index-pack: rationalize delta resolution code

Instead of having strange loops for walking unresolved deltas with the
same base duplicated in many places, let's rework the code so this is
done in a single place instead.  This simplifies callers quite a bit too.

Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/index-pack.c b/index-pack.c
index d3a4d31b4e92d69eb32d1a18ebb7be1f7470d1d1..82843e7e8df2a77ec1aca41acee5ac8834724586 100644 (file)
--- a/index-pack.c
+++ b/index-pack.c
@@ -244,7 +244,8 @@ static void link_base_data(struct base_data *base, struct base_data *c)
 
        c->base = base;
        c->child = NULL;
-       base_cache_used += c->size;
+       if (c->data)
+               base_cache_used += c->size;
        prune_base_data(c);
 }
 
@@ -494,8 +495,10 @@ static void *get_base_data(struct base_data *c)
                        free(raw);
                        if (!c->data)
                                bad_object(obj->idx.offset, "failed to apply delta");
-               } else
+               } else {
                        c->data = get_data_from_pack(obj);
+                       c->size = obj->size;
+               }
 
                base_cache_used += c->size;
                prune_base_data(c);
@@ -504,49 +507,73 @@ static void *get_base_data(struct base_data *c)
 }
 
 static void resolve_delta(struct object_entry *delta_obj,
-                         struct base_data *base_obj, enum object_type type)
+                         struct base_data *base, struct base_data *result)
 {
        void *delta_data;
        unsigned long delta_size;
-       union delta_base delta_base;
-       int j, first, last;
-       struct base_data result;
 
-       delta_obj->real_type = type;
+       delta_obj->real_type = base->obj->type;
        delta_data = get_data_from_pack(delta_obj);
        delta_size = delta_obj->size;
-       result.data = patch_delta(get_base_data(base_obj), base_obj->size,
-                            delta_data, delta_size,
-                            &result.size);
+       result->obj = delta_obj;
+       result->data = patch_delta(get_base_data(base), base->obj->size,
+                                  delta_data, delta_size, &result->size);
        free(delta_data);
-       if (!result.data)
+       if (!result->data)
                bad_object(delta_obj->idx.offset, "failed to apply delta");
-       sha1_object(result.data, result.size, type, delta_obj->idx.sha1);
+       sha1_object(result->data, result->size, delta_obj->real_type,
+                   delta_obj->idx.sha1);
        nr_resolved_deltas++;
+}
+
+static void find_unresolved_deltas(struct base_data *base,
+                                  struct base_data *prev_base)
+{
+       int i, ref, ref_first, ref_last, ofs, ofs_first, ofs_last;
+
+       /*
+        * This is a recursive function. Those brackets should help reducing
+        * stack usage by limiting the scope of the delta_base union.
+        */
+       {
+               union delta_base base_spec;
+
+               hashcpy(base_spec.sha1, base->obj->idx.sha1);
+               ref = !find_delta_children(&base_spec, &ref_first, &ref_last);
+
+               memset(&base_spec, 0, sizeof(base_spec));
+               base_spec.offset = base->obj->idx.offset;
+               ofs = !find_delta_children(&base_spec, &ofs_first, &ofs_last);
+       }
+
+       if (!ref && !ofs)
+               return;
 
-       result.obj = delta_obj;
-       link_base_data(base_obj, &result);
+       link_base_data(prev_base, base);
 
-       hashcpy(delta_base.sha1, delta_obj->idx.sha1);
-       if (!find_delta_children(&delta_base, &first, &last)) {
-               for (j = first; j <= last; j++) {
-                       struct object_entry *child = objects + deltas[j].obj_no;
-                       if (child->real_type == OBJ_REF_DELTA)
-                               resolve_delta(child, &result, type);
+       if (ref) {
+               for (i = ref_first; i <= ref_last; i++) {
+                       struct object_entry *child = objects + deltas[i].obj_no;
+                       if (child->real_type == OBJ_REF_DELTA) {
+                               struct base_data result;
+                               resolve_delta(child, base, &result);
+                               find_unresolved_deltas(&result, base);
+                       }
                }
        }
 
