/*

 * 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_PRIVATE_HH

#define HB_MAP_PRIVATE_HH

#include "hb-private.hh"

#include "hb-object-private.hh"

template <typename T>

inline uint32_t Hash (const T &v)

{

  /* Knuth's multiplicative method: */

  return (uint32_t) v * 2654435761u;

}

/*

 * hb_map_t

 */

struct hb_map_t

{

  struct item_t

  {

    hb_codepoint_t key;

    hb_codepoint_t value;

    inline bool is_unused (void) const { return key == INVALID; }

    inline bool is_tombstone (void) const { return key != INVALID && value == INVALID; }

  };

  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;

  inline void init_shallow (void)

  {

    successful = true;

    population = occupancy = 0;

    mask = 0;

    prime = 0;

    items = nullptr;

  }

  inline void init (void)

  {

    hb_object_init (this);

    init_shallow ();

  }

  inline void fini_shallow (void)

  {

    free (items);

  }

  inline void fini (void)

  {

    hb_object_fini (this);

    fini_shallow ();

  }

  inline bool resize (void)

  {

    if (unlikely (!successful)) return false;

    unsigned int power = _hb_bit_storage (population * 2 + 8);

    unsigned int new_size = 1u << power;

    item_t *new_items = (item_t *) malloc ((size_t) new_size * sizeof (item_t));

    if (unlikely (!new_items))

    {

      successful = false;

      return false;

    }

    memset (new_items, 0xFF, (size_t) new_size * sizeof (item_t));

    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].key != INVALID && old_items[i].value != INVALID)

          set (old_items[i].key, old_items[i].value);

    free (old_items);

    return true;

  }

  inline void set (hb_codepoint_t key, hb_codepoint_t value)

  {

    if (unlikely (!successful)) return;

    if (unlikely (key == INVALID)) return;

    if ((occupancy + occupancy / 2) >= mask && !resize ()) return;

    unsigned int i = bucket_for (key);

    if (value == INVALID && items[i].key != key)

      return; /* Trying to delete non-existent key. */

    if (!items[i].is_unused ())

    {

      occupancy--;

      if (items[i].is_tombstone ())

        population--;

    }

    items[i].key = key;

    items[i].value = value;

    occupancy++;

    if (!items[i].is_tombstone ())

      population++;

  }

  inline hb_codepoint_t get (hb_codepoint_t key) const

  {

    if (unlikely (!items)) return INVALID;

    unsigned int i = bucket_for (key);

    return items[i].key == key ? items[i].value : INVALID;

  }

  inline void del (hb_codepoint_t key)

  {

    set (key, INVALID);

  }

  inline bool has (hb_codepoint_t key) const

  {

    return get (key) != INVALID;

  }

  inline hb_codepoint_t operator [] (unsigned int key) const

  { return get (key); }

  static const hb_codepoint_t INVALID = HB_MAP_VALUE_INVALID;

  inline void clear (void)

  {

    memset (items, 0xFF, ((size_t) mask + 1) * sizeof (item_t));

    population = occupancy = 0;

  }

  inline bool is_empty (void) const

  {

    return population != 0;

  }

  inline unsigned int get_population () const

  {

    return population;

  }

  protected:

  inline unsigned int bucket_for (hb_codepoint_t key) const

  {

    unsigned int i = Hash (key) % prime;

    unsigned int step = 0;

    unsigned int tombstone = INVALID;

    while (!items[i].is_unused ())

    {

      if (items[i].key == key)

        return i;

      if (tombstone == INVALID && items[i].is_tombstone ())

        tombstone = i;

      i = (i + ++step) & mask;

    }

    return tombstone == INVALID ? i : tombstone;

  }

  static inline 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];

  }

};

#endif /* HB_MAP_PRIVATE_HH */