odb.h

#ifndef ODB_H
#define ODB_H

#include "object.h"
#include "oidset.h"
#include "oidmap.h"
#include "string-list.h"
#include "thread-utils.h"

struct cached_object_entry;
struct odb_source_inmemory;
struct packed_git;
struct repository;
struct strbuf;
struct strvec;

/*
 * Set this to 0 to prevent odb_read_object_info_extended() from fetching missing
 * blobs. This has a difference only if extensions.partialClone is set.
 *
 * Its default value is 1.
 */
extern int fetch_if_missing;

/*
 * Compute the exact path an alternate is at and returns it. In case of
 * error NULL is returned and the human readable error is added to `err`
 * `path` may be relative and should point to $GIT_DIR.
 * `err` must not be null.
 */
char *compute_alternate_path(const char *path, struct strbuf *err);

/*
 * The object database encapsulates access to objects in a repository. It
 * manages one or more sources that store the actual objects which are
 * configured via alternates.
 */
struct object_database {
	/* Repository that owns this database. */
	struct repository *repo;

	/*
	 * State of current object database transaction. Only one
	 * transaction may be pending at a time. Is NULL when no transaction is
	 * configured.
	 */
	struct odb_transaction *transaction;

	/*
	 * Set of all object directories; the main directory is first (and
	 * cannot be NULL after initialization). Subsequent directories are
	 * alternates.
	 */
	struct odb_source *sources;
	struct odb_source **sources_tail;
	struct kh_odb_path_map *source_by_path;

	int loaded_alternates;

	/*
	 * A list of alternate object directories loaded from the environment;
	 * this should not generally need to be accessed directly, but will
	 * populate the "sources" list when odb_prepare_alternates() is run.
	 */
	char *alternate_db;

	/*
	 * Objects that should be substituted by other objects
	 * (see git-replace(1)).
	 */
	struct oidmap replace_map;
	unsigned replace_map_initialized : 1;
	pthread_mutex_t replace_mutex; /* protect object replace functions */

	struct commit_graph *commit_graph;
	unsigned commit_graph_attempted : 1; /* if loading has been attempted */

	/*
	 * This is meant to hold a *small* number of objects that you would
	 * want odb_read_object() to be able to return, but yet you do not want
	 * to write them into the object store (e.g. a browse-only
	 * application).
	 */
	struct odb_source *inmemory_objects;

	/*
	 * A fast, rough count of the number of objects in the repository.
	 * These two fields are not meant for direct access. Use
	 * odb_count_objects() instead.
	 */
	unsigned long object_count;
	unsigned object_count_flags;
	unsigned object_count_valid : 1;

	/*
	 * Submodule source paths that will be added as additional sources to
	 * allow lookup of submodule objects via the main object database.
	 */
	struct string_list submodule_source_paths;
};

/*
 * Create a new object database for the given repository.
 *
 * If the primary source parameter is set it will override the usual primary
 * object directory derived from the repository's common directory. The
 * alternate sources are expected to be a PATH_SEP-separated list of secondary
 * sources. Note that these alternate sources will be added in addition to, not
 * instead of, the alternates identified by the primary source.
 *
 * Returns the newly created object database.
 */
struct object_database *odb_new(struct repository *repo,
				const char *primary_source,
				const char *alternate_sources);

/* Free the object database and release all resources. */
void odb_free(struct object_database *o);

/*
 * Close the object database and all of its sources so that any held resources
 * will be released. The database can still be used after closing it, in which
 * case these resources may be reallocated.
 */
void odb_close(struct object_database *o);

/*
 * Clear caches, reload alternates and then reload object sources so that new
 * objects may become accessible.
 */
void odb_reprepare(struct object_database *o);

/*
 * Find source by its object directory path. Returns a `NULL` pointer in case
 * the source could not be found.
 */
struct odb_source *odb_find_source(struct object_database *odb, const char *obj_dir);

/* Same as `odb_find_source()`, but dies in case the source doesn't exist. */
struct odb_source *odb_find_source_or_die(struct object_database *odb, const char *obj_dir);

/*
 * Replace the current writable object directory with the specified temporary
 * object directory; returns the former primary source.
 */
struct odb_source *odb_set_temporary_primary_source(struct object_database *odb,
						    const char *dir, int will_destroy);

/*
 * Restore the primary source that was previously replaced by
 * `odb_set_temporary_primary_source()`.
 */
void odb_restore_primary_source(struct object_database *odb,
				struct odb_source *restore_source,
				const char *old_path);

/*
 * Call odb_add_submodule_source_by_path() to add the submodule at the given
 * path to a list. The object stores of all submodules in that list will be
 * added as additional sources in the object store when looking up objects.
 */
void odb_add_submodule_source_by_path(struct object_database *odb,
				      const char *path);

