harfbuzz/src/hb-iter.hh

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/*
* 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_ITER_HH
#define HB_ITER_HH
#include "hb.hh"
/* Unified iterator object.
*
* The goal of this template is to make the same iterator interface
* available to all types, and make it very easy and compact to use.
* Iterator objects are small, light-weight, objects that can be
* copied by value. If the collection / object being iterated on
* is writable, then the iterator points to lvalues, otherwise it
* returns rvalues.
*
* The way to declare, initialize, and use iterators, eg.:
*
* Iter<const int *> s (src);
* Iter<int *> t (dst);
* for (; s && t; s++, t++)
* *s = *t;
*/
template <typename T>
struct Iter;
#if 0
template <typename T>
struct Iter
{
Iter (const T &c);
};
#endif
template <typename T>
struct Iter<T *>
{
/* Type of items. */
typedef T Value;
/* Constructors. */
Iter (T *array_, int length_) :
array (array_), length (MAX (length_, 0)) {}
template <unsigned int length_>
Iter (T (&array_)[length_]) :
array (array_), length (length_) {}
/* Emptiness. */
explicit_operator bool () const { return length; }
/* Current item. */
T &operator * ()
{
if (unlikely (!length)) return CrapOrNull(T);
return *array;
}
T &operator -> () { return (operator *); }
/* Next. */
Iter<T *> & operator ++ ()
{
if (unlikely (!length)) return *this;
array++;
length--;
return *this;
}
/* Might return void, or a copy of pre-increment iterator. */
void operator ++ (int)
{
if (unlikely (!length)) return;
array++;
length--;
}
/* Some iterators might implement len(). */
unsigned int len () const { return length; }
/* Some iterators might implement fast-forward.
* Only implement it if it's constant-time. */
void operator += (unsigned int n)
{
n = MIN (n, length);
array += n;
length -= n;
}
/* Some iterators might implement random-access.
* Only implement it if it's constant-time. */
Iter<T *> & operator [] (unsigned int i)
{
if (unlikely (i >= length)) return CrapOrNull(T);
return array[i];
}
private:
T *array;
unsigned int length;
};
/* XXX Remove
* Just to test these compile. */
static inline void
m ()
{
const int src[10] = {};
int dst[20];
Iter<const int *> s (src);
Iter<const int *> s2 (src, 5);
Iter<int *> t (dst);
s2 = s;
for (; s && t; ++s, ++t)
{
*t = *s;
}
}
#endif /* HB_ITER_HH */