f3504ea3dd
Lift code from GitHub to restrict delta computation so that an
object that exists in one fork is not made into a delta against
another object that does not appear in the same forked repository.
* cc/delta-islands:
pack-objects: move 'layer' into 'struct packing_data'
pack-objects: move tree_depth into 'struct packing_data'
t5320: tests for delta islands
repack: add delta-islands support
pack-objects: add delta-islands support
pack-objects: refactor code into compute_layer_order()
Add delta-islands.{c,h}
443 lines
12 KiB
C
443 lines
12 KiB
C
#ifndef PACK_OBJECTS_H
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#define PACK_OBJECTS_H
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#include "object-store.h"
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#include "thread-utils.h"
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#include "pack.h"
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#define DEFAULT_DELTA_CACHE_SIZE (256 * 1024 * 1024)
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#define OE_DFS_STATE_BITS 2
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#define OE_DEPTH_BITS 12
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#define OE_IN_PACK_BITS 10
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#define OE_Z_DELTA_BITS 20
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/*
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* Note that oe_set_size() becomes expensive when the given size is
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* above this limit. Don't lower it too much.
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*/
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#define OE_SIZE_BITS 31
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#define OE_DELTA_SIZE_BITS 23
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/*
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* State flags for depth-first search used for analyzing delta cycles.
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*
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* The depth is measured in delta-links to the base (so if A is a delta
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* against B, then A has a depth of 1, and B a depth of 0).
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*/
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enum dfs_state {
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DFS_NONE = 0,
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DFS_ACTIVE,
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DFS_DONE,
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DFS_NUM_STATES
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};
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/*
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* The size of struct nearly determines pack-objects's memory
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* consumption. This struct is packed tight for that reason. When you
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* add or reorder something in this struct, think a bit about this.
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*
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* basic object info
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* -----------------
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* idx.oid is filled up before delta searching starts. idx.crc32 is
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* only valid after the object is written out and will be used for
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* generating the index. idx.offset will be both gradually set and
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* used in writing phase (base objects get offset first, then deltas
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* refer to them)
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*
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* "size" is the uncompressed object size. Compressed size of the raw
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* data for an object in a pack is not stored anywhere but is computed
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* and made available when reverse .idx is made. Note that when a
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* delta is reused, "size" is the uncompressed _delta_ size, not the
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* canonical one after the delta has been applied.
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*
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* "hash" contains a path name hash which is used for sorting the
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* delta list and also during delta searching. Once prepare_pack()
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* returns it's no longer needed.
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*
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* source pack info
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* ----------------
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* The (in_pack, in_pack_offset) tuple contains the location of the
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* object in the source pack. in_pack_header_size allows quickly
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* skipping the header and going straight to the zlib stream.
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*
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* "type" and "in_pack_type" both describe object type. in_pack_type
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* may contain a delta type, while type is always the canonical type.
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*
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* deltas
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* ------
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* Delta links (delta, delta_child and delta_sibling) are created to
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* reflect that delta graph from the source pack then updated or added
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* during delta searching phase when we find better deltas.
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*
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* delta_child and delta_sibling are last needed in
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* compute_write_order(). "delta" and "delta_size" must remain valid
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* at object writing phase in case the delta is not cached.
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*
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* If a delta is cached in memory and is compressed, delta_data points
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* to the data and z_delta_size contains the compressed size. If it's
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* uncompressed [1], z_delta_size must be zero. delta_size is always
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* the uncompressed size and must be valid even if the delta is not
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* cached.
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*
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* [1] during try_delta phase we don't bother with compressing because
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* the delta could be quickly replaced with a better one.
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*/
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struct object_entry {
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struct pack_idx_entry idx;
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void *delta_data; /* cached delta (uncompressed) */
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off_t in_pack_offset;
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uint32_t hash; /* name hint hash */
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unsigned size_:OE_SIZE_BITS;
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unsigned size_valid:1;
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uint32_t delta_idx; /* delta base object */
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uint32_t delta_child_idx; /* deltified objects who bases me */
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uint32_t delta_sibling_idx; /* other deltified objects who
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* uses the same base as me
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*/
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unsigned delta_size_:OE_DELTA_SIZE_BITS; /* delta data size (uncompressed) */
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unsigned delta_size_valid:1;
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unsigned char in_pack_header_size;
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unsigned in_pack_idx:OE_IN_PACK_BITS; /* already in pack */
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unsigned z_delta_size:OE_Z_DELTA_BITS;
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unsigned type_valid:1;
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unsigned no_try_delta:1;
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unsigned type_:TYPE_BITS;
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unsigned in_pack_type:TYPE_BITS; /* could be delta */
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unsigned preferred_base:1; /*
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* we do not pack this, but is available
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* to be used as the base object to delta
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* objects against.
