diff options
Diffstat (limited to 'src/rand.c')
| -rw-r--r-- | src/rand.c | 93 |
1 files changed, 93 insertions, 0 deletions
diff --git a/src/rand.c b/src/rand.c new file mode 100644 index 0000000..e1e98e6 --- /dev/null +++ b/src/rand.c @@ -0,0 +1,93 @@ +/* Pseudo random number generation functions derived from the drand48() + * function obtained from pysam source code. + * + * This functions are used in order to replace the default math.random() + * Lua implementation with something having exactly the same behavior + * across different systems (by default Lua uses libc's rand() that is not + * required to implement a specific PRNG generating the same sequence + * in different systems if seeded with the same integer). + * + * The original code appears to be under the public domain. + * I modified it removing the non needed functions and all the + * 1960-style C coding stuff... + * + * ---------------------------------------------------------------------------- + * + * Copyright (c) 2010-2012, Salvatore Sanfilippo <antirez at gmail dot com> + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions are met: + * + * * Redistributions of source code must retain the above copyright notice, + * this list of conditions and the following disclaimer. + * * Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * * Neither the name of Redis nor the names of its contributors may be used + * to endorse or promote products derived from this software without + * specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" + * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE + * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR + * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF + * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS + * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN + * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) + * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE + * POSSIBILITY OF SUCH DAMAGE. + */ + +#include <stdint.h> + +#define N 16 +#define MASK ((1 << (N - 1)) + (1 << (N - 1)) - 1) +#define LOW(x) ((unsigned)(x) & MASK) +#define HIGH(x) LOW((x) >> N) +#define MUL(x, y, z) { int32_t l = (long)(x) * (long)(y); \ + (z)[0] = LOW(l); (z)[1] = HIGH(l); } +#define CARRY(x, y) ((int32_t)(x) + (long)(y) > MASK) +#define ADDEQU(x, y, z) (z = CARRY(x, (y)), x = LOW(x + (y))) +#define X0 0x330E +#define X1 0xABCD +#define X2 0x1234 +#define A0 0xE66D +#define A1 0xDEEC +#define A2 0x5 +#define C 0xB +#define SET3(x, x0, x1, x2) ((x)[0] = (x0), (x)[1] = (x1), (x)[2] = (x2)) +#define SETLOW(x, y, n) SET3(x, LOW((y)[n]), LOW((y)[(n)+1]), LOW((y)[(n)+2])) +#define SEED(x0, x1, x2) (SET3(x, x0, x1, x2), SET3(a, A0, A1, A2), c = C) +#define REST(v) for (i = 0; i < 3; i++) { xsubi[i] = x[i]; x[i] = temp[i]; } \ + return (v); +#define HI_BIT (1L << (2 * N - 1)) + +static uint32_t x[3] = { X0, X1, X2 }, a[3] = { A0, A1, A2 }, c = C; +static void next(void); + +int32_t redisLrand48(void) { + next(); + return (((int32_t)x[2] << (N - 1)) + (x[1] >> 1)); +} + +void redisSrand48(int32_t seedval) { + SEED(X0, LOW(seedval), HIGH(seedval)); +} + +static void next(void) { + uint32_t p[2], q[2], r[2], carry0, carry1; + + MUL(a[0], x[0], p); + ADDEQU(p[0], c, carry0); + ADDEQU(p[1], carry0, carry1); + MUL(a[0], x[1], q); + ADDEQU(p[1], q[0], carry0); + MUL(a[1], x[0], r); + x[2] = LOW(carry0 + carry1 + CARRY(p[1], r[0]) + q[1] + r[1] + + a[0] * x[2] + a[1] * x[1] + a[2] * x[0]); + x[1] = LOW(p[1] + r[0]); + x[0] = LOW(p[0]); +} |