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 "git-compat-util.h"
   9 #include "environment.h"
  10 #include "gettext.h"
  11 #include "name-hash.h"
  12 #include "object.h"
  13 #include "read-cache-ll.h"
  14 #include "thread-utils.h"
  15 #include "trace.h"
  16 #include "trace2.h"
  17 #include "sparse-index.h"
  18
  19 struct dir_entry {
  20         struct hashmap_entry ent;
  21         struct dir_entry *parent;
  22         int nr;
  23         unsigned int namelen;
  24         char name[FLEX_ARRAY];
  25 };
  26
  27 static int dir_entry_cmp(const void *cmp_data UNUSED,
  28                          const struct hashmap_entry *eptr,
  29                          const struct hashmap_entry *entry_or_key,
  30                          const void *keydata)
  31 {
  32         const struct dir_entry *e1, *e2;
  33         const char *name = keydata;
  34
  35         e1 = container_of(eptr, const struct dir_entry, ent);
  36         e2 = container_of(entry_or_key, const struct dir_entry, ent);
  37
  38         return e1->namelen != e2->namelen || strncasecmp(e1->name,
  39                         name ? name : e2->name, e1->namelen);
  40 }
  41
  42 static struct dir_entry *find_dir_entry__hash(struct index_state *istate,
  43                 const char *name, unsigned int namelen, unsigned int hash)
  44 {
  45         struct dir_entry key;
  46         hashmap_entry_init(&key.ent, hash);
  47         key.namelen = namelen;
  48         return hashmap_get_entry(&istate->dir_hash, &key, ent, name);
  49 }
  50
  51 static struct dir_entry *find_dir_entry(struct index_state *istate,
  52                 const char *name, unsigned int namelen)
  53 {
  54         return find_dir_entry__hash(istate, name, namelen, memihash(name, namelen));
  55 }
  56
  57 static struct dir_entry *hash_dir_entry(struct index_state *istate,
  58                 struct cache_entry *ce, int namelen)
  59 {
  60         /*
  61          * Throw each directory component in the hash for quick lookup
  62          * during a git status. Directory components are stored without their
  63          * closing slash.  Despite submodules being a directory, they never
  64          * reach this point, because they are stored
  65          * in index_state.name_hash (as ordinary cache_entries).
  66          */
  67         struct dir_entry *dir;
  68
  69         /* get length of parent directory */
  70         while (namelen > 0 && !is_dir_sep(ce->name[namelen - 1]))
  71                 namelen--;
  72         if (namelen <= 0)
  73                 return NULL;
  74         namelen--;
  75
  76         /* lookup existing entry for that directory */
  77         dir = find_dir_entry(istate, ce->name, namelen);
  78         if (!dir) {
  79                 /* not found, create it and add to hash table */
  80                 FLEX_ALLOC_MEM(dir, name, ce->name, namelen);
  81                 hashmap_entry_init(&dir->ent, memihash(ce->name, namelen));
  82                 dir->namelen = namelen;
  83                 hashmap_add(&istate->dir_hash, &dir->ent);
  84
  85                 /* recursively add missing parent directories */
  86                 dir->parent = hash_dir_entry(istate, ce, namelen);
  87         }
  88         return dir;
  89 }
  90
  91 static void add_dir_entry(struct index_state *istate, struct cache_entry *ce)
  92 {
  93         /* Add reference to the directory entry (and parents if 0). */
  94         struct dir_entry *dir = hash_dir_entry(istate, ce, ce_namelen(ce));
  95         while (dir && !(dir->nr++))
  96                 dir = dir->parent;
  97 }
  98
  99 static void remove_dir_entry(struct index_state *istate, struct cache_entry *ce)
 100 {
 101         /*
 102          * Release reference to the directory entry. If 0, remove and continue
 103          * with parent directory.
