src/hb-map.hh

/*
 * Copyright © 2018  Google, Inc.
 *
 *  This is part of HarfBuzz, a text shaping library.
 *
 * Permission is hereby granted, without written agreement and without
 * license or royalty fees, to use, copy, modify, and distribute this
 * software and its documentation for any purpose, provided that the
 * above copyright notice and the following two paragraphs appear in
 * all copies of this software.
 *
 * IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
 * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
 * ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
 * IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
 * DAMAGE.
 *
 * THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
 * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
 * FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
 * ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
 * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
 *
 * Google Author(s): Behdad Esfahbod
 */

#ifndef HB_MAP_HH
#define HB_MAP_HH

#include "hb.hh"


/*
 * hb_hashmap_t
 */

extern HB_INTERNAL const hb_codepoint_t minus_1;

template <typename K, typename V,
	  bool minus_one = false>
struct hb_hashmap_t
{
  hb_hashmap_t ()  { init (); }
  ~hb_hashmap_t () { fini (); }

  hb_hashmap_t (const hb_hashmap_t& o) : hb_hashmap_t () { resize (population); hb_copy (o, *this); }
  hb_hashmap_t (hb_hashmap_t&& o) : hb_hashmap_t () { hb_swap (*this, o); }
  hb_hashmap_t& operator= (const hb_hashmap_t& o)  { resize (population); hb_copy (o, *this); return *this; }
  hb_hashmap_t& operator= (hb_hashmap_t&& o)  { hb_swap (*this, o); return *this; }

  hb_hashmap_t (std::initializer_list<hb_pair_t<K, V>> lst) : hb_hashmap_t ()
  {
    for (auto&& item : lst)
      set (item.first, item.second);
  }
  template <typename Iterable,
	    hb_requires (hb_is_iterable (Iterable))>
  hb_hashmap_t (const Iterable &o) : hb_hashmap_t ()
  {
    auto iter = hb_iter (o);
    if (iter.is_random_access_iterator)
      resize (hb_len (iter));
    hb_copy (iter, *this);
  }

  struct item_t
  {
    K key;
    uint32_t hash : 30;
    uint32_t is_used_ : 1;
    uint32_t is_tombstone_ : 1;
    V value;

    bool is_used () const { return is_used_; }
    void set_used (bool is_used) { is_used_ = is_used; }
    bool is_tombstone () const { return is_tombstone_; }
    void set_tombstone (bool is_tombstone) { is_tombstone_ = is_tombstone; }
    bool is_real () const { return is_used_ && !is_tombstone_; }

    template <bool v = minus_one,
	      hb_enable_if (v == false)>
    static inline const V& default_value () { return Null(V); };
    template <bool v = minus_one,
	      hb_enable_if (v == true)>
    static inline const V& default_value ()
    {
      static_assert (hb_is_same (V, hb_codepoint_t), "");
      return minus_1;
    };

    void clear ()
    {
      new (std::addressof (key)) K ();
      new (std::addressof (value)) V ();
      hash = 0;
      is_used_ = false;
      is_tombstone_ = false;
    }

    bool operator == (const K &o) { return hb_deref (key) == hb_deref (o); }
    bool operator == (const item_t &o) { return *this == o.key; }
    hb_pair_t<K, V> get_pair() const { return hb_pair_t<K, V> (key, value); }
    hb_pair_t<const K &, const V &> get_pair_ref() const { return hb_pair_t<const K &, const V &> (key, value); }

    uint32_t total_hash () const
    { return (hash * 31) + hb_hash (value); }
  };

  hb_object_header_t header;
  bool successful; /* Allocations successful */
  unsigned int population; /* Not including tombstones. */
  unsigned int occupancy; /* Including tombstones. */
  unsigned int mask;
  unsigned int prime;
  item_t *items;

  friend void swap (hb_hashmap_t& a, hb_hashmap_t& b)
  {
    if (unlikely (!a.successful || !b.successful))
      return;
    hb_swap (a.population, b.population);
    hb_swap (a.occupancy, b.occupancy);
    hb_swap (a.mask, b.mask);
    hb_swap (a.prime, b.prime);
    hb_swap (a.items, b.items);
  }
  void init ()
  {
    hb_object_init (this);

    successful = true;
    population = occupancy = 0;
    mask = 0;
    prime = 0;
    items = nullptr;
  }
  void fini ()
  {
    hb_object_fini (this);

    if (likely (items)) {
      unsigned size = mask + 1;
      for (unsigned i = 0; i < size; i++)
        items[i].~item_t ();
      hb_free (items);
      items = nullptr;
    }
    population = occupancy = 0;
  }

