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 /*
  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  */
  18 static inline unsigned char icase_hash(unsigned char c)
  19 {
  20         return c & ~((c & 0x40) >> 1);
  21 }
  22
  23 static unsigned int hash_name(const char *name, int namelen)
  24 {
  25         unsigned int hash = 0x123;
  26
  27         while (namelen--) {
  28                 unsigned char c = *name++;
  29                 c = icase_hash(c);
  30                 hash = hash*101 + c;
  31         }
  32         return hash;
  33 }
  34
  35 struct 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
  43 static 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
  56 static struct dir_entry *hash_dir_entry(struct index_state *istate,
  57                 struct cache_entry *ce, int namelen)
  58 {
  59         /*
  60          * Throw each directory component in the hash for quick lookup
  61          * during a git status. Directory components are stored without their
  62          * closing slash.  Despite submodules being a directory, they never
  63          * reach this point, because they are stored
  64          * in index_state.name_hash (as ordinary cache_entries).
  65          *
  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.
  73          */
  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         namelen--;
  82
  83         /* lookup existing entry for that directory */
  84         dir = find_dir_entry(istate, ce->name, namelen);
  85         if (!dir) {
  86                 /* not found, create it and add to hash table */
  87                 void **pdir;
  88                 unsigned int hash = hash_name(ce->name, namelen);
  89
  90                 dir = xcalloc(1, sizeof(struct dir_entry));
  91                 dir->namelen = namelen;
  92                 dir->ce = ce;
  93
  94                 pdir = insert_hash(hash, dir, &istate->dir_hash);
  95                 if (pdir) {
  96                         dir->next = *pdir;
  97                         *pdir = dir;
  98                 }
  99
 100                 /* recursively add missing parent directories */
 101                 dir->parent = hash_dir_entry(istate, ce, namelen);
 102         }
 103         return dir;
 104 }
 105
 106 static void add_dir_entry(struct index_state *istate, struct cache_entry *ce)
 107 {
 108         /* Add reference to the directory entry (and parents if 0). */
 109         struct dir_entry *dir = hash_dir_entry(istate, ce, ce_namelen(ce));
 110         while (dir && !(dir->nr++))
 111                 dir = dir->parent;
 112 }
 113
 114 static void remove_dir_entry(struct index_state *istate, struct cache_entry *ce)
 115 {
 116         /*
 117          * Release reference to the directory entry (and parents if 0).
 118          *
 119          * Note: we do not remove / free the entry because there's no
 120          * hash.[ch]::remove_hash and dir->next may point to other entries
 121          * that are still valid, so we must not free the memory.
 122          */
 123         struct dir_entry *dir = hash_dir_entry(istate, ce, ce_namelen(ce));
 124         while (dir && dir->nr && !(--dir->nr))
 125                 dir = dir->parent;
 126 }
 127
 128 static void hash_index_entry(struct index_state *istate, struct cache_entry *ce)
 129 {
 130         void **pos;
 131         unsigned int hash;
 132
 133         if (ce->ce_flags & CE_HASHED)
 134                 return;
 135         ce->ce_flags |= CE_HASHED;
 136         ce->next = NULL;
 137         hash = hash_name(ce->name, ce_namelen(ce));
 138         pos = insert_hash(hash, ce, &istate->name_hash);
 139         if (pos) {
 140                 ce->next = *pos;
 141                 *pos = ce;
 142         }
 143
 144         if (ignore_case && !(ce->ce_flags & CE_UNHASHED))
 145                 add_dir_entry(istate, ce);
 146 }
 147
 148 static void lazy_init_name_hash(struct index_state *istate)
 149 {
 150         int nr;
 151
 152         if (istate->name_hash_initialized)
 153                 return;
 154         if (istate->cache_nr)
 155                 preallocate_hash(&istate->name_hash, istate->cache_nr);
 156         for (nr = 0; nr < istate->cache_nr; nr++)
 157                 hash_index_entry(istate, istate->cache[nr]);
 158         istate->name_hash_initialized = 1;
 159 }
 160
 161 void add_name_hash(struct index_state *istate, struct cache_entry *ce)
 162 {
 163         /* if already hashed, add reference to directory entries */
 164         if (ignore_case && (ce->ce_flags & CE_STATE_MASK) == CE_STATE_MASK)
 165                 add_dir_entry(istate, ce);
 166
 167         ce->ce_flags &= ~CE_UNHASHED;
 168         if (istate->name_hash_initialized)
 169                 hash_index_entry(istate, ce);
 170 }
 171
 172 /*
 173  * We don't actually *remove* it, we can just mark it invalid so that
 174  * we won't find it in lookups.
