/*

 * name-hash.c

 *

 * Hashing names in the index state

 *

 * Copyright (C) 2008 Linus Torvalds

 */

#include "git-compat-util.h"

#include "environment.h"

#include "gettext.h"

#include "name-hash.h"

#include "object.h"

#include "read-cache-ll.h"

#include "thread-utils.h"

#include "trace.h"

#include "trace2.h"

#include "sparse-index.h"

struct dir_entry {

  struct hashmap_entry ent;

  struct dir_entry *parent;

  int nr;

  unsigned int namelen;

  char name[FLEX_ARRAY];

};

static int dir_entry_cmp(const void *cmp_data UNUSED,

       const struct hashmap_entry *eptr,

       const struct hashmap_entry *entry_or_key,

       const void *keydata)

{

  const struct dir_entry *e1, *e2;

  const char *name = keydata;

  e1 = container_of(eptr, const struct dir_entry, ent);

  e2 = container_of(entry_or_key, const struct dir_entry, ent);

  return e1->namelen != e2->namelen || strncasecmp(e1->name,

      name ? name : e2->name, e1->namelen);

}

static struct dir_entry *find_dir_entry__hash(struct index_state *istate,

    const char *name, unsigned int namelen, unsigned int hash)

{

  struct dir_entry key;

  hashmap_entry_init(&key.ent, hash);

  key.namelen = namelen;

  return hashmap_get_entry(&istate->dir_hash, &key, ent, name);

}

static struct dir_entry *find_dir_entry(struct index_state *istate,

    const char *name, unsigned int namelen)

{

  return find_dir_entry__hash(istate, name, namelen, memihash(name, namelen));

}

static struct dir_entry *hash_dir_entry(struct index_state *istate,

    struct cache_entry *ce, int namelen)

{

  /*

   * Throw each directory component in the hash for quick lookup

   * during a git status. Directory components are stored without their

   * closing slash.  Despite submodules being a directory, they never

   * reach this point, because they are stored

   * in index_state.name_hash (as ordinary cache_entries).

   */

  struct dir_entry *dir;

  /* get length of parent directory */

  while (namelen > 0 && !is_dir_sep(ce->name[namelen - 1]))

    namelen--;

  if (namelen <= 0)

    return NULL;

  namelen--;

  /* lookup existing entry for that directory */

  dir = find_dir_entry(istate, ce->name, namelen);

  if (!dir) {

    /* not found, create it and add to hash table */

    FLEX_ALLOC_MEM(dir, name, ce->name, namelen);

    hashmap_entry_init(&dir->ent, memihash(ce->name, namelen));

    dir->namelen = namelen;

    hashmap_add(&istate->dir_hash, &dir->ent);

    /* recursively add missing parent directories */

    dir->parent = hash_dir_entry(istate, ce, namelen);

  }

  return dir;

}

static void add_dir_entry(struct index_state *istate, struct cache_entry *ce)

{

  /* Add reference to the directory entry (and parents if 0). */

  struct dir_entry *dir = hash_dir_entry(istate, ce, ce_namelen(ce));

  while (dir && !(dir->nr++))

    dir = dir->parent;

}

static void remove_dir_entry(struct index_state *istate, struct cache_entry *ce)

{

  /*

   * Release reference to the directory entry. If 0, remove and continue

   * with parent directory.

   */

  struct dir_entry *dir = hash_dir_entry(istate, ce, ce_namelen(ce));

  while (dir && !(--dir->nr)) {

    struct dir_entry *parent = dir->parent;

    hashmap_remove(&istate->dir_hash, &dir->ent, NULL);

    free(dir);

    dir = parent;

  }

}

static void hash_index_entry(struct index_state *istate, struct cache_entry *ce)

{

  if (ce->ce_flags & CE_HASHED)

    return;

  ce->ce_flags |= CE_HASHED;

  if (!S_ISSPARSEDIR(ce->ce_mode)) {

    hashmap_entry_init(&ce->ent, memihash(ce->name, ce_namelen(ce)));

    hashmap_add(&istate->name_hash, &ce->ent);