  void reset ()
  {
    successful = true;
    clear ();
  }

  bool in_error () const { return !successful; }

  bool resize (unsigned new_population = 0)
  {
    if (unlikely (!successful)) return false;

    unsigned int power = hb_bit_storage (hb_max (population, new_population) * 2 + 8);
    unsigned int new_size = 1u << power;
    item_t *new_items = (item_t *) hb_malloc ((size_t) new_size * sizeof (item_t));
    if (unlikely (!new_items))
    {
      successful = false;
      return false;
    }
    for (auto &_ : hb_iter (new_items, new_size))
      _.clear ();

    unsigned int old_size = mask + 1;
    item_t *old_items = items;

    /* Switch to new, empty, array. */
    population = occupancy = 0;
    mask = new_size - 1;
    prime = prime_for (power);
    items = new_items;

    /* Insert back old items. */
    if (old_items)
      for (unsigned int i = 0; i < old_size; i++)
      {
	if (old_items[i].is_real ())
	{
	  set_with_hash (old_items[i].key,
			 old_items[i].hash,
			 std::move (old_items[i].value));
	}
	old_items[i].~item_t ();
      }

    hb_free (old_items);

    return true;
  }

  template <typename VV>
  bool set (K key, VV&& value) { return set_with_hash (key, hb_hash (key), std::forward<VV> (value)); }

  const V& get (K key) const
  {
    if (unlikely (!items)) return item_t::default_value ();
    unsigned int i = bucket_for (key);
    return items[i].is_real () && items[i] == key ? items[i].value : item_t::default_value ();
  }

  void del (K key) { set_with_hash (key, hb_hash (key), item_t::default_value (), true); }

  /* Has interface. */
  typedef const V& value_t;
  value_t operator [] (K k) const { return get (k); }
  template <typename VV=V>
  bool has (K key, VV **vp = nullptr) const
  {
    if (unlikely (!items))
      return false;
    unsigned int i = bucket_for (key);
    if (items[i].is_real () && items[i] == key)
    {
      if (vp) *vp = &items[i].value;
      return true;
    }
    else
      return false;
  }
  /* Projection. */
  V operator () (K k) const { return get (k); }

  void clear ()
  {
    if (unlikely (!successful)) return;

    if (items)
      for (auto &_ : hb_iter (items, mask + 1))
	_.clear ();

    population = occupancy = 0;
  }

  bool is_empty () const { return population == 0; }
  explicit operator bool () const { return !is_empty (); }

  uint32_t hash () const
  {
    uint32_t h = 0;
    for (const auto &item : + hb_array (items, mask ? mask + 1 : 0)
			    | hb_filter (&item_t::is_real))
      h ^= item.total_hash ();
    return h;
  }

  bool is_equal (const hb_hashmap_t &other) const
  {
    if (population != other.population) return false;

    for (auto pair : iter ())
      if (get (pair.first) != pair.second)
        return false;

    return true;
  }
  bool operator == (const hb_hashmap_t &other) const { return is_equal (other); }
  bool operator != (const hb_hashmap_t &other) const { return !is_equal (other); }

  unsigned int get_population () const { return population; }

  /*
   * Iterator
   */
  auto iter () const HB_AUTO_RETURN
  (
    + hb_array (items, mask ? mask + 1 : 0)
    | hb_filter (&item_t::is_real)
    | hb_map (&item_t::get_pair)
  )
  auto iter_ref () const HB_AUTO_RETURN
  (
    + hb_array (items, mask ? mask + 1 : 0)
    | hb_filter (&item_t::is_real)
    | hb_map (&item_t::get_pair_ref)
  )
  auto keys () const HB_AUTO_RETURN
  (
    + hb_array (items, mask ? mask + 1 : 0)
    | hb_filter (&item_t::is_real)
    | hb_map (&item_t::key)
    | hb_map (hb_ridentity)
  )
  auto keys_ref () const HB_AUTO_RETURN
  (
    + hb_array (items, mask ? mask + 1 : 0)
    | hb_filter (&item_t::is_real)
    | hb_map (&item_t::key)
  )
  auto values () const HB_AUTO_RETURN
  (
    + hb_array (items, mask ? mask + 1 : 0)
    | hb_filter (&item_t::is_real)
    | hb_map (&item_t::value)
    | hb_map (hb_ridentity)
  )
  auto values_ref () const HB_AUTO_RETURN
  (
    + hb_array (items, mask ? mask + 1 : 0)
    | hb_filter (&item_t::is_real)
    | hb_map (&item_t::value)
  )

