cbdac04a |
1 | /* Pseudo random number generation functions derived from the drand48() |
2 | * function obtained from pysam source code. |
3 | * |
4 | * This functions are used in order to replace the default math.random() |
5 | * Lua implementation with something having exactly the same behavior |
6 | * across different systems (by default Lua uses libc's rand() that is not |
7 | * required to implement a specific PRNG generating the same sequence |
8 | * in different systems if seeded with the same integer). |
9 | * |
10 | * The original code appears to be under the public domain. |
11 | * I modified it removing the non needed functions and all the |
12 | * 1960-style C coding stuff... |
13 | * |
14 | * ---------------------------------------------------------------------------- |
15 | * |
16 | * Copyright (c) 2011, Salvatore Sanfilippo <antirez at gmail dot com> |
17 | * All rights reserved. |
18 | * |
19 | * Redistribution and use in source and binary forms, with or without |
20 | * modification, are permitted provided that the following conditions are met: |
21 | * |
22 | * * Redistributions of source code must retain the above copyright notice, |
23 | * this list of conditions and the following disclaimer. |
24 | * * Redistributions in binary form must reproduce the above copyright |
25 | * notice, this list of conditions and the following disclaimer in the |
26 | * documentation and/or other materials provided with the distribution. |
27 | * * Neither the name of Redis nor the names of its contributors may be used |
28 | * to endorse or promote products derived from this software without |
29 | * specific prior written permission. |
30 | * |
31 | * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" |
32 | * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
33 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
34 | * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE |
35 | * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR |
36 | * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF |
37 | * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS |
38 | * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN |
39 | * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) |
40 | * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE |
41 | * POSSIBILITY OF SUCH DAMAGE. |
42 | */ |
43 | |
44 | #include <stdint.h> |
45 | |
46 | #define N 16 |
47 | #define MASK ((1 << (N - 1)) + (1 << (N - 1)) - 1) |
48 | #define LOW(x) ((unsigned)(x) & MASK) |
49 | #define HIGH(x) LOW((x) >> N) |
50 | #define MUL(x, y, z) { int32_t l = (long)(x) * (long)(y); \ |
51 | (z)[0] = LOW(l); (z)[1] = HIGH(l); } |
52 | #define CARRY(x, y) ((int32_t)(x) + (long)(y) > MASK) |
53 | #define ADDEQU(x, y, z) (z = CARRY(x, (y)), x = LOW(x + (y))) |
54 | #define X0 0x330E |
55 | #define X1 0xABCD |
56 | #define X2 0x1234 |
57 | #define A0 0xE66D |
58 | #define A1 0xDEEC |
59 | #define A2 0x5 |
60 | #define C 0xB |
61 | #define SET3(x, x0, x1, x2) ((x)[0] = (x0), (x)[1] = (x1), (x)[2] = (x2)) |
62 | #define SETLOW(x, y, n) SET3(x, LOW((y)[n]), LOW((y)[(n)+1]), LOW((y)[(n)+2])) |
63 | #define SEED(x0, x1, x2) (SET3(x, x0, x1, x2), SET3(a, A0, A1, A2), c = C) |
64 | #define REST(v) for (i = 0; i < 3; i++) { xsubi[i] = x[i]; x[i] = temp[i]; } \ |
65 | return (v); |
66 | #define HI_BIT (1L << (2 * N - 1)) |
67 | |
68 | static uint32_t x[3] = { X0, X1, X2 }, a[3] = { A0, A1, A2 }, c = C; |
69 | static void next(); |
70 | |
71 | int32_t redisLrand48() { |
72 | next(); |
73 | return (((int32_t)x[2] << (N - 1)) + (x[1] >> 1)); |
74 | } |
75 | |
76 | void redisSrand48(int32_t seedval) { |
77 | SEED(X0, LOW(seedval), HIGH(seedval)); |
78 | } |
79 | |
80 | static void next() { |
81 | uint32_t p[2], q[2], r[2], carry0, carry1; |
82 | |
83 | MUL(a[0], x[0], p); |
84 | ADDEQU(p[0], c, carry0); |
85 | ADDEQU(p[1], carry0, carry1); |
86 | MUL(a[0], x[1], q); |
87 | ADDEQU(p[1], q[0], carry0); |
88 | MUL(a[1], x[0], r); |
89 | x[2] = LOW(carry0 + carry1 + CARRY(p[1], r[0]) + q[1] + r[1] + |
90 | a[0] * x[2] + a[1] * x[1] + a[2] * x[0]); |
91 | x[1] = LOW(p[1] + r[0]); |
92 | x[0] = LOW(p[0]); |
93 | } |