 175  *
 176  * Not only would we have to search the lists (simple enough), but
 177  * we'd also have to rehash other hash buckets in case this makes the
 178  * hash bucket empty (common). So it's much better to just mark
 179  * it.
 180  */
 181 void remove_name_hash(struct index_state *istate, struct cache_entry *ce)
 182 {
 183         /* if already hashed, release reference to directory entries */
 184         if (ignore_case && (ce->ce_flags & CE_STATE_MASK) == CE_HASHED)
 185                 remove_dir_entry(istate, ce);
 186
 187         ce->ce_flags |= CE_UNHASHED;
 188 }
 189
 190 static int slow_same_name(const char *name1, int len1, const char *name2, int len2)
 191 {
 192         if (len1 != len2)
 193                 return 0;
 194
 195         while (len1) {
 196                 unsigned char c1 = *name1++;
 197                 unsigned char c2 = *name2++;
 198                 len1--;
 199                 if (c1 != c2) {
 200                         c1 = toupper(c1);
 201                         c2 = toupper(c2);
 202                         if (c1 != c2)
 203                                 return 0;
 204                 }
 205         }
 206         return 1;
 207 }
 208
 209 static int same_name(const struct cache_entry *ce, const char *name, int namelen, int icase)
 210 {
 211         int len = ce_namelen(ce);
 212
 213         /*
 214          * Always do exact compare, even if we want a case-ignoring comparison;
 215          * we do the quick exact one first, because it will be the common case.
 216          */
 217         if (len == namelen && !cache_name_compare(name, namelen, ce->name, len))
 218                 return 1;
 219
 220         if (!icase)
 221                 return 0;
 222
 223         return slow_same_name(name, namelen, ce->name, len);
 224 }
 225
 226 struct cache_entry *index_dir_exists(struct index_state *istate, const char *name, int namelen)
 227 {
 228         struct cache_entry *ce;
 229         struct dir_entry *dir;
 230
 231         lazy_init_name_hash(istate);
 232         dir = find_dir_entry(istate, name, namelen);
 233         if (dir && dir->nr)
 234                 return dir->ce;
 235
 236         /*
 237          * It might be a submodule. Unlike plain directories, which are stored
 238          * in the dir-hash, submodules are stored in the name-hash, so check
 239          * there, as well.
 240          */
 241         ce = index_file_exists(istate, name, namelen, 1);
 242         if (ce && S_ISGITLINK(ce->ce_mode))
 243                 return ce;
 244
 245         return NULL;
 246 }
 247
 248 struct cache_entry *index_file_exists(struct index_state *istate, const char *name, int namelen, int icase)
 249 {
 250         unsigned int hash = hash_name(name, namelen);
 251         struct cache_entry *ce;
 252
 253         lazy_init_name_hash(istate);
 254         ce = lookup_hash(hash, &istate->name_hash);
 255
 256         while (ce) {
 257                 if (!(ce->ce_flags & CE_UNHASHED)) {
 258                         if (same_name(ce, name, namelen, icase))
 259                                 return ce;
 260                 }
 261                 ce = ce->next;
 262         }
 263         return NULL;
 264 }
 265
 266 struct cache_entry *index_name_exists(struct index_state *istate, const char *name, int namelen, int icase)
 267 {
 268         if (namelen > 0 && name[namelen - 1] == '/')
 269                 return index_dir_exists(istate, name, namelen - 1);
 270         return index_file_exists(istate, name, namelen, icase);
 271 }
 272
 273 static int free_dir_entry(void *entry, void *unused)
 274 {
 275         struct dir_entry *dir = entry;
 276         while (dir) {
 277                 struct dir_entry *next = dir->next;
 278                 free(dir);
 279                 dir = next;
 280         }
 281         return 0;
 282 }
 283
 284 void free_name_hash(struct index_state *istate)
 285 {
 286         if (!istate->name_hash_initialized)
 287                 return;
 288         istate->name_hash_initialized = 0;
 289         if (ignore_case)
 290                 /* free directory entries */
 291                 for_each_hash(&istate->dir_hash, free_dir_entry, NULL);
 292
 293         free_hash(&istate->name_hash);
 294         free_hash(&istate->dir_hash);
 295 }