dgrove@google.com
4c0f559d23
git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@15 260f80e4-7a28-3924-810f-c04153c831b5
29 lines
845 B
C++
29 lines
845 B
C++
// Copyright (c) 2011, the Dart project authors. Please see the AUTHORS file
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// for details. All rights reserved. Use of this source code is governed by a
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// BSD-style license that can be found in the LICENSE file.
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#include "vm/random.h"
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#include "vm/assert.h"
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#include "vm/isolate.h"
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namespace dart {
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// LSFR step with a period of 31-bits.
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// Based on http://en.wikipedia.org/wiki/Linear_feedback_shift_register
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static int32_t LinearFeedbackShiftRegisterStep(int32_t seed) {
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return (seed >> 1) ^ ((-(seed & 1)) & (1 << 30 | 1 << 27));
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}
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int32_t Random::RandomInt32() {
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Isolate* isolate = Isolate::Current();
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ASSERT(isolate != NULL);
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int32_t result = isolate->random_seed();
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int32_t new_random_seed = LinearFeedbackShiftRegisterStep(result);
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isolate->set_random_seed(new_random_seed);
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return result;
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}
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} // namespace dart
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