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synced 2025-10-14 08:17:59 +00:00
Merge pull request #2330 from libgit2/cmn/pack-unpack-loop
Make pack object lookup use loops
This commit is contained in:
Vicent Marti
commit
bcf9792f08
283
src/pack.c
283
src/pack.c
@ -514,72 +514,105 @@ int git_packfile_resolve_header(
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return error;
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}
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static int packfile_unpack_delta(
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git_rawobj *obj,
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struct git_pack_file *p,
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git_mwindow **w_curs,
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git_off_t *curpos,
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size_t delta_size,
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git_otype delta_type,
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git_off_t obj_offset)
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{
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git_off_t base_offset, base_key;
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git_rawobj base, delta;
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git_pack_cache_entry *cached = NULL;
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int error, found_base = 0;
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#define SMALL_STACK_SIZE 64
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base_offset = get_delta_base(p, w_curs, curpos, delta_type, obj_offset);
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git_mwindow_close(w_curs);
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if (base_offset == 0)
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return packfile_error("delta offset is zero");
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if (base_offset < 0) /* must actually be an error code */
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return (int)base_offset;
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/**
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* Generate the chain of dependencies which we need to get to the
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* object at `off`. `chain` is used a stack, popping gives the right
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* order to apply deltas on. If an object is found in the pack's base
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* cache, we stop calculating there.
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*/
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static int pack_dependency_chain(git_dependency_chain *chain_out,
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git_pack_cache_entry **cached_out, git_off_t *cached_off,
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struct pack_chain_elem *small_stack, size_t *stack_sz,
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struct git_pack_file *p, git_off_t obj_offset)
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{
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git_dependency_chain chain = GIT_ARRAY_INIT;
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git_mwindow *w_curs = NULL;
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git_off_t curpos = obj_offset, base_offset;
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int error = 0, use_heap = 0;
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size_t size, elem_pos;
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git_otype type;
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if (!p->bases.entries && (cache_init(&p->bases) < 0))
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return -1;
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base_key = base_offset; /* git_packfile_unpack modifies base_offset */
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if ((cached = cache_get(&p->bases, base_offset)) != NULL) {
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memcpy(&base, &cached->raw, sizeof(git_rawobj));
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found_base = 1;
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}
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elem_pos = 0;
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while (true) {
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struct pack_chain_elem *elem;
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git_pack_cache_entry *cached = NULL;
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if (!cached) { /* have to inflate it */
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error = git_packfile_unpack(&base, p, &base_offset);
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/* if we have a base cached, we can stop here instead */
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if ((cached = cache_get(&p->bases, obj_offset)) != NULL) {
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*cached_out = cached;
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*cached_off = obj_offset;
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break;
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}
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/* if we run out of space on the small stack, use the array */
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if (elem_pos == SMALL_STACK_SIZE) {
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git_array_init_to_size(chain, elem_pos);
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GITERR_CHECK_ARRAY(chain);
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memcpy(chain.ptr, small_stack, elem_pos * sizeof(struct pack_chain_elem));
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chain.size = elem_pos;
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use_heap = 1;
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}
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curpos = obj_offset;
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if (!use_heap) {
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elem = &small_stack[elem_pos];
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} else {
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elem = git_array_alloc(chain);
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if (!elem) {
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error = -1;
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goto on_error;
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}
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}
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elem->base_key = obj_offset;
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error = git_packfile_unpack_header(&size, &type, &p->mwf, &w_curs, &curpos);
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git_mwindow_close(&w_curs);
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/*
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* TODO: git.git tries to load the base from other packfiles
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* or loose objects.
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*
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* We'll need to do this in order to support thin packs.
