/*

 * Copyright © 2012  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_SET_PRIVATE_HH

#define HB_SET_PRIVATE_HH

#include "hb-private.hh"

#include "hb-object-private.hh"

/*

 * The set digests here implement various "filters" that support

 * "approximate member query".  Conceptually these are like Bloom

 * Filter and Quotient Filter, however, much smaller, faster, and

 * designed to fit the requirements of our uses for glyph coverage

 * queries.

 *

 * Our filters are highly accurate if the lookup covers fairly local

 * set of glyphs, but fully flooded and ineffective if coverage is

 * all over the place.

 *

 * The frozen-set can be used instead of a digest, to trade more

 * memory for 100% accuracy, but in practice, that doesn't look like

 * an attractive trade-off.

 */

template <typename mask_t, unsigned int shift>

struct hb_set_digest_lowest_bits_t

{

  ASSERT_POD ();

  static const unsigned int mask_bytes = sizeof (mask_t);

  static const unsigned int mask_bits = sizeof (mask_t) * 8;

  static const unsigned int num_bits = 0

				     + (mask_bytes >= 1 ? 3 : 0)

				     + (mask_bytes >= 2 ? 1 : 0)

				     + (mask_bytes >= 4 ? 1 : 0)

				     + (mask_bytes >= 8 ? 1 : 0)

				     + (mask_bytes >= 16? 1 : 0)

				     + 0;

  ASSERT_STATIC (shift < sizeof (hb_codepoint_t) * 8);

  ASSERT_STATIC (shift + num_bits <= sizeof (hb_codepoint_t) * 8);

  inline void init (void) {

    mask = 0;

  }

  inline void add (hb_codepoint_t g) {

    mask |= mask_for (g);

  }

  inline void add_range (hb_codepoint_t a, hb_codepoint_t b) {

    if ((b >> shift) - (a >> shift) >= mask_bits - 1)

      mask = (mask_t) -1;

    else {

      mask_t ma = mask_for (a);

      mask_t mb = mask_for (b);

      mask |= mb + (mb - ma) - (mb < ma);

    }

  }

  inline bool may_have (hb_codepoint_t g) const {

    return !!(mask & mask_for (g));

  }

  private:

  static inline mask_t mask_for (hb_codepoint_t g) {

    return ((mask_t) 1) << ((g >> shift) & (mask_bits - 1));

  }

  mask_t mask;

};

template <typename head_t, typename tail_t>

struct hb_set_digest_combiner_t

{

  ASSERT_POD ();

  inline void init (void) {

    head.init ();

    tail.init ();

  }

  inline void add (hb_codepoint_t g) {

    head.add (g);

    tail.add (g);

  }

  inline void add_range (hb_codepoint_t a, hb_codepoint_t b) {

    head.add_range (a, b);

    tail.add_range (a, b);

  }

  inline bool may_have (hb_codepoint_t g) const {

    return head.may_have (g) && tail.may_have (g);

  }

  private:

  head_t head;

  tail_t tail;

};

/*

 * hb_set_digest_t

 *

 * This is a combination of digests that performs "best".

 * There is not much science to this: it's a result of intuition

 * and testing.

 */

typedef hb_set_digest_combiner_t

<

  hb_set_digest_lowest_bits_t<unsigned long, 4>,

  hb_set_digest_combiner_t

  <

    hb_set_digest_lowest_bits_t<unsigned long, 0>,

    hb_set_digest_lowest_bits_t<unsigned long, 9>

  >

> hb_set_digest_t;

/*

 * hb_set_t

 */

/* TODO Make this faster and memmory efficient. */

struct hb_set_t

{

  friend struct hb_frozen_set_t;

  hb_object_header_t header;

  ASSERT_POD ();

  bool in_error;

  inline void init (void) {

    hb_object_init (this);

    clear ();

  }

  inline void fini (void) {

  }

  inline void clear (void) {

    if (unlikely (hb_object_is_inert (this)))

      return;

    in_error = false;

    memset (elts, 0, sizeof elts);

  }

  inline bool is_empty (void) const {

    for (unsigned int i = 0; i < ARRAY_LENGTH (elts); i++)

      if (elts[i])

        return false;

    return true;

  }

  inline void add (hb_codepoint_t g)

  {

    if (unlikely (in_error)) return;

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

    if (unlikely (g > MAX_G)) return;

    elt (g) |= mask (g);

  }

  inline void add_range (hb_codepoint_t a, hb_codepoint_t b)

  {

    if (unlikely (in_error)) return;

    /* TODO Speedup */

    for (unsigned int i = a; i < b + 1; i++)

      add (i);

  }

  inline void del (hb_codepoint_t g)

  {

    if (unlikely (in_error)) return;

    if (unlikely (g > MAX_G)) return;

    elt (g) &= ~mask (g);

  }

  inline void del_range (hb_codepoint_t a, hb_codepoint_t b)

  {

    if (unlikely (in_error)) return;

    /* TODO Speedup */

    for (unsigned int i = a; i < b + 1; i++)

      del (i);

  }

  inline bool has (hb_codepoint_t g) const

  {

    if (unlikely (g > MAX_G)) return false;

    return !!(elt (g) & mask (g));

  }

  inline bool intersects (hb_codepoint_t first,

			  hb_codepoint_t last) const

  {

    if (unlikely (first > MAX_G)) return false;

    if (unlikely (last  > MAX_G)) last = MAX_G;

    unsigned int end = last + 1;

    for (hb_codepoint_t i = first; i < end; i++)

      if (has (i))

        return true;

    return false;

