ref_cache: remove support for storing peeled values
[git/git.git] / 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 */