name-hash.c

   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
  11 struct dir_entry {
  12         struct hashmap_entry ent;
  13         struct dir_entry *parent;
  14         struct cache_entry *ce;
  15         int nr;
  16         unsigned int namelen;
  17 };
  18
  19 static int dir_entry_cmp(const struct dir_entry *e1,
  20                 const struct dir_entry *e2, const char *name)
  21 {
  22         return e1->namelen != e2->namelen || strncasecmp(e1->ce->name,
  23                         name ? name : e2->ce->name, e1->namelen);
  24 }
  25
  26 static struct dir_entry *find_dir_entry(struct index_state *istate,
  27                 const char *name, unsigned int namelen)
  28 {
  29         struct dir_entry key;
  30         hashmap_entry_init(&key, memihash(name, namelen));
  31         key.namelen = namelen;
  32         return hashmap_get(&istate->dir_hash, &key, name);
  33 }
  34
  35 static struct dir_entry *hash_dir_entry(struct index_state *istate,
  36                 struct cache_entry *ce, int namelen)
  37 {
  38         /*
  39          * Throw each directory component in the hash for quick lookup
  40          * during a git status. Directory components are stored without their
  41          * closing slash.  Despite submodules being a directory, they never
  42          * reach this point, because they are stored
  43          * in index_state.name_hash (as ordinary cache_entries).
  44          *
  45          * Note that the cache_entry stored with the dir_entry merely
  46          * supplies the name of the directory (up to dir_entry.namelen). We
  47          * track the number of 'active' files in a directory in dir_entry.nr,
  48          * so we can tell if the directory is still relevant, e.g. for git
  49          * status. However, if cache_entries are removed, we cannot pinpoint
  50          * an exact cache_entry that's still active. It is very possible that
  51          * multiple dir_entries point to the same cache_entry.
  52          */
  53         struct dir_entry *dir;
  54
  55         /* get length of parent directory */
  56         while (namelen > 0 && !is_dir_sep(ce->name[namelen - 1]))
  57                 namelen--;
  58         if (namelen <= 0)
  59                 return NULL;
  60         namelen--;
  61
  62         /* lookup existing entry for that directory */
  63         dir = find_dir_entry(istate, ce->name, namelen);
  64         if (!dir) {
  65                 /* not found, create it and add to hash table */
  66                 dir = xcalloc(1, sizeof(struct dir_entry));
  67                 hashmap_entry_init(dir, memihash(ce->name, namelen));
  68                 dir->namelen = namelen;
  69                 dir->ce = ce;
  70                 hashmap_add(&istate->dir_hash, dir);
  71
  72                 /* recursively add missing parent directories */
  73                 dir->parent = hash_dir_entry(istate, ce, namelen);
  74         }
  75         return dir;
  76 }
  77
  78 static void add_dir_entry(struct index_state *istate, struct cache_entry *ce)
  79 {
  80         /* Add reference to the directory entry (and parents if 0). */
  81         struct dir_entry *dir = hash_dir_entry(istate, ce, ce_namelen(ce));
  82         while (dir && !(dir->nr++))
  83                 dir = dir->parent;
  84 }
  85
  86 static void remove_dir_entry(struct index_state *istate, struct cache_entry *ce)
  87 {
  88         /*
  89          * Release reference to the directory entry (and parents if 0).
  90          *
  91          * Note: we do not remove / free the entry because there's no
  92          * hash.[ch]::remove_hash and dir->next may point to other entries
  93          * that are still valid, so we must not free the memory.
  94          */
  95         struct dir_entry *dir = hash_dir_entry(istate, ce, ce_namelen(ce));
  96         while (dir && dir->nr && !(--dir->nr))
  97                 dir = dir->parent;
  98 }
  99
 100 static void hash_index_entry(struct index_state *istate, struct cache_entry *ce)
 101 {
 102         void **pos;
 103         unsigned int hash;
 104
 105         if (ce->ce_flags & CE_HASHED)
 106                 return;
 107         ce->ce_flags |= CE_HASHED;
 108         ce->next = NULL;
 109         hash = memihash(ce->name, ce_namelen(ce));
 110         pos = insert_hash(hash, ce, &istate->name_hash);
 111         if (pos) {
 112                 ce->next = *pos;
 113                 *pos = ce;
 114         }
 115
 116         if (ignore_case && !(ce->ce_flags & CE_UNHASHED))
 117                 add_dir_entry(istate, ce);
 118 }
 119
 120 static void lazy_init_name_hash(struct index_state *istate)
 121 {
 122         int nr;
 123
 124         if (istate->name_hash_initialized)
 125                 return;
 126         if (istate->cache_nr)
 127                 preallocate_hash(&istate->name_hash, istate->cache_nr);
 128         hashmap_init(&istate->dir_hash, (hashmap_cmp_fn) dir_entry_cmp, 0);
 129         for (nr = 0; nr < istate->cache_nr; nr++)
 130                 hash_index_entry(istate, istate->cache[nr]);
 131         istate->name_hash_initialized = 1;
 132 }
 133
 134 void add_name_hash(struct index_state *istate, struct cache_entry *ce)
 135 {
 136         /* if already hashed, add reference to directory entries */
 137         if (ignore_case && (ce->ce_flags & CE_STATE_MASK) == CE_STATE_MASK)
 138                 add_dir_entry(istate, ce);
 139
 140         ce->ce_flags &= ~CE_UNHASHED;
 141         if (istate->name_hash_initialized)
 142                 hash_index_entry(istate, ce);
 143 }
 144
 145 /*
 146  * We don't actually *remove* it, we can just mark it invalid so that
 147  * we won't find it in lookups.
