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 #include "cache.h"
   9 #include "thread-utils.h"
  10
  11 struct dir_entry {
  12         struct hashmap_entry ent;
  13         struct dir_entry *parent;
  14         int nr;
  15         unsigned int namelen;
  16         char name[FLEX_ARRAY];
  17 };
  18
  19 static int dir_entry_cmp(const void *unused_cmp_data,
  20                          const void *entry,
  21                          const void *entry_or_key,
  22                          const void *keydata)
  23 {
  24         const struct dir_entry *e1 = entry;
  25         const struct dir_entry *e2 = entry_or_key;
  26         const char *name = keydata;
  27
  28         return e1->namelen != e2->namelen || strncasecmp(e1->name,
  29                         name ? name : e2->name, e1->namelen);
  30 }
  31
  32 static struct dir_entry *find_dir_entry__hash(struct index_state *istate,
  33                 const char *name, unsigned int namelen, unsigned int hash)
  34 {
  35         struct dir_entry key;
  36         hashmap_entry_init(&key.ent, hash);
  37         key.namelen = namelen;
  38         return hashmap_get_entry(&istate->dir_hash, &key, name,
  39                                         struct dir_entry, ent);
  40 }
  41
  42 static struct dir_entry *find_dir_entry(struct index_state *istate,
  43                 const char *name, unsigned int namelen)
  44 {
  45         return find_dir_entry__hash(istate, name, namelen, memihash(name, namelen));
  46 }
  47
  48 static struct dir_entry *hash_dir_entry(struct index_state *istate,
  49                 struct cache_entry *ce, int namelen)
  50 {
  51         /*
  52          * Throw each directory component in the hash for quick lookup
  53          * during a git status. Directory components are stored without their
  54          * closing slash.  Despite submodules being a directory, they never
  55          * reach this point, because they are stored
  56          * in index_state.name_hash (as ordinary cache_entries).
  57          */
  58         struct dir_entry *dir;
  59
  60         /* get length of parent directory */
  61         while (namelen > 0 && !is_dir_sep(ce->name[namelen - 1]))
  62                 namelen--;
  63         if (namelen <= 0)
  64                 return NULL;
  65         namelen--;
  66
  67         /* lookup existing entry for that directory */
  68         dir = find_dir_entry(istate, ce->name, namelen);
  69         if (!dir) {
  70                 /* not found, create it and add to hash table */
  71                 FLEX_ALLOC_MEM(dir, name, ce->name, namelen);
  72                 hashmap_entry_init(&dir->ent, memihash(ce->name, namelen));
  73                 dir->namelen = namelen;
  74                 hashmap_add(&istate->dir_hash, &dir->ent);
  75
  76                 /* recursively add missing parent directories */
  77                 dir->parent = hash_dir_entry(istate, ce, namelen);
  78         }
  79         return dir;
  80 }
  81
  82 static void add_dir_entry(struct index_state *istate, struct cache_entry *ce)
  83 {
  84         /* Add reference to the directory entry (and parents if 0). */
  85         struct dir_entry *dir = hash_dir_entry(istate, ce, ce_namelen(ce));
  86         while (dir && !(dir->nr++))
  87                 dir = dir->parent;
  88 }
  89
  90 static void remove_dir_entry(struct index_state *istate, struct cache_entry *ce)
  91 {
  92         /*
  93          * Release reference to the directory entry. If 0, remove and continue
  94          * with parent directory.