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*/
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if (error < 0)
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return error;
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goto on_error;
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elem->offset = curpos;
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elem->size = size;
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elem->type = type;
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elem->base_key = obj_offset;
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if (type != GIT_OBJ_OFS_DELTA && type != GIT_OBJ_REF_DELTA)
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break;
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base_offset = get_delta_base(p, &w_curs, &curpos, type, obj_offset);
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git_mwindow_close(&w_curs);
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if (base_offset == 0) {
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error = packfile_error("delta offset is zero");
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goto on_error;
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}
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if (base_offset < 0) { /* must actually be an error code */
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error = (int)base_offset;
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goto on_error;
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}
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/* we need to pass the pos *after* the delta-base bit */
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elem->offset = curpos;
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/* go through the loop again, but with the new object */
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obj_offset = base_offset;
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elem_pos++;
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}
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error = packfile_unpack_compressed(&delta, p, w_curs, curpos, delta_size, delta_type);
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git_mwindow_close(w_curs);
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if (error < 0) {
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if (!found_base)
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git__free(base.data);
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return error;
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}
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obj->type = base.type;
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error = git__delta_apply(obj, base.data, base.len, delta.data, delta.len);
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if (error < 0)
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goto on_error;
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if (found_base)
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git_atomic_dec(&cached->refcount);
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else if (cache_add(&p->bases, &base, base_key) < 0)
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git__free(base.data);
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*stack_sz = elem_pos + 1;
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*chain_out = chain;
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return error;
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on_error:
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git__free(delta.data);
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return error; /* error set by git__delta_apply */
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git_array_clear(chain);
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return error;
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}
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int git_packfile_unpack(
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@ -589,48 +622,138 @@ int git_packfile_unpack(
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{
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git_mwindow *w_curs = NULL;
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git_off_t curpos = *obj_offset;
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int error;
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size_t size = 0;
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git_otype type;
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int error, free_base = 0;
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git_dependency_chain chain = GIT_ARRAY_INIT;
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struct pack_chain_elem *elem = NULL, *stack;
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git_pack_cache_entry *cached = NULL;
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struct pack_chain_elem small_stack[SMALL_STACK_SIZE];
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size_t stack_size, elem_pos;
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git_otype base_type;
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/*
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* TODO: optionally check the CRC on the packfile
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*/
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error = pack_dependency_chain(&chain, &cached, obj_offset, small_stack, &stack_size, p, *obj_offset);
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if (error < 0)
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return error;
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obj->data = NULL;
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obj->len = 0;
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obj->type = GIT_OBJ_BAD;
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error = git_packfile_unpack_header(&size, &type, &p->mwf, &w_curs, &curpos);
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git_mwindow_close(&w_curs);
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/* let's point to the right stack */
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stack = chain.ptr ? chain.ptr : small_stack;
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elem_pos = stack_size;
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if (cached) {
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memcpy(obj, &cached->raw, sizeof(git_rawobj));
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base_type = obj->type;
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elem_pos--; /* stack_size includes the base, which isn't actually there */
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} else {
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elem = &stack[--elem_pos];
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base_type = elem->type;
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}
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if (error < 0)
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return error;
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switch (type) {
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case GIT_OBJ_OFS_DELTA:
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case GIT_OBJ_REF_DELTA:
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error = packfile_unpack_delta(
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obj, p, &w_curs, &curpos,
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size, type, *obj_offset);
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break;
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goto cleanup;
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switch (base_type) {
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case GIT_OBJ_COMMIT:
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case GIT_OBJ_TREE:
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case GIT_OBJ_BLOB:
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case GIT_OBJ_TAG:
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error = packfile_unpack_compressed(
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obj, p, &w_curs, &curpos,
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size, type);
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if (!cached) {
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curpos = elem->offset;
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error = packfile_unpack_compressed(obj, p, &w_curs, &curpos, elem->size, elem->type);
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git_mwindow_close(&w_curs);
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base_type = elem->type;
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}
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if (error < 0)
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goto cleanup;
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break;
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case GIT_OBJ_OFS_DELTA:
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case GIT_OBJ_REF_DELTA:
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error = packfile_error("dependency chain ends in a delta");
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goto cleanup;
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default:
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error = packfile_error("invalid packfile type in header");;
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break;
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error = packfile_error("invalid packfile type in header");
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goto cleanup;
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}
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*obj_offset = curpos;
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/*
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* Finding the object we want a cached base element is
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* problematic, as we need to make sure we don't accidentally
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* give the caller the cached object, which it would then feel
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* free to free, so we need to copy the data.
