replace-object: make replace operations thread-safe

[git] / object-store.h

#ifndef OBJECT_STORE_H
#define OBJECT_STORE_H

#include "cache.h"
#include "oidmap.h"
#include "list.h"
#include "sha1-array.h"
#include "strbuf.h"

struct object_directory {
        struct object_directory *next;

        /*
         * Used to store the results of readdir(3) calls when we are OK
         * sacrificing accuracy due to races for speed. That includes
         * object existence with OBJECT_INFO_QUICK, as well as
         * our search for unique abbreviated hashes. Don't use it for tasks
         * requiring greater accuracy!
         *
         * Be sure to call odb_load_loose_cache() before using.
         */
        char loose_objects_subdir_seen[256];
        struct oid_array loose_objects_cache[256];

        /*
         * Path to the alternative object store. If this is a relative path,
         * it is relative to the current working directory.
         */
        char *path;
};

void prepare_alt_odb(struct repository *r);
char *compute_alternate_path(const char *path, struct strbuf *err);
typedef int alt_odb_fn(struct object_directory *, void *);
int foreach_alt_odb(alt_odb_fn, void*);
typedef void alternate_ref_fn(const struct object_id *oid, void *);
void for_each_alternate_ref(alternate_ref_fn, void *);

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

/*
 * Add the directory to the in-memory list of alternates (along with any
 * recursive alternates it points to), but do not modify the on-disk alternates
 * file.
 */
void add_to_alternates_memory(const char *dir);

/*
 * Populate and return the loose object cache array corresponding to the
 * given object ID.
 */
struct oid_array *odb_loose_cache(struct object_directory *odb,
                                  const struct object_id *oid);

/* Empty the loose object cache for the specified object directory. */
void odb_clear_loose_cache(struct object_directory *odb);

struct packed_git {
        struct hashmap_entry packmap_ent;
        struct packed_git *next;
        struct list_head mru;
        struct pack_window *windows;
        off_t pack_size;
        const void *index_data;
        size_t index_size;
        uint32_t num_objects;
        uint32_t num_bad_objects;
        unsigned char *bad_object_sha1;
        int index_version;
        time_t mtime;
        int pack_fd;
        int index;              /* for builtin/pack-objects.c */
        unsigned pack_local:1,
                 pack_keep:1,
                 pack_keep_in_core:1,
                 freshened:1,
                 do_not_close:1,
                 pack_promisor:1,
                 multi_pack_index:1;
        unsigned char hash[GIT_MAX_RAWSZ];
        struct revindex_entry *revindex;
        /* something like ".git/objects/pack/xxxxx.pack" */
        char pack_name[FLEX_ARRAY]; /* more */
};

struct multi_pack_index;

static inline int pack_map_entry_cmp(const void *unused_cmp_data,
                                     const struct hashmap_entry *entry,
                                     const struct hashmap_entry *entry2,
                                     const void *keydata)
{
        const char *key = keydata;
        const struct packed_git *pg1, *pg2;

        pg1 = container_of(entry, const struct packed_git, packmap_ent);
        pg2 = container_of(entry2, const struct packed_git, packmap_ent);

        return strcmp(pg1->pack_name, key ? key : pg2->pack_name);
}

struct raw_object_store {
        /*
         * Set of all object directories; the main directory is first (and
         * cannot be NULL after initialization). Subsequent directories are
         * alternates.
         */
        struct object_directory *odb;
        struct object_directory **odb_tail;
        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 "odb" list when prepare_alt_odb() 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 */

        /*
         * private data
         *
         * should only be accessed directly by packfile.c and midx.c
         */
        struct multi_pack_index *multi_pack_index;

        /*
         * private data
         *
         * should only be accessed directly by packfile.c
         */

        struct packed_git *packed_git;
        /* A most-recently-used ordered version of the packed_git list. */
        struct list_head packed_git_mru;

        /*
         * A map of packfiles to packed_git structs for tracking which
         * packs have been loaded already.
         */
        struct hashmap pack_map;

