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[git/git.git] / name-hash.c
CommitLineData
96872bc2
LT
1/*
2 * name-hash.c
3 *
4 * Hashing names in the index state
5 *
6 * Copyright (C) 2008 Linus Torvalds
7 */
8#define NO_THE_INDEX_COMPATIBILITY_MACROS
9#include "cache.h"
10
cd2fef59
LT
11/*
12 * This removes bit 5 if bit 6 is set.
13 *
14 * That will make US-ASCII characters hash to their upper-case
15 * equivalent. We could easily do this one whole word at a time,
16 * but that's for future worries.
17 */
18static inline unsigned char icase_hash(unsigned char c)
19{
20 return c & ~((c & 0x40) >> 1);
21}
22
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23static unsigned int hash_name(const char *name, int namelen)
24{
25 unsigned int hash = 0x123;
26
c19387e7 27 while (namelen--) {
96872bc2 28 unsigned char c = *name++;
cd2fef59 29 c = icase_hash(c);
96872bc2 30 hash = hash*101 + c;
c19387e7 31 }
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32 return hash;
33}
34
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35struct dir_entry {
36 struct dir_entry *next;
37 struct dir_entry *parent;
38 struct cache_entry *ce;
39 int nr;
40 unsigned int namelen;
41};
42
43static struct dir_entry *find_dir_entry(struct index_state *istate,
44 const char *name, unsigned int namelen)
45{
46 unsigned int hash = hash_name(name, namelen);
47 struct dir_entry *dir;
48
49 for (dir = lookup_hash(hash, &istate->dir_hash); dir; dir = dir->next)
50 if (dir->namelen == namelen &&
51 !strncasecmp(dir->ce->name, name, namelen))
52 return dir;
53 return NULL;
54}
55
56static struct dir_entry *hash_dir_entry(struct index_state *istate,
57 struct cache_entry *ce, int namelen)
5102c617
JJ
58{
59 /*
60 * Throw each directory component in the hash for quick lookup
61 * during a git status. Directory components are stored with their
62 * closing slash. Despite submodules being a directory, they never
63 * reach this point, because they are stored without a closing slash
2092678c 64 * in index_state.name_hash (as ordinary cache_entries).
5102c617 65 *
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66 * Note that the cache_entry stored with the dir_entry merely
67 * supplies the name of the directory (up to dir_entry.namelen). We
68 * track the number of 'active' files in a directory in dir_entry.nr,
69 * so we can tell if the directory is still relevant, e.g. for git
70 * status. However, if cache_entries are removed, we cannot pinpoint
71 * an exact cache_entry that's still active. It is very possible that
72 * multiple dir_entries point to the same cache_entry.
5102c617 73 */
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74 struct dir_entry *dir;
75
76 /* get length of parent directory */
77 while (namelen > 0 && !is_dir_sep(ce->name[namelen - 1]))
78 namelen--;
79 if (namelen <= 0)
80 return NULL;
81
82 /* lookup existing entry for that directory */
83 dir = find_dir_entry(istate, ce->name, namelen);
84 if (!dir) {
85 /* not found, create it and add to hash table */
86 void **pdir;
87 unsigned int hash = hash_name(ce->name, namelen);
5102c617 88
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89 dir = xcalloc(1, sizeof(struct dir_entry));
90 dir->namelen = namelen;
91 dir->ce = ce;
92
93 pdir = insert_hash(hash, dir, &istate->dir_hash);
94 if (pdir) {
95 dir->next = *pdir;
96 *pdir = dir;
5102c617 97 }
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98
99 /* recursively add missing parent directories */
100 dir->parent = hash_dir_entry(istate, ce, namelen - 1);
5102c617 101 }
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102 return dir;
103}
104
105static void add_dir_entry(struct index_state *istate, struct cache_entry *ce)
106{
107 /* Add reference to the directory entry (and parents if 0). */
108 struct dir_entry *dir = hash_dir_entry(istate, ce, ce_namelen(ce));
109 while (dir && !(dir->nr++))
110 dir = dir->parent;
111}
112
113static void remove_dir_entry(struct index_state *istate, struct cache_entry *ce)
114{
115 /*
116 * Release reference to the directory entry (and parents if 0).
117 *
118 * Note: we do not remove / free the entry because there's no
119 * hash.[ch]::remove_hash and dir->next may point to other entries
120 * that are still valid, so we must not free the memory.
