refs: split `ref_cache` code into separate files
[git/git.git] / refs / ref-cache.h
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1#ifndef REFS_REF_CACHE_H
2#define REFS_REF_CACHE_H
3
4/*
5 * Information used (along with the information in ref_entry) to
6 * describe a single cached reference. This data structure only
7 * occurs embedded in a union in struct ref_entry, and only when
8 * (ref_entry->flag & REF_DIR) is zero.
9 */
10struct ref_value {
11 /*
12 * The name of the object to which this reference resolves
13 * (which may be a tag object). If REF_ISBROKEN, this is
14 * null. If REF_ISSYMREF, then this is the name of the object
15 * referred to by the last reference in the symlink chain.
16 */
17 struct object_id oid;
18
19 /*
20 * If REF_KNOWS_PEELED, then this field holds the peeled value
21 * of this reference, or null if the reference is known not to
22 * be peelable. See the documentation for peel_ref() for an
23 * exact definition of "peelable".
24 */
25 struct object_id peeled;
26};
27
28/*
29 * Information used (along with the information in ref_entry) to
30 * describe a level in the hierarchy of references. This data
31 * structure only occurs embedded in a union in struct ref_entry, and
32 * only when (ref_entry.flag & REF_DIR) is set. In that case,
33 * (ref_entry.flag & REF_INCOMPLETE) determines whether the references
34 * in the directory have already been read:
35 *
36 * (ref_entry.flag & REF_INCOMPLETE) unset -- a directory of loose
37 * or packed references, already read.
38 *
39 * (ref_entry.flag & REF_INCOMPLETE) set -- a directory of loose
40 * references that hasn't been read yet (nor has any of its
41 * subdirectories).
42 *
43 * Entries within a directory are stored within a growable array of
44 * pointers to ref_entries (entries, nr, alloc). Entries 0 <= i <
45 * sorted are sorted by their component name in strcmp() order and the
46 * remaining entries are unsorted.
47 *
48 * Loose references are read lazily, one directory at a time. When a
49 * directory of loose references is read, then all of the references
50 * in that directory are stored, and REF_INCOMPLETE stubs are created
51 * for any subdirectories, but the subdirectories themselves are not
52 * read. The reading is triggered by get_ref_dir().
53 */
54struct ref_dir {
55 int nr, alloc;
56
57 /*
58 * Entries with index 0 <= i < sorted are sorted by name. New
59 * entries are appended to the list unsorted, and are sorted
60 * only when required; thus we avoid the need to sort the list
61 * after the addition of every reference.
62 */
63 int sorted;
64
65 /* A pointer to the files_ref_store that contains this ref_dir. */
66 struct files_ref_store *ref_store;
67
68 struct ref_entry **entries;
69};
70
71/*
72 * Bit values for ref_entry::flag. REF_ISSYMREF=0x01,
73 * REF_ISPACKED=0x02, REF_ISBROKEN=0x04 and REF_BAD_NAME=0x08 are
74 * public values; see refs.h.
75 */
76
77/*
78 * The field ref_entry->u.value.peeled of this value entry contains
79 * the correct peeled value for the reference, which might be
80 * null_sha1 if the reference is not a tag or if it is broken.
81 */
82#define REF_KNOWS_PEELED 0x10
83
84/* ref_entry represents a directory of references */
85#define REF_DIR 0x20
86
87/*
88 * Entry has not yet been read from disk (used only for REF_DIR
89 * entries representing loose references)
90 */
91#define REF_INCOMPLETE 0x40
92
93/*
94 * A ref_entry represents either a reference or a "subdirectory" of
95 * references.
96 *
97 * Each directory in the reference namespace is represented by a
98 * ref_entry with (flags & REF_DIR) set and containing a subdir member
99 * that holds the entries in that directory that have been read so
100 * far. If (flags & REF_INCOMPLETE) is set, then the directory and
101 * its subdirectories haven't been read yet. REF_INCOMPLETE is only
102 * used for loose reference directories.
103 *
104 * References are represented by a ref_entry with (flags & REF_DIR)
105 * unset and a value member that describes the reference's value. The
106 * flag member is at the ref_entry level, but it is also needed to
107 * interpret the contents of the value field (in other words, a
108 * ref_value object is not very much use without the enclosing
109 * ref_entry).
110 *
111 * Reference names cannot end with slash and directories' names are
112 * always stored with a trailing slash (except for the top-level
113 * directory, which is always denoted by ""). This has two nice
114 * consequences: (1) when the entries in each subdir are sorted
115 * lexicographically by name (as they usually are), the references in
116 * a whole tree can be generated in lexicographic order by traversing
117 * the tree in left-to-right, depth-first order; (2) the names of
118 * references and subdirectories cannot conflict, and therefore the
119 * presence of an empty subdirectory does not block the creation of a
120 * similarly-named reference. (The fact that reference names with the
121 * same leading components can conflict *with each other* is a
122 * separate issue that is regulated by refs_verify_refname_available().)
123 *
124 * Please note that the name field contains the fully-qualified
125 * reference (or subdirectory) name. Space could be saved by only
126 * storing the relative names. But that would require the full names
127 * to be generated on the fly when iterating in do_for_each_ref(), and
128 * would break callback functions, who have always been able to assume
129 * that the name strings that they are passed will not be freed during
130 * the iteration.