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

        /*
         * Whether packed_git has already been populated with this repository's
         * packs.
         */
        unsigned packed_git_initialized : 1;
};

struct raw_object_store *raw_object_store_new(void);
void raw_object_store_clear(struct raw_object_store *o);

/*
 * Put in `buf` the name of the file in the local object database that
 * would be used to store a loose object with the specified oid.
 */
const char *loose_object_path(struct repository *r, struct strbuf *buf,
                              const struct object_id *oid);

void *map_loose_object(struct repository *r, const struct object_id *oid,
                       unsigned long *size);

void *read_object_file_extended(struct repository *r,
                                const struct object_id *oid,
                                enum object_type *type,
                                unsigned long *size, int lookup_replace);
static inline void *repo_read_object_file(struct repository *r,
                                          const struct object_id *oid,
                                          enum object_type *type,
                                          unsigned long *size)
{
        return read_object_file_extended(r, oid, type, size, 1);
}
#ifndef NO_THE_REPOSITORY_COMPATIBILITY_MACROS
#define read_object_file(oid, type, size) repo_read_object_file(the_repository, oid, type, size)
#endif

/* Read and unpack an object file into memory, write memory to an object file */
int oid_object_info(struct repository *r, const struct object_id *, unsigned long *);

int hash_object_file(const void *buf, unsigned long len,
                     const char *type, struct object_id *oid);

int write_object_file(const void *buf, unsigned long len,
                      const char *type, struct object_id *oid);

int hash_object_file_literally(const void *buf, unsigned long len,
                               const char *type, struct object_id *oid,
                               unsigned flags);

int pretend_object_file(void *, unsigned long, enum object_type,
                        struct object_id *oid);

int force_object_loose(const struct object_id *oid, time_t mtime);

/*
 * Open the loose object at path, check its hash, and return the contents,
 * type, and size. If the object is a blob, then "contents" may return NULL,
 * to allow streaming of large blobs.
 *
 * Returns 0 on success, negative on error (details may be written to stderr).
 */
int read_loose_object(const char *path,
                      const struct object_id *expected_oid,
                      enum object_type *type,
                      unsigned long *size,
                      void **contents);

#ifndef NO_THE_REPOSITORY_COMPATIBILITY_MACROS
#define has_sha1_file_with_flags(sha1, flags) repo_has_sha1_file_with_flags(the_repository, sha1, flags)
#define has_sha1_file(sha1) repo_has_sha1_file(the_repository, sha1)
#endif

/* Same as the above, except for struct object_id. */
int repo_has_object_file(struct repository *r, const struct object_id *oid);
int repo_has_object_file_with_flags(struct repository *r,
                                    const struct object_id *oid, int flags);
#ifndef NO_THE_REPOSITORY_COMPATIBILITY_MACROS
#define has_object_file(oid) repo_has_object_file(the_repository, oid)
#define has_object_file_with_flags(oid, flags) repo_has_object_file_with_flags(the_repository, oid, flags)
#endif

/*
 * Return true iff an alternate object database has a loose object
 * with the specified name.  This function does not respect replace
 * references.
 */
int has_loose_object_nonlocal(const struct object_id *);

void assert_oid_type(const struct object_id *oid, enum object_type expect);

struct object_info {
        /* Request */
        enum object_type *typep;
        unsigned long *sizep;
        off_t *disk_sizep;
        unsigned char *delta_base_sha1;
        struct strbuf *type_name;
        void **contentp;

        /* Response */
        enum {
                OI_CACHED,
                OI_LOOSE,
                OI_PACKED,
                OI_DBCACHED
        } 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;
                        unsigned int is_delta;
                } 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 {NULL}

