pack-objects.h - git - Git at Google

 #ifndef PACK_OBJECTS_H
 #define PACK_OBJECTS_H

 #include "object-store.h"
 #include "thread-utils.h"
 #include "pack.h"

 struct repository;

 #define DEFAULT_DELTA_CACHE_SIZE (256 * 1024 * 1024)

 #define OE_DFS_STATE_BITS	2
 #define OE_DEPTH_BITS		12
 #define OE_IN_PACK_BITS		10
 #define OE_Z_DELTA_BITS		20
 /*
  * Note that oe_set_size() becomes expensive when the given size is
  * above this limit. Don't lower it too much.
  */
 #define OE_SIZE_BITS		31
 #define OE_DELTA_SIZE_BITS	23

 /*
  * State flags for depth-first search used for analyzing delta cycles.
  *
  * The depth is measured in delta-links to the base (so if A is a delta
  * against B, then A has a depth of 1, and B a depth of 0).
  */
 enum dfs_state {
 	DFS_NONE = 0,
 	DFS_ACTIVE,
 	DFS_DONE,
 	DFS_NUM_STATES
 };

 /*
  * The size of struct nearly determines pack-objects's memory
  * consumption. This struct is packed tight for that reason. When you
  * add or reorder something in this struct, think a bit about this.
  *
  * basic object info
  * -----------------
  * idx.oid is filled up before delta searching starts. idx.crc32 is
  * only valid after the object is written out and will be used for
  * generating the index. idx.offset will be both gradually set and
  * used in writing phase (base objects get offset first, then deltas
  * refer to them)
  *
  * "size" is the uncompressed object size. Compressed size of the raw
  * data for an object in a pack is not stored anywhere but is computed
  * and made available when reverse .idx is made. Note that when a
  * delta is reused, "size" is the uncompressed _delta_ size, not the
  * canonical one after the delta has been applied.
  *
  * "hash" contains a path name hash which is used for sorting the
  * delta list and also during delta searching. Once prepare_pack()
  * returns it's no longer needed.
  *
  * source pack info
  * ----------------
  * The (in_pack, in_pack_offset) tuple contains the location of the
  * object in the source pack. in_pack_header_size allows quickly
  * skipping the header and going straight to the zlib stream.
  *
  * "type" and "in_pack_type" both describe object type. in_pack_type
  * may contain a delta type, while type is always the canonical type.
  *
  * deltas
  * ------
  * Delta links (delta, delta_child and delta_sibling) are created to
  * reflect that delta graph from the source pack then updated or added
  * during delta searching phase when we find better deltas.
  *
  * delta_child and delta_sibling are last needed in
  * compute_write_order(). "delta" and "delta_size" must remain valid
  * at object writing phase in case the delta is not cached.
  *
  * If a delta is cached in memory and is compressed, delta_data points
  * to the data and z_delta_size contains the compressed size. If it's
  * uncompressed [1], z_delta_size must be zero. delta_size is always
  * the uncompressed size and must be valid even if the delta is not
  * cached.
  *
  * [1] during try_delta phase we don't bother with compressing because
  * the delta could be quickly replaced with a better one.
  */
 struct object_entry {
 	struct pack_idx_entry idx;
 	void *delta_data;	/* cached delta (uncompressed) */
 	off_t in_pack_offset;
 	uint32_t hash;			/* name hint hash */
 	unsigned size_:OE_SIZE_BITS;
 	unsigned size_valid:1;
 	uint32_t delta_idx;	/* delta base object */
 	uint32_t delta_child_idx; /* deltified objects who bases me */
 	uint32_t delta_sibling_idx; /* other deltified objects who
 				     * uses the same base as me
 				     */
 	unsigned delta_size_:OE_DELTA_SIZE_BITS; /* delta data size (uncompressed) */
 	unsigned delta_size_valid:1;
 	unsigned char in_pack_header_size;
 	unsigned in_pack_idx:OE_IN_PACK_BITS;	/* already in pack */
 	unsigned z_delta_size:OE_Z_DELTA_BITS;
 	unsigned type_valid:1;
 	unsigned no_try_delta:1;
 	unsigned type_:TYPE_BITS;
 	unsigned in_pack_type:TYPE_BITS; /* could be delta */

