src/hb-array.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_ARRAY_HH
#define HB_ARRAY_HH

#include "hb.hh"
#include "hb-algs.hh"
#include "hb-iter.hh"
#include "hb-null.hh"


template <typename Type>
struct hb_sorted_array_t;

enum hb_not_found_t
{
  HB_NOT_FOUND_DONT_STORE,
  HB_NOT_FOUND_STORE,
  HB_NOT_FOUND_STORE_CLOSEST,
};


template <typename Type>
struct hb_array_t : hb_iter_with_fallback_t<hb_array_t<Type>, Type&>
{
  /*
   * Constructors.
   */
  hb_array_t () : arrayZ (nullptr), length (0), backwards_length (0) {}
  hb_array_t (Type *array_, unsigned int length_) : arrayZ (array_), length (length_), backwards_length (0) {}
  template <unsigned int length_>
  hb_array_t (Type (&array_)[length_]) : arrayZ (array_), length (length_), backwards_length (0) {}

  template <typename U,
	    hb_enable_if (hb_is_cr_convertible(U, Type))>
  hb_array_t (const hb_array_t<U> &o) :
    hb_iter_with_fallback_t<hb_array_t, Type&> (),
    arrayZ (o.arrayZ), length (o.length), backwards_length (o.backwards_length) {}
  template <typename U,
	    hb_enable_if (hb_is_cr_convertible(U, Type))>
  hb_array_t& operator = (const hb_array_t<U> &o)
  { arrayZ = o.arrayZ; length = o.length; backwards_length = o.backwards_length; return *this; }

  /*
   * Iterator implementation.
   */
  typedef Type& __item_t__;
  static constexpr bool is_random_access_iterator = true;
  Type& __item_at__ (unsigned i) const
  {
    if (unlikely (i >= length)) return CrapOrNull (Type);
    return arrayZ[i];
  }
  void __forward__ (unsigned n)
  {
    if (unlikely (n > length))
      n = length;
    length -= n;
    backwards_length += n;
    arrayZ += n;
  }
  void __rewind__ (unsigned n)
  {
    if (unlikely (n > backwards_length))
      n = backwards_length;
    length += n;
    backwards_length -= n;
    arrayZ -= n;
  }
  unsigned __len__ () const { return length; }
  /* Ouch. The operator== compares the contents of the array.  For range-based for loops,
   * it's best if we can just compare arrayZ, though comparing contents is still fast,
   * but also would require that Type has operator==.  As such, we optimize this operator
   * for range-based for loop and just compare arrayZ.  No need to compare length, as we
   * assume we're only compared to .end(). */
  bool operator != (const hb_array_t& o) const
  { return arrayZ != o.arrayZ; }

  /* Extra operators.
   */
  Type * operator & () const { return arrayZ; }
  operator hb_array_t<const Type> () { return hb_array_t<const Type> (arrayZ, length); }
  template <typename T> operator T * () const { return arrayZ; }

  HB_INTERNAL bool operator == (const hb_array_t &o) const;

  uint32_t hash () const {
    uint32_t current = 0;
    for (unsigned int i = 0; i < this->length; i++) {
      current = current * 31 + hb_hash (this->arrayZ[i]);
    }
    return current;
  }

  /*
   * Compare, Sort, and Search.
   */

  /* Note: our compare is NOT lexicographic; it also does NOT call Type::cmp. */
  int cmp (const hb_array_t &a) const
  {
    if (length != a.length)
      return (int) a.length - (int) length;
    return hb_memcmp (a.arrayZ, arrayZ, get_size ());
  }
  HB_INTERNAL static int cmp (const void *pa, const void *pb)
  {
    hb_array_t *a = (hb_array_t *) pa;
    hb_array_t *b = (hb_array_t *) pb;
    return b->cmp (*a);
  }

  template <typename T>
  Type *lsearch (const T &x, Type *not_found = nullptr)
  {
    unsigned i;
    return lfind (x, &i) ? &this->arrayZ[i] : not_found;
  }
  template <typename T>
  const Type *lsearch (const T &x, const Type *not_found = nullptr) const
  {
    unsigned i;
    return lfind (x, &i) ? &this->arrayZ[i] : not_found;
  }
  template <typename T>
  bool lfind (const T &x, unsigned *pos = nullptr,
	      hb_not_found_t not_found = HB_NOT_FOUND_DONT_STORE,
	      unsigned int to_store = (unsigned int) -1) const
  {
    for (unsigned i = 0; i < length; ++i)
      if (hb_equal (x, this->arrayZ[i]))
      {
	if (pos)
	  *pos = i;
	return true;
      }

