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legic write/simulate [Anon]

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This commit is contained in:
adam@algroup.co.uk 2010-05-06 11:24:01 +00:00
commit 3612a8a8e2
8 changed files with 636 additions and 32 deletions
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11
common/legic_prng.c
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@ -9,11 +9,13 @@
#include "legic_prng.h"
struct lfsr {
uint8_t a;
uint8_t b;
uint8_t a;
uint8_t b;
uint32_t c;
} lfsr;
void legic_prng_init(uint8_t init) {
lfsr.c = 0;
lfsr.a = init;
if(init == 0) /* hack to get a always 0 keystream */
lfsr.b = 0;
@ -22,12 +24,17 @@ void legic_prng_init(uint8_t init) {
}
void legic_prng_forward(int count) {
lfsr.c += count;
while(count--) {
lfsr.a = lfsr.a >> 1 | (lfsr.a ^ lfsr.a >> 6) << 6;
lfsr.b = lfsr.b >> 1 | (lfsr.b ^ lfsr.b >> 2 ^ lfsr.b >> 3 ^ lfsr.b >> 7) << 7;
}
}
int legic_prng_count() {
return lfsr.c;
}
uint8_t legic_prng_get_bit() {
uint8_t idx = 7 - ( (lfsr.a & 4) | (lfsr.a >> 2 & 2) | (lfsr.a >> 4 & 1) );
return lfsr.b >> idx & 1;