 104          */
 105         struct dir_entry *dir = hash_dir_entry(istate, ce, ce_namelen(ce));
 106         while (dir && !(--dir->nr)) {
 107                 struct dir_entry *parent = dir->parent;
 108                 hashmap_remove(&istate->dir_hash, &dir->ent, NULL);
 109                 free(dir);
 110                 dir = parent;
 111         }
 112 }
 113
 114 static void hash_index_entry(struct index_state *istate, struct cache_entry *ce)
 115 {
 116         if (ce->ce_flags & CE_HASHED)
 117                 return;
 118         ce->ce_flags |= CE_HASHED;
 119
 120         if (!S_ISSPARSEDIR(ce->ce_mode)) {
 121                 hashmap_entry_init(&ce->ent, memihash(ce->name, ce_namelen(ce)));
 122                 hashmap_add(&istate->name_hash, &ce->ent);
 123         }
 124
 125         if (ignore_case)
 126                 add_dir_entry(istate, ce);
 127 }
 128
 129 static int cache_entry_cmp(const void *cmp_data UNUSED,
 130                            const struct hashmap_entry *eptr,
 131                            const struct hashmap_entry *entry_or_key,
 132                            const void *remove)
 133 {
 134         const struct cache_entry *ce1, *ce2;
 135
 136         ce1 = container_of(eptr, const struct cache_entry, ent);
 137         ce2 = container_of(entry_or_key, const struct cache_entry, ent);
 138
 139         /*
 140          * For remove_name_hash, find the exact entry (pointer equality); for
 141          * index_file_exists, find all entries with matching hash code and
 142          * decide whether the entry matches in same_name.
 143          */
 144         return remove ? !(ce1 == ce2) : 0;
 145 }
 146
 147 static int lazy_try_threaded = 1;
 148 static int lazy_nr_dir_threads;
 149
 150 /*
 151  * Set a minimum number of cache_entries that we will handle per
 152  * thread and use that to decide how many threads to run (up to
 153  * the number on the system).
 154  *
 155  * For guidance setting the lower per-thread bound, see:
 156  *     t/helper/test-lazy-init-name-hash --analyze
 157  */
 158 #define LAZY_THREAD_COST (2000)
 159
 160 /*
 161  * We use n mutexes to guard n partitions of the "istate->dir_hash"
 162  * hashtable.  Since "find" and "insert" operations will hash to a
 163  * particular bucket and modify/search a single chain, we can say
 164  * that "all chains mod n" are guarded by the same mutex -- rather
 165  * than having a single mutex to guard the entire table.  (This does
 166  * require that we disable "rehashing" on the hashtable.)
 167  *
 168  * So, a larger value here decreases the probability of a collision
 169  * and the time that each thread must wait for the mutex.
 170  */
 171 #define LAZY_MAX_MUTEX   (32)
 172
 173 static pthread_mutex_t *lazy_dir_mutex_array;
 174
 175 /*
 176  * An array of lazy_entry items is used by the n threads in
 177  * the directory parse (first) phase to (lock-free) store the
 178  * intermediate results.  These values are then referenced by
 179  * the 2 threads in the second phase.
 180  */
 181 struct lazy_entry {
 182         struct dir_entry *dir;
 183         unsigned int hash_dir;
 184         unsigned int hash_name;
 185 };
 186
 187 /*
 188  * Decide if we want to use threads (if available) to load
 189  * the hash tables.  We set "lazy_nr_dir_threads" to zero when
 190  * it is not worth it.
 191  */
 192 static int lookup_lazy_params(struct index_state *istate)
 193 {
 194         int nr_cpus;
 195
 196         lazy_nr_dir_threads = 0;
 197
 198         if (!lazy_try_threaded)
 199                 return 0;
 200
 201         /*
 202          * If we are respecting case, just use the original
 203          * code to build the "istate->name_hash".  We don't
 204          * need the complexity here.
