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,deUint32 seed)36 void deRandom_init (deRandom* rnd, deUint32 seed)
37 {
38 	rnd->x = (deUint32)(-(int)seed ^ 123456789);
39 	rnd->y = (deUint32)(362436069 * seed);
40 	rnd->z = (deUint32)(521288629 ^ (seed >> 7));
41 	rnd->w = (deUint32)(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 deUint32 deRandom_getUint32 (deRandom* rnd)
50 {
51 	deUint32 w = rnd->w;
52 	deUint32 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 deUint64 deRandom_getUint64 (deRandom* rnd)
68 {
69 	deUint64 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)),
92 				 -DBL_MANT_DIG);
93 }
94 
95 /*--------------------------------------------------------------------*//*!
96  * \brief Get a pseudo random boolean value (DE_FALSE or DE_TRUE).
97  * \param rnd	Pointer to RNG.
98  * \return Random float number.
99  *//*--------------------------------------------------------------------*/
deRandom_getBool(deRandom * rnd)100 deBool deRandom_getBool (deRandom* rnd)
101 {
102 	deUint32 val = deRandom_getUint32(rnd);
103 	return ((val & 0xFFFFFF) < 0x800000);
104 }
105 
106 DE_END_EXTERN_C
107