 	unsigned preferred_base:1; /*
 				    * we do not pack this, but is available
 				    * to be used as the base object to delta
 				    * objects against.
 				    */
 	unsigned tagged:1; /* near the very tip of refs */
 	unsigned filled:1; /* assigned write-order */
 	unsigned dfs_state:OE_DFS_STATE_BITS;
 	unsigned depth:OE_DEPTH_BITS;
 	unsigned ext_base:1; /* delta_idx points outside packlist */

 	/*
 	 * pahole results on 64-bit linux (gcc and clang)
 	 *
 	 *   size: 80, bit_padding: 9 bits
 	 *
 	 * and on 32-bit (gcc)
 	 *
 	 *   size: 76, bit_padding: 9 bits
 	 */
 };

 struct packing_data {
 	struct repository *repo;
 	struct object_entry *objects;
 	uint32_t nr_objects, nr_alloc;

 	int32_t *index;
 	uint32_t index_size;

 	unsigned int *in_pack_pos;
 	unsigned long *delta_size;

 	/*
 	 * Only one of these can be non-NULL and they have different
 	 * sizes. if in_pack_by_idx is allocated, oe_in_pack() returns
 	 * the pack of an object using in_pack_idx field. If not,
 	 * in_pack[] array is used the same way as in_pack_pos[]
 	 */
 	struct packed_git **in_pack_by_idx;
 	struct packed_git **in_pack;

 	/*
 	 * During packing with multiple threads, protect the in-core
 	 * object database from concurrent accesses.
 	 */
 	pthread_mutex_t odb_lock;

 	/*
 	 * This list contains entries for bases which we know the other side
 	 * has (e.g., via reachability bitmaps), but which aren't in our
 	 * "objects" list.
 	 */
 	struct object_entry *ext_bases;
 	uint32_t nr_ext, alloc_ext;

 	uintmax_t oe_size_limit;
 	uintmax_t oe_delta_size_limit;

 	/* delta islands */
 	unsigned int *tree_depth;
 	unsigned char *layer;
 };

 void prepare_packing_data(struct repository *r, struct packing_data *pdata);

 /* Protect access to object database */
 static inline void packing_data_lock(struct packing_data *pdata)
 {
 	pthread_mutex_lock(&pdata->odb_lock);
 }
 static inline void packing_data_unlock(struct packing_data *pdata)
 {
 	pthread_mutex_unlock(&pdata->odb_lock);
 }

 struct object_entry *packlist_alloc(struct packing_data *pdata,
 				    const struct object_id *oid);

 struct object_entry *packlist_find(struct packing_data *pdata,
 				   const struct object_id *oid);

 static inline uint32_t pack_name_hash(const char *name)
 {
 	uint32_t c, hash = 0;

 	if (!name)
 		return 0;

 	/*
 	 * This effectively just creates a sortable number from the
 	 * last sixteen non-whitespace characters. Last characters
 	 * count "most", so things that end in ".c" sort together.
 	 */
 	while ((c = *name++) != 0) {
 		if (isspace(c))
 			continue;
 		hash = (hash >> 2) + (c << 24);
 	}
 	return hash;
 }

 static inline enum object_type oe_type(const struct object_entry *e)
 {
 	return e->type_valid ? e->type_ : OBJ_BAD;
 }

 static inline void oe_set_type(struct object_entry *e,
 			       enum object_type type)
 {
 	if (type >= OBJ_ANY)
 		BUG("OBJ_ANY cannot be set in pack-objects code");