  }

  if (ignore_case)

    add_dir_entry(istate, ce);

}

static int cache_entry_cmp(const void *cmp_data UNUSED,

         const struct hashmap_entry *eptr,

         const struct hashmap_entry *entry_or_key,

         const void *remove)

{

  const struct cache_entry *ce1, *ce2;

  ce1 = container_of(eptr, const struct cache_entry, ent);

  ce2 = container_of(entry_or_key, const struct cache_entry, ent);

  /*

   * For remove_name_hash, find the exact entry (pointer equality); for

   * index_file_exists, find all entries with matching hash code and

   * decide whether the entry matches in same_name.

   */

  return remove ? !(ce1 == ce2) : 0;

}

static int lazy_try_threaded = 1;

static int lazy_nr_dir_threads;

/*

 * Set a minimum number of cache_entries that we will handle per

 * thread and use that to decide how many threads to run (up to

 * the number on the system).

 *

 * For guidance setting the lower per-thread bound, see:

 *     t/helper/test-lazy-init-name-hash --analyze

 */

#define LAZY_THREAD_COST (2000)

/*

 * We use n mutexes to guard n partitions of the "istate->dir_hash"

 * hashtable.  Since "find" and "insert" operations will hash to a

 * particular bucket and modify/search a single chain, we can say

 * that "all chains mod n" are guarded by the same mutex -- rather

 * than having a single mutex to guard the entire table.  (This does

 * require that we disable "rehashing" on the hashtable.)

 *

 * So, a larger value here decreases the probability of a collision

 * and the time that each thread must wait for the mutex.

 */

#define LAZY_MAX_MUTEX   (32)

static pthread_mutex_t *lazy_dir_mutex_array;

/*

 * An array of lazy_entry items is used by the n threads in

 * the directory parse (first) phase to (lock-free) store the

 * intermediate results.  These values are then referenced by

 * the 2 threads in the second phase.

 */

struct lazy_entry {

  struct dir_entry *dir;

  unsigned int hash_dir;

  unsigned int hash_name;

};

/*

 * Decide if we want to use threads (if available) to load

 * the hash tables.  We set "lazy_nr_dir_threads" to zero when

 * it is not worth it.

 */

static int lookup_lazy_params(struct index_state *istate)

{

  int nr_cpus;

  lazy_nr_dir_threads = 0;

  if (!lazy_try_threaded)

    return 0;

  /*

   * If we are respecting case, just use the original

   * code to build the "istate->name_hash".  We don't

   * need the complexity here.

   */

  if (!ignore_case)

    return 0;

  nr_cpus = online_cpus();

  if (nr_cpus < 2)

    return 0;

  if (istate->cache_nr < 2 * LAZY_THREAD_COST)

    return 0;

  if (istate->cache_nr < nr_cpus * LAZY_THREAD_COST)

    nr_cpus = istate->cache_nr / LAZY_THREAD_COST;

  lazy_nr_dir_threads = nr_cpus;

  return lazy_nr_dir_threads;

}

/*

 * Initialize n mutexes for use when searching and inserting

 * into "istate->dir_hash".  All "dir" threads are trying

 * to insert partial pathnames into the hash as they iterate

 * over their portions of the index, so lock contention is

 * high.

 *

 * However, the hashmap is going to put items into bucket

 * chains based on their hash values.  Use that to create n

 * mutexes and lock on mutex[bucket(hash) % n].  This will

 * decrease the collision rate by (hopefully) a factor of n.

