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         if (ce->ce_flags & CE_HASHED)
 104                 return;
 105         ce->ce_flags |= CE_HASHED;
 106         hashmap_entry_init(ce, memihash(ce->name, ce_namelen(ce)));
 107         hashmap_add(&istate->name_hash, ce);
 108
 109         if (ignore_case)
 110                 add_dir_entry(istate, ce);
 111 }
 112
 113 static int cache_entry_cmp(const struct cache_entry *ce1,
 114                 const struct cache_entry *ce2, const void *remove)
 115 {
 116         /*
 117          * For remove_name_hash, find the exact entry (pointer equality); for
 118          * index_file_exists, find all entries with matching hash code and
 119          * decide whether the entry matches in same_name.
 120          */
 121         return remove ? !(ce1 == ce2) : 0;
 122 }
 123
 124 static void lazy_init_name_hash(struct index_state *istate)
 125 {
 126         int nr;
 127
 128         if (istate->name_hash_initialized)
 129                 return;
 130         hashmap_init(&istate->name_hash, (hashmap_cmp_fn) cache_entry_cmp,
 131                         istate->cache_nr);
 132         hashmap_init(&istate->dir_hash, (hashmap_cmp_fn) dir_entry_cmp, 0);
 133         for (nr = 0; nr < istate->cache_nr; nr++)
 134                 hash_index_entry(istate, istate->cache[nr]);
 135         istate->name_hash_initialized = 1;
 136 }
 137
 138 void add_name_hash(struct index_state *istate, struct cache_entry *ce)
 139 {
 140         if (istate->name_hash_initialized)
 141                 hash_index_entry(istate, ce);
 142 }
 143
 144 void remove_name_hash(struct index_state *istate, struct cache_entry *ce)
 145 {
 146         if (!istate->name_hash_initialized || !(ce->ce_flags & CE_HASHED))
 147                 return;
 148         ce->ce_flags &= ~CE_HASHED;
 149         hashmap_remove(&istate->name_hash, ce, ce);
 150
 151         if (ignore_case)
 152                 remove_dir_entry(istate, ce);
 153 }
 154
 155 static int slow_same_name(const char *name1, int len1, const char *name2, int len2)
 156 {
 157         if (len1 != len2)
 158                 return 0;
 159
 160         while (len1) {
 161                 unsigned char c1 = *name1++;
 162                 unsigned char c2 = *name2++;
 163                 len1--;
 164                 if (c1 != c2) {
 165                         c1 = toupper(c1);
 166                         c2 = toupper(c2);
 167                         if (c1 != c2)
 168                                 return 0;
 169                 }
 170         }
 171         return 1;
 172 }
 173
 174 static int same_name(const struct cache_entry *ce, const char *name, int namelen, int icase)
 175 {
 176         int len = ce_namelen(ce);
 177
 178         /*
 179          * Always do exact compare, even if we want a case-ignoring comparison;
 180          * we do the quick exact one first, because it will be the common case.
 181          */
 182         if (len == namelen && !memcmp(name, ce->name, len))
 183                 return 1;
 184
 185         if (!icase)
 186                 return 0;
 187
 188         return slow_same_name(name, namelen, ce->name, len);
 189 }
 190
 191 struct cache_entry *index_dir_exists(struct index_state *istate, const char *name, int namelen)
 192 {
 193         struct cache_entry *ce;
 194         struct dir_entry *dir;
 195
 196         lazy_init_name_hash(istate);
 197         dir = find_dir_entry(istate, name, namelen);
 198         if (dir && dir->nr)
 199                 return dir->ce;
 200
 201         /*
 202          * It might be a submodule. Unlike plain directories, which are stored
 203          * in the dir-hash, submodules are stored in the name-hash, so check
 204          * there, as well.
 205          */
 206         ce = index_file_exists(istate, name, namelen, 1);
 207         if (ce && S_ISGITLINK(ce->ce_mode))
 208                 return ce;
 209
 210         return NULL;
 211 }
 212
 213 struct cache_entry *index_file_exists(struct index_state *istate, const char *name, int namelen, int icase)
 214 {
 215         struct cache_entry *ce;
 216         struct hashmap_entry key;
 217
 218         lazy_init_name_hash(istate);
 219
 220         hashmap_entry_init(&key, memihash(name, namelen));
 221         ce = hashmap_get(&istate->name_hash, &key, NULL);
 222         while (ce) {
 223                 if (same_name(ce, name, namelen, icase))
 224                         return ce;
 225                 ce = hashmap_get_next(&istate->name_hash, ce);
 226         }
 227         return NULL;
 228 }
 229
 230 void free_name_hash(struct index_state *istate)
 231 {
 232         if (!istate->name_hash_initialized)
 233                 return;
 234         istate->name_hash_initialized = 0;
 235
 236         hashmap_free(&istate->name_hash, 0);
 237         hashmap_free(&istate->dir_hash, 1);
 238 }