wip

Signed-off-by: Pin <wf6DJd8a3xSSCZbn@protonmail.com>

include/CRCLib.h

@@ -0,0 +1,51 @@
+/* Table of CRCs of all 8-bit messages. */
+unsigned long crc_table[256];
+   
+/* Flag: has the table been computed? Initially false. */
+int crc_table_computed = 0;
+   
+/* Make the table for a fast CRC. */
+void make_crc_table(void)
+{
+  unsigned long c;
+  int n, k;
+   
+  for (n = 0; n < 256; n++) {
+    c = (unsigned long) n;
+    for (k = 0; k < 8; k++) {
+      if (c & 1)
+        c = 0xedb88320L ^ (c >> 1);
+      else
+        c = c >> 1;
+    }
+    crc_table[n] = c;
+  }
+  crc_table_computed = 1;
+}
+  
+
+/* Update a running CRC with the bytes buf[0..len-1]--the CRC
+   should be initialized to all 1's, and the transmitted value
+   is the 1's complement of the final running CRC (see the
+   crc() routine below). */
+   
+unsigned long update_crc(unsigned long crc, unsigned char *buf,
+                         int len)
+{
+  unsigned long c = crc;
+  int n;
+   
+  if (!crc_table_computed)
+    make_crc_table();
+  for (n = 0; n < len; n++) {
+    c = crc_table[(c ^ buf[n]) & 0xff] ^ (c >> 8);
+  }
+  return c;
+}
+   
+/* Return the CRC of the bytes buf[0..len-1]. */
+unsigned long crc(unsigned char *buf, int len)
+{
+  return update_crc(0xffffffffL, buf, len) ^ 0xffffffffL;
+}
+