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*/
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unsigned tagged:1; /* near the very tip of refs */
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unsigned filled:1; /* assigned write-order */
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unsigned dfs_state:OE_DFS_STATE_BITS;
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unsigned depth:OE_DEPTH_BITS;
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unsigned ext_base:1; /* delta_idx points outside packlist */
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/*
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* pahole results on 64-bit linux (gcc and clang)
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*
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* size: 80, bit_padding: 9 bits
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*
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* and on 32-bit (gcc)
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*
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* size: 76, bit_padding: 9 bits
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*/
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};
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struct packing_data {
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struct object_entry *objects;
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uint32_t nr_objects, nr_alloc;
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int32_t *index;
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uint32_t index_size;
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unsigned int *in_pack_pos;
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unsigned long *delta_size;
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/*
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* Only one of these can be non-NULL and they have different
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* sizes. if in_pack_by_idx is allocated, oe_in_pack() returns
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* the pack of an object using in_pack_idx field. If not,
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* in_pack[] array is used the same way as in_pack_pos[]
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*/
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struct packed_git **in_pack_by_idx;
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struct packed_git **in_pack;
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#ifndef NO_PTHREADS
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pthread_mutex_t lock;
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#endif
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/*
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* This list contains entries for bases which we know the other side
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* has (e.g., via reachability bitmaps), but which aren't in our
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* "objects" list.
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*/
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struct object_entry *ext_bases;
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uint32_t nr_ext, alloc_ext;
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uintmax_t oe_size_limit;
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uintmax_t oe_delta_size_limit;
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/* delta islands */
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unsigned int *tree_depth;
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unsigned char *layer;
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};
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void prepare_packing_data(struct packing_data *pdata);
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static inline void packing_data_lock(struct packing_data *pdata)
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{
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#ifndef NO_PTHREADS
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pthread_mutex_lock(&pdata->lock);
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#endif
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}
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static inline void packing_data_unlock(struct packing_data *pdata)
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{
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#ifndef NO_PTHREADS
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pthread_mutex_unlock(&pdata->lock);
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#endif
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}
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struct object_entry *packlist_alloc(struct packing_data *pdata,
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const unsigned char *sha1,
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uint32_t index_pos);
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struct object_entry *packlist_find(struct packing_data *pdata,
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const unsigned char *sha1,
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uint32_t *index_pos);
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static inline uint32_t pack_name_hash(const char *name)
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{
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uint32_t c, hash = 0;
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if (!name)
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return 0;
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/*
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* This effectively just creates a sortable number from the
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* last sixteen non-whitespace characters. Last characters
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* count "most", so things that end in ".c" sort together.
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*/
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while ((c = *name++) != 0) {
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if (isspace(c))
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continue;
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hash = (hash >> 2) + (c << 24);
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}
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return hash;
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}
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static inline enum object_type oe_type(const struct object_entry *e)
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{
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return e->type_valid ? e->type_ : OBJ_BAD;
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}
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static inline void oe_set_type(struct object_entry *e,
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enum object_type type)
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{
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if (type >= OBJ_ANY)
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BUG("OBJ_ANY cannot be set in pack-objects code");
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e->type_valid = type >= OBJ_NONE;
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e->type_ = (unsigned)type;
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}
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static inline unsigned int oe_in_pack_pos(const struct packing_data *pack,
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const struct object_entry *e)
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{
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return pack->in_pack_pos[e - pack->objects];
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}
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static inline void oe_set_in_pack_pos(const struct packing_data *pack,
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const struct object_entry *e,
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unsigned int pos)
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{
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pack->in_pack_pos[e - pack->objects] = pos;
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}
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static inline struct packed_git *oe_in_pack(const struct packing_data *pack,
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const struct object_entry *e)
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{
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if (pack->in_pack_by_idx)
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return pack->in_pack_by_idx[e->in_pack_idx];
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else
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return pack->in_pack[e - pack->objects];
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}
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void oe_map_new_pack(struct packing_data *pack,
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struct packed_git *p);
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static inline void oe_set_in_pack(struct packing_data *pack,
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struct object_entry *e,
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struct packed_git *p)
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{
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if (!p->index)
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oe_map_new_pack(pack, p);
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if (pack->in_pack_by_idx)
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e->in_pack_idx = p->index;
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else
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pack->in_pack[e - pack->objects] = p;
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}
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static inline struct object_entry *oe_delta(
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const struct packing_data *pack,
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const struct object_entry *e)
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{
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if (!e->delta_idx)
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return NULL;
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if (e->ext_base)
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return &pack->ext_bases[e->delta_idx - 1];
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else
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return &pack->objects[e->delta_idx - 1];
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}
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static inline void oe_set_delta(struct packing_data *pack,
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struct object_entry *e,
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struct object_entry *delta)
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{
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if (delta)
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e->delta_idx = (delta - pack->objects) + 1;
