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. If 0, remove and continue
  90          * with parent directory.
  91          */
  92         struct dir_entry *dir = hash_dir_entry(istate, ce, ce_namelen(ce));
  93         while (dir && !(--dir->nr)) {
  94                 struct dir_entry *parent = dir->parent;
  95                 hashmap_remove(&istate->dir_hash, dir, NULL);
  96                 free(dir);
  97                 dir = parent;
  98         }
  99 }
 100
 101 static void hash_index_entry(struct index_state *istate, struct cache_entry *ce)
 102 {
 103         void **pos;
 104         unsigned int hash;
 105
 106         if (ce->ce_flags & CE_HASHED)
 107                 return;
 108         ce->ce_flags |= CE_HASHED;
 109         ce->next = NULL;
 110         hash = memihash(ce->name, ce_namelen(ce));
 111         pos = insert_hash(hash, ce, &istate->name_hash);
 112         if (pos) {
 113                 ce->next = *pos;
 114                 *pos = ce;
 115         }
 116
 117         if (ignore_case && !(ce->ce_flags & CE_UNHASHED))
 118                 add_dir_entry(istate, ce);
 119 }
 120
 121 static void lazy_init_name_hash(struct index_state *istate)
 122 {
 123         int nr;
 124
 125         if (istate->name_hash_initialized)
 126                 return;
 127         if (istate->cache_nr)
 128                 preallocate_hash(&istate->name_hash, istate->cache_nr);
 129         hashmap_init(&istate->dir_hash, (hashmap_cmp_fn) dir_entry_cmp, 0);
 130         for (nr = 0; nr < istate->cache_nr; nr++)
 131                 hash_index_entry(istate, istate->cache[nr]);
 132         istate->name_hash_initialized = 1;
 133 }
 134
 135 void add_name_hash(struct index_state *istate, struct cache_entry *ce)
 136 {
 137         /* if already hashed, add reference to directory entries */
 138         if (ignore_case && (ce->ce_flags & CE_STATE_MASK) == CE_STATE_MASK)
 139                 add_dir_entry(istate, ce);
 140
 141         ce->ce_flags &= ~CE_UNHASHED;
 142         if (istate->name_hash_initialized)
 143                 hash_index_entry(istate, ce);
 144 }
 145
 146 /*
 147  * We don't actually *remove* it, we can just mark it invalid so that
 148  * we won't find it in lookups.
 149  *
 150  * Not only would we have to search the lists (simple enough), but
 151  * we'd also have to rehash other hash buckets in case this makes the
 152  * hash bucket empty (common). So it's much better to just mark
 153  * it.
 154  */
 155 void remove_name_hash(struct index_state *istate, struct cache_entry *ce)
 156 {
 157         /* if already hashed, release reference to directory entries */
 158         if (ignore_case && (ce->ce_flags & CE_STATE_MASK) == CE_HASHED)
 159                 remove_dir_entry(istate, ce);
 160
 161         ce->ce_flags |= CE_UNHASHED;
 162 }
 163
 164 static int slow_same_name(const char *name1, int len1, const char *name2, int len2)
 165 {
 166         if (len1 != len2)
 167                 return 0;
 168
 169         while (len1) {
 170                 unsigned char c1 = *name1++;
 171                 unsigned char c2 = *name2++;
 172                 len1--;
 173                 if (c1 != c2) {
 174                         c1 = toupper(c1);
 175                         c2 = toupper(c2);
 176                         if (c1 != c2)
 177                                 return 0;
 178                 }
 179         }
 180         return 1;
 181 }
 182
 183 static int same_name(const struct cache_entry *ce, const char *name, int namelen, int icase)
 184 {
 185         int len = ce_namelen(ce);
 186
 187         /*
 188          * Always do exact compare, even if we want a case-ignoring comparison;
 189          * we do the quick exact one first, because it will be the common case.
 190          */
 191         if (len == namelen && !cache_name_compare(name, namelen, ce->name, len))
 192                 return 1;
 193
 194         if (!icase)
 195                 return 0;
 196
 197         return slow_same_name(name, namelen, ce->name, len);
 198 }
 199
 200 struct cache_entry *index_dir_exists(struct index_state *istate, const char *name, int namelen)
 201 {
 202         struct cache_entry *ce;
 203         struct dir_entry *dir;
 204
 205         lazy_init_name_hash(istate);
 206         dir = find_dir_entry(istate, name, namelen);
 207         if (dir && dir->nr)
 208                 return dir->ce;
 209
 210         /*
 211          * It might be a submodule. Unlike plain directories, which are stored
 212          * in the dir-hash, submodules are stored in the name-hash, so check
 213          * there, as well.
 214          */
 215         ce = index_file_exists(istate, name, namelen, 1);
 216         if (ce && S_ISGITLINK(ce->ce_mode))
 217                 return ce;
 218
 219         return NULL;
 220 }
 221
 222 struct cache_entry *index_file_exists(struct index_state *istate, const char *name, int namelen, int icase)
 223 {
 224         unsigned int hash = memihash(name, namelen);
 225         struct cache_entry *ce;
 226
 227         lazy_init_name_hash(istate);
 228         ce = lookup_hash(hash, &istate->name_hash);
 229
 230         while (ce) {
 231                 if (!(ce->ce_flags & CE_UNHASHED)) {
 232                         if (same_name(ce, name, namelen, icase))
 233                                 return ce;
 234                 }
 235                 ce = ce->next;
 236         }
 237         return NULL;
 238 }
 239
 240 struct cache_entry *index_name_exists(struct index_state *istate, const char *name, int namelen, int icase)
 241 {
 242         if (namelen > 0 && name[namelen - 1] == '/')
 243                 return index_dir_exists(istate, name, namelen - 1);
 244         return index_file_exists(istate, name, namelen, icase);
 245 }
 246
 247 void free_name_hash(struct index_state *istate)
 248 {
 249         if (!istate->name_hash_initialized)
 250                 return;
 251         istate->name_hash_initialized = 0;
 252
 253         free_hash(&istate->name_hash);
 254         hashmap_free(&istate->dir_hash, 1);
 255 }