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+/*
+ * hash_64 - 64 bit Fowler/Noll/Vo-0 FNV-1a hash code
+ *
+ * @(#) $Revision: 5.1 $
+ * @(#) $Id: hash_64a.c,v 5.1 2009/06/30 09:01:38 chongo Exp $
+ * @(#) $Source: /usr/local/src/cmd/fnv/RCS/hash_64a.c,v $
+ *
+ ***
+ *
+ * Fowler/Noll/Vo hash
+ *
+ * The basis of this hash algorithm was taken from an idea sent
+ * as reviewer comments to the IEEE POSIX P1003.2 committee by:
+ *
+ * Phong Vo (http://www.research.att.com/info/kpv/)
+ * Glenn Fowler (http://www.research.att.com/~gsf/)
+ *
+ * In a subsequent ballot round:
+ *
+ * Landon Curt Noll (http://www.isthe.com/chongo/)
+ *
+ * improved on their algorithm. Some people tried this hash
+ * and found that it worked rather well. In an EMail message
+ * to Landon, they named it the ``Fowler/Noll/Vo'' or FNV hash.
+ *
+ * FNV hashes are designed to be fast while maintaining a low
+ * collision rate. The FNV speed allows one to quickly hash lots
+ * of data while maintaining a reasonable collision rate. See:
+ *
+ * http://www.isthe.com/chongo/tech/comp/fnv/index.html
+ *
+ * for more details as well as other forms of the FNV hash.
+ *
+ ***
+ *
+ * To use the recommended 64 bit FNV-1a hash, pass FNV1A_64_INIT as the
+ * Fnv64_t hashval argument to fnv_64a_buf() or fnv_64a_str().
+ *
+ ***
+ *
+ * Please do not copyright this code. This code is in the public domain.
+ *
+ * LANDON CURT NOLL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
+ * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO
+ * EVENT SHALL LANDON CURT NOLL BE LIABLE FOR ANY SPECIAL, INDIRECT OR
+ * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF
+ * USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
+ * OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+ * PERFORMANCE OF THIS SOFTWARE.
+ *
+ * By:
+ * chongo <Landon Curt Noll> /\oo/\
+ * http://www.isthe.com/chongo/
+ *
+ * Share and Enjoy! :-)
+ */
+
+#include <stdlib.h>
+#include "fnv.h"
+
+
+/*
+ * FNV-1a defines the initial basis to be non-zero
+ */
+#if !defined(HAVE_64BIT_LONG_LONG)
+const Fnv64_t fnv1a_64_init = { 0x84222325, 0xcbf29ce4 };
+#endif /* ! HAVE_64BIT_LONG_LONG */
+
+
+/*
+ * 64 bit magic FNV-1a prime
+ */
+#if defined(HAVE_64BIT_LONG_LONG)
+#define FNV_64_PRIME ((Fnv64_t)0x100000001b3ULL)
+#else /* HAVE_64BIT_LONG_LONG */
+#define FNV_64_PRIME_LOW ((unsigned long)0x1b3) /* lower bits of FNV prime */
+#define FNV_64_PRIME_SHIFT (8) /* top FNV prime shift above 2^32 */
+#endif /* HAVE_64BIT_LONG_LONG */
+
+
+/*
+ * fnv_64a_buf - perform a 64 bit Fowler/Noll/Vo FNV-1a hash on a buffer
+ *
+ * input:
+ * buf - start of buffer to hash
+ * len - length of buffer in octets
+ * hval - previous hash value or 0 if first call
+ *
+ * returns:
+ * 64 bit hash as a static hash type
+ *
+ * NOTE: To use the recommended 64 bit FNV-1a hash, use FNV1A_64_INIT as the
+ * hval arg on the first call to either fnv_64a_buf() or fnv_64a_str().