  95          */
  96         struct dir_entry *dir = hash_dir_entry(istate, ce, ce_namelen(ce));
  97         while (dir && !(--dir->nr)) {
  98                 struct dir_entry *parent = dir->parent;
  99                 hashmap_remove(&istate->dir_hash, &dir->ent, NULL);
 100                 free(dir);
 101                 dir = parent;
 102         }
 103 }
 104
 105 static void hash_index_entry(struct index_state *istate, struct cache_entry *ce)
 106 {
 107         if (ce->ce_flags & CE_HASHED)
 108                 return;
 109         ce->ce_flags |= CE_HASHED;
 110         hashmap_entry_init(&ce->ent, memihash(ce->name, ce_namelen(ce)));
 111         hashmap_add(&istate->name_hash, &ce->ent);
 112
 113         if (ignore_case)
 114                 add_dir_entry(istate, ce);
 115 }
 116
 117 static int cache_entry_cmp(const void *unused_cmp_data,
 118                            const void *entry,
 119                            const void *entry_or_key,
 120                            const void *remove)
 121 {
 122         const struct cache_entry *ce1 = entry;
 123         const struct cache_entry *ce2 = entry_or_key;
 124         /*
 125          * For remove_name_hash, find the exact entry (pointer equality); for
 126          * index_file_exists, find all entries with matching hash code and
 127          * decide whether the entry matches in same_name.
 128          */
 129         return remove ? !(ce1 == ce2) : 0;
 130 }
 131
 132 static int lazy_try_threaded = 1;
 133 static int lazy_nr_dir_threads;
 134
 135 /*
 136  * Set a minimum number of cache_entries that we will handle per
 137  * thread and use that to decide how many threads to run (upto
 138  * the number on the system).
 139  *
 140  * For guidance setting the lower per-thread bound, see:
 141  *     t/helper/test-lazy-init-name-hash --analyze
 142  */
 143 #define LAZY_THREAD_COST (2000)
 144
 145 /*
 146  * We use n mutexes to guard n partitions of the "istate->dir_hash"
 147  * hashtable.  Since "find" and "insert" operations will hash to a
 148  * particular bucket and modify/search a single chain, we can say
 149  * that "all chains mod n" are guarded by the same mutex -- rather
 150  * than having a single mutex to guard the entire table.  (This does
 151  * require that we disable "rehashing" on the hashtable.)
 152  *
 153  * So, a larger value here decreases the probability of a collision
 154  * and the time that each thread must wait for the mutex.
 155  */
 156 #define LAZY_MAX_MUTEX   (32)
 157
 158 static pthread_mutex_t *lazy_dir_mutex_array;
 159
 160 /*
 161  * An array of lazy_entry items is used by the n threads in
 162  * the directory parse (first) phase to (lock-free) store the
 163  * intermediate results.  These values are then referenced by
 164  * the 2 threads in the second phase.
 165  */
 166 struct lazy_entry {
 167         struct dir_entry *dir;
 168         unsigned int hash_dir;
 169         unsigned int hash_name;
 170 };
 171
 172 /*
 173  * Decide if we want to use threads (if available) to load
 174  * the hash tables.  We set "lazy_nr_dir_threads" to zero when
 175  * it is not worth it.
 176  */
 177 static int lookup_lazy_params(struct index_state *istate)
 178 {
 179         int nr_cpus;
 180
 181         lazy_nr_dir_threads = 0;
 182
 183         if (!lazy_try_threaded)
 184                 return 0;
 185
 186         /*
 187          * If we are respecting case, just use the original
 188          * code to build the "istate->name_hash".  We don't
 189          * need the complexity here.
 190          */
 191         if (!ignore_case)
 192                 return 0;
 193
 194         nr_cpus = online_cpus();
 195         if (nr_cpus < 2)
 196                 return 0;
 197
 198         if (istate->cache_nr < 2 * LAZY_THREAD_COST)
 199                 return 0;
 200
 201         if (istate->cache_nr < nr_cpus * LAZY_THREAD_COST)
 202                 nr_cpus = istate->cache_nr / LAZY_THREAD_COST;
 203         lazy_nr_dir_threads = nr_cpus;
 204         return lazy_nr_dir_threads;
 205 }
 206
 207 /*
 208  * Initialize n mutexes for use when searching and inserting
 209  * into "istate->dir_hash".  All "dir" threads are trying
 210  * to insert partial pathnames into the hash as they iterate
 211  * over their portions of the index, so lock contention is
 212  * high.