 205          */
 206         if (!ignore_case)
 207                 return 0;
 208
 209         nr_cpus = online_cpus();
 210         if (nr_cpus < 2)
 211                 return 0;
 212
 213         if (istate->cache_nr < 2 * LAZY_THREAD_COST)
 214                 return 0;
 215
 216         if (istate->cache_nr < nr_cpus * LAZY_THREAD_COST)
 217                 nr_cpus = istate->cache_nr / LAZY_THREAD_COST;
 218         lazy_nr_dir_threads = nr_cpus;
 219         return lazy_nr_dir_threads;
 220 }
 221
 222 /*
 223  * Initialize n mutexes for use when searching and inserting
 224  * into "istate->dir_hash".  All "dir" threads are trying
 225  * to insert partial pathnames into the hash as they iterate
 226  * over their portions of the index, so lock contention is
 227  * high.
 228  *
 229  * However, the hashmap is going to put items into bucket
 230  * chains based on their hash values.  Use that to create n
 231  * mutexes and lock on mutex[bucket(hash) % n].  This will
 232  * decrease the collision rate by (hopefully) a factor of n.
 233  */
 234 static void init_dir_mutex(void)
 235 {
 236         int j;
 237
 238         CALLOC_ARRAY(lazy_dir_mutex_array, LAZY_MAX_MUTEX);
 239
 240         for (j = 0; j < LAZY_MAX_MUTEX; j++)
 241                 init_recursive_mutex(&lazy_dir_mutex_array[j]);
 242 }
 243
 244 static void cleanup_dir_mutex(void)
 245 {
 246         int j;
 247
 248         for (j = 0; j < LAZY_MAX_MUTEX; j++)
 249                 pthread_mutex_destroy(&lazy_dir_mutex_array[j]);
 250
 251         free(lazy_dir_mutex_array);
 252 }
 253
 254 static void lock_dir_mutex(int j)
 255 {
 256         pthread_mutex_lock(&lazy_dir_mutex_array[j]);
 257 }
 258
 259 static void unlock_dir_mutex(int j)
 260 {
 261         pthread_mutex_unlock(&lazy_dir_mutex_array[j]);
 262 }
 263
 264 static inline int compute_dir_lock_nr(
 265         const struct hashmap *map,
 266         unsigned int hash)
 267 {
 268         return hashmap_bucket(map, hash) % LAZY_MAX_MUTEX;
 269 }
 270
 271 static struct dir_entry *hash_dir_entry_with_parent_and_prefix(
 272         struct index_state *istate,
 273         struct dir_entry *parent,
 274         struct strbuf *prefix)
 275 {
 276         struct dir_entry *dir;
 277         unsigned int hash;
 278         int lock_nr;
 279
 280         /*
 281          * Either we have a parent directory and path with slash(es)
 282          * or the directory is an immediate child of the root directory.
 283          */
 284         assert((parent != NULL) ^ (strchr(prefix->buf, '/') == NULL));
 285
 286         if (parent)
 287                 hash = memihash_cont(parent->ent.hash,
 288                         prefix->buf + parent->namelen,
 289                         prefix->len - parent->namelen);
 290         else
 291                 hash = memihash(prefix->buf, prefix->len);
 292
 293         lock_nr = compute_dir_lock_nr(&istate->dir_hash, hash);
 294         lock_dir_mutex(lock_nr);
 295
 296         dir = find_dir_entry__hash(istate, prefix->buf, prefix->len, hash);
 297         if (!dir) {
 298                 FLEX_ALLOC_MEM(dir, name, prefix->buf, prefix->len);
 299                 hashmap_entry_init(&dir->ent, hash);
 300                 dir->namelen = prefix->len;
 301                 dir->parent = parent;
 302                 hashmap_add(&istate->dir_hash, &dir->ent);
 303
 304                 if (parent) {
 305                         unlock_dir_mutex(lock_nr);
 306
 307                         /* All I really need here is an InterlockedIncrement(&(parent->nr)) */
 308                         lock_nr = compute_dir_lock_nr(&istate->dir_hash, parent->ent.hash);
 309                         lock_dir_mutex(lock_nr);
 310                         parent->nr++;
 311                 }
 312         }
 313
 314         unlock_dir_mutex(lock_nr);
 315
 316         return dir;
 317 }
 318
 319 /*
 320  * handle_range_1() and handle_range_dir() are derived from
 321  * clear_ce_flags_1() and clear_ce_flags_dir() in unpack-trees.c
 322  * and handle the iteration over the entire array of index entries.
