--- /dev/null
+/* Copyright abandoned; this code is in the public domain. */
+/* Provided to GNUnet by peter@horizon.com */
+
+/*
+ * Adapted for GeekOS by David Hovemeyer
+ * Code downloaded from OVM (http://www.ovmj.org)
+ */
+
+#include <geekos/crc32.h>
+#include <geekos/kassert.h>
+#include <geekos/serial.h>
+#include <geekos/debug.h>
+
+#define POLYNOMIAL (ulong_t)0xedb88320
+static ulong_t crc_table[256];
+
+/*
+ * This routine writes each crc_table entry exactly once,
+ * with the correct final value. Thus, it is safe to call
+ * even on a table that someone else is using concurrently.
+ */
+void Init_CRC32(void) {
+ unsigned int i, j;
+ ulong_t h = 1;
+ PrintBoth("Initializing CRC32\n");
+ crc_table[0] = 0;
+ for (i = 128; i; i >>= 1) {
+ h = (h >> 1) ^ ((h & 1) ? POLYNOMIAL : 0);
+ /* h is now crc_table[i] */
+ for (j = 0; j < 256; j += 2*i)
+ crc_table[i+j] = crc_table[j] ^ h;
+ }
+}
+
+/*
+ * This computes the standard preset and inverted CRC, as used
+ * by most networking standards. Start by passing in an initial
+ * chaining value of 0, and then pass in the return value from the
+ * previous crc32() call. The final return value is the CRC.
+ * Note that this is a little-endian CRC, which is best used with
+ * data transmitted lsbit-first, and it should, itself, be appended
+ * to data in little-endian byte and bit order to preserve the
+ * property of detecting all burst errors of length 32 bits or less.
+ */
+ulong_t crc32(ulong_t crc, char const *buf, size_t len) {
+ KASSERT(crc_table[255] != 0);
+ crc ^= 0xffffffff;
+ while (len--)
+ crc = (crc >> 8) ^ crc_table[(crc ^ *buf++) & 0xff];
+ return crc ^ 0xffffffff;
+}
+
+/* end of crc32.c */