+ */
+Fnv64_t
+fnv_64a_buf(void *buf, size_t len, Fnv64_t hval)
+{
+ unsigned char *bp = (unsigned char *)buf; /* start of buffer */
+ unsigned char *be = bp + len; /* beyond end of buffer */
+
+#if defined(HAVE_64BIT_LONG_LONG)
+ /*
+ * FNV-1a hash each octet of the buffer
+ */
+ while (bp < be) {
+
+ /* xor the bottom with the current octet */
+ hval ^= (Fnv64_t)*bp++;
+
+ /* multiply by the 64 bit FNV magic prime mod 2^64 */
+#if defined(NO_FNV_GCC_OPTIMIZATION)
+ hval *= FNV_64_PRIME;
+#else /* NO_FNV_GCC_OPTIMIZATION */
+ hval += (hval << 1) + (hval << 4) + (hval << 5) +
+ (hval << 7) + (hval << 8) + (hval << 40);
+#endif /* NO_FNV_GCC_OPTIMIZATION */
+ }
+
+#else /* HAVE_64BIT_LONG_LONG */
+
+ unsigned long val[4]; /* hash value in base 2^16 */
+ unsigned long tmp[4]; /* tmp 64 bit value */
+
+ /*
+ * Convert Fnv64_t hval into a base 2^16 array
+ */
+ val[0] = hval.w32[0];
+ val[1] = (val[0] >> 16);
+ val[0] &= 0xffff;
+ val[2] = hval.w32[1];
+ val[3] = (val[2] >> 16);
+ val[2] &= 0xffff;
+
+ /*
+ * FNV-1a hash each octet of the buffer
+ */
+ while (bp < be) {
+
+ /* xor the bottom with the current octet */
+ val[0] ^= (unsigned long)*bp++;
+
+ /*
+ * multiply by the 64 bit FNV magic prime mod 2^64
+ *
+ * Using 0x100000001b3 we have the following digits base 2^16:
+ *
+ * 0x0 0x100 0x0 0x1b3
+ *
+ * which is the same as:
+ *
+ * 0x0 1<<FNV_64_PRIME_SHIFT 0x0 FNV_64_PRIME_LOW
+ */
+ /* multiply by the lowest order digit base 2^16 */
+ tmp[0] = val[0] * FNV_64_PRIME_LOW;
+ tmp[1] = val[1] * FNV_64_PRIME_LOW;
+ tmp[2] = val[2] * FNV_64_PRIME_LOW;
+ tmp[3] = val[3] * FNV_64_PRIME_LOW;
+ /* multiply by the other non-zero digit */
+ tmp[2] += val[0] << FNV_64_PRIME_SHIFT; /* tmp[2] += val[0] * 0x100 */
+ tmp[3] += val[1] << FNV_64_PRIME_SHIFT; /* tmp[3] += val[1] * 0x100 */
+ /* propagate carries */
+ tmp[1] += (tmp[0] >> 16);
+ val[0] = tmp[0] & 0xffff;
+ tmp[2] += (tmp[1] >> 16);
+ val[1] = tmp[1] & 0xffff;
+ val[3] = tmp[3] + (tmp[2] >> 16);
+ val[2] = tmp[2] & 0xffff;
+ /*
+ * Doing a val[3] &= 0xffff; is not really needed since it simply
+ * removes multiples of 2^64. We can discard these excess bits
+ * outside of the loop when we convert to Fnv64_t.
+ */
+ }
+
+ /*
+ * Convert base 2^16 array back into an Fnv64_t
+ */
+ hval.w32[1] = ((val[3]<<16) | val[2]);
+ hval.w32[0] = ((val[1]<<16) | val[0]);
+
+#endif /* HAVE_64BIT_LONG_LONG */
+
+ /* return our new hash value */
+ return hval;
+}
+
+
+/*
+ * fnv_64a_str - perform a 64 bit Fowler/Noll/Vo FNV-1a hash on a buffer
+ *
+ * input:
+ * buf - start of buffer to hash
+ * hval - previous hash value or 0 if first call
+ *
+ * returns:
+ * 64 bit hash as a static hash type
+ *
+ * NOTE: To use the recommended 64 bit FNV-1a hash, use FNV1A_64_INIT as the
+ * hval arg on the first call to either fnv_64a_buf() or fnv_64a_str().
