| 1 | /*
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| 2 | * Copyright (C) 2009 Apple Inc. All rights reserved.
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| 3 | *
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| 4 | * Redistribution and use in source and binary forms, with or without
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| 5 | * modification, are permitted provided that the following conditions
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| 6 | * are met:
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| 7 | * 1. Redistributions of source code must retain the above copyright
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| 8 | * notice, this list of conditions and the following disclaimer.
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| 9 | * 2. Redistributions in binary form must reproduce the above copyright
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| 10 | * notice, this list of conditions and the following disclaimer in the
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| 11 | * documentation and/or other materials provided with the distribution.
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| 12 | *
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| 13 | * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
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| 14 | * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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| 15 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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| 16 | * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
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| 17 | * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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| 18 | * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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| 19 | * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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| 20 | * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
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| 21 | * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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| 22 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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| 23 | * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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| 24 | *
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| 25 | *
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| 26 | * Copyright (c) 2009 Ian C. Bullard
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| 27 | *
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| 28 | * Permission is hereby granted, free of charge, to any person
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| 29 | * obtaining a copy of this software and associated documentation
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| 30 | * files (the "Software"), to deal in the Software without
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| 31 | * restriction, including without limitation the rights to use,
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| 32 | * copy, modify, merge, publish, distribute, sublicense, and/or sell
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| 33 | * copies of the Software, and to permit persons to whom the
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| 34 | * Software is furnished to do so, subject to the following
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| 35 | * conditions:
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| 36 | *
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| 37 | * The above copyright notice and this permission notice shall be
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| 38 | * included in all copies or substantial portions of the Software.
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| 39 | *
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| 40 | * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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| 41 | * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
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| 42 | * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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| 43 | * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
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| 44 | * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
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| 45 | * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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| 46 | * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
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| 47 | * OTHER DEALINGS IN THE SOFTWARE.
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| 48 | */
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| 49 |
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| 50 | #ifndef WeakRandom_h
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| 51 | #define WeakRandom_h
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| 52 |
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| 53 | #include <limits.h>
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| 54 | #include <wtf/StdLibExtras.h>
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| 55 |
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| 56 | namespace JSC {
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| 57 |
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| 58 | class WeakRandom {
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| 59 | public:
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| 60 | WeakRandom(unsigned seed)
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| 61 | : m_low(seed ^ 0x49616E42)
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| 62 | , m_high(seed)
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| 63 | {
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| 64 | }
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| 65 |
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| 66 | double get()
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| 67 | {
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| 68 | return advance() / (UINT_MAX + 1.0);
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| 69 | }
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| 70 |
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| 71 | private:
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| 72 | unsigned advance()
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| 73 | {
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| 74 | m_high = (m_high << 16) + (m_high >> 16);
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| 75 | m_high += m_low;
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| 76 | m_low += m_high;
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| 77 | return m_high;
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| 78 | }
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| 79 |
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| 80 | unsigned m_low;
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| 81 | unsigned m_high;
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| 82 | };
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| 83 |
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| 84 | } // namespace JSC
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| 85 |
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| 86 | #endif // WeakRandom_h
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