 */

static void init_dir_mutex(void)

{

  int j;

  CALLOC_ARRAY(lazy_dir_mutex_array, LAZY_MAX_MUTEX);

  for (j = 0; j < LAZY_MAX_MUTEX; j++)

    init_recursive_mutex(&lazy_dir_mutex_array[j]);

}

static void cleanup_dir_mutex(void)

{

  int j;

  for (j = 0; j < LAZY_MAX_MUTEX; j++)

    pthread_mutex_destroy(&lazy_dir_mutex_array[j]);

  free(lazy_dir_mutex_array);

}

static void lock_dir_mutex(int j)

{

  pthread_mutex_lock(&lazy_dir_mutex_array[j]);

}

static void unlock_dir_mutex(int j)

{

  pthread_mutex_unlock(&lazy_dir_mutex_array[j]);

}

static inline int compute_dir_lock_nr(

  const struct hashmap *map,

  unsigned int hash)

{

  return hashmap_bucket(map, hash) % LAZY_MAX_MUTEX;

}

static struct dir_entry *hash_dir_entry_with_parent_and_prefix(

  struct index_state *istate,

  struct dir_entry *parent,

  struct strbuf *prefix)

{

  struct dir_entry *dir;

  unsigned int hash;

  int lock_nr;

  /*

   * Either we have a parent directory and path with slash(es)

   * or the directory is an immediate child of the root directory.

   */

  assert((parent != NULL) ^ (strchr(prefix->buf, '/') == NULL));

  if (parent)

    hash = memihash_cont(parent->ent.hash,

      prefix->buf + parent->namelen,

      prefix->len - parent->namelen);

  else

    hash = memihash(prefix->buf, prefix->len);

  lock_nr = compute_dir_lock_nr(&istate->dir_hash, hash);

  lock_dir_mutex(lock_nr);

  dir = find_dir_entry__hash(istate, prefix->buf, prefix->len, hash);

  if (!dir) {

    FLEX_ALLOC_MEM(dir, name, prefix->buf, prefix->len);

    hashmap_entry_init(&dir->ent, hash);

    dir->namelen = prefix->len;

    dir->parent = parent;

    hashmap_add(&istate->dir_hash, &dir->ent);

    if (parent) {

      unlock_dir_mutex(lock_nr);

      /* All I really need here is an InterlockedIncrement(&(parent->nr)) */

      lock_nr = compute_dir_lock_nr(&istate->dir_hash, parent->ent.hash);

      lock_dir_mutex(lock_nr);

      parent->nr++;

    }

  }

  unlock_dir_mutex(lock_nr);

  return dir;

}

/*

 * handle_range_1() and handle_range_dir() are derived from

 * clear_ce_flags_1() and clear_ce_flags_dir() in unpack-trees.c

 * and handle the iteration over the entire array of index entries.

 * They use recursion for adjacent entries in the same parent

 * directory.

 */

static int handle_range_1(

  struct index_state *istate,

  int k_start,

  int k_end,

  struct dir_entry *parent,

  struct strbuf *prefix,

  struct lazy_entry *lazy_entries);

static int handle_range_dir(

  struct index_state *istate,

  int k_start,

  int k_end,

  struct dir_entry *parent,

  struct strbuf *prefix,

  struct lazy_entry *lazy_entries,

  struct dir_entry **dir_new_out)

{

  int rc, k;

  int input_prefix_len = prefix->len;

  struct dir_entry *dir_new;

  dir_new = hash_dir_entry_with_parent_and_prefix(istate, parent, prefix);

  strbuf_addch(prefix, '/');

  /*

   * Scan forward in the index array for index entries having the same

   * path prefix (that are also in this directory).

   */

  if (k_start + 1 >= k_end)

    k = k_end;

  else if (strncmp(istate->cache[k_start + 1]->name, prefix->buf, prefix->len) > 0)

    k = k_start + 1;

  else if (strncmp(istate->cache[k_end - 1]->name, prefix->buf, prefix->len) == 0)

    k = k_end;

  else {

    int begin = k_start;

    int end = k_end;

    assert(begin >= 0);

    while (begin < end) {

      int mid = begin + ((end - begin) >> 1);

      int cmp = strncmp(istate->cache[mid]->name, prefix->buf, prefix->len);

      if (cmp == 0) /* mid has same prefix; look in second part */

        begin = mid + 1;

      else if (cmp > 0) /* mid is past group; look in first part */

        end = mid;

      else

        die("cache entry out of order");

    }

    k = begin;

  }

  /*

   * Recurse and process what we can of this subset [k_start, k).

