1#include "mupdf/fitz.h"
2
3/* The pseudo-random number generator in this file is based on the MIT licensed
4 * implementation in musl libc. */
5
6#include <string.h>
7
8/* The seed is initialized in context.c as follows:
9 * static uint16_t __seed48[7] = { 0, 0, 0, 0xe66d, 0xdeec, 0x5, 0xb };
10 */
11
12static uint64_t fz_rand48_step(uint16_t *xi, uint16_t *lc)
13{
14 uint64_t a, x;
15 x = xi[0] | (xi[1]+0U)<<16 | (xi[2]+0ULL)<<32;
16 a = lc[0] | (lc[1]+0U)<<16 | (lc[2]+0ULL)<<32;
17 x = a*x + lc[3];
18 xi[0] = x;
19 xi[1] = x>>16;
20 xi[2] = x>>32;
21 return x & 0xffffffffffffull;
22}
23
24double fz_erand48(fz_context *ctx, uint16_t s[3])
25{
26 union {
27 uint64_t u;
28 double f;
29 } x = { 0x3ff0000000000000ULL | fz_rand48_step(s, ctx->seed48+3)<<4 };
30 return x.f - 1.0;
31}
32
33/*
34 Pseudo-random numbers using a linear congruential algorithm and 48-bit
35 integer arithmetic.
36*/
37double fz_drand48(fz_context *ctx)
38{
39 return fz_erand48(ctx, ctx->seed48);
40}
41
42int32_t fz_nrand48(fz_context *ctx, uint16_t s[3])
43{
44 return fz_rand48_step(s, ctx->seed48+3) >> 17;
45}
46
47int32_t fz_lrand48(fz_context *ctx)
48{
49 return fz_nrand48(ctx, ctx->seed48);
50}
51
52int32_t fz_jrand48(fz_context *ctx, uint16_t s[3])
53{
54 return (int32_t)(fz_rand48_step(s, ctx->seed48+3) >> 16);
55}
56
57int32_t fz_mrand48(fz_context *ctx)
58{
59 return fz_jrand48(ctx, ctx->seed48);
60}
61
62void fz_lcong48(fz_context *ctx, uint16_t p[7])
63{
64 memcpy(ctx->seed48, p, sizeof ctx->seed48);
65}
66
67uint16_t *fz_seed48(fz_context *ctx, uint16_t *s)
68{
69 static uint16_t p[3];
70 memcpy(p, ctx->seed48, sizeof p);
71 memcpy(ctx->seed48, s, sizeof p);
72 return p;
73}
74
75void fz_srand48(fz_context *ctx, int32_t seed)
76{
77 uint16_t p[3] = { 0x330e, seed, seed>>16 };
78 fz_seed48(ctx, p);
79}
80
81/*
82 Fill block with len bytes of pseudo-randomness.
83*/
84void fz_memrnd(fz_context *ctx, unsigned char *data, int len)
85{
86 while (len-- > 0)
87 *data++ = (unsigned char)fz_lrand48(ctx);
88}
89