121 */
122 struct dir_entry *dir = hash_dir_entry(istate, ce, ce_namelen(ce));
123 while (dir && dir->nr && !(--dir->nr))
124 dir = dir->parent;
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JJ
125}
126
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127static void hash_index_entry(struct index_state *istate, struct cache_entry *ce)
128{
129 void **pos;
130 unsigned int hash;
131
132 if (ce->ce_flags & CE_HASHED)
133 return;
134 ce->ce_flags |= CE_HASHED;
2092678c 135 ce->next = NULL;
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136 hash = hash_name(ce->name, ce_namelen(ce));
137 pos = insert_hash(hash, ce, &istate->name_hash);
138 if (pos) {
139 ce->next = *pos;
140 *pos = ce;
141 }
5102c617 142
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143 if (ignore_case && !(ce->ce_flags & CE_UNHASHED))
144 add_dir_entry(istate, ce);
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145}
146
147static void lazy_init_name_hash(struct index_state *istate)
148{
149 int nr;
150
151 if (istate->name_hash_initialized)
152 return;
c7359281
NTND
153 if (istate->cache_nr)
154 preallocate_hash(&istate->name_hash, istate->cache_nr);
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LT
155 for (nr = 0; nr < istate->cache_nr; nr++)
156 hash_index_entry(istate, istate->cache[nr]);
157 istate->name_hash_initialized = 1;
158}
159
160void add_name_hash(struct index_state *istate, struct cache_entry *ce)
161{
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162 /* if already hashed, add reference to directory entries */
163 if (ignore_case && (ce->ce_flags & CE_STATE_MASK) == CE_STATE_MASK)
164 add_dir_entry(istate, ce);
165
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166 ce->ce_flags &= ~CE_UNHASHED;
167 if (istate->name_hash_initialized)
168 hash_index_entry(istate, ce);
169}
170
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171/*
172 * We don't actually *remove* it, we can just mark it invalid so that
173 * we won't find it in lookups.
174 *
175 * Not only would we have to search the lists (simple enough), but
176 * we'd also have to rehash other hash buckets in case this makes the
177 * hash bucket empty (common). So it's much better to just mark
178 * it.
179 */
180void remove_name_hash(struct index_state *istate, struct cache_entry *ce)
181{
182 /* if already hashed, release reference to directory entries */
183 if (ignore_case && (ce->ce_flags & CE_STATE_MASK) == CE_HASHED)
184 remove_dir_entry(istate, ce);
185
186 ce->ce_flags |= CE_UNHASHED;
187}
188
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189static int slow_same_name(const char *name1, int len1, const char *name2, int len2)
190{
191 if (len1 != len2)
192 return 0;
193
194 while (len1) {
195 unsigned char c1 = *name1++;
196 unsigned char c2 = *name2++;
197 len1--;
198 if (c1 != c2) {
199 c1 = toupper(c1);
200 c2 = toupper(c2);
201 if (c1 != c2)
202 return 0;
203 }
204 }
205 return 1;
206}
207
208static int same_name(const struct cache_entry *ce, const char *name, int namelen, int icase)
209{
210 int len = ce_namelen(ce);
211
212 /*
213 * Always do exact compare, even if we want a case-ignoring comparison;
214 * we do the quick exact one first, because it will be the common case.
215 */
216 if (len == namelen && !cache_name_compare(name, namelen, ce->name, len))
217 return 1;
218
5102c617
JJ
219 if (!icase)
220 return 0;
221
2092678c 222 return slow_same_name(name, namelen, ce->name, len);
cd2fef59
LT
223}
224
225struct cache_entry *index_name_exists(struct index_state *istate, const char *name, int namelen, int icase)
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LT
226{
227 unsigned int hash = hash_name(name, namelen);
228 struct cache_entry *ce;
229
230 lazy_init_name_hash(istate);
231 ce = lookup_hash(hash, &istate->name_hash);
232
233 while (ce) {
234 if (!(ce->ce_flags & CE_UNHASHED)) {
cd2fef59 235 if (same_name(ce, name, namelen, icase))
df292c79 236 return ce;
96872bc2 237 }
2092678c 238 ce = ce->next;
96872bc2 239 }
5102c617
JJ
240
241 /*
2092678c
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242 * When looking for a directory (trailing '/'), it might be a
243 * submodule or a directory. Despite submodules being directories,
5102c617 244 * they are stored in the name hash without a closing slash.
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245 * When ignore_case is 1, directories are stored in a separate hash
246 * table *with* their closing slash.
5102c617
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247 *
248 * The side effect of this storage technique is we have need to
2092678c 249 * lookup the directory in a separate hash table, and if not found
5102c617
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250 * remove the slash from name and perform the lookup again without
251 * the slash. If a match is made, S_ISGITLINK(ce->mode) will be
252 * true.
253 */
254 if (icase && name[namelen - 1] == '/') {
2092678c
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255 struct dir_entry *dir = find_dir_entry(istate, name, namelen);
256 if (dir && dir->nr)
257 return dir->ce;
258
5102c617
JJ
259 ce = index_name_exists(istate, name, namelen - 1, icase);
260 if (ce && S_ISGITLINK(ce->ce_mode))
261 return ce;
262 }
df292c79 263 return NULL;
96872bc2 264}
2092678c
KB
265
266static int free_dir_entry(void *entry, void *unused)
267{
268 struct dir_entry *dir = entry;
269 while (dir) {
270 struct dir_entry *next = dir->next;
271 free(dir);
272 dir = next;
273 }
274 return 0;
275}
276
277void free_name_hash(struct index_state *istate)
278{
279 if (!istate->name_hash_initialized)
280 return;
281 istate->name_hash_initialized = 0;
282 if (ignore_case)
283 /* free directory entries */
284 for_each_hash(&istate->dir_hash, free_dir_entry, NULL);
285
286 free_hash(&istate->name_hash);
287 free_hash(&istate->dir_hash);
288}