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 =
      20             :       Handle<FixedDoubleArray>::cast(isolate->factory()->NewFixedDoubleArray(
      21         111 :           kCacheSize, AllocationType::kOld));
      22       14319 :   for (int i = 0; i < kCacheSize; i++) cache->set(i, 0);
      23         111 :   native_context->set_math_random_cache(*cache);
      24             :   Handle<PodArray<State>> pod =
      25             :       PodArray<State>::New(isolate, 1, AllocationType::kOld);
      26         222 :   native_context->set_math_random_state(*pod);
      27         111 :   ResetContext(*native_context);
      28         111 : }
      29             : 
      30         352 : void MathRandom::ResetContext(Context native_context) {
      31         352 :   native_context->set_math_random_index(Smi::zero());
      32         352 :   State state = {0, 0};
      33         704 :   PodArray<State>::cast(native_context->math_random_state())->set(0, state);
      34         352 : }
      35             : 
      36       60697 : Address MathRandom::RefillCache(Isolate* isolate, Address raw_native_context) {
      37       60697 :   Context native_context = Context::cast(Object(raw_native_context));
      38             :   DisallowHeapAllocation no_gc;
      39             :   PodArray<State> pod =
      40       60697 :       PodArray<State>::cast(native_context->math_random_state());
      41       60697 :   State state = pod->get(0);
      42             :   // Initialize state if not yet initialized. If a fixed random seed was
      43             :   // requested, use it to reset our state the first time a script asks for
      44             :   // random numbers in this context. This ensures the script sees a consistent
      45             :   // sequence.
      46       60697 :   if (state.s0 == 0 && state.s1 == 0) {
      47             :     uint64_t seed;
      48         183 :     if (FLAG_random_seed != 0) {
      49         183 :       seed = FLAG_random_seed;
      50             :     } else {
      51           0 :       isolate->random_number_generator()->NextBytes(&seed, sizeof(seed));
      52             :     }
      53         183 :     state.s0 = base::RandomNumberGenerator::MurmurHash3(seed);
      54         183 :     state.s1 = base::RandomNumberGenerator::MurmurHash3(~seed);
      55         183 :     CHECK(state.s0 != 0 || state.s1 != 0);
      56             :   }
      57             : 
      58             :   FixedDoubleArray cache =
      59       60697 :       FixedDoubleArray::cast(native_context->math_random_cache());
      60             :   // Create random numbers.
      61     7829913 :   for (int i = 0; i < kCacheSize; i++) {
      62             :     // Generate random numbers using xorshift128+.
      63             :     base::RandomNumberGenerator::XorShift128(&state.s0, &state.s1);
      64     3884608 :     cache->set(i, base::RandomNumberGenerator::ToDouble(state.s0));
      65             :   }
      66             :   pod->set(0, state);
      67             : 
      68             :   Smi new_index = Smi::FromInt(kCacheSize);
      69       60697 :   native_context->set_math_random_index(new_index);
      70       60697 :   return new_index.ptr();
      71             : }
      72             : 
      73             : }  // namespace internal
      74      122036 : }  // namespace v8