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*/
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if (cached && stack_size == 1) {
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void *data = obj->data;
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obj->data = git__malloc(obj->len + 1);
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GITERR_CHECK_ALLOC(obj->data);
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memcpy(obj->data, data, obj->len + 1);
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git_atomic_dec(&cached->refcount);
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goto cleanup;
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}
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/* we now apply each consecutive delta until we run out */
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while (elem_pos > 0 && !error) {
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git_rawobj base, delta;
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/*
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* We can now try to add the base to the cache, as
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* long as it's not already the cached one.
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*/
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if (!cached)
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free_base = !!cache_add(&p->bases, obj, elem->base_key);
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elem = &stack[elem_pos - 1];
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curpos = elem->offset;
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error = packfile_unpack_compressed(&delta, p, &w_curs, &curpos, elem->size, elem->type);
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git_mwindow_close(&w_curs);
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if (error < 0)
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break;
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/* the current object becomes the new base, on which we apply the delta */
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base = *obj;
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obj->data = NULL;
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obj->len = 0;
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obj->type = GIT_OBJ_BAD;
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error = git__delta_apply(obj, base.data, base.len, delta.data, delta.len);
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obj->type = base_type;
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/*
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* We usually don't want to free the base at this
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* point, as we put it into the cache in the previous
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* iteration. free_base lets us know that we got the
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* base object directly from the packfile, so we can free it.
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*/
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git__free(delta.data);
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if (free_base) {
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free_base = 0;
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git__free(base.data);
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}
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if (cached) {
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git_atomic_dec(&cached->refcount);
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cached = NULL;
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}
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if (error < 0)
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break;
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elem_pos--;
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}
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cleanup:
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if (error < 0)
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git__free(obj->data);
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if (elem)
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*obj_offset = elem->offset;
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git_array_clear(chain);
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return error;
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}
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@ -660,7 +783,7 @@ int git_packfile_stream_open(git_packfile_stream *obj, struct git_pack_file *p,
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st = inflateInit(&obj->zstream);
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if (st != Z_OK) {
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git__free(obj);
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giterr_set(GITERR_ZLIB, "Failed to inflate packfile");
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giterr_set(GITERR_ZLIB, "failed to init packfile stream");
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return -1;
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}
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@ -691,7 +814,7 @@ ssize_t git_packfile_stream_read(git_packfile_stream *obj, void *buffer, size_t
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written = len - obj->zstream.avail_out;
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if (st != Z_OK && st != Z_STREAM_END) {
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giterr_set(GITERR_ZLIB, "Failed to inflate packfile");
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giterr_set(GITERR_ZLIB, "error reading from the zlib stream");
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return -1;
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}
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@ -736,7 +859,7 @@ int packfile_unpack_compressed(
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st = inflateInit(&stream);
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if (st != Z_OK) {
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git__free(buffer);
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giterr_set(GITERR_ZLIB, "Failed to inflate packfile");
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giterr_set(GITERR_ZLIB, "failed to init zlib stream on unpack");
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return -1;
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}
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@ -763,7 +886,7 @@ int packfile_unpack_compressed(
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if ((st != Z_STREAM_END) || stream.total_out != size) {
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git__free(buffer);
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giterr_set(GITERR_ZLIB, "Failed to inflate packfile");
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giterr_set(GITERR_ZLIB, "error inflating zlib stream");
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return -1;
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}
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10
src/pack.h
10
src/pack.h
@ -17,6 +17,7 @@
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#include "mwindow.h"
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#include "odb.h"
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#include "oidmap.h"
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#include "array.h"
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#define GIT_PACK_FILE_MODE 0444
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@ -60,6 +61,15 @@ typedef struct git_pack_cache_entry {
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git_rawobj raw;
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} git_pack_cache_entry;
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struct pack_chain_elem {
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git_off_t base_key;
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git_off_t offset;
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size_t size;
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git_otype type;
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};
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typedef git_array_t(struct pack_chain_elem) git_dependency_chain;
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#include "offmap.h"
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GIT__USE_OFFMAP;
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