/*
 * Iterate through all alternates of the database and execute the provided
 * callback function for each of them. Stop iterating once the callback
 * function returns a non-zero value, in which case the value is bubbled up
 * from the callback.
 */
typedef int odb_for_each_alternate_fn(struct odb_source *, void *);
int odb_for_each_alternate(struct object_database *odb,
			   odb_for_each_alternate_fn cb, void *payload);

/*
 * Iterate through all alternates of the database and yield their respective
 * references.
 */
typedef void odb_for_each_alternate_ref_fn(const struct object_id *oid, void *);
void odb_for_each_alternate_ref(struct object_database *odb,
				odb_for_each_alternate_ref_fn cb, void *payload);

/*
 * Create a temporary file rooted in the primary alternate's directory, or die
 * on failure. The filename is taken from "pattern", which should have the
 * usual "XXXXXX" trailer, and the resulting filename is written into the
 * "template" buffer. Returns the open descriptor.
 */
int odb_mkstemp(struct object_database *odb,
		struct strbuf *temp_filename, const char *pattern);

/*
 * Prepare alternate object sources for the given database by reading
 * "objects/info/alternates" and opening the respective sources.
 */
void odb_prepare_alternates(struct object_database *odb);

/*
 * Check whether the object database has any alternates. The primary object
 * source does not count as alternate.
 */
int odb_has_alternates(struct object_database *odb);

/*
 * Add the directory to the on-disk alternates file; the new entry will also
 * take effect in the current process.
 */
void odb_add_to_alternates_file(struct object_database *odb,
				const char *dir);

/*
 * Add the directory to the in-memory list of alternate sources (along with any
 * recursive alternates it points to), but do not modify the on-disk alternates
 * file.
 */
struct odb_source *odb_add_to_alternates_memory(struct object_database *odb,
						const char *dir);

/*
 * Read an object from the database. Returns the object data and assigns object
 * type and size to the `type` and `size` pointers, if these pointers are
 * non-NULL. Returns a `NULL` pointer in case the object does not exist.
 *
 * This function dies on corrupt objects; the callers who want to deal with
 * them should arrange to call odb_read_object_info_extended() and give error
 * messages themselves.
 */
void *odb_read_object(struct object_database *odb,
		      const struct object_id *oid,
		      enum object_type *type,
		      size_t *size);

void *odb_read_object_peeled(struct object_database *odb,
			     const struct object_id *oid,
			     enum object_type required_type,
			     size_t *size,
			     struct object_id *oid_ret);

/*
 * Add an object file to the in-memory object store, without writing it
 * to disk.
 *
 * Callers are responsible for calling write_object_file to record the
 * object in persistent storage before writing any other new objects
 * that reference it.
 */
int odb_pretend_object(struct object_database *odb,
		       void *buf, size_t len, enum object_type type,
		       struct object_id *oid);

struct object_info {
	/* Request */
	enum object_type *typep;
	size_t *sizep;
	off_t *disk_sizep;
	struct object_id *delta_base_oid;
	void **contentp;

	/*
	 * The time the given looked-up object has been last modified.
	 *
	 * Note: the mtime may be ambiguous in case the object exists multiple
	 * times in the object database. It is thus _not_ recommended to use
	 * this field outside of contexts where you would read every instance
	 * of the object, like for example with `odb_for_each_object()`. As it
	 * is impossible to say at the ODB level what the intent of the caller
	 * is (e.g. whether to find the oldest or newest object), it is the
	 * responsibility of the caller to disambiguate the mtimes.
	 */
	time_t *mtimep;

	/* Response */
	enum {
		OI_CACHED,
		OI_LOOSE,
		OI_PACKED,
	} whence;
	union {
		/*
		 * struct {
		 * 	... Nothing to expose in this case
		 * } cached;
		 * struct {
		 * 	... Nothing to expose in this case
		 * } loose;
		 */
		struct {
			struct packed_git *pack;
			off_t offset;
			enum packed_object_type {
				PACKED_OBJECT_TYPE_UNKNOWN,
				PACKED_OBJECT_TYPE_FULL,
				PACKED_OBJECT_TYPE_OFS_DELTA,
				PACKED_OBJECT_TYPE_REF_DELTA,
			} type;
		} packed;
	} u;
};

/*
 * Initializer for a "struct object_info" that wants no items. You may
 * also memset() the memory to all-zeroes.
 */
#define OBJECT_INFO_INIT { 0 }

/* Flags that can be passed to `odb_read_object_info_extended()`. */
enum object_info_flags {
	/* Invoke lookup_replace_object() on the given hash. */
	OBJECT_INFO_LOOKUP_REPLACE = (1 << 0),

