/*
- * Copyright (c) 2008, 2009 Nicira Networks.
+ * Copyright (c) 2008, 2009, 2010 Nicira Networks.
*
- * Permission to use, copy, modify, and/or distribute this software for any
- * purpose with or without fee is hereby granted, provided that the above
- * copyright notice and this permission notice appear in all copies.
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
*
- * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
- * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
- * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
- * ANY SPECIAL, DIRECT, 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.
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
*/
#ifndef HASH_H
#define HASH_H 1
+#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include <string.h>
+#include "util.h"
/* This is the public domain lookup3 hash by Bob Jenkins from
* http://burtleburtle.net/bob/c/lookup3.c, modified for style. */
} while (0)
uint32_t hash_words(const uint32_t *, size_t n_word, uint32_t basis);
+uint32_t hash_2words(uint32_t, uint32_t);
+uint32_t hash_3words(uint32_t, uint32_t, uint32_t);
uint32_t hash_bytes(const void *, size_t n_bytes, uint32_t basis);
static inline uint32_t hash_string(const char *s, uint32_t basis)
}
/* This is Bob Jenkins' integer hash from
- * http://burtleburtle.net/bob/hash/integer.html, modified for style. */
+ * http://burtleburtle.net/bob/hash/integer.html, modified for style.
+ *
+ * This hash is faster than hash_2words(), but it isn't as good when 'basis' is
+ * important. So use this function for speed or hash_2words() for hash
+ * quality. */
static inline uint32_t hash_int(uint32_t x, uint32_t basis)
{
x -= x << 6;
x ^= x >> 17;
x -= x << 9;
x ^= x << 4;
+ x += basis;
x -= x << 3;
x ^= x << 10;
x ^= x >> 15;
- return x + basis;
+ return x;
+}
+
+/* An attempt at a useful 1-bit hash function. Has not been analyzed for
+ * quality. */
+static inline uint32_t hash_boolean(bool x, uint32_t basis)
+{
+ enum { P0 = 0xc2b73583 }; /* This is hash_int(1, 0). */
+ enum { P1 = 0xe90f1258 }; /* This is hash_int(2, 0). */
+ return (x ? P0 : P1) ^ HASH_ROT(basis, 1);
+}
+
+static inline uint32_t hash_double(double x, uint32_t basis)
+{
+ uint32_t value[2];
+ BUILD_ASSERT_DECL(sizeof x == sizeof value);
+
+ memcpy(value, &x, sizeof value);
+ return hash_3words(value[0], value[1], basis);
+}
+
+static inline uint32_t hash_pointer(const void *p, uint32_t basis)
+{
+ /* Often pointers are hashed simply by casting to integer type, but that
+ * has pitfalls since the lower bits of a pointer are often all 0 for
+ * alignment reasons. It's hard to guess where the entropy really is, so
+ * we give up here and just use a high-quality hash function.
+ *
+ * The double cast suppresses a warning on 64-bit systems about casting to
+ * an integer to different size. That's OK in this case, since most of the
+ * entropy in the pointer is almost certainly in the lower 32 bits. */
+ return hash_int((uint32_t) (uintptr_t) p, basis);
}
#endif /* hash.h */