1 /*-------------------------------------------------------------------------
2 * drawElements Base Portability Library
3 * -------------------------------------
4 *
5 * Copyright 2014 The Android Open Source Project
6 *
7 * Licensed under the Apache License, Version 2.0 (the "License");
8 * you may not use this file except in compliance with the License.
9 * You may obtain a copy of the License at
10 *
11 * http://www.apache.org/licenses/LICENSE-2.0
12 *
13 * Unless required by applicable law or agreed to in writing, software
14 * distributed under the License is distributed on an "AS IS" BASIS,
15 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
16 * See the License for the specific language governing permissions and
17 * limitations under the License.
18 *
19 *//*!
20 * \file
21 * \brief Random number generation.
22 *//*--------------------------------------------------------------------*/
23
24 #include "deRandom.h"
25
26 #include <float.h>
27 #include <math.h>
28
29 DE_BEGIN_EXTERN_C
30
31 /*--------------------------------------------------------------------*//*!
32 * \brief Initialize a random number generator with a given seed.
33 * \param rnd RNG to initialize.
34 * \param seed Seed value used for random values.
35 *//*--------------------------------------------------------------------*/
deRandom_init(deRandom * rnd,uint32_t seed)36 void deRandom_init(deRandom *rnd, uint32_t seed)
37 {
38 rnd->x = (uint32_t)(-(int)seed ^ 123456789);
39 rnd->y = (uint32_t)(362436069 * seed);
40 rnd->z = (uint32_t)(521288629 ^ (seed >> 7));
41 rnd->w = (uint32_t)(88675123 ^ (seed << 3));
42 }
43
44 /*--------------------------------------------------------------------*//*!
45 * \brief Get a pseudo random uint32.
46 * \param rnd Pointer to RNG.
47 * \return Random uint32 number.
48 *//*--------------------------------------------------------------------*/
deRandom_getUint32(deRandom * rnd)49 uint32_t deRandom_getUint32(deRandom *rnd)
50 {
51 uint32_t w = rnd->w;
52 uint32_t t;
53
54 t = rnd->x ^ (rnd->x << 11);
55 rnd->x = rnd->y;
56 rnd->y = rnd->z;
57 rnd->z = w;
58 rnd->w = w = (w ^ (w >> 19)) ^ (t ^ (t >> 8));
59 return w;
60 }
61
62 /*--------------------------------------------------------------------*//*!
63 * \brief Get a pseudo random uint64.
64 * \param rnd Pointer to RNG.
65 * \return Random uint64 number.
66 *//*--------------------------------------------------------------------*/
deRandom_getUint64(deRandom * rnd)67 uint64_t deRandom_getUint64(deRandom *rnd)
68 {
69 uint64_t x = deRandom_getUint32(rnd);
70 return x << 32 | deRandom_getUint32(rnd);
71 }
72
73 /*--------------------------------------------------------------------*//*!
74 * \brief Get a pseudo random float in range [0, 1[.
75 * \param rnd Pointer to RNG.
76 * \return Random float number.
77 *//*--------------------------------------------------------------------*/
deRandom_getFloat(deRandom * rnd)78 float deRandom_getFloat(deRandom *rnd)
79 {
80 return (float)(deRandom_getUint32(rnd) & 0xFFFFFFFu) / (float)(0xFFFFFFFu + 1);
81 }
82
83 /*--------------------------------------------------------------------*//*!
84 * \brief Get a pseudo random float in range [0, 1[.
85 * \param rnd Pointer to RNG.
86 * \return Random float number.
87 *//*--------------------------------------------------------------------*/
deRandom_getDouble(deRandom * rnd)88 double deRandom_getDouble(deRandom *rnd)
89 {
90 DE_STATIC_ASSERT(FLT_RADIX == 2);
91 return ldexp((double)(deRandom_getUint64(rnd) & ((1ull << DBL_MANT_DIG) - 1)), -DBL_MANT_DIG);
92 }
93
94 /*--------------------------------------------------------------------*//*!
95 * \brief Get a pseudo random boolean value (false or true).
96 * \param rnd Pointer to RNG.
97 * \return Random float number.
98 *//*--------------------------------------------------------------------*/
deRandom_getBool(deRandom * rnd)99 bool deRandom_getBool(deRandom *rnd)
100 {
101 uint32_t val = deRandom_getUint32(rnd);
102 return ((val & 0xFFFFFF) < 0x800000);
103 }
104
105 DE_END_EXTERN_C
106