Merge pull request #33 from osysltd/patch-2

[proxmark3-svn] / common / crc.c

diff --git a/common/crc.c b/common/crc.c
index 72e6f0248751001e44210e412cabcc76ad5370d4..2f11f5f45f6c97386ffb6a595b014b05bd7a3e3b 100644 (file)
--- a/common/crc.c
+++ b/common/crc.c
@@ -43,6 +43,8 @@ void crc_update(crc_t *crc, uint32_t indata, int data_width){
        crc->state ^= indata << (crc->order - data_width);
        
        for( uint8_t bit = data_width; bit > 0; --bit) {
+               
+               
                 // Try to divide the current data bit.
                if (crc->state & crc->topbit)
                        crc->state = (crc->state << 1) ^ crc->polynom;
@@ -51,6 +53,22 @@ void crc_update(crc_t *crc, uint32_t indata, int data_width){
        }
 }
 
+void crc_update2(crc_t *crc, uint32_t data, int data_width)
+{
+       if (crc->refin) data = reflect(data, data_width);
+       
+       int i;
+       for(i=0; i<data_width; i++) {
+               int oldstate = crc->state;
+               crc->state = crc->state >> 1;
+               if( (oldstate^data) & 1 ) {
+                       crc->state ^= crc->polynom;
+               }
+               data >>= 1;
+       }
+}
+
+
 uint32_t crc_finish(crc_t *crc) {
        uint32_t val = crc->state;
        if (crc->refout) val = reflect(val, crc->order);
@@ -83,6 +101,14 @@ uint32_t CRC8Maxim(uint8_t *buff, size_t size) {
 }
 
 // width=4  poly=0xC, reversed poly=0x7  init=0x5   refin=true  refout=true  xorout=0x0000  check=  name="CRC-4/LEGIC"
+uint32_t CRC4Legic(uint8_t *cmd, size_t size) {
+       crc_t crc;
+       crc_init_ref(&crc, 4, 0x19 >> 1, 0x5, 0, TRUE, TRUE);
+       crc_update2(&crc, 1, 1); /* CMD_READ */
+       crc_update2(&crc, cmd[0], 8);
+       crc_update2(&crc, cmd[1], 8);
+       return reflect(crc_finish(&crc), 4);    
+}
 // width=8  poly=0x63, reversed poly=0x8D  init=0x55  refin=true  refout=true  xorout=0x0000  check=0xC6  name="CRC-8/LEGIC"
 // the CRC needs to be reversed before returned.
 uint32_t CRC8Legic(uint8_t *buff, size_t size) {