source: rtems-libbsd/freebsd/sys/sys/fnv_hash.h

/*-
 * Fowler / Noll / Vo Hash (FNV Hash)
 * http://www.isthe.com/chongo/tech/comp/fnv/
 *
 * This is an implementation of the algorithms posted above.
 * This file is placed in the public domain by Peter Wemm.
 *
 * $FreeBSD$
 */
#ifndef _SYS_FNV_HASH_H_
#define _SYS_FNV_HASH_H_

typedef u_int32_t Fnv32_t;
typedef u_int64_t Fnv64_t;

#define FNV1_32_INIT ((Fnv32_t) 33554467UL)
#define FNV1_64_INIT ((Fnv64_t) 0xcbf29ce484222325ULL)

#define FNV_32_PRIME ((Fnv32_t) 0x01000193UL)
#define FNV_64_PRIME ((Fnv64_t) 0x100000001b3ULL)

static __inline Fnv32_t
fnv_32_buf(const void *buf, size_t len, Fnv32_t hval)
{
        const u_int8_t *s = (const u_int8_t *)buf;

        while (len-- != 0) {
                hval *= FNV_32_PRIME;
                hval ^= *s++;
        }
        return hval;
}

static __inline Fnv32_t
fnv_32_str(const char *str, Fnv32_t hval)
{
        const u_int8_t *s = (const u_int8_t *)str;
        Fnv32_t c;

        while ((c = *s++) != 0) {
                hval *= FNV_32_PRIME;
                hval ^= c;
        }
        return hval;
}

#ifndef __rtems__
static __inline Fnv64_t
fnv_64_buf(const void *buf, size_t len, Fnv64_t hval)
{
        const u_int8_t *s = (const u_int8_t *)buf;

        while (len-- != 0) {
                hval *= FNV_64_PRIME;
                hval ^= *s++;
        }
        return hval;
}

static __inline Fnv64_t
fnv_64_str(const char *str, Fnv64_t hval)
{
        const u_int8_t *s = (const u_int8_t *)str;
        u_register_t c;          /* 32 bit on i386, 64 bit on alpha */

        while ((c = *s++) != 0) {
                hval *= FNV_64_PRIME;
                hval ^= c;
        }
        return hval;
}
#endif /* __rtems__ */
#endif /* _SYS_FNV_HASH_H_ */