 323  * They use recursion for adjacent entries in the same parent
 324  * directory.
 325  */
 326 static int handle_range_1(
 327         struct index_state *istate,
 328         int k_start,
 329         int k_end,
 330         struct dir_entry *parent,
 331         struct strbuf *prefix,
 332         struct lazy_entry *lazy_entries);
 333
 334 static int handle_range_dir(
 335         struct index_state *istate,
 336         int k_start,
 337         int k_end,
 338         struct dir_entry *parent,
 339         struct strbuf *prefix,
 340         struct lazy_entry *lazy_entries,
 341         struct dir_entry **dir_new_out)
 342 {
 343         int rc, k;
 344         int input_prefix_len = prefix->len;
 345         struct dir_entry *dir_new;
 346
 347         dir_new = hash_dir_entry_with_parent_and_prefix(istate, parent, prefix);
 348
 349         strbuf_addch(prefix, '/');
 350
 351         /*
 352          * Scan forward in the index array for index entries having the same
 353          * path prefix (that are also in this directory).
 354          */
 355         if (k_start + 1 >= k_end)
 356                 k = k_end;
 357         else if (strncmp(istate->cache[k_start + 1]->name, prefix->buf, prefix->len) > 0)
 358                 k = k_start + 1;
 359         else if (strncmp(istate->cache[k_end - 1]->name, prefix->buf, prefix->len) == 0)
 360                 k = k_end;
 361         else {
 362                 int begin = k_start;
 363                 int end = k_end;
 364                 assert(begin >= 0);
 365                 while (begin < end) {
 366                         int mid = begin + ((end - begin) >> 1);
 367                         int cmp = strncmp(istate->cache[mid]->name, prefix->buf, prefix->len);
 368                         if (cmp == 0) /* mid has same prefix; look in second part */
 369                                 begin = mid + 1;
 370                         else if (cmp > 0) /* mid is past group; look in first part */
 371                                 end = mid;
 372                         else
 373                                 die("cache entry out of order");
 374                 }
 375                 k = begin;
 376         }
 377
 378         /*
 379          * Recurse and process what we can of this subset [k_start, k).
 380          */
 381         rc = handle_range_1(istate, k_start, k, dir_new, prefix, lazy_entries);
 382
 383         strbuf_setlen(prefix, input_prefix_len);
 384
 385         *dir_new_out = dir_new;
 386         return rc;
 387 }
 388
 389 static int handle_range_1(
 390         struct index_state *istate,
 391         int k_start,
 392         int k_end,
 393         struct dir_entry *parent,
 394         struct strbuf *prefix,
 395         struct lazy_entry *lazy_entries)
 396 {
 397         int input_prefix_len = prefix->len;
 398         int k = k_start;
 399
 400         while (k < k_end) {
 401                 struct cache_entry *ce_k = istate->cache[k];
 402                 const char *name, *slash;
 403
 404                 if (prefix->len && strncmp(ce_k->name, prefix->buf, prefix->len))
 405                         break;
 406
 407                 name = ce_k->name + prefix->len;
 408                 slash = strchr(name, '/');
 409
 410                 if (slash) {
 411                         int len = slash - name;
 412                         int processed;
 413                         struct dir_entry *dir_new;
 414
 415                         strbuf_add(prefix, name, len);
 416                         processed = handle_range_dir(istate, k, k_end, parent, prefix, lazy_entries, &dir_new);
 417                         if (processed) {
 418                                 k += processed;
 419                                 strbuf_setlen(prefix, input_prefix_len);
 420                                 continue;
 421                         }
 422
 423                         strbuf_addch(prefix, '/');
 424                         processed = handle_range_1(istate, k, k_end, dir_new, prefix, lazy_entries);
 425                         k += processed;
 426                         strbuf_setlen(prefix, input_prefix_len);
 427                         continue;
 428                 }
 429
 430                 /*
 431                  * It is too expensive to take a lock to insert "ce_k"
 432                  * into "istate->name_hash" and increment the ref-count
 433                  * on the "parent" dir.  So we defer actually updating
 434                  * permanent data structures until phase 2 (where we
 435                  * can change the locking requirements) and simply
 436                  * accumulate our current results into the lazy_entries
 437                  * data array).
