the responsibility of the embedder to install 97 // it is the responsibility of the embedder to install
98 // an entropy source using v8::V8::SetEntropySource(), 98 // an entropy source using v8::V8::SetEntropySource(),
99 // which provides reasonable entropy, see: 99 // which provides reasonable entropy, see:
100 // https://code.google.com/p/v8/issues/detail?id=2905 100 // https://code.google.com/p/v8/issues/detail?id=2905
101 int64_t seed = Time::NowFromSystemTime().ToInternalValue() << 24; 101 int64_t seed = Time::NowFromSystemTime().ToInternalValue() << 24;
102 seed ^= TimeTicks::HighResNow().ToInternalValue() << 16; 102 seed ^= TimeTicks::HighResolutionNow().ToInternalValue() << 16;
103 seed ^= TimeTicks::Now().ToInternalValue() << 8; 103 seed ^= TimeTicks::Now().ToInternalValue() << 8;
104 SetSeed(seed); 104 SetSeed(seed);
105 #endif // V8_OS_CYGWIN || V8_OS_WIN 105 #endif // V8_OS_CYGWIN || V8_OS_WIN
106 } 106 }
107 107
108 108
109 int RandomNumberGenerator::NextInt(int max) { 109 int RandomNumberGenerator::NextInt(int max) {
110 ASSERT_LE(0, max); 110 ASSERT_LE(0, max);
111 111
112 // Fast path if max is a power of 2. 112 // Fast path if max is a power of 2.
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144 seed_ = seed; 144 seed_ = seed;
145 return static_cast<int>(seed >> (48 - bits)); 145 return static_cast<int>(seed >> (48 - bits));
146 } 146 }
147 147
148 148
149 void RandomNumberGenerator::SetSeed(int64_t seed) { 149 void RandomNumberGenerator::SetSeed(int64_t seed) {
150 seed_ = (seed ^ kMultiplier) & kMask; 150 seed_ = (seed ^ kMultiplier) & kMask;
151 } 151 }
152 152
153 } } // namespace v8::internal 153 } } // namespace v8::internal
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