| // Copyright (c) 2012, the Dart project authors. Please see the AUTHORS file |
| // for details. All rights reserved. Use of this source code is governed by a |
| // BSD-style license that can be found in the LICENSE file. |
| |
| #include "vm/random.h" |
| |
| #include "platform/assert.h" |
| #include "vm/isolate.h" |
| |
| namespace dart { |
| |
| // LSFR step with a period of 31-bits. |
| // Based on http://en.wikipedia.org/wiki/Linear_feedback_shift_register |
| static int32_t LinearFeedbackShiftRegisterStep(int32_t seed) { |
| return (seed >> 1) ^ ((-(seed & 1)) & (1 << 30 | 1 << 27)); |
| } |
| |
| |
| int32_t Random::RandomInt32() { |
| Isolate* isolate = Isolate::Current(); |
| ASSERT(isolate != NULL); |
| int32_t result = isolate->random_seed(); |
| int32_t new_random_seed = LinearFeedbackShiftRegisterStep(result); |
| isolate->set_random_seed(new_random_seed); |
| return result; |
| } |
| |
| } // namespace dart |
