diff options
| -rw-r--r-- | lib/hash.c | 23 | ||||
| -rw-r--r-- | lib/hash.h | 13 |
2 files changed, 22 insertions, 14 deletions
diff --git a/lib/hash.c b/lib/hash.c index 63b4784fc..61e17b278 100644 --- a/lib/hash.c +++ b/lib/hash.c @@ -1,5 +1,5 @@ /* - * Copyright (c) 2008, 2009 Nicira Networks. + * Copyright (c) 2008, 2009, 2010 Nicira Networks. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. @@ -52,21 +52,24 @@ hash_words(const uint32_t *p, size_t n, uint32_t basis) return c; } -/* Returns the hash of the pair of aligned 32-bit words at 'p', starting from - * 'basis'. */ +/* Returns the hash of 'a', 'b', and 'c'. */ uint32_t -hash_2words(const uint32_t *p, uint32_t basis) +hash_3words(uint32_t a, uint32_t b, uint32_t c) { - uint32_t a, b, c; - - a = b = c = 0xdeadbeef + (2 << 2) + basis; - b += p[1]; - a += p[0]; + a += 0xdeadbeef; + b += 0xdeadbeef; + c += 0xdeadbeef; HASH_FINAL(a, b, c); - return c; } +/* Returns the hash of 'a' and 'b'. */ +uint32_t +hash_2words(uint32_t a, uint32_t b) +{ + return hash_3words(a, b, 0); +} + /* Returns the hash of the 'n' bytes at 'p', starting from 'basis'. */ uint32_t hash_bytes(const void *p_, size_t n, uint32_t basis) diff --git a/lib/hash.h b/lib/hash.h index 5f6409cb1..109612fb7 100644 --- a/lib/hash.h +++ b/lib/hash.h @@ -1,5 +1,5 @@ /* - * Copyright (c) 2008, 2009 Nicira Networks. + * Copyright (c) 2008, 2009, 2010 Nicira Networks. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. @@ -49,7 +49,8 @@ } 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_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) @@ -58,7 +59,11 @@ 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; @@ -87,7 +92,7 @@ static inline uint32_t hash_double(double x, uint32_t basis) BUILD_ASSERT_DECL(sizeof x == sizeof value); memcpy(value, &x, sizeof value); - return hash_2words(value, basis); + return hash_3words(value[0], value[1], basis); } static inline uint32_t hash_pointer(const void *p, uint32_t basis) |