   */

  rc = handle_range_1(istate, k_start, k, dir_new, prefix, lazy_entries);

  strbuf_setlen(prefix, input_prefix_len);

  *dir_new_out = dir_new;

  return rc;

}

static int handle_range_1(

  struct index_state *istate,

  int k_start,

  int k_end,

  struct dir_entry *parent,

  struct strbuf *prefix,

  struct lazy_entry *lazy_entries)

{

  int input_prefix_len = prefix->len;

  int k = k_start;

  while (k < k_end) {

    struct cache_entry *ce_k = istate->cache[k];

    const char *name, *slash;

    if (prefix->len && strncmp(ce_k->name, prefix->buf, prefix->len))

      break;

    name = ce_k->name + prefix->len;

    slash = strchr(name, '/');

    if (slash) {

      int len = slash - name;

      int processed;

      struct dir_entry *dir_new;

      strbuf_add(prefix, name, len);

      processed = handle_range_dir(istate, k, k_end, parent, prefix, lazy_entries, &dir_new);

      if (processed) {

        k += processed;

        strbuf_setlen(prefix, input_prefix_len);

        continue;

      }

      strbuf_addch(prefix, '/');

      processed = handle_range_1(istate, k, k_end, dir_new, prefix, lazy_entries);

      k += processed;

      strbuf_setlen(prefix, input_prefix_len);

      continue;

    }

    /*

     * It is too expensive to take a lock to insert "ce_k"

     * into "istate->name_hash" and increment the ref-count

     * on the "parent" dir.  So we defer actually updating

     * permanent data structures until phase 2 (where we

     * can change the locking requirements) and simply

     * accumulate our current results into the lazy_entries

     * data array).

     *

     * We do not need to lock the lazy_entries array because

     * we have exclusive access to the cells in the range

     * [k_start,k_end) that this thread was given.

     */

    lazy_entries[k].dir = parent;

    if (parent) {

      lazy_entries[k].hash_name = memihash_cont(

        parent->ent.hash,

        ce_k->name + parent->namelen,

        ce_namelen(ce_k) - parent->namelen);

      lazy_entries[k].hash_dir = parent->ent.hash;

    } else {

      lazy_entries[k].hash_name = memihash(ce_k->name, ce_namelen(ce_k));

    }

    k++;

  }

  return k - k_start;

}

struct lazy_dir_thread_data {

  pthread_t pthread;

  struct index_state *istate;

  struct lazy_entry *lazy_entries;

  int k_start;

  int k_end;

};

static void *lazy_dir_thread_proc(void *_data)

{

  struct lazy_dir_thread_data *d = _data;

  struct strbuf prefix = STRBUF_INIT;

  handle_range_1(d->istate, d->k_start, d->k_end, NULL, &prefix, d->lazy_entries);

  strbuf_release(&prefix);

  return NULL;

}

struct lazy_name_thread_data {

  pthread_t pthread;

  struct index_state *istate;

  struct lazy_entry *lazy_entries;

};

static void *lazy_name_thread_proc(void *_data)

{

  struct lazy_name_thread_data *d = _data;

  int k;

  for (k = 0; k < d->istate->cache_nr; k++) {

    struct cache_entry *ce_k = d->istate->cache[k];

    ce_k->ce_flags |= CE_HASHED;

    hashmap_entry_init(&ce_k->ent, d->lazy_entries[k].hash_name);

    hashmap_add(&d->istate->name_hash, &ce_k->ent);

  }

  return NULL;

}

static inline void lazy_update_dir_ref_counts(

  struct index_state *istate,

  struct lazy_entry *lazy_entries)

