int git_packfile_unpack()

in src/pack.c [616:763]

• 103 lines of code
• 24 McCabe index (conditional complexity)

int git_packfile_unpack(
	git_rawobj *obj,
	struct git_pack_file *p,
	off64_t *obj_offset)
{
	git_mwindow *w_curs = NULL;
	off64_t curpos = *obj_offset;
	int error, free_base = 0;
	git_dependency_chain chain = GIT_ARRAY_INIT;
	struct pack_chain_elem *elem = NULL, *stack;
	git_pack_cache_entry *cached = NULL;
	struct pack_chain_elem small_stack[SMALL_STACK_SIZE];
	size_t stack_size = 0, elem_pos, alloclen;
	git_object_t base_type;

	/*
	 * TODO: optionally check the CRC on the packfile
	 */

	error = pack_dependency_chain(&chain, &cached, obj_offset, small_stack, &stack_size, p, *obj_offset);
	if (error < 0)
		return error;

	obj->data = NULL;
	obj->len = 0;
	obj->type = GIT_OBJECT_INVALID;

	/* let's point to the right stack */
	stack = chain.ptr ? chain.ptr : small_stack;

	elem_pos = stack_size;
	if (cached) {
		memcpy(obj, &cached->raw, sizeof(git_rawobj));
		base_type = obj->type;
		elem_pos--;	/* stack_size includes the base, which isn't actually there */
	} else {
		elem = &stack[--elem_pos];
		base_type = elem->type;
	}

	switch (base_type) {
	case GIT_OBJECT_COMMIT:
	case GIT_OBJECT_TREE:
	case GIT_OBJECT_BLOB:
	case GIT_OBJECT_TAG:
		if (!cached) {
			curpos = elem->offset;
			error = packfile_unpack_compressed(obj, p, &w_curs, &curpos, elem->size, elem->type);
			git_mwindow_close(&w_curs);
			base_type = elem->type;
		}
		if (error < 0)
			goto cleanup;
		break;
	case GIT_OBJECT_OFS_DELTA:
	case GIT_OBJECT_REF_DELTA:
		error = packfile_error("dependency chain ends in a delta");
		goto cleanup;
	default:
		error = packfile_error("invalid packfile type in header");
		goto cleanup;
	}

	/*
	 * Finding the object we want a cached base element is
	 * problematic, as we need to make sure we don't accidentally
	 * give the caller the cached object, which it would then feel
	 * free to free, so we need to copy the data.
	 */
	if (cached && stack_size == 1) {
		void *data = obj->data;

		GIT_ERROR_CHECK_ALLOC_ADD(&alloclen, obj->len, 1);
		obj->data = git__malloc(alloclen);
		GIT_ERROR_CHECK_ALLOC(obj->data);

		memcpy(obj->data, data, obj->len + 1);
		git_atomic_dec(&cached->refcount);
		goto cleanup;
	}

	/* we now apply each consecutive delta until we run out */
	while (elem_pos > 0 && !error) {
		git_rawobj base, delta;

		/*
		 * We can now try to add the base to the cache, as
		 * long as it's not already the cached one.
		 */
		if (!cached)
			free_base = !!cache_add(&cached, &p->bases, obj, elem->base_key);

		elem = &stack[elem_pos - 1];
		curpos = elem->offset;
		error = packfile_unpack_compressed(&delta, p, &w_curs, &curpos, elem->size, elem->type);
		git_mwindow_close(&w_curs);

		if (error < 0) {
			/* We have transferred ownership of the data to the cache. */
			obj->data = NULL;
			break;
		}

		/* the current object becomes the new base, on which we apply the delta */
		base = *obj;
		obj->data = NULL;
		obj->len = 0;
		obj->type = GIT_OBJECT_INVALID;

		error = git_delta_apply(&obj->data, &obj->len, base.data, base.len, delta.data, delta.len);
		obj->type = base_type;

		/*
		 * We usually don't want to free the base at this
		 * point, as we put it into the cache in the previous
		 * iteration. free_base lets us know that we got the
		 * base object directly from the packfile, so we can free it.
		 */
		git__free(delta.data);
		if (free_base) {
			free_base = 0;
			git__free(base.data);
		}

		if (cached) {
			git_atomic_dec(&cached->refcount);
			cached = NULL;
		}

		if (error < 0)
			break;

		elem_pos--;
	}

cleanup:
	if (error < 0) {
		git__free(obj->data);
		if (cached)
			git_atomic_dec(&cached->refcount);
	}

	if (elem)
		*obj_offset = curpos;

	git_array_clear(chain);
	return error;
}