refs/ref-cache.h

   1 #ifndef REFS_REF_CACHE_H
   2 #define REFS_REF_CACHE_H
   3
   4 struct ref_dir;
   5
   6 /*
   7  * If this ref_cache is filled lazily, this function is used to load
   8  * information into the specified ref_dir (shallow or deep, at the
   9  * option of the ref_store). dirname includes a trailing slash.
  10  */
  11 typedef void fill_ref_dir_fn(struct ref_store *ref_store,
  12                              struct ref_dir *dir, const char *dirname);
  13
  14 struct ref_cache {
  15         struct ref_entry *root;
  16
  17         /* A pointer to the ref_store whose cache this is: */
  18         struct ref_store *ref_store;
  19
  20         /*
  21          * Function used (if necessary) to lazily-fill cache. May be
  22          * NULL.
  23          */
  24         fill_ref_dir_fn *fill_ref_dir;
  25 };
  26
  27 /*
  28  * Information used (along with the information in ref_entry) to
  29  * describe a single cached reference.  This data structure only
  30  * occurs embedded in a union in struct ref_entry, and only when
  31  * (ref_entry->flag & REF_DIR) is zero.
  32  */
  33 struct ref_value {
  34         /*
  35          * The name of the object to which this reference resolves
  36          * (which may be a tag object).  If REF_ISBROKEN, this is
  37          * null.  If REF_ISSYMREF, then this is the name of the object
  38          * referred to by the last reference in the symlink chain.
  39          */
  40         struct object_id oid;
  41 };
  42
  43 /*
  44  * Information used (along with the information in ref_entry) to
  45  * describe a level in the hierarchy of references.  This data
  46  * structure only occurs embedded in a union in struct ref_entry, and
  47  * only when (ref_entry.flag & REF_DIR) is set.  In that case,
  48  * (ref_entry.flag & REF_INCOMPLETE) determines whether the references
  49  * in the directory have already been read:
  50  *
  51  *     (ref_entry.flag & REF_INCOMPLETE) unset -- a directory of loose
  52  *         or packed references, already read.
  53  *
  54  *     (ref_entry.flag & REF_INCOMPLETE) set -- a directory of loose
  55  *         references that hasn't been read yet (nor has any of its
  56  *         subdirectories).
  57  *
  58  * Entries within a directory are stored within a growable array of
  59  * pointers to ref_entries (entries, nr, alloc).  Entries 0 <= i <
  60  * sorted are sorted by their component name in strcmp() order and the
  61  * remaining entries are unsorted.
  62  *
  63  * Loose references are read lazily, one directory at a time.  When a
  64  * directory of loose references is read, then all of the references
  65  * in that directory are stored, and REF_INCOMPLETE stubs are created
  66  * for any subdirectories, but the subdirectories themselves are not
  67  * read.  The reading is triggered by get_ref_dir().
  68  */
  69 struct ref_dir {
  70         int nr, alloc;
  71
  72         /*
  73          * Entries with index 0 <= i < sorted are sorted by name.  New
  74          * entries are appended to the list unsorted, and are sorted
  75          * only when required; thus we avoid the need to sort the list
  76          * after the addition of every reference.
  77          */
  78         int sorted;
  79
  80         /* The ref_cache containing this entry: */
  81         struct ref_cache *cache;
  82
  83         struct ref_entry **entries;
  84 };
  85
  86 /*
  87  * Bit values for ref_entry::flag.  REF_ISSYMREF=0x01,
  88  * REF_ISPACKED=0x02, REF_ISBROKEN=0x04 and REF_BAD_NAME=0x08 are
  89  * public values; see refs.h.
  90  */
  91
  92 /* ref_entry represents a directory of references */
  93 #define REF_DIR 0x10
  94
  95 /*
  96  * Entry has not yet been read from disk (used only for REF_DIR
  97  * entries representing loose references)
  98  */
  99 #define REF_INCOMPLETE 0x20
 100
 101 /*
 102  * A ref_entry represents either a reference or a "subdirectory" of
 103  * references.
 104  *
 105  * Each directory in the reference namespace is represented by a
 106  * ref_entry with (flags & REF_DIR) set and containing a subdir member
 107  * that holds the entries in that directory that have been read so
 108  * far.  If (flags & REF_INCOMPLETE) is set, then the directory and
 109  * its subdirectories haven't been read yet.  REF_INCOMPLETE is only
 110  * used for loose reference directories.
 111  *
 112  * References are represented by a ref_entry with (flags & REF_DIR)
 113  * unset and a value member that describes the reference's value.  The
 114  * flag member is at the ref_entry level, but it is also needed to
 115  * interpret the contents of the value field (in other words, a
 116  * ref_value object is not very much use without the enclosing
 117  * ref_entry).
 118  *
 119  * Reference names cannot end with slash and directories' names are
 120  * always stored with a trailing slash (except for the top-level
 121  * directory, which is always denoted by "").  This has two nice
 122  * consequences: (1) when the entries in each subdir are sorted
 123  * lexicographically by name (as they usually are), the references in
 124  * a whole tree can be generated in lexicographic order by traversing
 125  * the tree in left-to-right, depth-first order; (2) the names of
 126  * references and subdirectories cannot conflict, and therefore the
 127  * presence of an empty subdirectory does not block the creation of a
 128  * similarly-named reference.  (The fact that reference names with the
 129  * same leading components can conflict *with each other* is a
 130  * separate issue that is regulated by refs_verify_refname_available().)
