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107 lines
3.6 KiB
107 lines
3.6 KiB
/*-------------------------------------------------------------------------
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* drawElements Base Portability Library
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* -------------------------------------
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*
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* Copyright 2014 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*
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*//*!
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* \file
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* \brief Random number generation.
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*//*--------------------------------------------------------------------*/
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#include "deRandom.h"
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#include <float.h>
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#include <math.h>
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DE_BEGIN_EXTERN_C
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/*--------------------------------------------------------------------*//*!
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* \brief Initialize a random number generator with a given seed.
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* \param rnd RNG to initialize.
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* \param seed Seed value used for random values.
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*//*--------------------------------------------------------------------*/
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void deRandom_init (deRandom* rnd, deUint32 seed)
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{
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rnd->x = (deUint32)(-(int)seed ^ 123456789);
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rnd->y = (deUint32)(362436069 * seed);
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rnd->z = (deUint32)(521288629 ^ (seed >> 7));
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rnd->w = (deUint32)(88675123 ^ (seed << 3));
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}
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/*--------------------------------------------------------------------*//*!
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* \brief Get a pseudo random uint32.
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* \param rnd Pointer to RNG.
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* \return Random uint32 number.
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*//*--------------------------------------------------------------------*/
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deUint32 deRandom_getUint32 (deRandom* rnd)
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{
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deUint32 w = rnd->w;
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deUint32 t;
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t = rnd->x ^ (rnd->x << 11);
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rnd->x = rnd->y;
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rnd->y = rnd->z;
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rnd->z = w;
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rnd->w = w = (w ^ (w >> 19)) ^ (t ^ (t >> 8));
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return w;
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}
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/*--------------------------------------------------------------------*//*!
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* \brief Get a pseudo random uint64.
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* \param rnd Pointer to RNG.
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* \return Random uint64 number.
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*//*--------------------------------------------------------------------*/
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deUint64 deRandom_getUint64 (deRandom* rnd)
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{
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deUint64 x = deRandom_getUint32(rnd);
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return x << 32 | deRandom_getUint32(rnd);
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}
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/*--------------------------------------------------------------------*//*!
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* \brief Get a pseudo random float in range [0, 1[.
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* \param rnd Pointer to RNG.
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* \return Random float number.
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*//*--------------------------------------------------------------------*/
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float deRandom_getFloat (deRandom* rnd)
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{
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return (float)(deRandom_getUint32(rnd) & 0xFFFFFFFu) / (float)(0xFFFFFFFu+1);
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}
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/*--------------------------------------------------------------------*//*!
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* \brief Get a pseudo random float in range [0, 1[.
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* \param rnd Pointer to RNG.
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* \return Random float number.
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*//*--------------------------------------------------------------------*/
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double deRandom_getDouble (deRandom* rnd)
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{
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DE_STATIC_ASSERT(FLT_RADIX == 2);
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return ldexp((double)(deRandom_getUint64(rnd) & ((1ull << DBL_MANT_DIG) - 1)),
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-DBL_MANT_DIG);
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}
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/*--------------------------------------------------------------------*//*!
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* \brief Get a pseudo random boolean value (DE_FALSE or DE_TRUE).
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* \param rnd Pointer to RNG.
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* \return Random float number.
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*//*--------------------------------------------------------------------*/
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deBool deRandom_getBool (deRandom* rnd)
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{
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deUint32 val = deRandom_getUint32(rnd);
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return ((val & 0xFFFFFF) < 0x800000);
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}
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DE_END_EXTERN_C
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