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Diffstat (limited to 'refs/ref-cache.h')
| -rw-r--r-- | refs/ref-cache.h | 267 |
1 files changed, 267 insertions, 0 deletions
diff --git a/refs/ref-cache.h b/refs/ref-cache.h new file mode 100644 index 000000000..794f000fd --- /dev/null +++ b/refs/ref-cache.h @@ -0,0 +1,267 @@ +#ifndef REFS_REF_CACHE_H +#define REFS_REF_CACHE_H + +struct ref_dir; + +/* + * If this ref_cache is filled lazily, this function is used to load + * information into the specified ref_dir (shallow or deep, at the + * option of the ref_store). dirname includes a trailing slash. + */ +typedef void fill_ref_dir_fn(struct ref_store *ref_store, + struct ref_dir *dir, const char *dirname); + +struct ref_cache { + struct ref_entry *root; + + /* A pointer to the ref_store whose cache this is: */ + struct ref_store *ref_store; + + /* + * Function used (if necessary) to lazily-fill cache. May be + * NULL. + */ + fill_ref_dir_fn *fill_ref_dir; +}; + +/* + * Information used (along with the information in ref_entry) to + * describe a single cached reference. This data structure only + * occurs embedded in a union in struct ref_entry, and only when + * (ref_entry->flag & REF_DIR) is zero. + */ +struct ref_value { + /* + * The name of the object to which this reference resolves + * (which may be a tag object). If REF_ISBROKEN, this is + * null. If REF_ISSYMREF, then this is the name of the object + * referred to by the last reference in the symlink chain. + */ + struct object_id oid; + + /* + * If REF_KNOWS_PEELED, then this field holds the peeled value + * of this reference, or null if the reference is known not to + * be peelable. See the documentation for peel_ref() for an + * exact definition of "peelable". + */ + struct object_id peeled; +}; + +/* + * Information used (along with the information in ref_entry) to + * describe a level in the hierarchy of references. This data + * structure only occurs embedded in a union in struct ref_entry, and + * only when (ref_entry.flag & REF_DIR) is set. In that case, + * (ref_entry.flag & REF_INCOMPLETE) determines whether the references + * in the directory have already been read: + * + * (ref_entry.flag & REF_INCOMPLETE) unset -- a directory of loose + * or packed references, already read. + * + * (ref_entry.flag & REF_INCOMPLETE) set -- a directory of loose + * references that hasn't been read yet (nor has any of its + * subdirectories). + * + * Entries within a directory are stored within a growable array of + * pointers to ref_entries (entries, nr, alloc). Entries 0 <= i < + * sorted are sorted by their component name in strcmp() order and the + * remaining entries are unsorted. + * + * Loose references are read lazily, one directory at a time. When a + * directory of loose references is read, then all of the references + * in that directory are stored, and REF_INCOMPLETE stubs are created + * for any subdirectories, but the subdirectories themselves are not + * read. The reading is triggered by get_ref_dir(). + */ +struct ref_dir { + int nr, alloc; + + /* + * Entries with index 0 <= i < sorted are sorted by name. New + * entries are appended to the list unsorted, and are sorted + * only when required; thus we avoid the need to sort the list + * after the addition of every reference. + */ + int sorted; + + /* The ref_cache containing this entry: */ + struct ref_cache *cache; + + struct ref_entry **entries; +}; + +/* + * Bit values for ref_entry::flag. REF_ISSYMREF=0x01, + * REF_ISPACKED=0x02, REF_ISBROKEN=0x04 and REF_BAD_NAME=0x08 are + * public values; see refs.h. + */ + +/* + * The field ref_entry->u.value.peeled of this value entry contains + * the correct peeled value for the reference, which might be + * null_sha1 if the reference is not a tag or if it is broken. + */ +#define REF_KNOWS_PEELED 0x10 + +/* ref_entry represents a directory of references */ +#define REF_DIR 0x20 + +/* + * Entry has not yet been read from disk (used only for REF_DIR + * entries representing loose references) + */ +#define REF_INCOMPLETE 0x40 + +/* + * A ref_entry represents either a reference or a "subdirectory" of + * references. + * + * Each directory in the reference namespace is represented by a + * ref_entry with (flags & REF_DIR) set and containing a subdir member + * that holds the entries in that directory that have been read so + * far. If (flags & REF_INCOMPLETE) is set, then the directory and + * its subdirectories haven't been read yet. REF_INCOMPLETE is only + * used for loose reference directories. + * + * References are represented by a ref_entry with (flags & REF_DIR) + * unset and a value member that describes the reference's value. The + * flag member is at the ref_entry level, but it is also needed to + * interpret the contents of the value field (in other words, a + * ref_value object is not very much use without the enclosing + * ref_entry). + * + * Reference names cannot end with slash and directories' names are + * always stored with a trailing slash (except for the top-level + * directory, which is always denoted by ""). This has two nice + * consequences: (1) when the entries in each subdir are sorted + * lexicographically by name (as they usually are), the references in + * a whole tree can be