 131  *
 132  * Please note that the name field contains the fully-qualified
 133  * reference (or subdirectory) name.  Space could be saved by only
 134  * storing the relative names.  But that would require the full names
 135  * to be generated on the fly when iterating in do_for_each_ref(), and
 136  * would break callback functions, who have always been able to assume
 137  * that the name strings that they are passed will not be freed during
 138  * the iteration.
 139  */
 140 struct ref_entry {
 141         unsigned char flag; /* ISSYMREF? ISPACKED? */
 142         union {
 143                 struct ref_value value; /* if not (flags&REF_DIR) */
 144                 struct ref_dir subdir; /* if (flags&REF_DIR) */
 145         } u;
 146         /*
 147          * The full name of the reference (e.g., "refs/heads/master")
 148          * or the full name of the directory with a trailing slash
 149          * (e.g., "refs/heads/"):
 150          */
 151         char name[FLEX_ARRAY];
 152 };
 153
 154 /*
 155  * Return the index of the entry with the given refname from the
 156  * ref_dir (non-recursively), sorting dir if necessary.  Return -1 if
 157  * no such entry is found.  dir must already be complete.
 158  */
 159 int search_ref_dir(struct ref_dir *dir, const char *refname, size_t len);
 160
 161 struct ref_dir *get_ref_dir(struct ref_entry *entry);
 162
 163 /*
 164  * Create a struct ref_entry object for the specified dirname.
 165  * dirname is the name of the directory with a trailing slash (e.g.,
 166  * "refs/heads/") or "" for the top-level directory.
 167  */
 168 struct ref_entry *create_dir_entry(struct ref_cache *cache,
 169                                    const char *dirname, size_t len,
 170                                    int incomplete);
 171
 172 struct ref_entry *create_ref_entry(const char *refname,
 173                                    const struct object_id *oid, int flag);
 174
 175 /*
 176  * Return a pointer to a new `ref_cache`. Its top-level starts out
 177  * marked incomplete. If `fill_ref_dir` is non-NULL, it is the
 178  * function called to fill in incomplete directories in the
 179  * `ref_cache` when they are accessed. If it is NULL, then the whole
 180  * `ref_cache` must be filled (including clearing its directories'
 181  * `REF_INCOMPLETE` bits) before it is used, and `refs` can be NULL,
 182  * too.
 183  */
 184 struct ref_cache *create_ref_cache(struct ref_store *refs,
 185                                    fill_ref_dir_fn *fill_ref_dir);
 186
 187 /*
 188  * Free the `ref_cache` and all of its associated data.
 189  */
 190 void free_ref_cache(struct ref_cache *cache);
 191
 192 /*
 193  * Add a ref_entry to the end of dir (unsorted).  Entry is always
 194  * stored directly in dir; no recursion into subdirectories is
 195  * done.
 196  */
 197 void add_entry_to_dir(struct ref_dir *dir, struct ref_entry *entry);
 198
 199 /*
 200  * Remove the entry with the given name from dir, recursing into
 201  * subdirectories as necessary.  If refname is the name of a directory
 202  * (i.e., ends with '/'), then remove the directory and its contents.
 203  * If the removal was successful, return the number of entries
 204  * remaining in the directory entry that contained the deleted entry.
 205  * If the name was not found, return -1.  Please note that this
 206  * function only deletes the entry from the cache; it does not delete
 207  * it from the filesystem or ensure that other cache entries (which
 208  * might be symbolic references to the removed entry) are updated.
 209  * Nor does it remove any containing dir entries that might be made
 210  * empty by the removal.  dir must represent the top-level directory
 211  * and must already be complete.
 212  */
 213 int remove_entry_from_dir(struct ref_dir *dir, const char *refname);
 214
 215 /*
 216  * Add a ref_entry to the ref_dir (unsorted), recursing into
 217  * subdirectories as necessary.  dir must represent the top-level
 218  * directory.  Return 0 on success.
 219  */
 220 int add_ref_entry(struct ref_dir *dir, struct ref_entry *ref);
 221
 222 /*
 223  * Find the value entry with the given name in dir, sorting ref_dirs
 224  * and recursing into subdirectories as necessary.  If the name is not
 225  * found or it corresponds to a directory entry, return NULL.
 226  */
 227 struct ref_entry *find_ref_entry(struct ref_dir *dir, const char *refname);
 228
 229 /*
 230  * Start iterating over references in `cache`. If `prefix` is
 231  * specified, only include references whose names start with that
 232  * prefix. If `prime_dir` is true, then fill any incomplete
 233  * directories before beginning the iteration. The output is ordered
 234  * by refname.
 235  */
 236 struct ref_iterator *cache_ref_iterator_begin(struct ref_cache *cache,
 237                                               const char *prefix,
 238                                               int prime_dir);
 239
 240 #endif /* REFS_REF_CACHE_H */