 148  *
 149  * Not only would we have to search the lists (simple enough), but
 150  * we'd also have to rehash other hash buckets in case this makes the
 151  * hash bucket empty (common). So it's much better to just mark
 152  * it.
 153  */
 154 void remove_name_hash(struct index_state *istate, struct cache_entry *ce)
 155 {
 156         /* if already hashed, release reference to directory entries */
 157         if (ignore_case && (ce->ce_flags & CE_STATE_MASK) == CE_HASHED)
 158                 remove_dir_entry(istate, ce);
 159
 160         ce->ce_flags |= CE_UNHASHED;
 161 }
 162
 163 static int slow_same_name(const char *name1, int len1, const char *name2, int len2)
 164 {
 165         if (len1 != len2)
 166                 return 0;
 167
 168         while (len1) {
 169                 unsigned char c1 = *name1++;
 170                 unsigned char c2 = *name2++;
 171                 len1--;
 172                 if (c1 != c2) {
 173                         c1 = toupper(c1);
 174                         c2 = toupper(c2);
 175                         if (c1 != c2)
 176                                 return 0;
 177                 }
 178         }
 179         return 1;
 180 }
 181
 182 static int same_name(const struct cache_entry *ce, const char *name, int namelen, int icase)
 183 {
 184         int len = ce_namelen(ce);
 185
 186         /*
 187          * Always do exact compare, even if we want a case-ignoring comparison;
 188          * we do the quick exact one first, because it will be the common case.
 189          */
 190         if (len == namelen && !cache_name_compare(name, namelen, ce->name, len))
 191                 return 1;
 192
 193         if (!icase)
 194                 return 0;
 195
 196         return slow_same_name(name, namelen, ce->name, len);
 197 }
 198
 199 struct cache_entry *index_dir_exists(struct index_state *istate, const char *name, int namelen)
 200 {
 201         struct cache_entry *ce;
 202         struct dir_entry *dir;
 203
 204         lazy_init_name_hash(istate);
 205         dir = find_dir_entry(istate, name, namelen);
 206         if (dir && dir->nr)
 207                 return dir->ce;
 208
 209         /*
 210          * It might be a submodule. Unlike plain directories, which are stored
 211          * in the dir-hash, submodules are stored in the name-hash, so check
 212          * there, as well.
 213          */
 214         ce = index_file_exists(istate, name, namelen, 1);
 215         if (ce && S_ISGITLINK(ce->ce_mode))
 216                 return ce;
 217
 218         return NULL;
 219 }
 220
 221 struct cache_entry *index_file_exists(struct index_state *istate, const char *name, int namelen, int icase)
 222 {
 223         unsigned int hash = memihash(name, namelen);
 224         struct cache_entry *ce;
 225
 226         lazy_init_name_hash(istate);
 227         ce = lookup_hash(hash, &istate->name_hash);
 228
 229         while (ce) {
 230                 if (!(ce->ce_flags & CE_UNHASHED)) {
 231                         if (same_name(ce, name, namelen, icase))
 232                                 return ce;
 233                 }
 234                 ce = ce->next;
 235         }
 236         return NULL;
 237 }
 238
 239 struct cache_entry *index_name_exists(struct index_state *istate, const char *name, int namelen, int icase)
 240 {
 241         if (namelen > 0 && name[namelen - 1] == '/')
 242                 return index_dir_exists(istate, name, namelen - 1);
 243         return index_file_exists(istate, name, namelen, icase);
 244 }
 245
 246 void free_name_hash(struct index_state *istate)
 247 {
 248         if (!istate->name_hash_initialized)
 249                 return;
 250         istate->name_hash_initialized = 0;
 251
 252         free_hash(&istate->name_hash);
 253         hashmap_free(&istate->dir_hash, 1);
 254 }