 438                  *
 439                  * We do not need to lock the lazy_entries array because
 440                  * we have exclusive access to the cells in the range
 441                  * [k_start,k_end) that this thread was given.
 442                  */
 443                 lazy_entries[k].dir = parent;
 444                 if (parent) {
 445                         lazy_entries[k].hash_name = memihash_cont(
 446                                 parent->ent.hash,
 447                                 ce_k->name + parent->namelen,
 448                                 ce_namelen(ce_k) - parent->namelen);
 449                         lazy_entries[k].hash_dir = parent->ent.hash;
 450                 } else {
 451                         lazy_entries[k].hash_name = memihash(ce_k->name, ce_namelen(ce_k));
 452                 }
 453
 454                 k++;
 455         }
 456
 457         return k - k_start;
 458 }
 459
 460 struct lazy_dir_thread_data {
 461         pthread_t pthread;
 462         struct index_state *istate;
 463         struct lazy_entry *lazy_entries;
 464         int k_start;
 465         int k_end;
 466 };
 467
 468 static void *lazy_dir_thread_proc(void *_data)
 469 {
 470         struct lazy_dir_thread_data *d = _data;
 471         struct strbuf prefix = STRBUF_INIT;
 472         handle_range_1(d->istate, d->k_start, d->k_end, NULL, &prefix, d->lazy_entries);
 473         strbuf_release(&prefix);
 474         return NULL;
 475 }
 476
 477 struct lazy_name_thread_data {
 478         pthread_t pthread;
 479         struct index_state *istate;
 480         struct lazy_entry *lazy_entries;
 481 };
 482
 483 static void *lazy_name_thread_proc(void *_data)
 484 {
 485         struct lazy_name_thread_data *d = _data;
 486         int k;
 487
 488         for (k = 0; k < d->istate->cache_nr; k++) {
 489                 struct cache_entry *ce_k = d->istate->cache[k];
 490                 ce_k->ce_flags |= CE_HASHED;
 491                 hashmap_entry_init(&ce_k->ent, d->lazy_entries[k].hash_name);
 492                 hashmap_add(&d->istate->name_hash, &ce_k->ent);
 493         }
 494
 495         return NULL;
 496 }
 497
 498 static inline void lazy_update_dir_ref_counts(
 499         struct index_state *istate,
 500         struct lazy_entry *lazy_entries)
 501 {
 502         int k;
 503
 504         for (k = 0; k < istate->cache_nr; k++) {
 505                 if (lazy_entries[k].dir)
 506                         lazy_entries[k].dir->nr++;
 507         }
 508 }
 509
 510 static void threaded_lazy_init_name_hash(
 511         struct index_state *istate)
 512 {
 513         int err;
 514         int nr_each;
 515         int k_start;
 516         int t;
 517         struct lazy_entry *lazy_entries;
 518         struct lazy_dir_thread_data *td_dir;
 519         struct lazy_name_thread_data *td_name;
 520
 521         if (!HAVE_THREADS)
 522                 return;
 523
 524         k_start = 0;
 525         nr_each = DIV_ROUND_UP(istate->cache_nr, lazy_nr_dir_threads);
 526
 527         CALLOC_ARRAY(lazy_entries, istate->cache_nr);
 528         CALLOC_ARRAY(td_dir, lazy_nr_dir_threads);
 529         CALLOC_ARRAY(td_name, 1);
 530
 531         init_dir_mutex();
 532
 533         /*
 534          * Phase 1:
 535          * Build "istate->dir_hash" using n "dir" threads (and a read-only index).
