// Copyright 2014 the V8 project authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#include "src/runtime/runtime-utils.h"
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#include "src/arguments.h"
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#include "src/base/utils/random-number-generator.h"
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#include "src/bootstrapper.h"
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#include "src/counters.h"
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#include "src/double.h"
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#include "src/objects-inl.h"
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namespace v8 {
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namespace internal {
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RUNTIME_FUNCTION(Runtime_GenerateRandomNumbers) {
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HandleScope scope(isolate);
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DCHECK_EQ(0, args.length());
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Handle<Context> native_context = isolate->native_context();
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DCHECK_EQ(0, native_context->math_random_index()->value());
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static const int kCacheSize = 64;
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static const int kState0Offset = kCacheSize - 1;
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static const int kState1Offset = kState0Offset - 1;
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// The index is decremented before used to access the cache.
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static const int kInitialIndex = kState1Offset;
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Handle<FixedDoubleArray> cache;
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uint64_t state0 = 0;
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uint64_t state1 = 0;
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if (native_context->math_random_cache()->IsFixedDoubleArray()) {
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cache = Handle<FixedDoubleArray>(
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FixedDoubleArray::cast(native_context->math_random_cache()), isolate);
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state0 = double_to_uint64(cache->get_scalar(kState0Offset));
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state1 = double_to_uint64(cache->get_scalar(kState1Offset));
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} else {
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cache = Handle<FixedDoubleArray>::cast(
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isolate->factory()->NewFixedDoubleArray(kCacheSize, TENURED));
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native_context->set_math_random_cache(*cache);
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// Initialize state if not yet initialized. If a fixed random seed was
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// requested, use it to reset our state the first time a script asks for
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// random numbers in this context. This ensures the script sees a consistent
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// sequence.
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if (FLAG_random_seed != 0) {
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state0 = FLAG_random_seed;
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state1 = FLAG_random_seed;
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} else {
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while (state0 == 0 || state1 == 0) {
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isolate->random_number_generator()->NextBytes(&state0, sizeof(state0));
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isolate->random_number_generator()->NextBytes(&state1, sizeof(state1));
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}
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}
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}
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DisallowHeapAllocation no_gc;
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FixedDoubleArray* raw_cache = *cache;
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// Create random numbers.
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for (int i = 0; i < kInitialIndex; i++) {
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// Generate random numbers using xorshift128+.
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base::RandomNumberGenerator::XorShift128(&state0, &state1);
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raw_cache->set(i, base::RandomNumberGenerator::ToDouble(state0, state1));
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}
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// Persist current state.
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raw_cache->set(kState0Offset, uint64_to_double(state0));
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raw_cache->set(kState1Offset, uint64_to_double(state1));
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return Smi::FromInt(kInitialIndex);
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}
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} // namespace internal
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} // namespace v8
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