  }

  inline bool is_equal (const hb_set_t *other) const

  {

    for (unsigned int i = 0; i < ELTS; i++)

      if (elts[i] != other->elts[i])

        return false;

    return true;

  }

  inline void set (const hb_set_t *other)

  {

    if (unlikely (in_error)) return;

    for (unsigned int i = 0; i < ELTS; i++)

      elts[i] = other->elts[i];

  }

  inline void union_ (const hb_set_t *other)

  {

    if (unlikely (in_error)) return;

    for (unsigned int i = 0; i < ELTS; i++)

      elts[i] |= other->elts[i];

  }

  inline void intersect (const hb_set_t *other)

  {

    if (unlikely (in_error)) return;

    for (unsigned int i = 0; i < ELTS; i++)

      elts[i] &= other->elts[i];

  }

  inline void subtract (const hb_set_t *other)

  {

    if (unlikely (in_error)) return;

    for (unsigned int i = 0; i < ELTS; i++)

      elts[i] &= ~other->elts[i];

  }

  inline void symmetric_difference (const hb_set_t *other)

  {

    if (unlikely (in_error)) return;

    for (unsigned int i = 0; i < ELTS; i++)

      elts[i] ^= other->elts[i];

  }

  inline void invert (void)

  {

    if (unlikely (in_error)) return;

    for (unsigned int i = 0; i < ELTS; i++)

      elts[i] = ~elts[i];

  }

  inline bool next (hb_codepoint_t *codepoint) const

  {

    if (unlikely (*codepoint == INVALID)) {

      hb_codepoint_t i = get_min ();

      if (i != INVALID) {

        *codepoint = i;

	return true;

      } else {

	*codepoint = INVALID;

        return false;

      }

    }

    for (hb_codepoint_t i = *codepoint + 1; i < MAX_G + 1; i++)

      if (has (i)) {

        *codepoint = i;

	return true;

      }

    *codepoint = INVALID;

    return false;

  }

  inline bool next_range (hb_codepoint_t *first, hb_codepoint_t *last) const

  {

    hb_codepoint_t i;

    i = *last;

    if (!next (&i))

    {

      *last = *first = INVALID;

      return false;

    }

    *last = *first = i;

    while (next (&i) && i == *last + 1)

      (*last)++;

    return true;

  }

  inline unsigned int get_population (void) const

  {

    unsigned int count = 0;

    for (unsigned int i = 0; i < ELTS; i++)

      count += _hb_popcount32 (elts[i]);

    return count;

  }

  inline hb_codepoint_t get_min (void) const

  {

    for (unsigned int i = 0; i < ELTS; i++)

      if (elts[i])

	for (unsigned int j = 0; j < BITS; j++)

	  if (elts[i] & (1u << j))

	    return i * BITS + j;

    return INVALID;

  }

  inline hb_codepoint_t get_max (void) const

  {

    for (unsigned int i = ELTS; i; i--)

      if (elts[i - 1])

	for (unsigned int j = BITS; j; j--)

	  if (elts[i - 1] & (1u << (j - 1)))

	    return (i - 1) * BITS + (j - 1);

    return INVALID;

  }

  typedef uint32_t elt_t;

  static const unsigned int MAX_G = 65536 - 1; /* XXX Fix this... */

  static const unsigned int SHIFT = 5;

  static const unsigned int BITS = (1 << SHIFT);

  static const unsigned int MASK = BITS - 1;

  static const unsigned int ELTS = (MAX_G + 1 + (BITS - 1)) / BITS;

  static  const hb_codepoint_t INVALID = HB_SET_VALUE_INVALID;

  elt_t &elt (hb_codepoint_t g) { return elts[g >> SHIFT]; }

  elt_t const &elt (hb_codepoint_t g) const { return elts[g >> SHIFT]; }

  elt_t mask (hb_codepoint_t g) const { return elt_t (1) << (g & MASK); }

  elt_t elts[ELTS]; /* XXX 8kb */

  ASSERT_STATIC (sizeof (elt_t) * 8 == BITS);

  ASSERT_STATIC (sizeof (elt_t) * 8 * ELTS > MAX_G);

};

struct hb_frozen_set_t

{

  static const unsigned int SHIFT = hb_set_t::SHIFT;

  static const unsigned int BITS = hb_set_t::BITS;

  static const unsigned int MASK = hb_set_t::MASK;

  typedef hb_set_t::elt_t elt_t;

  inline void init (const hb_set_t &set)

  {

    start = count = 0;

    elts = NULL;

    unsigned int max = set.get_max ();

    if (max == set.INVALID)

      return;

    unsigned int min = set.get_min ();

    const elt_t &min_elt = set.elt (min);

    start = min & ~MASK;

    count = max - start + 1;

    unsigned int num_elts = (count + BITS - 1) / BITS;

    unsigned int elts_size = num_elts * sizeof (elt_t);

    elts = (elt_t *) malloc (elts_size);

    if (unlikely (!elts))

    {

      start = count = 0;

      return;

    }

    memcpy (elts, &min_elt, elts_size);

  }

  inline void fini (void)

  {

    if (elts)

      free (elts);

  }

  inline bool has (hb_codepoint_t g) const

  {

    /* hb_codepoint_t is unsigned. */

    g -= start;

    if (unlikely (g > count)) return false;

    return !!(elt (g) & mask (g));

  }

  elt_t const &elt (hb_codepoint_t g) const { return elts[g >> SHIFT]; }

  elt_t mask (hb_codepoint_t g) const { return elt_t (1) << (g & MASK); }

  private:

  hb_codepoint_t start, count;

  elt_t *elts;

};

#endif /* HB_SET_PRIVATE_HH */