]> git.zerfleddert.de Git - proxmark3-svn/blame - common/prng.c
CHG: added some comments when changing the HAS_512_FLASH macro directive.
[proxmark3-svn] / common / prng.c
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f4d0ffd1 1//-----------------------------------------------------------------------------
2//-----------------------------------------------------------------------------
3// Burtle Prng - Modified. 42iterations instead of 20.
4// ref: http://burtleburtle.net/bob/rand/smallprng.html
5//-----------------------------------------------------------------------------
6#include "prng.h"
7
8#define rot(x,k) (((x)<<(k))|((x)>>(32-(k))))
9uint32_t burtle_get_mod( prng_ctx *x ) {
10 uint32_t e = x->a - rot(x->b, 21);
11 x->a = x->b ^ rot(x->c, 19);
12 x->b = x->c + rot(x->d, 6);
13 x->c = x->d + e;
14 x->d = e + x->a;
15 return x->d;
16}
17
18void burtle_init_mod(prng_ctx *x, uint32_t seed ) {
19 x->a = 0xf1ea5eed;
20 x->b = x->c = x->d = seed;
21 for (uint8_t i=0; i < 42; ++i) {
22 (void)burtle_get_mod(x);
23 }
24}
25
26void burtle_init(prng_ctx *x, uint32_t seed ) {
27 uint32_t i;
28 x->a = 0xf1ea5eed, x->b = x->c = x->d = seed;
29 for (i=0; i < 20; ++i) {
30 (void)burtle_get_mod(x);
31 }
32}
33
34
35uint32_t GetSimplePrng( uint32_t seed ){
36 seed *= 0x19660D;
37 seed += 0x3C6EF35F;
38 return seed;
39}
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