/* Invoke lookup_replace_object() on the given hash */
#define OBJECT_INFO_LOOKUP_REPLACE 1
/* Allow reading from a loose object file of unknown/bogus type */
#define OBJECT_INFO_ALLOW_UNKNOWN_TYPE 2
/* Do not check cached storage */
#define OBJECT_INFO_SKIP_CACHED 4
/* Do not retry packed storage after checking packed and loose storage */
#define OBJECT_INFO_QUICK 8
/* Do not check loose object */
#define OBJECT_INFO_IGNORE_LOOSE 16
/*
 * Do not attempt to fetch the object if missing (even if fetch_is_missing is
 * nonzero).
 */
#define OBJECT_INFO_SKIP_FETCH_OBJECT 32
/*
 * This is meant for bulk prefetching of missing blobs in a partial
 * clone. Implies OBJECT_INFO_SKIP_FETCH_OBJECT and OBJECT_INFO_QUICK
 */
#define OBJECT_INFO_FOR_PREFETCH (OBJECT_INFO_SKIP_FETCH_OBJECT | OBJECT_INFO_QUICK)

int oid_object_info_extended(struct repository *r,
                             const struct object_id *,
                             struct object_info *, unsigned flags);

/*
 * Iterate over the files in the loose-object parts of the object
 * directory "path", triggering the following callbacks:
 *
 *  - loose_object is called for each loose object we find.
 *
 *  - loose_cruft is called for any files that do not appear to be
 *    loose objects. Note that we only look in the loose object
 *    directories "objects/[0-9a-f]{2}/", so we will not report
 *    "objects/foobar" as cruft.
 *
 *  - loose_subdir is called for each top-level hashed subdirectory
 *    of the object directory (e.g., "$OBJDIR/f0"). It is called
 *    after the objects in the directory are processed.
 *
 * Any callback that is NULL will be ignored. Callbacks returning non-zero
 * will end the iteration.
 *
 * In the "buf" variant, "path" is a strbuf which will also be used as a
 * scratch buffer, but restored to its original contents before
 * the function returns.
 */
typedef int each_loose_object_fn(const struct object_id *oid,
                                 const char *path,
                                 void *data);
typedef int each_loose_cruft_fn(const char *basename,
                                const char *path,
                                void *data);
typedef int each_loose_subdir_fn(unsigned int nr,
                                 const char *path,
                                 void *data);
int for_each_file_in_obj_subdir(unsigned int subdir_nr,
                                struct strbuf *path,
                                each_loose_object_fn obj_cb,
                                each_loose_cruft_fn cruft_cb,
                                each_loose_subdir_fn subdir_cb,
                                void *data);
int for_each_loose_file_in_objdir(const char *path,
                                  each_loose_object_fn obj_cb,
                                  each_loose_cruft_fn cruft_cb,
                                  each_loose_subdir_fn subdir_cb,
                                  void *data);
int for_each_loose_file_in_objdir_buf(struct strbuf *path,
                                      each_loose_object_fn obj_cb,
                                      each_loose_cruft_fn cruft_cb,
                                      each_loose_subdir_fn subdir_cb,
                                      void *data);

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

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

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

/*
 * Iterate over all accessible loose objects without respect to
 * reachability. By default, this includes both local and alternate objects.
 * The order in which objects are visited is unspecified.
 *
 * Any flags specific to packs are ignored.
 */
int for_each_loose_object(each_loose_object_fn, void *,
                          enum for_each_object_flags flags);

/*
 * Iterate over all accessible packed objects without respect to reachability.
 * By default, this includes both local and alternate packs.
 *
 * Note that some objects may appear twice if they are found in multiple packs.
 * Each pack is visited in an unspecified order. By default, objects within a
 * pack are visited in pack-idx order (i.e., sorted by oid).
 */
typedef int each_packed_object_fn(const struct object_id *oid,
                                  struct packed_git *pack,
                                  uint32_t pos,
                                  void *data);
int for_each_object_in_pack(struct packed_git *p,
                            each_packed_object_fn, void *data,
                            enum for_each_object_flags flags);
int for_each_packed_object(each_packed_object_fn, void *,
                           enum for_each_object_flags flags);

#endif /* OBJECT_STORE_H */