 	e->type_valid = type >= OBJ_NONE;
 	e->type_ = (unsigned)type;
 }

 static inline unsigned int oe_in_pack_pos(const struct packing_data *pack,
 					  const struct object_entry *e)
 {
 	return pack->in_pack_pos[e - pack->objects];
 }

 static inline void oe_set_in_pack_pos(const struct packing_data *pack,
 				      const struct object_entry *e,
 				      unsigned int pos)
 {
 	pack->in_pack_pos[e - pack->objects] = pos;
 }

 static inline struct packed_git *oe_in_pack(const struct packing_data *pack,
 					    const struct object_entry *e)
 {
 	if (pack->in_pack_by_idx)
 		return pack->in_pack_by_idx[e->in_pack_idx];
 	else
 		return pack->in_pack[e - pack->objects];
 }

 void oe_map_new_pack(struct packing_data *pack);

 static inline void oe_set_in_pack(struct packing_data *pack,
 				  struct object_entry *e,
 				  struct packed_git *p)
 {
 	if (pack->in_pack_by_idx) {
 		if (p->index) {
 			e->in_pack_idx = p->index;
 			return;
 		}
 		/*
 		 * We're accessing packs by index, but this pack doesn't have
 		 * an index (e.g., because it was added since we created the
 		 * in_pack_by_idx array). Bail to oe_map_new_pack(), which
 		 * will convert us to using the full in_pack array, and then
 		 * fall through to our in_pack handling.
 		 */
 		oe_map_new_pack(pack);
 	}
 	pack->in_pack[e - pack->objects] = p;
 }

 void oe_set_delta_ext(struct packing_data *pack,
 		      struct object_entry *e,
 		      const struct object_id *oid);

 static inline unsigned int oe_tree_depth(struct packing_data *pack,
 					 struct object_entry *e)
 {
 	if (!pack->tree_depth)
 		return 0;
 	return pack->tree_depth[e - pack->objects];
 }

 static inline void oe_set_layer(struct packing_data *pack,
 				struct object_entry *e,
 				unsigned char layer)
 {
 	if (!pack->layer)
 		CALLOC_ARRAY(pack->layer, pack->nr_alloc);
 	pack->layer[e - pack->objects] = layer;
 }

 #endif
	#ifndef PACK_OBJECTS_H
	#define PACK_OBJECTS_H

	#include "object-store.h"
	#include "thread-utils.h"
	#include "pack.h"

	struct repository;

	#define DEFAULT_DELTA_CACHE_SIZE (256 * 1024 * 1024)

	#define OE_DFS_STATE_BITS 2
	#define OE_DEPTH_BITS 12
	#define OE_IN_PACK_BITS 10
	#define OE_Z_DELTA_BITS 20
	/*
	* Note that oe_set_size() becomes expensive when the given size is
	* above this limit. Don't lower it too much.
	*/
	#define OE_SIZE_BITS 31
	#define OE_DELTA_SIZE_BITS 23

	/*
	* State flags for depth-first search used for analyzing delta cycles.
	*
	* The depth is measured in delta-links to the base (so if A is a delta
	* against B, then A has a depth of 1, and B a depth of 0).
	*/
	enum dfs_state {
	DFS_NONE = 0,
	DFS_ACTIVE,
	DFS_DONE,
	DFS_NUM_STATES
	};