	/* Do not reprepare object sources when the first lookup has failed. */
	OBJECT_INFO_QUICK = (1 << 1),

	/*
	 * Do not attempt to fetch the object if missing (even if fetch_is_missing is
	 * nonzero).
	 */
	OBJECT_INFO_SKIP_FETCH_OBJECT = (1 << 2),

	/* Die if object corruption (not just an object being missing) was detected. */
	OBJECT_INFO_DIE_IF_CORRUPT = (1 << 3),

	/*
	 * We have already tried reading the object, but it couldn't be found
	 * via any of the attached sources, and are now doing a second read.
	 * This second read asks the individual sources to also evaluate
	 * whether any on-disk state may have changed that may have caused the
	 * object to appear.
	 *
	 * This flag is for internal use, only. The second read only occurs
	 * when `OBJECT_INFO_QUICK` was not passed.
	 */
	OBJECT_INFO_SECOND_READ = (1 << 4),

	/*
	 * This is meant for bulk prefetching of missing blobs in a partial
	 * clone. Implies OBJECT_INFO_SKIP_FETCH_OBJECT and OBJECT_INFO_QUICK.
	 */
	OBJECT_INFO_FOR_PREFETCH = (OBJECT_INFO_SKIP_FETCH_OBJECT | OBJECT_INFO_QUICK),
};

/*
 * Read object info from the object database and populate the `object_info`
 * structure. Returns 0 on success, a negative error code otherwise.
 */
int odb_read_object_info_extended(struct object_database *odb,
				  const struct object_id *oid,
				  struct object_info *oi,
				  enum object_info_flags flags);

/*
 * Read a subset of object info for the given object ID. Returns an `enum
 * object_type` on success, a negative error code otherwise. If successful and
 * `sizep` is non-NULL, then the size of the object will be written to the
 * pointer.
 */
int odb_read_object_info(struct object_database *odb,
			 const struct object_id *oid,
			 size_t *sizep);

enum odb_has_object_flags {
	/* Retry packed storage after checking packed and loose storage */
	ODB_HAS_OBJECT_RECHECK_PACKED = (1 << 0),
	/* Allow fetching the object in case the repository has a promisor remote. */
	ODB_HAS_OBJECT_FETCH_PROMISOR = (1 << 1),
};

/*
 * Returns 1 if the object exists. This function will not lazily fetch objects
 * in a partial clone by default.
 */
int odb_has_object(struct object_database *odb,
		   const struct object_id *oid,
		   enum odb_has_object_flags flags);

int odb_freshen_object(struct object_database *odb,
		       const struct object_id *oid);

void odb_assert_oid_type(struct object_database *odb,
			 const struct object_id *oid, enum object_type expect);

/*
 * Enabling the object read lock allows multiple threads to safely call the
 * following functions in parallel: odb_read_object(),
 * odb_read_object_peeled(), odb_read_object_info() and odb().
 *
 * obj_read_lock() and obj_read_unlock() may also be used to protect other
 * section which cannot execute in parallel with object reading. Since the used
 * lock is a recursive mutex, these sections can even contain calls to object
 * reading functions. However, beware that in these cases zlib inflation won't
 * be performed in parallel, losing performance.
 *
 * TODO: odb_read_object_info_extended()'s call stack has a recursive behavior. If
 * any of its callees end up calling it, this recursive call won't benefit from
 * parallel inflation.
 */
void enable_obj_read_lock(void);
void disable_obj_read_lock(void);

extern int obj_read_use_lock;
extern pthread_mutex_t obj_read_mutex;

static inline void obj_read_lock(void)
{
	if(obj_read_use_lock)
		pthread_mutex_lock(&obj_read_mutex);
}

static inline void obj_read_unlock(void)
{
	if(obj_read_use_lock)
		pthread_mutex_unlock(&obj_read_mutex);
}

/* Flags for for_each_*_object(). */
enum odb_for_each_object_flags {
	/* Iterate only over local objects, not alternates. */
	ODB_FOR_EACH_OBJECT_LOCAL_ONLY = (1<<0),

	/* Only iterate over packs obtained from the promisor remote. */
	ODB_FOR_EACH_OBJECT_PROMISOR_ONLY = (1<<1),

	/*
	 * Visit objects within a pack in packfile order rather than .idx order
	 */
	ODB_FOR_EACH_OBJECT_PACK_ORDER = (1<<2),

	/* Only iterate over packs that are not marked as kept in-core. */
	ODB_FOR_EACH_OBJECT_SKIP_IN_CORE_KEPT_PACKS = (1<<3),

