Line data    Source code

       1             : // Copyright 2018 the V8 project authors. All rights reserved.
       2             : // Use of this source code is governed by a BSD-style license that can be
       3             : // found in the LICENSE file.
       4             : 
       5             : #include "src/math-random.h"
       6             : 
       7             : #include "src/assert-scope.h"
       8             : #include "src/base/utils/random-number-generator.h"
       9             : #include "src/contexts-inl.h"
      10             : #include "src/isolate.h"
      11             : #include "src/objects/fixed-array.h"
      12             : #include "src/objects/smi.h"
      13             : 
      14             : namespace v8 {
      15             : namespace internal {
      16             : 
      17         111 : void MathRandom::InitializeContext(Isolate* isolate,
      18             :                                    Handle<Context> native_context) {
      19             :   Handle<FixedDoubleArray> cache = Handle<FixedDoubleArray>::cast(
      20         111 :       isolate->factory()->NewFixedDoubleArray(kCacheSize, TENURED));
      21        7215 :   for (int i = 0; i < kCacheSize; i++) cache->set(i, 0);
      22         111 :   native_context->set_math_random_cache(*cache);
      23         111 :   Handle<PodArray<State>> pod = PodArray<State>::New(isolate, 1, TENURED);
      24         222 :   native_context->set_math_random_state(*pod);
      25         111 :   ResetContext(*native_context);
      26         111 : }
      27             : 
      28         342 : void MathRandom::ResetContext(Context native_context) {
      29         342 :   native_context->set_math_random_index(Smi::zero());
      30         342 :   State state = {0, 0};
      31         684 :   PodArray<State>::cast(native_context->math_random_state())->set(0, state);
      32         342 : }
      33             : 
      34       62903 : Address MathRandom::RefillCache(Isolate* isolate, Address raw_native_context) {
      35       62903 :   Context native_context = Context::cast(Object(raw_native_context));
      36             :   DisallowHeapAllocation no_gc;
      37             :   PodArray<State> pod =
      38      125806 :       PodArray<State>::cast(native_context->math_random_state());
      39       62903 :   State state = pod->get(0);
      40             :   // Initialize state if not yet initialized. If a fixed random seed was
      41             :   // requested, use it to reset our state the first time a script asks for
      42             :   // random numbers in this context. This ensures the script sees a consistent
      43             :   // sequence.
      44       62903 :   if (state.s0 == 0 && state.s1 == 0) {
      45             :     uint64_t seed;
      46         174 :     if (FLAG_random_seed != 0) {
      47         174 :       seed = FLAG_random_seed;
      48             :     } else {
      49           0 :       isolate->random_number_generator()->NextBytes(&seed, sizeof(seed));
      50             :     }
      51         174 :     state.s0 = base::RandomNumberGenerator::MurmurHash3(seed);
      52         174 :     state.s1 = base::RandomNumberGenerator::MurmurHash3(~seed);
      53         174 :     CHECK(state.s0 != 0 || state.s1 != 0);
      54             :   }
      55             : 
      56             :   FixedDoubleArray cache =
      57      125806 :       FixedDoubleArray::cast(native_context->math_random_cache());
      58             :   // Create random numbers.
      59     4088695 :   for (int i = 0; i < kCacheSize; i++) {
      60             :     // Generate random numbers using xorshift128+.
      61             :     base::RandomNumberGenerator::XorShift128(&state.s0, &state.s1);
      62             :     cache->set(i, base::RandomNumberGenerator::ToDouble(state.s0));
      63             :   }
      64             :   pod->set(0, state);
      65             : 
      66             :   Smi new_index = Smi::FromInt(kCacheSize);
      67       62903 :   native_context->set_math_random_index(new_index);
      68       62903 :   return new_index.ptr();
      69             : }
      70             : 
      71             : }  // namespace internal
      72      183867 : }  // namespace v8