+ */
+Fnv64_t
+fnv_64a_str(char *str, Fnv64_t hval)
+{
+ unsigned char *s = (unsigned char *)str; /* unsigned string */
+
+#if defined(HAVE_64BIT_LONG_LONG)
+
+ /*
+ * FNV-1a hash each octet of the string
+ */
+ while (*s) {
+
+ /* xor the bottom with the current octet */
+ hval ^= (Fnv64_t)*s++;
+
+ /* multiply by the 64 bit FNV magic prime mod 2^64 */
+#if defined(NO_FNV_GCC_OPTIMIZATION)
+ hval *= FNV_64_PRIME;
+#else /* NO_FNV_GCC_OPTIMIZATION */
+ hval += (hval << 1) + (hval << 4) + (hval << 5) +
+ (hval << 7) + (hval << 8) + (hval << 40);
+#endif /* NO_FNV_GCC_OPTIMIZATION */
+ }
+
+#else /* !HAVE_64BIT_LONG_LONG */
+
+ unsigned long val[4]; /* hash value in base 2^16 */
+ unsigned long tmp[4]; /* tmp 64 bit value */
+
+ /*
+ * Convert Fnv64_t hval into a base 2^16 array
+ */
+ val[0] = hval.w32[0];
+ val[1] = (val[0] >> 16);
+ val[0] &= 0xffff;
+ val[2] = hval.w32[1];
+ val[3] = (val[2] >> 16);
+ val[2] &= 0xffff;
+
+ /*
+ * FNV-1a hash each octet of the string
+ */
+ while (*s) {
+
+ /* xor the bottom with the current octet */
+
+ /*
+ * multiply by the 64 bit FNV magic prime mod 2^64
+ *
+ * Using 1099511628211, we have the following digits base 2^16:
+ *
+ * 0x0 0x100 0x0 0x1b3
+ *
+ * which is the same as:
+ *
+ * 0x0 1<<FNV_64_PRIME_SHIFT 0x0 FNV_64_PRIME_LOW
+ */
+ /* multiply by the lowest order digit base 2^16 */
+ tmp[0] = val[0] * FNV_64_PRIME_LOW;
+ tmp[1] = val[1] * FNV_64_PRIME_LOW;
+ tmp[2] = val[2] * FNV_64_PRIME_LOW;
+ tmp[3] = val[3] * FNV_64_PRIME_LOW;
+ /* multiply by the other non-zero digit */
+ tmp[2] += val[0] << FNV_64_PRIME_SHIFT; /* tmp[2] += val[0] * 0x100 */
+ tmp[3] += val[1] << FNV_64_PRIME_SHIFT; /* tmp[3] += val[1] * 0x100 */
+ /* propagate carries */
+ tmp[1] += (tmp[0] >> 16);
+ val[0] = tmp[0] & 0xffff;
+ tmp[2] += (tmp[1] >> 16);
+ val[1] = tmp[1] & 0xffff;
+ val[3] = tmp[3] + (tmp[2] >> 16);
+ val[2] = tmp[2] & 0xffff;
+ /*
+ * Doing a val[3] &= 0xffff; is not really needed since it simply
+ * removes multiples of 2^64. We can discard these excess bits
+ * outside of the loop when we convert to Fnv64_t.
+ */
+ val[0] ^= (unsigned long)(*s++);
+ }
+
+ /*
+ * Convert base 2^16 array back into an Fnv64_t
+ */
+ hval.w32[1] = ((val[3]<<16) | val[2]);
+ hval.w32[0] = ((val[1]<<16) | val[0]);
+
+#endif /* !HAVE_64BIT_LONG_LONG */
+
+ /* return our new hash value */
+ return hval;
+}