 213  *
 214  * However, the hashmap is going to put items into bucket
 215  * chains based on their hash values.  Use that to create n
 216  * mutexes and lock on mutex[bucket(hash) % n].  This will
 217  * decrease the collision rate by (hopefully) by a factor of n.
 218  */
 219 static void init_dir_mutex(void)
 220 {
 221         int j;
 222
 223         lazy_dir_mutex_array = xcalloc(LAZY_MAX_MUTEX, sizeof(pthread_mutex_t));
 224
 225         for (j = 0; j < LAZY_MAX_MUTEX; j++)
 226                 init_recursive_mutex(&lazy_dir_mutex_array[j]);
 227 }
 228
 229 static void cleanup_dir_mutex(void)
 230 {
 231         int j;
 232
 233         for (j = 0; j < LAZY_MAX_MUTEX; j++)
 234                 pthread_mutex_destroy(&lazy_dir_mutex_array[j]);
 235
 236         free(lazy_dir_mutex_array);
 237 }
 238
 239 static void lock_dir_mutex(int j)
 240 {
 241         pthread_mutex_lock(&lazy_dir_mutex_array[j]);
 242 }
 243
 244 static void unlock_dir_mutex(int j)
 245 {
 246         pthread_mutex_unlock(&lazy_dir_mutex_array[j]);
 247 }
 248
 249 static inline int compute_dir_lock_nr(
 250         const struct hashmap *map,
 251         unsigned int hash)
 252 {
 253         return hashmap_bucket(map, hash) % LAZY_MAX_MUTEX;
 254 }
 255
 256 static struct dir_entry *hash_dir_entry_with_parent_and_prefix(
 257         struct index_state *istate,
 258         struct dir_entry *parent,
 259         struct strbuf *prefix)
 260 {
 261         struct dir_entry *dir;
 262         unsigned int hash;
 263         int lock_nr;
 264
 265         /*
 266          * Either we have a parent directory and path with slash(es)
 267          * or the directory is an immediate child of the root directory.
 268          */
 269         assert((parent != NULL) ^ (strchr(prefix->buf, '/') == NULL));
 270
 271         if (parent)
 272                 hash = memihash_cont(parent->ent.hash,
 273                         prefix->buf + parent->namelen,
 274                         prefix->len - parent->namelen);
 275         else
 276                 hash = memihash(prefix->buf, prefix->len);
 277
 278         lock_nr = compute_dir_lock_nr(&istate->dir_hash, hash);
 279         lock_dir_mutex(lock_nr);
 280
 281         dir = find_dir_entry__hash(istate, prefix->buf, prefix->len, hash);
 282         if (!dir) {
 283                 FLEX_ALLOC_MEM(dir, name, prefix->buf, prefix->len);
 284                 hashmap_entry_init(&dir->ent, hash);
 285                 dir->namelen = prefix->len;
 286                 dir->parent = parent;
 287                 hashmap_add(&istate->dir_hash, &dir->ent);
 288
 289                 if (parent) {
 290                         unlock_dir_mutex(lock_nr);
 291
 292                         /* All I really need here is an InterlockedIncrement(&(parent->nr)) */
 293                         lock_nr = compute_dir_lock_nr(&istate->dir_hash, parent->ent.hash);
 294                         lock_dir_mutex(lock_nr);
 295                         parent->nr++;
 296                 }
 297         }
 298
 299         unlock_dir_mutex(lock_nr);
 300
 301         return dir;
 302 }
 303
 304 /*
 305  * handle_range_1() and handle_range_dir() are derived from
 306  * clear_ce_flags_1() and clear_ce_flags_dir() in unpack-trees.c
 307  * and handle the iteration over the entire array of index entries.
 308  * They use recursion for adjacent entries in the same parent
 309  * directory.
