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Side by Side Diff: runtime/lib/math_patch.dart

Issue 59773007: - Add a per-isolate pseudo random number generator to the (Closed) Base URL: http://dart.googlecode.com/svn/branches/bleeding_edge/dart/
Patch Set: Created 7 years, 1 month ago
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1 // Copyright (c) 2012, the Dart project authors. Please see the AUTHORS file 1 // Copyright (c) 2012, the Dart project authors. Please see the AUTHORS file
2 // for details. All rights reserved. Use of this source code is governed by a 2 // for details. All rights reserved. Use of this source code is governed by a
3 // BSD-style license that can be found in the LICENSE file. 3 // BSD-style license that can be found in the LICENSE file.
4 4
5 import "dart:typed_data"; 5 import "dart:typed_data";
6 6
7 // A VM patch of the dart:math library. 7 // A VM patch of the dart:math library.
8 8
9 // If [x] is an [int] and [exponent] is a non-negative [int], the result is 9 // If [x] is an [int] and [exponent] is a non-negative [int], the result is
10 // an [int], otherwise the result is a [double]. 10 // an [int], otherwise the result is a [double].
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106 106
107 // Implements: 107 // Implements:
108 // var state = ((_A * (_state[kSTATE_LO])) + _state[kSTATE_HI]) & _MASK_64; 108 // var state = ((_A * (_state[kSTATE_LO])) + _state[kSTATE_HI]) & _MASK_64;
109 // _state[kSTATE_LO] = state & _MASK_32; 109 // _state[kSTATE_LO] = state & _MASK_32;
110 // _state[kSTATE_HI] = state >> 32; 110 // _state[kSTATE_HI] = state >> 32;
111 // This is a native to prevent 64-bit operations in Dart, which 111 // This is a native to prevent 64-bit operations in Dart, which
112 // fail with --throw_on_javascript_int_overflow. 112 // fail with --throw_on_javascript_int_overflow.
113 void _nextState() native "Random_nextState"; 113 void _nextState() native "Random_nextState";
114 114
115 int nextInt(int max) { 115 int nextInt(int max) {
116 // TODO(srdjan): Remove the 'limit' check once optimizing comparison of 116 // TODO(srdjan): Remove the 'limit' check once optimizing comparison of
117 // Smi-s with Mint constants. 117 // Smi-s with Mint constants.
118 final limit = 0x3FFFFFFF; 118 final limit = 0x3FFFFFFF;
119 if (max <= 0 || ((max > limit) && (max > _POW2_32))) { 119 if (max <= 0 || ((max > limit) && (max > _POW2_32))) {
120 throw new ArgumentError("max must be positive and < 2^32:" 120 throw new ArgumentError("max must be positive and < 2^32:"
121 " $max"); 121 " $max");
122 } 122 }
123 if ((max & -max) == max) { 123 if ((max & -max) == max) {
124 // Fast case for powers of two. 124 // Fast case for powers of two.
125 _nextState(); 125 _nextState();
126 return _state[kSTATE_LO] & (max - 1); 126 return _state[kSTATE_LO] & (max - 1);
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159 static int _nextSeed() { 159 static int _nextSeed() {
160 if (_prng == null) { 160 if (_prng == null) {
161 // TODO(iposva): Use system to get a random seed. 161 // TODO(iposva): Use system to get a random seed.
162 _prng = new Random(new DateTime.now().millisecondsSinceEpoch); 162 _prng = new Random(new DateTime.now().millisecondsSinceEpoch);
163 } 163 }
164 // Trigger the PRNG once to change the internal state. 164 // Trigger the PRNG once to change the internal state.
165 _prng._nextState(); 165 _prng._nextState();
166 return _prng._state[kSTATE_LO]; 166 return _prng._state[kSTATE_LO];
167 } 167 }
168 } 168 }
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