	/*
	* The size of struct nearly determines pack-objects's memory
	* consumption. This struct is packed tight for that reason. When you
	* add or reorder something in this struct, think a bit about this.
	*
	* basic object info
	* -----------------
	* idx.oid is filled up before delta searching starts. idx.crc32 is
	* only valid after the object is written out and will be used for
	* generating the index. idx.offset will be both gradually set and
	* used in writing phase (base objects get offset first, then deltas
	* refer to them)
	*
	* "size" is the uncompressed object size. Compressed size of the raw
	* data for an object in a pack is not stored anywhere but is computed
	* and made available when reverse .idx is made. Note that when a
	* delta is reused, "size" is the uncompressed _delta_ size, not the
	* canonical one after the delta has been applied.
	*
	* "hash" contains a path name hash which is used for sorting the
	* delta list and also during delta searching. Once prepare_pack()
	* returns it's no longer needed.
	*
	* source pack info
	* ----------------
	* The (in_pack, in_pack_offset) tuple contains the location of the
	* object in the source pack. in_pack_header_size allows quickly
	* skipping the header and going straight to the zlib stream.
	*
	* "type" and "in_pack_type" both describe object type. in_pack_type
	* may contain a delta type, while type is always the canonical type.
	*
	* deltas
	* ------
	* Delta links (delta, delta_child and delta_sibling) are created to
	* reflect that delta graph from the source pack then updated or added
	* during delta searching phase when we find better deltas.
	*
	* delta_child and delta_sibling are last needed in
	* compute_write_order(). "delta" and "delta_size" must remain valid
	* at object writing phase in case the delta is not cached.
	*
	* If a delta is cached in memory and is compressed, delta_data points
	* to the data and z_delta_size contains the compressed size. If it's
	* uncompressed [1], z_delta_size must be zero. delta_size is always
	* the uncompressed size and must be valid even if the delta is not
	* cached.
	*
	* [1] during try_delta phase we don't bother with compressing because
	* the delta could be quickly replaced with a better one.
	*/
	struct object_entry {
	struct pack_idx_entry idx;
	void delta_data; / cached delta (uncompressed) */
	off_t in_pack_offset;
	uint32_t hash; /* name hint hash */
	unsigned size_:OE_SIZE_BITS;
	unsigned size_valid:1;
	uint32_t delta_idx; /* delta base object */
	uint32_t delta_child_idx; /* deltified objects who bases me */
	uint32_t delta_sibling_idx; /* other deltified objects who
	* uses the same base as me
	*/
	unsigned delta_size_:OE_DELTA_SIZE_BITS; /* delta data size (uncompressed) */
	unsigned delta_size_valid:1;
	unsigned char in_pack_header_size;
	unsigned in_pack_idx:OE_IN_PACK_BITS; /* already in pack */
	unsigned z_delta_size:OE_Z_DELTA_BITS;
	unsigned type_valid:1;
	unsigned no_try_delta:1;
	unsigned type_:TYPE_BITS;
	unsigned in_pack_type:TYPE_BITS; /* could be delta */

	unsigned preferred_base:1; /*
	* we do not pack this, but is available
	* to be used as the base object to delta
	* objects against.
	*/
	unsigned tagged:1; /* near the very tip of refs */
	unsigned filled:1; /* assigned write-order */
	unsigned dfs_state:OE_DFS_STATE_BITS;
	unsigned depth:OE_DEPTH_BITS;
	unsigned ext_base:1; /* delta_idx points outside packlist */

	/*
	* pahole results on 64-bit linux (gcc and clang)
	*
	* size: 80, bit_padding: 9 bits
	*
	* and on 32-bit (gcc)
	*
	* size: 76, bit_padding: 9 bits
	*/
	};

	struct packing_data {
	struct repository *repo;
	struct object_entry *objects;
	uint32_t nr_objects, nr_alloc;

	int32_t *index;
	uint32_t index_size;

	unsigned int *in_pack_pos;
	unsigned long *delta_size;

	/*
	* Only one of these can be non-NULL and they have different
	* sizes. if in_pack_by_idx is allocated, oe_in_pack() returns
	* the pack of an object using in_pack_idx field. If not,
	* in_pack[] array is used the same way as in_pack_pos[]
	*/
	struct packed_git **in_pack_by_idx;
	struct packed_git **in_pack;

	/*
	* During packing with multiple threads, protect the in-core
	* object database from concurrent accesses.
	*/
	pthread_mutex_t odb_lock;

