Andrew's git - gitweb.git/blob

   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 */
  18static inline unsigned char icase_hash(unsigned char c)
  19{
  20        return c & ~((c & 0x40) >> 1);
  21}
  22
  23static 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
  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)
  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
  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
  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);
  88
  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;
  97                }
  98
  99                /* recursively add missing parent directories */
 100                dir->parent = hash_dir_entry(istate, ce, namelen - 1);
 101        }
 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;
 125}
 126
 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;
 135        ce->next = NULL;
 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        }
 142
 143        if (ignore_case && !(ce->ce_flags & CE_UNHASHED))
 144                add_dir_entry(istate, ce);
 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;
 153        if (istate->cache_nr)
 154                preallocate_hash(&istate->name_hash, istate->cache_nr);
 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{
 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
 166        ce->ce_flags &= ~CE_UNHASHED;
 167        if (istate->name_hash_initialized)
 168                hash_index_entry(istate, ce);
 169}
 170
 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
 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
 219        if (!icase)
 220                return 0;
 221
 222        return slow_same_name(name, namelen, ce->name, len);
 223}
 224
 225struct cache_entry *index_name_exists(struct index_state *istate, const char *name, int namelen, int icase)
 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)) {
 235                        if (same_name(ce, name, namelen, icase))
 236                                return ce;
 237                }
 238                ce = ce->next;
 239        }
 240
 241        /*
 242         * When looking for a directory (trailing '/'), it might be a
 243         * submodule or a directory. Despite submodules being directories,
 244         * they are stored in the name hash without a closing slash.
 245         * When ignore_case is 1, directories are stored in a separate hash
 246         * table *with* their closing slash.
 247         *
 248         * The side effect of this storage technique is we have need to
 249         * lookup the directory in a separate hash table, and if not found
 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] == '/') {
 255                struct dir_entry *dir = find_dir_entry(istate, name, namelen);
 256                if (dir && dir->nr)
 257                        return dir->ce;
 258
 259                ce = index_name_exists(istate, name, namelen - 1, icase);
 260                if (ce && S_ISGITLINK(ce->ce_mode))
 261                        return ce;
 262        }
 263        return NULL;
 264}
 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}