    if (pos)
    {
      switch (not_found)
      {
	case HB_NOT_FOUND_DONT_STORE:
	  break;

	case HB_NOT_FOUND_STORE:
	  *pos = to_store;
	  break;

	case HB_NOT_FOUND_STORE_CLOSEST:
	  *pos = length;
	  break;
      }
    }
    return false;
  }

  hb_sorted_array_t<Type> qsort (int (*cmp_)(const void*, const void*))
  {
    if (likely (length))
      hb_qsort (arrayZ, length, this->get_item_size (), cmp_);
    return hb_sorted_array_t<Type> (*this);
  }
  hb_sorted_array_t<Type> qsort ()
  {
    if (likely (length))
      hb_qsort (arrayZ, length, this->get_item_size (), Type::cmp);
    return hb_sorted_array_t<Type> (*this);
  }
  void qsort (unsigned int start, unsigned int end)
  {
    end = hb_min (end, length);
    assert (start <= end);
    if (likely (start < end))
      hb_qsort (arrayZ + start, end - start, this->get_item_size (), Type::cmp);
  }

  /*
   * Other methods.
   */

  unsigned int get_size () const { return length * this->get_item_size (); }

  /*
   * Reverse the order of items in this array in the range [start, end).
   */
  void reverse (unsigned start = 0, unsigned end = -1)
  {
    start = hb_min (start, length);
    end = hb_min (end, length);

    if (end < start + 2)
      return;

    for (unsigned lhs = start, rhs = end - 1; lhs < rhs; lhs++, rhs--) {
      Type temp = arrayZ[rhs];
      arrayZ[rhs] = arrayZ[lhs];
      arrayZ[lhs] = temp;
    }
  }

  hb_array_t sub_array (unsigned int start_offset = 0, unsigned int *seg_count = nullptr /* IN/OUT */) const
  {
    if (!start_offset && !seg_count)
      return *this;

    unsigned int count = length;
    if (unlikely (start_offset > count))
      count = 0;
    else
      count -= start_offset;
    if (seg_count)
      count = *seg_count = hb_min (count, *seg_count);
    return hb_array_t (arrayZ + start_offset, count);
  }
  hb_array_t sub_array (unsigned int start_offset, unsigned int seg_count) const
  { return sub_array (start_offset, &seg_count); }

  hb_array_t truncate (unsigned length) const { return sub_array (0, length); }

  template <typename T,
	    unsigned P = sizeof (Type),
	    hb_enable_if (P == 1)>
  const T *as () const
  { return length < hb_min_size (T) ? &Null (T) : reinterpret_cast<const T *> (arrayZ); }

  template <typename T,
	    unsigned P = sizeof (Type),
	    hb_enable_if (P == 1)>
  bool check_range (const T *p, unsigned int size = T::static_size) const
  {
    return arrayZ <= ((const char *) p)
	&& ((const char *) p) <= arrayZ + length
	&& (unsigned int) (arrayZ + length - (const char *) p) >= size;
  }

  /* Only call if you allocated the underlying array using hb_malloc() or similar. */
  void fini ()
  { hb_free ((void *) arrayZ); arrayZ = nullptr; length = 0; }

  template <typename hb_serialize_context_t>
  hb_array_t copy (hb_serialize_context_t *c) const
  {
    TRACE_SERIALIZE (this);
    auto* out = c->start_embed (arrayZ);
    if (unlikely (!c->extend_size (out, get_size ()))) return_trace (hb_array_t ());
    for (unsigned i = 0; i < length; i++)
      out[i] = arrayZ[i]; /* TODO: add version that calls c->copy() */
    return_trace (hb_array_t (out, length));
  }

  template <typename hb_sanitize_context_t>
  bool sanitize (hb_sanitize_context_t *c) const
  { return c->check_array (arrayZ, length); }