 536          */
 537         for (t = 0; t < lazy_nr_dir_threads; t++) {
 538                 struct lazy_dir_thread_data *td_dir_t = td_dir + t;
 539                 td_dir_t->istate = istate;
 540                 td_dir_t->lazy_entries = lazy_entries;
 541                 td_dir_t->k_start = k_start;
 542                 k_start += nr_each;
 543                 if (k_start > istate->cache_nr)
 544                         k_start = istate->cache_nr;
 545                 td_dir_t->k_end = k_start;
 546                 err = pthread_create(&td_dir_t->pthread, NULL, lazy_dir_thread_proc, td_dir_t);
 547                 if (err)
 548                         die(_("unable to create lazy_dir thread: %s"), strerror(err));
 549         }
 550         for (t = 0; t < lazy_nr_dir_threads; t++) {
 551                 struct lazy_dir_thread_data *td_dir_t = td_dir + t;
 552                 if (pthread_join(td_dir_t->pthread, NULL))
 553                         die("unable to join lazy_dir_thread");
 554         }
 555
 556         /*
 557          * Phase 2:
 558          * Iterate over all index entries and add them to the "istate->name_hash"
 559          * using a single "name" background thread.
 560          * (Testing showed it wasn't worth running more than 1 thread for this.)
 561          *
 562          * Meanwhile, finish updating the parent directory ref-counts for each
 563          * index entry using the current thread.  (This step is very fast and
 564          * doesn't need threading.)
 565          */
 566         td_name->istate = istate;
 567         td_name->lazy_entries = lazy_entries;
 568         err = pthread_create(&td_name->pthread, NULL, lazy_name_thread_proc, td_name);
 569         if (err)
 570                 die(_("unable to create lazy_name thread: %s"), strerror(err));
 571
 572         lazy_update_dir_ref_counts(istate, lazy_entries);
 573
 574         err = pthread_join(td_name->pthread, NULL);
 575         if (err)
 576                 die(_("unable to join lazy_name thread: %s"), strerror(err));
 577
 578         cleanup_dir_mutex();
 579
 580         free(td_name);
 581         free(td_dir);
 582         free(lazy_entries);
 583 }
 584
 585 static void lazy_init_name_hash(struct index_state *istate)
 586 {
 587
 588         if (istate->name_hash_initialized)
 589                 return;
 590         trace_performance_enter();
 591         trace2_region_enter("index", "name-hash-init", istate->repo);
 592         hashmap_init(&istate->name_hash, cache_entry_cmp, NULL, istate->cache_nr);
 593         hashmap_init(&istate->dir_hash, dir_entry_cmp, NULL, istate->cache_nr);
 594
 595         if (lookup_lazy_params(istate)) {
 596                 /*
 597                  * Disable item counting and automatic rehashing because
 598                  * we do per-chain (mod n) locking rather than whole hashmap
 599                  * locking and we need to prevent the table-size from changing
 600                  * and bucket items from being redistributed.
 601                  */
 602                 hashmap_disable_item_counting(&istate->dir_hash);
 603                 threaded_lazy_init_name_hash(istate);
 604                 hashmap_enable_item_counting(&istate->dir_hash);
 605         } else {
 606                 int nr;
 607                 for (nr = 0; nr < istate->cache_nr; nr++)
 608                         hash_index_entry(istate, istate->cache[nr]);
 609         }
 610
 611         istate->name_hash_initialized = 1;
 612         trace2_region_leave("index", "name-hash-init", istate->repo);
 613         trace_performance_leave("initialize name hash");
 614 }
 615
 616 /*
 617  * A test routine for t/helper/ sources.
 618  *
 619  * Returns the number of threads used or 0 when
 620  * the non-threaded code path was used.
 621  *
 622  * Requesting threading WILL NOT override guards
 623  * in lookup_lazy_params().