 310  */
 311 static int handle_range_1(
 312         struct index_state *istate,
 313         int k_start,
 314         int k_end,
 315         struct dir_entry *parent,
 316         struct strbuf *prefix,
 317         struct lazy_entry *lazy_entries);
 318
 319 static int handle_range_dir(
 320         struct index_state *istate,
 321         int k_start,
 322         int k_end,
 323         struct dir_entry *parent,
 324         struct strbuf *prefix,
 325         struct lazy_entry *lazy_entries,
 326         struct dir_entry **dir_new_out)
 327 {
 328         int rc, k;
 329         int input_prefix_len = prefix->len;
 330         struct dir_entry *dir_new;
 331
 332         dir_new = hash_dir_entry_with_parent_and_prefix(istate, parent, prefix);
 333
 334         strbuf_addch(prefix, '/');
 335
 336         /*
 337          * Scan forward in the index array for index entries having the same
 338          * path prefix (that are also in this directory).
 339          */
 340         if (k_start + 1 >= k_end)
 341                 k = k_end;
 342         else if (strncmp(istate->cache[k_start + 1]->name, prefix->buf, prefix->len) > 0)
 343                 k = k_start + 1;
 344         else if (strncmp(istate->cache[k_end - 1]->name, prefix->buf, prefix->len) == 0)
 345                 k = k_end;
 346         else {
 347                 int begin = k_start;
 348                 int end = k_end;
 349                 assert(begin >= 0);
 350                 while (begin < end) {
 351                         int mid = begin + ((end - begin) >> 1);
 352                         int cmp = strncmp(istate->cache[mid]->name, prefix->buf, prefix->len);
 353                         if (cmp == 0) /* mid has same prefix; look in second part */
 354                                 begin = mid + 1;
 355                         else if (cmp > 0) /* mid is past group; look in first part */
 356                                 end = mid;
 357                         else
 358                                 die("cache entry out of order");
 359                 }
 360                 k = begin;
 361         }
 362
 363         /*
 364          * Recurse and process what we can of this subset [k_start, k).
 365          */
 366         rc = handle_range_1(istate, k_start, k, dir_new, prefix, lazy_entries);
 367
 368         strbuf_setlen(prefix, input_prefix_len);
 369
 370         *dir_new_out = dir_new;
 371         return rc;
 372 }
 373
 374 static int handle_range_1(
 375         struct index_state *istate,
 376         int k_start,
 377         int k_end,
 378         struct dir_entry *parent,
 379         struct strbuf *prefix,
 380         struct lazy_entry *lazy_entries)
 381 {
 382         int input_prefix_len = prefix->len;
 383         int k = k_start;
 384
 385         while (k < k_end) {
 386                 struct cache_entry *ce_k = istate->cache[k];
 387                 const char *name, *slash;
 388
 389                 if (prefix->len && strncmp(ce_k->name, prefix->buf, prefix->len))
 390                         break;
 391
 392                 name = ce_k->name + prefix->len;
 393                 slash = strchr(name, '/');
 394
 395                 if (slash) {
 396                         int len = slash - name;
 397                         int processed;
 398                         struct dir_entry *dir_new;
 399
 400                         strbuf_add(prefix, name, len);
 401                         processed = handle_range_dir(istate, k, k_end, parent, prefix, lazy_entries, &dir_new);
 402                         if (processed) {
 403                                 k += processed;
 404                                 strbuf_setlen(prefix, input_prefix_len);
 405                                 continue;
 406                         }
 407
 408                         strbuf_addch(prefix, '/');
 409                         processed = handle_range_1(istate, k, k_end, dir_new, prefix, lazy_entries);
 410                         k += processed;
 411                         strbuf_setlen(prefix, input_prefix_len);
 412                         continue;
 413                 }
 414
 415                 /*
 416                  * It is too expensive to take a lock to insert "ce_k"
 417                  * into "istate->name_hash" and increment the ref-count
 418                  * on the "parent" dir.  So we defer actually updating
 419                  * permanent data structures until phase 2 (where we
 420                  * can change the locking requirements) and simply
 421                  * accumulate our current results into the lazy_entries
 422                  * data array).
