#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(const uint32_t *, uint32_t basis);
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)
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_2words(value, 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 */