77 lines
2.7 KiB
C++
77 lines
2.7 KiB
C++
/*
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Copyright (c) 2009-2010 Christopher A. Taylor. All rights reserved.
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions are met:
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* Redistributions of source code must retain the above copyright notice,
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this list of conditions and the following disclaimer.
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* Redistributions in binary form must reproduce the above copyright notice,
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this list of conditions and the following disclaimer in the documentation
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and/or other materials provided with the distribution.
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* Neither the name of LibCat nor the names of its contributors may be used
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to endorse or promote products derived from this software without
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specific prior written permission.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
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LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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POSSIBILITY OF SUCH DAMAGE.
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*/
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#ifndef CAT_I_RANDOM_HPP
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#define CAT_I_RANDOM_HPP
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#include <cat/Platform.hpp>
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namespace cat {
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// Pseudo-random number generators will derive from IRandom and implement its public methods
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// WARNING: Not seeded by default. Be sure to call Initialize() before Generate()
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class IRandom
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{
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public:
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virtual ~IRandom() {}
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// Generate a 32-bit random number
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virtual u32 Generate() = 0;
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// Generate a variable number of random bytes
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virtual void Generate(void *buffer, int bytes) = 0;
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public:
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// Generate a 32-bit random number in the range [low..high] inclusive
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u32 GenerateUnbiased(u32 low, u32 high)
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{
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u32 range = high - low;
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// Round range up to the next pow(2)-1 using a Stanford Bit Twiddling Hack
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u32 v = range - 1;
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v |= v >> 1;
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v |= v >> 2;
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v |= v >> 4;
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v |= v >> 8;
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v |= v >> 16;
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// Generate an unbiased random number in the inclusive range [0..(high-low)]
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u32 x;
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do x = Generate() & v;
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while (x > range);
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return low + x;
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}
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};
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} // namespace cat
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#endif // CAT_I_RANDOM_HPP
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