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// Copyright 2018 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "src/math-random.h"
#include "src/assert-scope.h"
#include "src/base/utils/random-number-generator.h"
#include "src/contexts-inl.h"
#include "src/isolate.h"
#include "src/objects/fixed-array.h"
#include "src/objects/smi.h"
namespace v8 {
namespace internal {
void MathRandom::InitializeContext(Isolate* isolate,
Handle<Context> native_context) {
Handle<FixedDoubleArray> cache = Handle<FixedDoubleArray>::cast(
isolate->factory()->NewFixedDoubleArray(kCacheSize, TENURED));
for (int i = 0; i < kCacheSize; i++) cache->set(i, 0);
native_context->set_math_random_cache(*cache);
Handle<PodArray<State>> pod = PodArray<State>::New(isolate, 1, TENURED);
native_context->set_math_random_state(*pod);
ResetContext(*native_context);
}
void MathRandom::ResetContext(Context native_context) {
native_context->set_math_random_index(Smi::zero());
State state = {0, 0};
PodArray<State>::cast(native_context->math_random_state())->set(0, state);
}
Address MathRandom::RefillCache(Isolate* isolate, Address raw_native_context) {
Context native_context = Context::cast(Object(raw_native_context));
DisallowHeapAllocation no_gc;
PodArray<State> pod =
PodArray<State>::cast(native_context->math_random_state());
State state = pod->get(0);
// Initialize state if not yet initialized. If a fixed random seed was
// requested, use it to reset our state the first time a script asks for
// random numbers in this context. This ensures the script sees a consistent
// sequence.
if (state.s0 == 0 && state.s1 == 0) {
uint64_t seed;
if (FLAG_random_seed != 0) {
seed = FLAG_random_seed;
} else {
isolate->random_number_generator()->NextBytes(&seed, sizeof(seed));
}
state.s0 = base::RandomNumberGenerator::MurmurHash3(seed);
state.s1 = base::RandomNumberGenerator::MurmurHash3(~seed);
CHECK(state.s0 != 0 || state.s1 != 0);
}
FixedDoubleArray cache =
FixedDoubleArray::cast(native_context->math_random_cache());
// Create random numbers.
for (int i = 0; i < kCacheSize; i++) {
// Generate random numbers using xorshift128+.
base::RandomNumberGenerator::XorShift128(&state.s0, &state.s1);
cache->set(i, base::RandomNumberGenerator::ToDouble(state.s0));
}
pod->set(0, state);
Smi new_index = Smi::FromInt(kCacheSize);
native_context->set_math_random_index(new_index);
return new_index.ptr();
}
} // namespace internal
} // namespace v8
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