X-Git-Url: https://git.ozlabs.org/?p=ccan;a=blobdiff_plain;f=ccan%2Fcrc%2Fcrc.h;h=d3184cb1a7b606fdb9c9e8bf9327321633e4dda8;hp=16994fc397597be61e550b755647734e34fd4ee4;hb=4f14d7bbd5afcda4fd0f1f70e8c9aae2a929c4d4;hpb=96b6d6f132aeec31adc0dfd0836f67e052694ac7

diff --git a/ccan/crc/crc.h b/ccan/crc/crc.h
index 16994fc3..d3184cb1 100644
--- a/ccan/crc/crc.h
+++ b/ccan/crc/crc.h
@@ -4,12 +4,101 @@
 #include <stdlib.h>
 
 /**
- * crc32 - 32 bit crc of string of bytes
+ * 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:
+ *	// Check that iovec has the crc we expect (Castagnoli version)
+ *	bool check_crc(uint32_t expected, const struct iovec *iov, int iovcnt)
+ *	{
+ *		uint32_t crc = 0;
+ *		while (iovcnt >= 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);
+
+/**
+ * crc32c_table - Get the Castagnoli CRC table
+ *
+ * For special effects, you might want direct access to the table; this is
+ * the standard 256-entry table for this algorithm.
+ *
+ * In theory, this might need to malloc(), and thus return NULL.
+ *
+ * Example:
+ *	// This dumb code only handles Castagnoli, so assert that here.
+ *	void check_user_crc_table(const uint32_t *usertab)
+ *	{
+ *		const uint32_t *ctab = crc32c_table();
+ *		if (!ctab || memcmp(ctab, usertab, 1024) != 0)
+ *			abort();
+ *	}
+ */
+const uint32_t *crc32c_table(void);
+
+/**
+ * crc32_ieee - IEEE 802.3 32 bit crc of string of bytes
+ * @start_crc: the initial crc (usually 0)
  * @buf: pointer to bytes
  * @size: length of buffer
  *
  * 32 bit CRC checksum using polynomial
  * X^32+X^26+X^23+X^22+X^16+X^12+X^11+X^10+X^8+X^7+X^5+X^4+X^2+X^1+X^0.
+ *
+ * See crc32c() for details.
  */
-uint32_t crc32(const void *buf, size_t size);
+uint32_t crc32_ieee(uint32_t start_crc, const void *buf, size_t size);
+
+/**
+ * crc32_ieee_table - Get the IEEE 802.3 CRC table
+ *
+ * See crc32c_table() for details.
+ */
+const uint32_t *crc32_ieee_table(void);
+
+/**
+ * crc64_iso - ISO 3309
+ * @start_crc: the initial crc (usually 0)
+ * @buf: pointer to bytes
+ * @size: length of buffer
+ *
+ * 64 bit CRC checksum using polynomial
+ * X^64 + X^4 + X^3 + X^1 + X^0
+ *
+ * See crc32c() for details.
+ */
+uint64_t crc64_iso(uint64_t start_crc, const void *buf, size_t size);
+
+/**
+ * crc64_iso_table - Get the ISO 3309 CRC table
+ *
+ * See crc32c_table() for details.
+ */
+const uint64_t *crc64_iso_table(void);
+
 #endif /* CCAN_CRC_H */