proxmark3/client/prng.c

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//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------
// Burtle Prng - Modified. 42iterations instead of 20.
// ref: http://burtleburtle.net/bob/rand/smallprng.html
//-----------------------------------------------------------------------------
#include "prng.h"
#define rot(x,k) (((x)<<(k))|((x)>>(32-(k))))
uint32_t burtle_get_mod(prng_ctx *x) {
uint32_t e = x->a - rot(x->b, 21);
x->a = x->b ^ rot(x->c, 19);
x->b = x->c + rot(x->d, 6);
x->c = x->d + e;
x->d = e + x->a;
return x->d;
}
void burtle_init_mod(prng_ctx *x, uint32_t seed) {
x->a = 0xf1ea5eed;
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x->b = x->c = x->d = seed;
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for (uint8_t i = 0; i < 42; ++i) {
(void)burtle_get_mod(x);
}
}
void burtle_init(prng_ctx *x, uint32_t seed) {
uint32_t i;
x->a = 0xf1ea5eed, x->b = x->c = x->d = seed;
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for (i = 0; i < 20; ++i) {
(void)burtle_get_mod(x);
}
}
uint32_t GetSimplePrng(uint32_t seed) {
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seed *= 0x19660D;
seed += 0x3C6EF35F;
return seed;
}