generated in lexicographic order by traversing + * the tree in left-to-right, depth-first order; (2) the names of + * references and subdirectories cannot conflict, and therefore the + * presence of an empty subdirectory does not block the creation of a + * similarly-named reference. (The fact that reference names with the + * same leading components can conflict *with each other* is a + * separate issue that is regulated by refs_verify_refname_available().) + * + * Please note that the name field contains the fully-qualified + * reference (or subdirectory) name. Space could be saved by only + * storing the relative names. But that would require the full names + * to be generated on the fly when iterating in do_for_each_ref(), and + * would break callback functions, who have always been able to assume + * that the name strings that they are passed will not be freed during + * the iteration. + */ +struct ref_entry { + unsigned char flag; /* ISSYMREF? ISPACKED? */ + union { + struct ref_value value; /* if not (flags&REF_DIR) */ + struct ref_dir subdir; /* if (flags&REF_DIR) */ + } u; + /* + * The full name of the reference (e.g., "refs/heads/master") + * or the full name of the directory with a trailing slash + * (e.g., "refs/heads/"): + */ + char name[FLEX_ARRAY]; +}; + +/* + * Return the index of the entry with the given refname from the + * ref_dir (non-recursively), sorting dir if necessary. Return -1 if + * no such entry is found. dir must already be complete. + */ +int search_ref_dir(struct ref_dir *dir, const char *refname, size_t len); + +struct ref_dir *get_ref_dir(struct ref_entry *entry); + +/* + * Create a struct ref_entry object for the specified dirname. + * dirname is the name of the directory with a trailing slash (e.g., + * "refs/heads/") or "" for the top-level directory. + */ +struct ref_entry *create_dir_entry(struct ref_cache *cache, + const char *dirname, size_t len, + int incomplete); + +struct ref_entry *create_ref_entry(const char *refname, + const struct object_id *oid, int flag); + +/* + * Return a pointer to a new `ref_cache`. Its top-level starts out + * marked incomplete. If `fill_ref_dir` is non-NULL, it is the + * function called to fill in incomplete directories in the + * `ref_cache` when they are accessed. If it is NULL, then the whole + * `ref_cache` must be filled (including clearing its directories' + * `REF_INCOMPLETE` bits) before it is used, and `refs` can be NULL, + * too. + */ +struct ref_cache *create_ref_cache(struct ref_store *refs, + fill_ref_dir_fn *fill_ref_dir); + +/* + * Free the `ref_cache` and all of its associated data. + */ +void free_ref_cache(struct ref_cache *cache); + +/* + * Add a ref_entry to the end of dir (unsorted). Entry is always + * stored directly in dir; no recursion into subdirectories is + * done. + */ +void add_entry_to_dir(struct ref_dir *dir, struct ref_entry *entry); + +/* + * Remove the entry with the given name from dir, recursing into + * subdirectories as necessary. If refname is the name of a directory + * (i.e., ends with '/'), then remove the directory and its contents. + * If the removal was successful, return the number of entries + * remaining in the directory entry that contained the deleted entry. + * If the name was not found, return -1. Please note that this + * function only deletes the entry from the cache; it does not delete + * it from the filesystem or ensure that other cache entries (which + * might be symbolic references to the removed entry) are updated. + * Nor does it remove any containing dir entries that might be made + * empty by the removal. dir must represent the top-level directory + * and must already be complete. + */ +int remove_entry_from_dir(struct ref_dir *dir, const char *refname); + +/* + * Add a ref_entry to the ref_dir (unsorted), recursing into + * subdirectories as necessary. dir must represent the top-level + * directory. Return 0 on success. + */ +int add_ref_entry(struct ref_dir *dir, struct ref_entry *ref); + +/* + * Find the value entry with the given name in dir, sorting ref_dirs + * and recursing into subdirectories as necessary. If the name is not + * found or it corresponds to a directory entry, return NULL. + */ +struct ref_entry *find_ref_entry(struct ref_dir *dir, const char *refname); + +/* + * Start iterating over references in `cache`. If `prefix` is + * specified, only include references whose names start with that + * prefix. If `prime_dir` is true, then fill any incomplete + * directories before beginning the iteration. + */ +struct ref_iterator *cache_ref_iterator_begin(struct ref_cache *cache, + const char *prefix, + int prime_dir); + +/* + * Peel the entry (if possible) and return its new peel_status. If + * repeel is true, re-peel the entry even if there is an old peeled + * value that is already stored in it. + * + * It is OK to call this function with a packed reference entry that + * might be stale and might even refer to an object that has since + * been garbage-collected. In such a case, if the entry has + * REF_KNOWS_PEELED then leave the status unchanged and return + * PEEL_PEELED or PEEL_NON_TAG; otherwise, return PEEL_INVALID. + */ +enum peel_status peel_entry(struct ref_entry *entry, int repeel); + +#endif /* REFS_REF_CACHE_H */ |