ccan/crc32c: new module for accelerated CRC32 (on x86-64).

[ccan] / ccan / crc32c / crc32c.h

diff --git a/ccan/crc32c/crc32c.h b/ccan/crc32c/crc32c.h
new file mode 100644 (file)
index 0000000..49e3337
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+++ b/ccan/crc32c/crc32c.h
@@ -0,0 +1,48 @@
+/* Licensed under MIT - see LICENSE file for details */
+#ifndef CCAN_CRC32C_H
+#define CCAN_CRC32C_H
+#include <stdint.h>
+#include <stdlib.h>
+
+/**
+ * crc32c - Castagnoli 32 bit crc of string of bytes
+ * @start_crc: the initial crc (usually 0)
+ * @buf: pointer to bytes
+ * @size: length of buffer
+ *
+ * If you don't know what crc32 to use, use this one: it's the best.
+ *
+ * @Article{castagnoli-crc,
+ * author =       { Guy Castagnoli and Stefan Braeuer and Martin Herrman},
+ * title =        {{Optimization of Cyclic Redundancy-Check Codes with 24
+ *                 and 32 Parity Bits}},
+ * journal =      IEEE Transactions on Communication,
+ * year =         {1993},
+ * volume =       {41},
+ * number =       {6},
+ * pages =        {},
+ * month =        {June},
+ *}
+ * 32 bit CRC checksum using polynomial
+ * X^32+X^28+X^27+X^26+X^25+X^23+X^22+X^20+X^19+X^18+X^14+X^13+X^11+X^10+X^9+X^8+X^6+X^0.
+ *
+ * You can calculate the CRC of non-contiguous arrays by passing @start_crc
+ * as 0 the first time, and the current crc result from then on.
+ *
+ * Example:
+ *     #include <sys/uio.h>
+ *     ...
+ *     // Check that iovec has the crc we expect (Castagnoli version)
+ *     static bool check_crc(uint32_t expected, const struct iovec *iov, int l)
+ *     {
+ *             uint32_t crc = 0;
+ *             while (l >= 0) {
+ *                     crc = crc32c(crc, iov->iov_base, iov->iov_len);
+ *                     iov++;
+ *             }
+ *             return crc == expected;
+ *     }
+ */
+uint32_t crc32c(uint32_t start_crc, const void *buf, size_t size);
+
+#endif /* CCAN_CRC32C_H */