 624  */
 625 int test_lazy_init_name_hash(struct index_state *istate, int try_threaded)
 626 {
 627         lazy_nr_dir_threads = 0;
 628         lazy_try_threaded = try_threaded;
 629
 630         lazy_init_name_hash(istate);
 631
 632         return lazy_nr_dir_threads;
 633 }
 634
 635 void add_name_hash(struct index_state *istate, struct cache_entry *ce)
 636 {
 637         if (istate->name_hash_initialized)
 638                 hash_index_entry(istate, ce);
 639 }
 640
 641 void remove_name_hash(struct index_state *istate, struct cache_entry *ce)
 642 {
 643         if (!istate->name_hash_initialized || !(ce->ce_flags & CE_HASHED))
 644                 return;
 645         ce->ce_flags &= ~CE_HASHED;
 646         hashmap_remove(&istate->name_hash, &ce->ent, ce);
 647
 648         if (ignore_case)
 649                 remove_dir_entry(istate, ce);
 650 }
 651
 652 static int slow_same_name(const char *name1, int len1, const char *name2, int len2)
 653 {
 654         if (len1 != len2)
 655                 return 0;
 656
 657         while (len1) {
 658                 unsigned char c1 = *name1++;
 659                 unsigned char c2 = *name2++;
 660                 len1--;
 661                 if (c1 != c2) {
 662                         c1 = toupper(c1);
 663                         c2 = toupper(c2);
 664                         if (c1 != c2)
 665                                 return 0;
 666                 }
 667         }
 668         return 1;
 669 }
 670
 671 static int same_name(const struct cache_entry *ce, const char *name, int namelen, int icase)
 672 {
 673         int len = ce_namelen(ce);
 674
 675         /*
 676          * Always do exact compare, even if we want a case-ignoring comparison;
 677          * we do the quick exact one first, because it will be the common case.
 678          */
 679         if (len == namelen && !memcmp(name, ce->name, len))
 680                 return 1;
 681
 682         if (!icase)
 683                 return 0;
 684
 685         return slow_same_name(name, namelen, ce->name, len);
 686 }
 687
 688 int index_dir_find(struct index_state *istate, const char *name, int namelen,
 689                    struct strbuf *canonical_path)
 690 {
 691         struct dir_entry *dir;
 692
 693         lazy_init_name_hash(istate);
 694         expand_to_path(istate, name, namelen, 0);
 695         dir = find_dir_entry(istate, name, namelen);
 696
 697         if (canonical_path && dir && dir->nr) {
 698                 strbuf_reset(canonical_path);
 699                 strbuf_add(canonical_path, dir->name, dir->namelen);
 700         }
 701
 702         return dir && dir->nr;
 703 }
 704
 705 void adjust_dirname_case(struct index_state *istate, char *name)
 706 {
 707         const char *startPtr = name;
 708         const char *ptr = startPtr;
 709
 710         lazy_init_name_hash(istate);
 711         expand_to_path(istate, name, strlen(name), 0);
 712         while (*ptr) {
 713                 while (*ptr && *ptr != '/')
 714                         ptr++;
 715
 716                 if (*ptr == '/') {
 717                         struct dir_entry *dir;
 718
 719                         dir = find_dir_entry(istate, name, ptr - name);
 720                         if (dir) {
 721                                 memcpy((void *)startPtr, dir->name + (startPtr - name), ptr - startPtr);
 722                                 startPtr = ptr + 1;
 723                         }
 724                         ptr++;
 725                 }
 726         }
 727 }
 728
 729 struct cache_entry *index_file_exists(struct index_state *istate, const char *name, int namelen, int icase)
 730 {
 731         struct cache_entry *ce;
 732         unsigned int hash = memihash(name, namelen);
 733
 734         lazy_init_name_hash(istate);
 735         expand_to_path(istate, name, namelen, icase);
 736
 737         ce = hashmap_get_entry_from_hash(&istate->name_hash, hash, NULL,
 738                                          struct cache_entry, ent);
 739         hashmap_for_each_entry_from(&istate->name_hash, ce, ent) {
 740                 if (same_name(ce, name, namelen, icase))
 741                         return ce;
 742         }
 743         return NULL;
 744 }
 745
 746 void free_name_hash(struct index_state *istate)
 747 {
 748         if (!istate->name_hash_initialized)
 749                 return;
 750         istate->name_hash_initialized = 0;
 751
 752         hashmap_clear(&istate->name_hash);
 753         hashmap_clear_and_free(&istate->dir_hash, struct dir_entry, ent);
 754 }