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else
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e->delta_idx = 0;
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}
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void oe_set_delta_ext(struct packing_data *pack,
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struct object_entry *e,
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const unsigned char *sha1);
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static inline struct object_entry *oe_delta_child(
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const struct packing_data *pack,
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const struct object_entry *e)
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{
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if (e->delta_child_idx)
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return &pack->objects[e->delta_child_idx - 1];
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return NULL;
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}
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static inline void oe_set_delta_child(struct packing_data *pack,
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struct object_entry *e,
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struct object_entry *delta)
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{
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if (delta)
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e->delta_child_idx = (delta - pack->objects) + 1;
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else
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e->delta_child_idx = 0;
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}
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static inline struct object_entry *oe_delta_sibling(
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const struct packing_data *pack,
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const struct object_entry *e)
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{
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if (e->delta_sibling_idx)
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return &pack->objects[e->delta_sibling_idx - 1];
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return NULL;
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}
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static inline void oe_set_delta_sibling(struct packing_data *pack,
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struct object_entry *e,
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struct object_entry *delta)
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{
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if (delta)
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e->delta_sibling_idx = (delta - pack->objects) + 1;
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else
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e->delta_sibling_idx = 0;
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}
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unsigned long oe_get_size_slow(struct packing_data *pack,
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const struct object_entry *e);
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static inline unsigned long oe_size(struct packing_data *pack,
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const struct object_entry *e)
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{
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if (e->size_valid)
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return e->size_;
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return oe_get_size_slow(pack, e);
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}
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static inline int oe_size_less_than(struct packing_data *pack,
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const struct object_entry *lhs,
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unsigned long rhs)
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{
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if (lhs->size_valid)
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return lhs->size_ < rhs;
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if (rhs < pack->oe_size_limit) /* rhs < 2^x <= lhs ? */
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return 0;
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return oe_get_size_slow(pack, lhs) < rhs;
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}
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static inline int oe_size_greater_than(struct packing_data *pack,
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const struct object_entry *lhs,
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unsigned long rhs)
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{
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if (lhs->size_valid)
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return lhs->size_ > rhs;
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if (rhs < pack->oe_size_limit) /* rhs < 2^x <= lhs ? */
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return 1;
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return oe_get_size_slow(pack, lhs) > rhs;
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}
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static inline void oe_set_size(struct packing_data *pack,
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struct object_entry *e,
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unsigned long size)
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{
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if (size < pack->oe_size_limit) {
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e->size_ = size;
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e->size_valid = 1;
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} else {
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e->size_valid = 0;
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if (oe_get_size_slow(pack, e) != size)
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BUG("'size' is supposed to be the object size!");
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}
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}
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static inline unsigned long oe_delta_size(struct packing_data *pack,
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const struct object_entry *e)
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{
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if (e->delta_size_valid)
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return e->delta_size_;
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/*
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* pack->detla_size[] can't be NULL because oe_set_delta_size()
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* must have been called when a new delta is saved with
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* oe_set_delta().
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* If oe_delta() returns NULL (i.e. default state, which means
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* delta_size_valid is also false), then the caller must never
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* call oe_delta_size().
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*/
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return pack->delta_size[e - pack->objects];
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}
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static inline void oe_set_delta_size(struct packing_data *pack,
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struct object_entry *e,
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unsigned long size)
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{
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if (size < pack->oe_delta_size_limit) {
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e->delta_size_ = size;
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e->delta_size_valid = 1;
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} else {
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packing_data_lock(pack);
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if (!pack->delta_size)
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ALLOC_ARRAY(pack->delta_size, pack->nr_alloc);
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packing_data_unlock(pack);
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pack->delta_size[e - pack->objects] = size;
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e->delta_size_valid = 0;
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}
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}
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static inline unsigned int oe_tree_depth(struct packing_data *pack,
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struct object_entry *e)
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{
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if (!pack->tree_depth)
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return 0;
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return pack->tree_depth[e - pack->objects];
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}
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static inline void oe_set_tree_depth(struct packing_data *pack,
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struct object_entry *e,
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unsigned int tree_depth)
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{
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if (!pack->tree_depth)
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ALLOC_ARRAY(pack->tree_depth, pack->nr_objects);
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pack->tree_depth[e - pack->objects] = tree_depth;
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}
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static inline unsigned char oe_layer(struct packing_data *pack,
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struct object_entry *e)
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{
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if (!pack->layer)
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return 0;
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return pack->layer[e - pack->objects];
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}
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static inline void oe_set_layer(struct packing_data *pack,
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struct object_entry *e,
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unsigned char layer)
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{
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if (!pack->layer)
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ALLOC_ARRAY(pack->layer, pack->nr_objects);
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pack->layer[e - pack->objects] = layer;
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}
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#endif
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