On Fri, 28 Feb 2014, Michael Haggerty wrote:

> Signed-off-by: Michael Haggerty <mhag...@alum.mit.edu>

Acked-by: Nicolas Pitre <n...@fluxnic.net>

> ---
>  object.c | 29 ++++++++++++++++++++++++++++-
>  object.h |  7 +++++++
>  2 files changed, 35 insertions(+), 1 deletion(-)
> 
> diff --git a/object.c b/object.c
> index 584f7ac..57a0890 100644
> --- a/object.c
> +++ b/object.c
> @@ -43,14 +43,32 @@ int type_from_string(const char *str)
>       die("invalid object type \"%s\"", str);
>  }
>  
> +/*
> + * Return a numerical hash value between 0 and n-1 for the object with
> + * the specified sha1.  n must be a power of 2.  Please note that the
> + * return value is *not* consistent across computer architectures.
> + */
>  static unsigned int hash_obj(const unsigned char *sha1, unsigned int n)
>  {
>       unsigned int hash;
> +
> +     /*
> +      * Since the sha1 is essentially random, we just take the
> +      * required number of bits directly from the first
> +      * sizeof(unsigned int) bytes of sha1.  First we have to copy
> +      * the bytes into a properly aligned integer.  If we cared
> +      * about getting consistent results across architectures, we
> +      * would have to call ntohl() here, too.
> +      */
>       memcpy(&hash, sha1, sizeof(unsigned int));
> -     /* Assumes power-of-2 hash sizes in grow_object_hash */
>       return hash & (n - 1);
>  }
>  
> +/*
> + * Insert obj into the hash table hash, which has length size (which
> + * must be a power of 2).  On collisions, simply overflow to the next
> + * empty bucket.
> + */
>  static void insert_obj_hash(struct object *obj, struct object **hash, 
> unsigned int size)
>  {
>       unsigned int j = hash_obj(obj->sha1, size);
> @@ -63,6 +81,10 @@ static void insert_obj_hash(struct object *obj, struct 
> object **hash, unsigned i
>       hash[j] = obj;
>  }
>  
> +/*
> + * Look up the record for the given sha1 in the hash map stored in
> + * obj_hash.  Return NULL if it was not found.
> + */
>  struct object *lookup_object(const unsigned char *sha1)
>  {
>       unsigned int i, first;
> @@ -92,6 +114,11 @@ struct object *lookup_object(const unsigned char *sha1)
>       return obj;
>  }
>  
> +/*
> + * Increase the size of the hash map stored in obj_hash to the next
> + * power of 2 (but at least 32).  Copy the existing values to the new
> + * hash map.
> + */
>  static void grow_object_hash(void)
>  {
>       int i;
> diff --git a/object.h b/object.h
> index dc5df8c..732bf4d 100644
> --- a/object.h
> +++ b/object.h
> @@ -42,7 +42,14 @@ struct object {
>  extern const char *typename(unsigned int type);
>  extern int type_from_string(const char *str);
>  
> +/*
> + * Return the current number of buckets in the object hashmap.
> + */
>  extern unsigned int get_max_object_index(void);
> +
> +/*
> + * Return the object from the specified bucket in the object hashmap.
> + */
>  extern struct object *get_indexed_object(unsigned int);
>  
>  /*
> -- 
> 1.8.5.3
> 
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