  /*
   * Members
   */

  public:
  Type *arrayZ;
  unsigned int length;
  unsigned int backwards_length;
};
template <typename T> inline hb_array_t<T>
hb_array (T *array, unsigned int length)
{ return hb_array_t<T> (array, length); }
template <typename T, unsigned int length_> inline hb_array_t<T>
hb_array (T (&array_)[length_])
{ return hb_array_t<T> (array_); }

template <typename Type>
struct hb_sorted_array_t :
	hb_iter_t<hb_sorted_array_t<Type>, Type&>,
	hb_array_t<Type>
{
  typedef hb_iter_t<hb_sorted_array_t, Type&> iter_base_t;
  HB_ITER_USING (iter_base_t);
  static constexpr bool is_random_access_iterator = true;
  static constexpr bool is_sorted_iterator = true;

  hb_sorted_array_t () : hb_array_t<Type> () {}
  hb_sorted_array_t (Type *array_, unsigned int length_) : hb_array_t<Type> (array_, length_) {}
  template <unsigned int length_>
  hb_sorted_array_t (Type (&array_)[length_]) : hb_array_t<Type> (array_) {}

  template <typename U,
	    hb_enable_if (hb_is_cr_convertible(U, Type))>
  hb_sorted_array_t (const hb_array_t<U> &o) :
    hb_iter_t<hb_sorted_array_t, Type&> (),
    hb_array_t<Type> (o) {}
  template <typename U,
	    hb_enable_if (hb_is_cr_convertible(U, Type))>
  hb_sorted_array_t& operator = (const hb_array_t<U> &o)
  { hb_array_t<Type> (*this) = o; return *this; }

  /* Iterator implementation. */
  bool operator != (const hb_sorted_array_t& o) const
  { return this->arrayZ != o.arrayZ || this->length != o.length; }

  hb_sorted_array_t sub_array (unsigned int start_offset, unsigned int *seg_count /* IN/OUT */) const
  { return hb_sorted_array_t (((const hb_array_t<Type> *) (this))->sub_array (start_offset, seg_count)); }
  hb_sorted_array_t sub_array (unsigned int start_offset, unsigned int seg_count) const
  { return sub_array (start_offset, &seg_count); }

  hb_sorted_array_t truncate (unsigned length) const { return sub_array (0, length); }

  template <typename T>
  Type *bsearch (const T &x, Type *not_found = nullptr)
  {
    unsigned int i;
    return bfind (x, &i) ? &this->arrayZ[i] : not_found;
  }
  template <typename T>
  const Type *bsearch (const T &x, const Type *not_found = nullptr) const
  {
    unsigned int i;
    return bfind (x, &i) ? &this->arrayZ[i] : not_found;
  }
  template <typename T>
  bool bfind (const T &x, unsigned int *i = nullptr,
	      hb_not_found_t not_found = HB_NOT_FOUND_DONT_STORE,
	      unsigned int to_store = (unsigned int) -1) const
  {
    unsigned pos;

    if (bsearch_impl (x, &pos))
    {
      if (i)
	*i = pos;
      return true;
    }

    if (i)
    {
      switch (not_found)
      {
	case HB_NOT_FOUND_DONT_STORE:
	  break;

	case HB_NOT_FOUND_STORE:
	  *i = to_store;
	  break;

	case HB_NOT_FOUND_STORE_CLOSEST:
	  *i = pos;
	  break;
      }
    }
    return false;
  }
  template <typename T>
  bool bsearch_impl (const T &x, unsigned *pos) const
  {
    return hb_bsearch_impl (pos,
			    x,
			    this->arrayZ,
			    this->length,
			    sizeof (Type),
			    _hb_cmp_method<T, Type>);
  }
};
template <typename T> inline hb_sorted_array_t<T>
hb_sorted_array (T *array, unsigned int length)
{ return hb_sorted_array_t<T> (array, length); }
template <typename T, unsigned int length_> inline hb_sorted_array_t<T>
hb_sorted_array (T (&array_)[length_])
{ return hb_sorted_array_t<T> (array_); }

template <typename T>
bool hb_array_t<T>::operator == (const hb_array_t<T> &o) const
{
  if (o.length != this->length) return false;
  for (unsigned int i = 0; i < this->length; i++) {
    if (this->arrayZ[i] != o.arrayZ[i]) return false;
  }
  return true;
}

/* TODO Specialize opeator== for hb_bytes_t and hb_ubytes_t. */

template <>
inline uint32_t hb_array_t<const char>::hash () const {
  uint32_t current = 0;
  for (unsigned int i = 0; i < this->length; i++)
    current = current * 31 + (uint32_t) (this->arrayZ[i] * 2654435761u);
  return current;
}

template <>
inline uint32_t hb_array_t<const unsigned char>::hash () const {
  uint32_t current = 0;
  for (unsigned int i = 0; i < this->length; i++)
    current = current * 31 + (uint32_t) (this->arrayZ[i] * 2654435761u);
  return current;
}


typedef hb_array_t<const char> hb_bytes_t;
typedef hb_array_t<const unsigned char> hb_ubytes_t;



#endif /* HB_ARRAY_HH */