  /* Sink interface. */
  hb_hashmap_t& operator << (const hb_pair_t<K, V>& v)
  { set (v.first, v.second); return *this; }

  protected:

  template <typename VV>
  bool set_with_hash (K key, uint32_t hash, VV&& value, bool is_delete=false)
  {
    if (unlikely (!successful)) return false;
    if (unlikely ((occupancy + occupancy / 2) >= mask && !resize ())) return false;
    unsigned int i = bucket_for_hash (key, hash);

    if (is_delete && items[i].key != key)
      return true; /* Trying to delete non-existent key. */

    if (items[i].is_used ())
    {
      occupancy--;
      if (!items[i].is_tombstone ())
	population--;
    }

    items[i].key = key;
    items[i].value = std::forward<VV> (value);
    items[i].hash = hash;
    items[i].set_used (true);
    items[i].set_tombstone (is_delete);

    occupancy++;
    if (!is_delete)
      population++;

    return true;
  }

  unsigned int bucket_for (const K &key) const
  {
    return bucket_for_hash (key, hb_hash (key));
  }

  unsigned int bucket_for_hash (const K &key, uint32_t hash) const
  {
    hash &= 0x3FFFFFFF; // We only store lower 30bit of hash
    unsigned int i = hash % prime;
    unsigned int step = 0;
    unsigned int tombstone = (unsigned) -1;
    while (items[i].is_used ())
    {
      if (items[i].hash == hash && items[i] == key)
	return i;
      if (tombstone == (unsigned) -1 && items[i].is_tombstone ())
	tombstone = i;
      i = (i + ++step) & mask;
    }
    return tombstone == (unsigned) -1 ? i : tombstone;
  }

  static unsigned int prime_for (unsigned int shift)
  {
    /* Following comment and table copied from glib. */
    /* Each table size has an associated prime modulo (the first prime
     * lower than the table size) used to find the initial bucket. Probing
     * then works modulo 2^n. The prime modulo is necessary to get a
     * good distribution with poor hash functions.
     */
    /* Not declaring static to make all kinds of compilers happy... */
    /*static*/ const unsigned int prime_mod [32] =
    {
      1,          /* For 1 << 0 */
      2,
      3,
      7,
      13,
      31,
      61,
      127,
      251,
      509,
      1021,
      2039,
      4093,
      8191,
      16381,
      32749,
      65521,      /* For 1 << 16 */
      131071,
      262139,
      524287,
      1048573,
      2097143,
      4194301,
      8388593,
      16777213,
      33554393,
      67108859,
      134217689,
      268435399,
      536870909,
      1073741789,
      2147483647  /* For 1 << 31 */
    };

    if (unlikely (shift >= ARRAY_LENGTH (prime_mod)))
      return prime_mod[ARRAY_LENGTH (prime_mod) - 1];

    return prime_mod[shift];
  }
};

/*
 * hb_map_t
 */

struct hb_map_t : hb_hashmap_t<hb_codepoint_t,
			       hb_codepoint_t,
			       true>
{
  using hashmap = hb_hashmap_t<hb_codepoint_t,
			       hb_codepoint_t,
			       true>;

  ~hb_map_t () = default;
  hb_map_t () : hashmap () {}
  hb_map_t (const hb_map_t &o) : hashmap ((hashmap &) o) {}
  hb_map_t (hb_map_t &&o) : hashmap (std::move ((hashmap &) o)) {}
  hb_map_t& operator= (const hb_map_t&) = default;
  hb_map_t& operator= (hb_map_t&&) = default;
  hb_map_t (std::initializer_list<hb_pair_t<hb_codepoint_t, hb_codepoint_t>> lst) : hashmap (lst) {}
  template <typename Iterable,
	    hb_requires (hb_is_iterable (Iterable))>
  hb_map_t (const Iterable &o) : hashmap (o) {}
};

template <typename K, typename V>
static inline
hb_hashmap_t<K, V>* hb_hashmap_create ()
{
  using hashmap = hb_hashmap_t<K, V>;
  hashmap* map;
  if (!(map = hb_object_create<hashmap> ()))
    return nullptr;

  return map;
}

template <typename K, typename V>
static inline
void hb_hashmap_destroy (hb_hashmap_t<K, V>* map)
{
  if (!hb_object_destroy (map))
    return;

  hb_free (map);
}

namespace hb {

template <typename K, typename V>
struct vtable<hb_hashmap_t<K, V>>
{
  static constexpr auto destroy = hb_hashmap_destroy<K,V>;
};

}


#endif /* HB_MAP_HH */