 423                  *
 424                  * We do not need to lock the lazy_entries array because
 425                  * we have exclusive access to the cells in the range
 426                  * [k_start,k_end) that this thread was given.
 427                  */
 428                 lazy_entries[k].dir = parent;
 429                 if (parent) {
 430                         lazy_entries[k].hash_name = memihash_cont(
 431                                 parent->ent.hash,
 432                                 ce_k->name + parent->namelen,
 433                                 ce_namelen(ce_k) - parent->namelen);
 434                         lazy_entries[k].hash_dir = parent->ent.hash;
 435                 } else {
 436                         lazy_entries[k].hash_name = memihash(ce_k->name, ce_namelen(ce_k));
 437                 }
 438
 439                 k++;
 440         }
 441
 442         return k - k_start;
 443 }
 444
 445 struct lazy_dir_thread_data {
 446         pthread_t pthread;
 447         struct index_state *istate;
 448         struct lazy_entry *lazy_entries;
 449         int k_start;
 450         int k_end;
 451 };
 452
 453 static void *lazy_dir_thread_proc(void *_data)
 454 {
 455         struct lazy_dir_thread_data *d = _data;
 456         struct strbuf prefix = STRBUF_INIT;
 457         handle_range_1(d->istate, d->k_start, d->k_end, NULL, &prefix, d->lazy_entries);
 458         strbuf_release(&prefix);
 459         return NULL;
 460 }
 461
 462 struct lazy_name_thread_data {
 463         pthread_t pthread;
 464         struct index_state *istate;
 465         struct lazy_entry *lazy_entries;
 466 };
 467
 468 static void *lazy_name_thread_proc(void *_data)
 469 {
 470         struct lazy_name_thread_data *d = _data;
 471         int k;
 472
 473         for (k = 0; k < d->istate->cache_nr; k++) {
 474                 struct cache_entry *ce_k = d->istate->cache[k];
 475                 ce_k->ce_flags |= CE_HASHED;
 476                 hashmap_entry_init(&ce_k->ent, d->lazy_entries[k].hash_name);
 477                 hashmap_add(&d->istate->name_hash, &ce_k->ent);
 478         }
 479
 480         return NULL;
 481 }
 482
 483 static inline void lazy_update_dir_ref_counts(
 484         struct index_state *istate,
 485         struct lazy_entry *lazy_entries)
 486 {
 487         int k;
 488
 489         for (k = 0; k < istate->cache_nr; k++) {
 490                 if (lazy_entries[k].dir)
 491                         lazy_entries[k].dir->nr++;
 492         }
 493 }
 494
 495 static void threaded_lazy_init_name_hash(
 496         struct index_state *istate)
 497 {
 498         int err;
 499         int nr_each;
 500         int k_start;
 501         int t;
 502         struct lazy_entry *lazy_entries;
 503         struct lazy_dir_thread_data *td_dir;
 504         struct lazy_name_thread_data *td_name;
 505
 506         if (!HAVE_THREADS)
 507                 return;
 508
 509         k_start = 0;
 510         nr_each = DIV_ROUND_UP(istate->cache_nr, lazy_nr_dir_threads);
 511
 512         lazy_entries = xcalloc(istate->cache_nr, sizeof(struct lazy_entry));
 513         td_dir = xcalloc(lazy_nr_dir_threads, sizeof(struct lazy_dir_thread_data));
 514         td_name = xcalloc(1, sizeof(struct lazy_name_thread_data));
 515
 516         init_dir_mutex();
 517
 518         /*
 519          * Phase 1:
 520          * Build "istate->dir_hash" using n "dir" threads (and a read-only index).
