Add generic CRC calculation code

[proxmark3-svn] / common / crc.c

diff --git a/common/crc.c b/common/crc.c
new file mode 100644 (file)
index 0000000..817272e
--- /dev/null
+++ b/common/crc.c
@@ -0,0 +1,41 @@
+/*
+ * crc.c
+ *
+ * Generic CRC calculation code.
+ * 
+ */
+
+#include "crc.h"
+
+void crc_init(crc_t *crc, int order, uint32_t polynom, uint32_t initial_value, uint32_t final_xor)
+{
+       crc->order = order;
+       crc->polynom = polynom;
+       crc->initial_value = initial_value;
+       crc->final_xor = final_xor;
+       crc->mask = (1L<<order)-1;
+       crc_clear(crc);
+}
+
+void crc_update(crc_t *crc, uint32_t data, int 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;
+       }
+}
+
+void crc_clear(crc_t *crc)
+{
+       crc->state = crc->initial_value & crc->mask;
+}
+
+uint32_t crc_finish(crc_t *crc)
+{
+       return ( crc->state ^ crc->final_xor ) & crc->mask;
+}