-       memset(&delta_base, 0, sizeof(delta_base));
-       delta_base.offset = delta_obj->idx.offset;
-       if (!find_delta_children(&delta_base, &first, &last)) {
-               for (j = first; j <= last; j++) {
-                       struct object_entry *child = objects + deltas[j].obj_no;
-                       if (child->real_type == OBJ_OFS_DELTA)
-                               resolve_delta(child, &result, type);
+       if (ofs) {
+               for (i = ofs_first; i <= ofs_last; i++) {
+                       struct object_entry *child = objects + deltas[i].obj_no;
+                       if (child->real_type == OBJ_OFS_DELTA) {
+                               struct base_data result;
+                               resolve_delta(child, base, &result);
+                               find_unresolved_deltas(&result, base);
+                       }
                }
        }
 
-       unlink_base_data(&result);
+       unlink_base_data(base);
 }
 
 static int compare_delta_entry(const void *a, const void *b)
@@ -622,37 +649,13 @@ static void parse_pack_objects(unsigned char *sha1)
                progress = start_progress("Resolving deltas", nr_deltas);
        for (i = 0; i < nr_objects; i++) {
                struct object_entry *obj = &objects[i];
-               union delta_base base;
-               int j, ref, ref_first, ref_last, ofs, ofs_first, ofs_last;
                struct base_data base_obj;
 
                if (obj->type == OBJ_REF_DELTA || obj->type == OBJ_OFS_DELTA)
                        continue;
-               hashcpy(base.sha1, obj->idx.sha1);
-               ref = !find_delta_children(&base, &ref_first, &ref_last);
-               memset(&base, 0, sizeof(base));
-               base.offset = obj->idx.offset;
-               ofs = !find_delta_children(&base, &ofs_first, &ofs_last);
-               if (!ref && !ofs)
-                       continue;
-               base_obj.data = get_data_from_pack(obj);
-               base_obj.size = obj->size;
                base_obj.obj = obj;
-               link_base_data(NULL, &base_obj);
-
-               if (ref)
-                       for (j = ref_first; j <= ref_last; j++) {
-                               struct object_entry *child = objects + deltas[j].obj_no;
-                               if (child->real_type == OBJ_REF_DELTA)
-                                       resolve_delta(child, &base_obj, obj->type);
-                       }
-               if (ofs)
-                       for (j = ofs_first; j <= ofs_last; j++) {
-                               struct object_entry *child = objects + deltas[j].obj_no;
-                               if (child->real_type == OBJ_OFS_DELTA)
-                                       resolve_delta(child, &base_obj, obj->type);
-                       }
-               unlink_base_data(&base_obj);
+               base_obj.data = NULL;
+               find_unresolved_deltas(&base_obj, NULL);
                display_progress(progress, nr_resolved_deltas);
        }
 }
@@ -745,7 +748,6 @@ static void fix_unresolved_deltas(struct sha1file *f, int nr_unresolved)
        for (i = 0; i < n; i++) {
                struct delta_entry *d = sorted_by_pos[i];
                enum object_type type;
-               int j, first, last;
                struct base_data base_obj;
 
                if (objects[d->obj_no].real_type != OBJ_REF_DELTA)
@@ -759,16 +761,7 @@ static void fix_unresolved_deltas(struct sha1file *f, int nr_unresolved)
                        die("local object %s is corrupt", sha1_to_hex(d->base.sha1));
                base_obj.obj = append_obj_to_pack(f, d->base.sha1,
                                        base_obj.data, base_obj.size, type);
-               link_base_data(NULL, &base_obj);
-
-               find_delta_children(&d->base, &first, &last);
-               for (j = first; j <= last; j++) {
-                       struct object_entry *child = objects + deltas[j].obj_no;
-                       if (child->real_type == OBJ_REF_DELTA)
-                               resolve_delta(child, &base_obj, type);
-               }
-
-               unlink_base_data(&base_obj);
+               find_unresolved_deltas(&base_obj, NULL);
                display_progress(progress, nr_resolved_deltas);
        }
        free(sorted_by_pos);