mirror of
https://git.proxmox.com/git/libgit2
synced 2026-01-03 19:59:33 +00:00
pack: use a cache for delta bases when unpacking
Bring back the use of the delta base cache for unpacking objects. When generating the delta chain, we stop when we find a delta base in the pack's cache and use that as the starting point.
This commit is contained in:
Carlos Martín Nieto
parent
2acdf4b854
commit
a332e91c92
145
src/pack.c
145
src/pack.c
@ -42,8 +42,9 @@ static int pack_entry_find_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`. As we use a stack, the latest is the base object,
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* the rest are deltas.
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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, struct git_pack_file *p, git_off_t off);
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@ -521,67 +522,6 @@ 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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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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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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if (!cached) { /* have to inflate it */
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error = git_packfile_unpack(&base, p, &base_offset);
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if (error < 0)
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return error;
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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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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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}
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int git_packfile_unpack(
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git_rawobj *obj,
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struct git_pack_file *p,
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@ -589,10 +529,10 @@ 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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git_dependency_chain chain;
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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;
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git_pack_cache_entry *cached = NULL;
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git_otype base_type;
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/*
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@ -609,16 +549,38 @@ int git_packfile_unpack(
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/* the first one is the base, so we expand that one */
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elem = git_array_pop(chain);
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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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if (elem->cached) {
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cached = elem->cached_entry;
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memcpy(obj, &cached->raw, sizeof(git_rawobj));
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base_type = obj->type;
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} else {
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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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free_base = 1;
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}
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if (error < 0)
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goto cleanup;
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base_type = elem->type;
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/*
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* Finding the object we want as the 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 && git_array_size(chain) == 0) {
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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 (git_array_size(chain) > 0) {
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while (git_array_size(chain) > 0 && !error) {
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git_rawobj base, delta;
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elem = git_array_pop(chain);
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@ -636,16 +598,39 @@ int git_packfile_unpack(
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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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git__free(base.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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obj->type = base_type;
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/* only try to cache if we're not handing this buffer off to the caller */
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if (git_array_size(chain) > 0 &&
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(error = cache_add(&p->bases, obj, elem->base_key)) < 0)
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goto cleanup;
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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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*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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@ -1248,8 +1233,12 @@ static int pack_dependency_chain(git_dependency_chain *chain_out, struct git_pac
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size_t size;
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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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while (!found_base && error == 0) {
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struct pack_chain_elem *elem;
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git_pack_cache_entry *cached = NULL;
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curpos = obj_offset;
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elem = git_array_alloc(chain);
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@ -1262,13 +1251,23 @@ static int pack_dependency_chain(git_dependency_chain *chain_out, struct git_pac
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if (error < 0)
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return error;
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elem->cached = 0;
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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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switch (type) {
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case GIT_OBJ_OFS_DELTA:
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case GIT_OBJ_REF_DELTA:
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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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elem->cached_entry = cached;
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elem->cached = 1;
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found_base = 1;
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break;
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}
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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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@ -62,9 +62,14 @@ typedef struct git_pack_cache_entry {
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} git_pack_cache_entry;
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struct pack_chain_elem {
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int cached;
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git_off_t base_key;
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/* if we don't have it cached we have this */
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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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/* if cached, we have this instead */
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git_pack_cache_entry *cached_entry;
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};
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typedef git_array_t(struct pack_chain_elem) git_dependency_chain;
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