Add CRC32 implementation

1 files changed, 35 insertions, 0 deletions

diff --git a/prototype/fw/src/crc32.c b/prototype/fw/src/crc32.c
new file mode 100644
index 0000000..4b03fbb
--- /dev/null
+++ b/prototype/fw/src/crc32.c
@@ -0,0 +1,35 @@
+#include "crc32.h"
+#include <unistd.h>
+
+/* Polynomial: 0xEDB88320 */
+
+/* python3:
+ * In [26]: apply = lambda st: ((st>>1) ^ 0xEDB88320) if (st & 1) else (st>>1)
+ * In [27]: print(',\n'.join([ '0x{:08x}'.format(apply(apply(apply(apply(x))))) for x in range(16) ]))
+ */
+uint32_t crc32_table[16] = {
+	0x00000000,
+	0x1db71064,
+	0x3b6e20c8,
+	0x26d930ac,
+	0x76dc4190,
+	0x6b6b51f4,
+	0x4db26158,
+	0x5005713c,
+	0xedb88320,
+	0xf00f9344,
+	0xd6d6a3e8,
+	0xcb61b38c,
+	0x9b64c2b0,
+	0x86d3d2d4,
+	0xa00ae278,
+	0xbdbdf21c
+};
+
+crc32_t crc32_update(crc32_t state, uint8_t c)
+{
+	state ^= c;
+	state = (state>>4) ^ crc32_table[state&0xf];
+	state = (state>>4) ^ crc32_table[state&0xf];
+	return state;
+}