restore #755 reverted after #757 (#761)

[proxmark3-svn] / common / legic_prng.c

diff --git a/common/legic_prng.c b/common/legic_prng.c
index 54d2466e41b7d8557f573595c967182b4487d276..4f3b1ffee1167ab51a067502451cb4e634c88cef 100644 (file)
--- a/common/legic_prng.c
+++ b/common/legic_prng.c
@@ -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;