	/* Only iterate over packs that do not have .keep files. */
	ODB_FOR_EACH_OBJECT_SKIP_ON_DISK_KEPT_PACKS = (1<<4),
};

/*
 * A callback function that can be used to iterate through objects. If given,
 * the optional `oi` parameter will be populated the same as if you would call
 * `odb_read_object_info()`.
 *
 * Returning a non-zero error code will cause iteration to abort. The error
 * code will be propagated.
 */
typedef int (*odb_for_each_object_cb)(const struct object_id *oid,
				      struct object_info *oi,
				      void *cb_data);

/*
 * Options that can be passed to `odb_for_each_object()` and its
 * backend-specific implementations.
 */
struct odb_for_each_object_options {
	/* A bitfield of `odb_for_each_object_flags`. */
	enum odb_for_each_object_flags flags;

	/*
	 * If set, only iterate through objects whose first `prefix_hex_len`
	 * hex characters matches the given prefix.
	 */
	const struct object_id *prefix;
	size_t prefix_hex_len;
};

/*
 * Iterate through all objects contained in the object database. Note that
 * objects may be iterated over multiple times in case they are either stored
 * in different backends or in case they are stored in multiple sources.
 * If an object info request is given, then the object info will be read and
 * passed to the callback as if `odb_read_object_info()` was called for the
 * object.
 *
 * Returning a non-zero error code from the callback function will cause
 * iteration to abort. The error code will be propagated.
 *
 * Returns 0 on success, a negative error code in case a failure occurred, or
 * an arbitrary non-zero error code returned by the callback itself.
 */
int odb_for_each_object_ext(struct object_database *odb,
			    const struct object_info *request,
			    odb_for_each_object_cb cb,
			    void *cb_data,
			    const struct odb_for_each_object_options *opts);

/* Same as `odb_for_each_object_ext()` with `opts.flags` set to the given flags. */
int odb_for_each_object(struct object_database *odb,
			const struct object_info *request,
			odb_for_each_object_cb cb,
			void *cb_data,
			enum odb_for_each_object_flags flags);

enum odb_count_objects_flags {
	/*
	 * Instead of providing an accurate count, allow the number of objects
	 * to be approximated. Details of how this approximation works are
	 * subject to the specific source's implementation.
	 */
	ODB_COUNT_OBJECTS_APPROXIMATE = (1 << 0),
};

/*
 * Count the number of objects in the given object database. This object count
 * may double-count objects that are stored in multiple backends, or which are
 * stored multiple times in a single backend.
 *
 * Returns 0 on success, a negative error code otherwise. The number of objects
 * will be assigned to the `out` pointer on success.
 */
int odb_count_objects(struct object_database *odb,
		      enum odb_count_objects_flags flags,
		      unsigned long *out);

/*
 * Given an object ID, find the minimum required length required to make the
 * object ID unique across the whole object database.
 *
 * The `min_len` determines the minimum abbreviated length that'll be returned
 * by this function. If `min_len < 0`, then the function will set a sensible
 * default minimum abbreviation length.
 *
 * Returns 0 on success, a negative error code otherwise. The computed length
 * will be assigned to `*out`.
 */
int odb_find_abbrev_len(struct object_database *odb,
			const struct object_id *oid,
			int min_len,
			unsigned *out);

enum odb_write_object_flags {
	/*
	 * By default, `odb_write_object()` does not actually write anything
	 * into the object store, but only computes the object ID. This flag
	 * changes that so that the object will be written as a loose object
	 * and persisted.
	 */
	ODB_WRITE_OBJECT_PERSIST = (1 << 0),

	/*
	 * Do not print an error in case something goes wrong.
	 */
	ODB_WRITE_OBJECT_SILENT = (1 << 1),
};

/*
 * Write an object into the object database. The object is being written into
 * the local alternate of the repository. If provided, the converted object ID
 * as well as the compatibility object ID are written to the respective
 * pointers.
 *
 * Returns 0 on success, a negative error code otherwise.
 */
int odb_write_object_ext(struct object_database *odb,
			 const void *buf, unsigned long len,
			 enum object_type type,
			 struct object_id *oid,
			 struct object_id *compat_oid,
			 enum odb_write_object_flags flags);

static inline int odb_write_object(struct object_database *odb,
				   const void *buf, unsigned long len,
				   enum object_type type,
				   struct object_id *oid)
{
	return odb_write_object_ext(odb, buf, len, type, oid, NULL, 0);
}

struct odb_write_stream;

int odb_write_object_stream(struct object_database *odb,
			    struct odb_write_stream *stream, size_t len,
			    struct object_id *oid);

void parse_alternates(const char *string,
		      int sep,
		      const char *relative_base,
		      struct strvec *out);

#endif /* ODB_H */