{

  int k;

  for (k = 0; k < istate->cache_nr; k++) {

    if (lazy_entries[k].dir)

      lazy_entries[k].dir->nr++;

  }

}

static void threaded_lazy_init_name_hash(

  struct index_state *istate)

{

  int err;

  int nr_each;

  int k_start;

  int t;

  struct lazy_entry *lazy_entries;

  struct lazy_dir_thread_data *td_dir;

  struct lazy_name_thread_data *td_name;

  if (!HAVE_THREADS)

    return;

  k_start = 0;

  nr_each = DIV_ROUND_UP(istate->cache_nr, lazy_nr_dir_threads);

  CALLOC_ARRAY(lazy_entries, istate->cache_nr);

  CALLOC_ARRAY(td_dir, lazy_nr_dir_threads);

  CALLOC_ARRAY(td_name, 1);

  init_dir_mutex();

  /*

   * Phase 1:

   * Build "istate->dir_hash" using n "dir" threads (and a read-only index).

   */

  for (t = 0; t < lazy_nr_dir_threads; t++) {

    struct lazy_dir_thread_data *td_dir_t = td_dir + t;

    td_dir_t->istate = istate;

    td_dir_t->lazy_entries = lazy_entries;

    td_dir_t->k_start = k_start;

    k_start += nr_each;

    if (k_start > istate->cache_nr)

      k_start = istate->cache_nr;

    td_dir_t->k_end = k_start;

    err = pthread_create(&td_dir_t->pthread, NULL, lazy_dir_thread_proc, td_dir_t);

    if (err)

      die(_("unable to create lazy_dir thread: %s"), strerror(err));

  }

  for (t = 0; t < lazy_nr_dir_threads; t++) {

    struct lazy_dir_thread_data *td_dir_t = td_dir + t;

    if (pthread_join(td_dir_t->pthread, NULL))

      die("unable to join lazy_dir_thread");

  }

  /*

   * Phase 2:

   * Iterate over all index entries and add them to the "istate->name_hash"

   * using a single "name" background thread.

   * (Testing showed it wasn't worth running more than 1 thread for this.)

   *

   * Meanwhile, finish updating the parent directory ref-counts for each

   * index entry using the current thread.  (This step is very fast and

   * doesn't need threading.)

   */

  td_name->istate = istate;

  td_name->lazy_entries = lazy_entries;

  err = pthread_create(&td_name->pthread, NULL, lazy_name_thread_proc, td_name);

  if (err)

    die(_("unable to create lazy_name thread: %s"), strerror(err));

  lazy_update_dir_ref_counts(istate, lazy_entries);

  err = pthread_join(td_name->pthread, NULL);

  if (err)

    die(_("unable to join lazy_name thread: %s"), strerror(err));

  cleanup_dir_mutex();

  free(td_name);

  free(td_dir);

  free(lazy_entries);

}

static void lazy_init_name_hash(struct index_state *istate)

{

  if (istate->name_hash_initialized)

    return;

  trace_performance_enter();

  trace2_region_enter("index", "name-hash-init", istate->repo);

  hashmap_init(&istate->name_hash, cache_entry_cmp, NULL, istate->cache_nr);

  hashmap_init(&istate->dir_hash, dir_entry_cmp, NULL, istate->cache_nr);

  if (lookup_lazy_params(istate)) {

    /*

     * Disable item counting and automatic rehashing because

     * we do per-chain (mod n) locking rather than whole hashmap

     * locking and we need to prevent the table-size from changing

     * and bucket items from being redistributed.

     */

    hashmap_disable_item_counting(&istate->dir_hash);

    threaded_lazy_init_name_hash(istate);

    hashmap_enable_item_counting(&istate->dir_hash);

  } else {

    int nr;

    for (nr = 0; nr < istate->cache_nr; nr++)

      hash_index_entry(istate, istate->cache[nr]);

  }

  istate->name_hash_initialized = 1;

  trace2_region_leave("index", "name-hash-init", istate->repo);

  trace_performance_leave("initialize name hash");

}

/*

 * A test routine for t/helper/ sources.

