[ovs-dev] [murmurhash 3/4] hash: Change mhash_finish() data measurement from words to bytes.

Ethan Jackson ethan at nicira.com
Tue Jan 22 21:37:07 UTC 2013


Acked-by: Ethan Jackson <ethan at nicira.com>

Sorry it took a while to get around to this.  Looks good, thanks.

Ethan

On Fri, Dec 14, 2012 at 4:33 PM, Ben Pfaff <blp at nicira.com> wrote:
> murmurhash includes an xor with the number of bytes hashed in its finishing
> step.  Until now, we've only had murmurhash for full words, but an upcoming
> commit adds murmurhash for bytes, so the finishing function will need to
> take a count of bytes instead.
>
> Signed-off-by: Ben Pfaff <blp at nicira.com>
> ---
>  lib/flow.c |    4 ++--
>  lib/hash.c |    2 +-
>  lib/hash.h |    4 ++--
>  3 files changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/lib/flow.c b/lib/flow.c
> index ce9e6c6..89488e5 100644
> --- a/lib/flow.c
> +++ b/lib/flow.c
> @@ -1125,7 +1125,7 @@ miniflow_hash_in_minimask(const struct miniflow *flow,
>          }
>      }
>
> -    return mhash_finish(hash, p - mask->masks.values);
> +    return mhash_finish(hash, (p - mask->masks.values) * 4);
>  }
>
>  /* Returns a hash value for the bits of 'flow' where there are 1-bits in
> @@ -1154,7 +1154,7 @@ flow_hash_in_minimask(const struct flow *flow, const struct minimask *mask,
>          }
>      }
>
> -    return mhash_finish(hash, p - mask->masks.values);
> +    return mhash_finish(hash, (p - mask->masks.values) * 4);
>  }
>
>  /* Initializes 'dst' as a copy of 'src'.  The caller must eventually free 'dst'
> diff --git a/lib/hash.c b/lib/hash.c
> index 41ad1bf..8cee5d0 100644
> --- a/lib/hash.c
> +++ b/lib/hash.c
> @@ -115,5 +115,5 @@ mhash_words(const uint32_t p[], size_t n_words, uint32_t basis)
>      for (i = 0; i < n_words; i++) {
>          hash = mhash_add(hash, p[i]);
>      }
> -    return mhash_finish(hash, n_words);
> +    return mhash_finish(hash, n_words * 4);
>  }
> diff --git a/lib/hash.h b/lib/hash.h
> index 96866c4..d33924f 100644
> --- a/lib/hash.h
> +++ b/lib/hash.h
> @@ -149,9 +149,9 @@ static inline uint32_t mhash_add(uint32_t hash, uint32_t data)
>      return hash * 5 + 0xe6546b64;
>  }
>
> -static inline uint32_t mhash_finish(uint32_t hash, size_t n)
> +static inline uint32_t mhash_finish(uint32_t hash, size_t n_bytes)
>  {
> -    hash ^= n * 4;
> +    hash ^= n_bytes;
>      hash ^= hash >> 16;
>      hash *= 0x85ebca6b;
>      hash ^= hash >> 13;
> --
> 1.7.2.5
>
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