 521          */
 522         for (t = 0; t < lazy_nr_dir_threads; t++) {
 523                 struct lazy_dir_thread_data *td_dir_t = td_dir + t;
 524                 td_dir_t->istate = istate;
 525                 td_dir_t->lazy_entries = lazy_entries;
 526                 td_dir_t->k_start = k_start;
 527                 k_start += nr_each;
 528                 if (k_start > istate->cache_nr)
 529                         k_start = istate->cache_nr;
 530                 td_dir_t->k_end = k_start;
 531                 err = pthread_create(&td_dir_t->pthread, NULL, lazy_dir_thread_proc, td_dir_t);
 532                 if (err)
 533                         die(_("unable to create lazy_dir thread: %s"), strerror(err));
 534         }
 535         for (t = 0; t < lazy_nr_dir_threads; t++) {
 536                 struct lazy_dir_thread_data *td_dir_t = td_dir + t;
 537                 if (pthread_join(td_dir_t->pthread, NULL))
 538                         die("unable to join lazy_dir_thread");
 539         }
 540
 541         /*
 542          * Phase 2:
 543          * Iterate over all index entries and add them to the "istate->name_hash"
 544          * using a single "name" background thread.
 545          * (Testing showed it wasn't worth running more than 1 thread for this.)
 546          *
 547          * Meanwhile, finish updating the parent directory ref-counts for each
 548          * index entry using the current thread.  (This step is very fast and
 549          * doesn't need threading.)
 550          */
 551         td_name->istate = istate;
 552         td_name->lazy_entries = lazy_entries;
 553         err = pthread_create(&td_name->pthread, NULL, lazy_name_thread_proc, td_name);
 554         if (err)
 555                 die(_("unable to create lazy_name thread: %s"), strerror(err));
 556
 557         lazy_update_dir_ref_counts(istate, lazy_entries);
 558
 559         err = pthread_join(td_name->pthread, NULL);
 560         if (err)
 561                 die(_("unable to join lazy_name thread: %s"), strerror(err));
 562
 563         cleanup_dir_mutex();
 564
 565         free(td_name);
 566         free(td_dir);
 567         free(lazy_entries);
 568 }
 569
 570 static void lazy_init_name_hash(struct index_state *istate)
 571 {
 572
 573         if (istate->name_hash_initialized)
 574                 return;
 575         trace_performance_enter();
 576         hashmap_init(&istate->name_hash, cache_entry_cmp, NULL, istate->cache_nr);
 577         hashmap_init(&istate->dir_hash, dir_entry_cmp, NULL, istate->cache_nr);
 578
 579         if (lookup_lazy_params(istate)) {
 580                 /*
 581                  * Disable item counting and automatic rehashing because
 582                  * we do per-chain (mod n) locking rather than whole hashmap
 583                  * locking and we need to prevent the table-size from changing
 584                  * and bucket items from being redistributed.
 585                  */
 586                 hashmap_disable_item_counting(&istate->dir_hash);
 587                 threaded_lazy_init_name_hash(istate);
 588                 hashmap_enable_item_counting(&istate->dir_hash);
 589         } else {
 590                 int nr;
 591                 for (nr = 0; nr < istate->cache_nr; nr++)
 592                         hash_index_entry(istate, istate->cache[nr]);
 593         }
 594
 595         istate->name_hash_initialized = 1;
 596         trace_performance_leave("initialize name hash");
 597 }
 598
 599 /*
 600  * A test routine for t/helper/ sources.
 601  *
 602  * Returns the number of threads used or 0 when
 603  * the non-threaded code path was used.
 604  *
 605  * Requesting threading WILL NOT override guards
 606  * in lookup_lazy_params().
