git object hash cleanups

This IMNSHO cleans up the object hashing.

The hash expansion is separated out into a function of its own, the hash
array (and size) names are made more obvious, and the code is generally
made to look a bit more like the object-ref hashing.

It also gets rid of "find_object()" returning an index (or negative
position if no object is found), since that is made redundant by the
simplified object rehashing. The basic operation is now "lookup_object()"
which just returns the object itself.

There's an almost unmeasurable speed increase, but more importantly, I
think the end result is more readable.

Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>

diff --git a/object.c b/object.c
index 31c77ea03a2083ce9ed7c71a2b4d90fb6b944c78..37277f94384fff1320381a370dd4d6c91a4ded2c 100644 (file)
--- a/object.c
+++ b/object.c
@@ -5,88 +5,97 @@
 #include "commit.h"
 #include "tag.h"
 
-static struct object **objs;
-static int nr_objs, obj_allocs;
+static struct object **obj_hash;
+static int nr_objs, obj_hash_size;
 
 unsigned int get_max_object_index(void)
 {
-       return obj_allocs;
+       return obj_hash_size;
 }
 
 struct object *get_indexed_object(unsigned int idx)
 {
-       return objs[idx];
+       return obj_hash[idx];
 }
 
 const char *type_names[] = {
        "none", "blob", "tree", "commit", "bad"
 };
 
+static unsigned int hash_obj(struct object *obj, unsigned int n)
+{
+       unsigned int hash = *(unsigned int *)obj->sha1;
+       return hash % n;
+}
+
+static void insert_obj_hash(struct object *obj, struct object **hash, unsigned int size)
+{
+       int j = hash_obj(obj, size);
+
+       while (hash[j]) {
+               j++;
+               if (j >= size)
+                       j = 0;
+       }
+       hash[j] = obj;
+}
+
 static int hashtable_index(const unsigned char *sha1)
 {
        unsigned int i;
        memcpy(&i, sha1, sizeof(unsigned int));
-       return (int)(i % obj_allocs);
+       return (int)(i % obj_hash_size);
 }
 
-static int find_object(const unsigned char *sha1)
+struct object *lookup_object(const unsigned char *sha1)
 {
        int i;
+       struct object *obj;
 
-       if (!objs)
-               return -1;
+       if (!obj_hash)
+               return NULL;
 
        i = hashtable_index(sha1);
-       while (objs[i]) {
-               if (memcmp(sha1, objs[i]->sha1, 20) == 0)
-                       return i;
+       while ((obj = obj_hash[i]) != NULL) {
+               if (!memcmp(sha1, obj->sha1, 20))
+                       break;
                i++;
-               if (i == obj_allocs)
+               if (i == obj_hash_size)
                        i = 0;
        }
-       return -1 - i;
+       return obj;
 }
 
-struct object *lookup_object(const unsigned char *sha1)
+static void grow_object_hash(void)
 {
-       int pos = find_object(sha1);
-       if (pos >= 0)
-               return objs[pos];
-       return NULL;
+       int i;
+       int new_hash_size = obj_hash_size < 32 ? 32 : 2 * obj_hash_size;
+       struct object **new_hash;
+
+       new_hash = calloc(new_hash_size, sizeof(struct object *));
+       for (i = 0; i < obj_hash_size; i++) {
+               struct object *obj = obj_hash[i];
+               if (!obj)
+                       continue;
+               insert_obj_hash(obj, new_hash, new_hash_size);
+       }
+       free(obj_hash);
+       obj_hash = new_hash;
+       obj_hash_size = new_hash_size;
 }
 
 void created_object(const unsigned char *sha1, struct object *obj)
 {
-       int pos;
-
        obj->parsed = 0;
-       memcpy(obj->sha1, sha1, 20);
-       obj->type = TYPE_NONE;
        obj->used = 0;
+       obj->type = TYPE_NONE;
+       obj->flags = 0;
+       memcpy(obj->sha1, sha1, 20);
 
-       if (obj_allocs - 1 <= nr_objs * 2) {
-               int i, count = obj_allocs;
-               obj_allocs = (obj_allocs < 32 ? 32 : 2 * obj_allocs);
-               objs = xrealloc(objs, obj_allocs * sizeof(struct object *));
-               memset(objs + count, 0, (obj_allocs - count)
-                               * sizeof(struct object *));
-               for (i = 0; i < obj_allocs; i++)
-                       if (objs[i]) {
-                               int j = find_object(objs[i]->sha1);
-                               if (j != i) {
-                                       j = -1 - j;
-                                       objs[j] = objs[i];
-                                       objs[i] = NULL;
-                               }
-                       }
-       }
-
-       pos = find_object(sha1);
-       if (pos >= 0)
-               die("Inserting %s twice\n", sha1_to_hex(sha1));
-       pos = -pos-1;
+       if (obj_hash_size - 1 <= nr_objs * 2)
+               grow_object_hash();
 
-       objs[pos] = obj;
+       insert_obj_hash(obj, obj_hash, obj_hash_size);
        nr_objs++;
 }