 *

 * Returns the number of threads used or 0 when

 * the non-threaded code path was used.

 *

 * Requesting threading WILL NOT override guards

 * in lookup_lazy_params().

 */

int test_lazy_init_name_hash(struct index_state *istate, int try_threaded)

{

  lazy_nr_dir_threads = 0;

  lazy_try_threaded = try_threaded;

  lazy_init_name_hash(istate);

  return lazy_nr_dir_threads;

}

void add_name_hash(struct index_state *istate, struct cache_entry *ce)

{

  if (istate->name_hash_initialized)

    hash_index_entry(istate, ce);

}

void remove_name_hash(struct index_state *istate, struct cache_entry *ce)

{

  if (!istate->name_hash_initialized || !(ce->ce_flags & CE_HASHED))

    return;

  ce->ce_flags &= ~CE_HASHED;

  hashmap_remove(&istate->name_hash, &ce->ent, ce);

  if (ignore_case)

    remove_dir_entry(istate, ce);

}

static int slow_same_name(const char *name1, int len1, const char *name2, int len2)

{

  if (len1 != len2)

    return 0;

  while (len1) {

    unsigned char c1 = *name1++;

    unsigned char c2 = *name2++;

    len1--;

    if (c1 != c2) {

      c1 = toupper(c1);

      c2 = toupper(c2);

      if (c1 != c2)

        return 0;

    }

  }

  return 1;

}

static int same_name(const struct cache_entry *ce, const char *name, int namelen, int icase)

{

  int len = ce_namelen(ce);

  /*

   * Always do exact compare, even if we want a case-ignoring comparison;

   * we do the quick exact one first, because it will be the common case.

   */

  if (len == namelen && !memcmp(name, ce->name, len))

    return 1;

  if (!icase)

    return 0;

  return slow_same_name(name, namelen, ce->name, len);

}

int index_dir_find(struct index_state *istate, const char *name, int namelen,

       struct strbuf *canonical_path)

{

  struct dir_entry *dir;

  lazy_init_name_hash(istate);

  expand_to_path(istate, name, namelen, 0);

  dir = find_dir_entry(istate, name, namelen);

  if (canonical_path && dir && dir->nr) {

    strbuf_reset(canonical_path);

    strbuf_add(canonical_path, dir->name, dir->namelen);

  }

  return dir && dir->nr;

}

void adjust_dirname_case(struct index_state *istate, char *name)

{

  const char *startPtr = name;

  const char *ptr = startPtr;

  lazy_init_name_hash(istate);

  expand_to_path(istate, name, strlen(name), 0);

  while (*ptr) {

    while (*ptr && *ptr != '/')

      ptr++;

    if (*ptr == '/') {

      struct dir_entry *dir;

      dir = find_dir_entry(istate, name, ptr - name);

      if (dir) {

        memcpy((void *)startPtr, dir->name + (startPtr - name), ptr - startPtr);

        startPtr = ptr + 1;

      }

      ptr++;

    }

  }

}

struct cache_entry *index_file_exists(struct index_state *istate, const char *name, int namelen, int icase)

{

  struct cache_entry *ce;

  unsigned int hash = memihash(name, namelen);

  lazy_init_name_hash(istate);

  expand_to_path(istate, name, namelen, icase);

  ce = hashmap_get_entry_from_hash(&istate->name_hash, hash, NULL,

           struct cache_entry, ent);

  hashmap_for_each_entry_from(&istate->name_hash, ce, ent) {

    if (same_name(ce, name, namelen, icase))

      return ce;

  }

  return NULL;

}

void free_name_hash(struct index_state *istate)

{

  if (!istate->name_hash_initialized)

    return;

  istate->name_hash_initialized = 0;

  hashmap_clear(&istate->name_hash);

  hashmap_clear_and_free(&istate->dir_hash, struct dir_entry, ent);

}