 607  */
 608 int test_lazy_init_name_hash(struct index_state *istate, int try_threaded)
 609 {
 610         lazy_nr_dir_threads = 0;
 611         lazy_try_threaded = try_threaded;
 612
 613         lazy_init_name_hash(istate);
 614
 615         return lazy_nr_dir_threads;
 616 }
 617
 618 void add_name_hash(struct index_state *istate, struct cache_entry *ce)
 619 {
 620         if (istate->name_hash_initialized)
 621                 hash_index_entry(istate, ce);
 622 }
 623
 624 void remove_name_hash(struct index_state *istate, struct cache_entry *ce)
 625 {
 626         if (!istate->name_hash_initialized || !(ce->ce_flags & CE_HASHED))
 627                 return;
 628         ce->ce_flags &= ~CE_HASHED;
 629         hashmap_remove(&istate->name_hash, &ce->ent, ce);
 630
 631         if (ignore_case)
 632                 remove_dir_entry(istate, ce);
 633 }
 634
 635 static int slow_same_name(const char *name1, int len1, const char *name2, int len2)
 636 {
 637         if (len1 != len2)
 638                 return 0;
 639
 640         while (len1) {
 641                 unsigned char c1 = *name1++;
 642                 unsigned char c2 = *name2++;
 643                 len1--;
 644                 if (c1 != c2) {
 645                         c1 = toupper(c1);
 646                         c2 = toupper(c2);
 647                         if (c1 != c2)
 648                                 return 0;
 649                 }
 650         }
 651         return 1;
 652 }
 653
 654 static int same_name(const struct cache_entry *ce, const char *name, int namelen, int icase)
 655 {
 656         int len = ce_namelen(ce);
 657
 658         /*
 659          * Always do exact compare, even if we want a case-ignoring comparison;
 660          * we do the quick exact one first, because it will be the common case.
 661          */
 662         if (len == namelen && !memcmp(name, ce->name, len))
 663                 return 1;
 664
 665         if (!icase)
 666                 return 0;
 667
 668         return slow_same_name(name, namelen, ce->name, len);
 669 }
 670
 671 int index_dir_exists(struct index_state *istate, const char *name, int namelen)
 672 {
 673         struct dir_entry *dir;
 674
 675         lazy_init_name_hash(istate);
 676         dir = find_dir_entry(istate, name, namelen);
 677         return dir && dir->nr;
 678 }
 679
 680 void adjust_dirname_case(struct index_state *istate, char *name)
 681 {
 682         const char *startPtr = name;
 683         const char *ptr = startPtr;
 684
 685         lazy_init_name_hash(istate);
 686         while (*ptr) {
 687                 while (*ptr && *ptr != '/')
 688                         ptr++;
 689
 690                 if (*ptr == '/') {
 691                         struct dir_entry *dir;
 692
 693                         dir = find_dir_entry(istate, name, ptr - name);
 694                         if (dir) {
 695                                 memcpy((void *)startPtr, dir->name + (startPtr - name), ptr - startPtr);
 696                                 startPtr = ptr + 1;
 697                         }
 698                         ptr++;
 699                 }
 700         }
 701 }
 702
 703 struct cache_entry *index_file_exists(struct index_state *istate, const char *name, int namelen, int icase)
 704 {
 705         struct cache_entry *ce;
 706         unsigned int hash = memihash(name, namelen);
 707
 708         lazy_init_name_hash(istate);
 709
 710         ce = hashmap_get_entry_from_hash(&istate->name_hash, hash, NULL,
 711                                          struct cache_entry, ent);
 712         hashmap_for_each_entry_from(&istate->name_hash, ce,
 713                                         struct cache_entry, ent) {
 714                 if (same_name(ce, name, namelen, icase))
 715                         return ce;
 716         }
 717         return NULL;
 718 }
 719
 720 void free_name_hash(struct index_state *istate)
 721 {
 722         if (!istate->name_hash_initialized)
 723                 return;
 724         istate->name_hash_initialized = 0;
 725
 726         hashmap_free(&istate->name_hash, 0);
 727         hashmap_free(&istate->dir_hash, 1);
 728 }