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index-pack: rationalize delta resolution code
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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>
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Nicolas Pitre authored and Junio C Hamano committed Oct 18, 2008
1 parent 46dc1b0 commit 9441b61
Showing 1 changed file with 58 additions and 65 deletions.
123 changes: 58 additions & 65 deletions index-pack.c
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Original file line number Diff line number Diff line change
Expand Up @@ -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);
}

Expand Down Expand Up @@ -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);
Expand All @@ -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)
Expand Down Expand Up @@ -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);
}
}
Expand Down Expand Up @@ -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)
Expand All @@ -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);
Expand Down

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