	/*
	* This list contains entries for bases which we know the other side
	* has (e.g., via reachability bitmaps), but which aren't in our
	* "objects" list.
	*/
	struct object_entry *ext_bases;
	uint32_t nr_ext, alloc_ext;

	uintmax_t oe_size_limit;
	uintmax_t oe_delta_size_limit;

	/* delta islands */
	unsigned int *tree_depth;
	unsigned char *layer;
	};

	void prepare_packing_data(struct repository r, struct packing_data pdata);

	/* Protect access to object database */
	static inline void packing_data_lock(struct packing_data *pdata)
	{
	pthread_mutex_lock(&pdata->odb_lock);
	}
	static inline void packing_data_unlock(struct packing_data *pdata)
	{
	pthread_mutex_unlock(&pdata->odb_lock);
	}

	struct object_entry packlist_alloc(struct packing_data pdata,
	const struct object_id *oid);

	struct object_entry packlist_find(struct packing_data pdata,
	const struct object_id *oid);

	static inline uint32_t pack_name_hash(const char *name)
	{
	uint32_t c, hash = 0;

	if (!name)
	return 0;

	/*
	* This effectively just creates a sortable number from the
	* last sixteen non-whitespace characters. Last characters
	* count "most", so things that end in ".c" sort together.
	*/
	while ((c = *name++) != 0) {
	if (isspace(c))
	continue;
	hash = (hash >> 2) + (c << 24);
	}
	return hash;
	}

	static inline enum object_type oe_type(const struct object_entry *e)
	{
	return e->type_valid ? e->type_ : OBJ_BAD;
	}

	static inline void oe_set_type(struct object_entry *e,
	enum object_type type)
	{
	if (type >= OBJ_ANY)
	BUG("OBJ_ANY cannot be set in pack-objects code");

	e->type_valid = type >= OBJ_NONE;
	e->type_ = (unsigned)type;
	}

	static inline unsigned int oe_in_pack_pos(const struct packing_data *pack,
	const struct object_entry *e)
	{
	return pack->in_pack_pos[e - pack->objects];
	}

	static inline void oe_set_in_pack_pos(const struct packing_data *pack,
	const struct object_entry *e,
	unsigned int pos)
	{
	pack->in_pack_pos[e - pack->objects] = pos;
	}

	static inline struct packed_git oe_in_pack(const struct packing_data pack,
	const struct object_entry *e)
	{
	if (pack->in_pack_by_idx)
	return pack->in_pack_by_idx[e->in_pack_idx];
	else
	return pack->in_pack[e - pack->objects];
	}

	void oe_map_new_pack(struct packing_data *pack);

	static inline void oe_set_in_pack(struct packing_data *pack,
	struct object_entry *e,
	struct packed_git *p)
	{
	if (pack->in_pack_by_idx) {
	if (p->index) {
	e->in_pack_idx = p->index;
	return;
	}
	/*
	* We're accessing packs by index, but this pack doesn't have
	* an index (e.g., because it was added since we created the
	* in_pack_by_idx array). Bail to oe_map_new_pack(), which
	* will convert us to using the full in_pack array, and then
	* fall through to our in_pack handling.
	*/
	oe_map_new_pack(pack);
	}
	pack->in_pack[e - pack->objects] = p;
	}

	void oe_set_delta_ext(struct packing_data *pack,
	struct object_entry *e,
	const struct object_id *oid);

	static inline unsigned int oe_tree_depth(struct packing_data *pack,
	struct object_entry *e)
	{
	if (!pack->tree_depth)
	return 0;
	return pack->tree_depth[e - pack->objects];
	}

	static inline void oe_set_layer(struct packing_data *pack,
	struct object_entry *e,
	unsigned char layer)
	{
	if (!pack->layer)
	CALLOC_ARRAY(pack->layer, pack->nr_alloc);
	pack->layer[e - pack->objects] = layer;
	}

	#endif