131 */
132struct ref_entry {
133 unsigned char flag; /* ISSYMREF? ISPACKED? */
134 union {
135 struct ref_value value; /* if not (flags&REF_DIR) */
136 struct ref_dir subdir; /* if (flags&REF_DIR) */
137 } u;
138 /*
139 * The full name of the reference (e.g., "refs/heads/master")
140 * or the full name of the directory with a trailing slash
141 * (e.g., "refs/heads/"):
142 */
143 char name[FLEX_ARRAY];
144};
145
146/*
147 * Return the index of the entry with the given refname from the
148 * ref_dir (non-recursively), sorting dir if necessary. Return -1 if
149 * no such entry is found. dir must already be complete.
150 */
151int search_ref_dir(struct ref_dir *dir, const char *refname, size_t len);
152
153struct ref_dir *get_ref_dir(struct ref_entry *entry);
154
155/*
156 * Create a struct ref_entry object for the specified dirname.
157 * dirname is the name of the directory with a trailing slash (e.g.,
158 * "refs/heads/") or "" for the top-level directory.
159 */
160struct ref_entry *create_dir_entry(struct files_ref_store *ref_store,
161 const char *dirname, size_t len,
162 int incomplete);
163
164struct ref_entry *create_ref_entry(const char *refname,
165 const unsigned char *sha1, int flag,
166 int check_name);
167
168void free_ref_entry(struct ref_entry *entry);
169
170/*
171 * Add a ref_entry to the end of dir (unsorted). Entry is always
172 * stored directly in dir; no recursion into subdirectories is
173 * done.
174 */
175void add_entry_to_dir(struct ref_dir *dir, struct ref_entry *entry);
176
177/*
178 * Remove the entry with the given name from dir, recursing into
179 * subdirectories as necessary. If refname is the name of a directory
180 * (i.e., ends with '/'), then remove the directory and its contents.
181 * If the removal was successful, return the number of entries
182 * remaining in the directory entry that contained the deleted entry.
183 * If the name was not found, return -1. Please note that this
184 * function only deletes the entry from the cache; it does not delete
185 * it from the filesystem or ensure that other cache entries (which
186 * might be symbolic references to the removed entry) are updated.
187 * Nor does it remove any containing dir entries that might be made
188 * empty by the removal. dir must represent the top-level directory
189 * and must already be complete.
190 */
191int remove_entry_from_dir(struct ref_dir *dir, const char *refname);
192
193/*
194 * Add a ref_entry to the ref_dir (unsorted), recursing into
195 * subdirectories as necessary. dir must represent the top-level
196 * directory. Return 0 on success.
197 */
198int add_ref_entry(struct ref_dir *dir, struct ref_entry *ref);
199
200/*
201 * If refname is a reference name, find the ref_dir within the dir
202 * tree that should hold refname. If refname is a directory name
203 * (i.e., it ends in '/'), then return that ref_dir itself. dir must
204 * represent the top-level directory and must already be complete.
205 * Sort ref_dirs and recurse into subdirectories as necessary. If
206 * mkdir is set, then create any missing directories; otherwise,
207 * return NULL if the desired directory cannot be found.
208 */
209struct ref_dir *find_containing_dir(struct ref_dir *dir,
210 const char *refname, int mkdir);
211
212/*
213 * Find the value entry with the given name in dir, sorting ref_dirs
214 * and recursing into subdirectories as necessary. If the name is not
215 * found or it corresponds to a directory entry, return NULL.
216 */
217struct ref_entry *find_ref_entry(struct ref_dir *dir, const char *refname);
218
219struct ref_iterator *cache_ref_iterator_begin(struct ref_dir *dir);
220
221typedef int each_ref_entry_fn(struct ref_entry *entry, void *cb_data);
222
223/*
224 * Call fn for each reference in dir that has index in the range
225 * offset <= index < dir->nr. Recurse into subdirectories that are in
226 * that index range, sorting them before iterating. This function
227 * does not sort dir itself; it should be sorted beforehand. fn is
228 * called for all references, including broken ones.
229 */
230int do_for_each_entry_in_dir(struct ref_dir *dir, int offset,
231 each_ref_entry_fn fn, void *cb_data);
232
233/*
234 * Peel the entry (if possible) and return its new peel_status. If
235 * repeel is true, re-peel the entry even if there is an old peeled
236 * value that is already stored in it.
237 *
238 * It is OK to call this function with a packed reference entry that
239 * might be stale and might even refer to an object that has since
240 * been garbage-collected. In such a case, if the entry has
241 * REF_KNOWS_PEELED then leave the status unchanged and return
242 * PEEL_PEELED or PEEL_NON_TAG; otherwise, return PEEL_INVALID.
243 */
244enum peel_status peel_entry(struct ref_entry *entry, int repeel);
245
246/*
247 * Load all of the refs from `dir` into our in-memory cache.
248 */
249void prime_ref_dir(struct ref_dir *dir);
250
251#endif /* REFS_REF_CACHE_H */