1/*
2 * Copyright © 2018 Google, Inc.
3 * Copyright © 2019 Facebook, Inc.
4 *
5 * This is part of HarfBuzz, a text shaping library.
6 *
7 * Permission is hereby granted, without written agreement and without
8 * license or royalty fees, to use, copy, modify, and distribute this
9 * software and its documentation for any purpose, provided that the
10 * above copyright notice and the following two paragraphs appear in
11 * all copies of this software.
12 *
13 * IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
14 * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
15 * ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
16 * IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
17 * DAMAGE.
18 *
19 * THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
20 * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
21 * FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS
22 * ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
23 * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
24 *
25 * Google Author(s): Behdad Esfahbod
26 * Facebook Author(s): Behdad Esfahbod
27 */
28
29#ifndef HB_ITER_HH
30#define HB_ITER_HH
31
32#include "hb.hh"
33#include "hb-algs.hh"
34#include "hb-meta.hh"
35
36
37/* Unified iterator object.
38 *
39 * The goal of this template is to make the same iterator interface
40 * available to all types, and make it very easy and compact to use.
41 * hb_iter_tator objects are small, light-weight, objects that can be
42 * copied by value. If the collection / object being iterated on
43 * is writable, then the iterator returns lvalues, otherwise it
44 * returns rvalues.
45 *
46 * TODO Document more.
47 *
48 * If iterator implementation implements operator!=, then can be
49 * used in range-based for loop. That comes free if the iterator
50 * is random-access. Otherwise, the range-based for loop incurs
51 * one traversal to find end(), which can be avoided if written
52 * as a while-style for loop, or if iterator implements a faster
53 * __end__() method.
54 * TODO When opting in for C++17, address this by changing return
55 * type of .end()?
56 */
57
58/*
59 * Base classes for iterators.
60 */
61
62/* Base class for all iterators. */
63template <typename iter_t, typename Item = typename iter_t::__item_t__>
64struct hb_iter_t
65{
66 typedef Item item_t;
67 constexpr unsigned get_item_size () const { return hb_static_size (Item); }
68 static constexpr bool is_iterator = true;
69 static constexpr bool is_random_access_iterator = false;
70 static constexpr bool is_sorted_iterator = false;
71
72 private:
73 /* https://en.wikipedia.org/wiki/Curiously_recurring_template_pattern */
74 const iter_t* thiz () const { return static_cast<const iter_t *> (this); }
75 iter_t* thiz () { return static_cast< iter_t *> (this); }
76 public:
77
78 /* TODO:
79 * Port operators below to use hb_enable_if to sniff which method implements
80 * an operator and use it, and remove hb_iter_fallback_mixin_t completely. */
81
82 /* Operators. */
83 iter_t iter () const { return *thiz(); }
84 iter_t operator + () const { return *thiz(); }
85 iter_t begin () const { return *thiz(); }
86 iter_t end () const { return thiz()->__end__ (); }
87 explicit operator bool () const { return thiz()->__more__ (); }
88 unsigned len () const { return thiz()->__len__ (); }
89 /* The following can only be enabled if item_t is reference type. Otherwise
90 * it will be returning pointer to temporary rvalue.
91 * TODO Use a wrapper return type to fix for non-reference type. */
92 template <typename T = item_t,
93 hb_enable_if (hb_is_reference (T))>
94 hb_remove_reference<item_t>* operator -> () const { return hb_addressof (**thiz()); }
95 item_t operator * () const { return thiz()->__item__ (); }
96 item_t operator * () { return thiz()->__item__ (); }
97 item_t operator [] (unsigned i) const { return thiz()->__item_at__ (i); }
98 item_t operator [] (unsigned i) { return thiz()->__item_at__ (i); }
99 iter_t& operator += (unsigned count) & { thiz()->__forward__ (count); return *thiz(); }
100 iter_t operator += (unsigned count) && { thiz()->__forward__ (count); return *thiz(); }
101 iter_t& operator ++ () & { thiz()->__next__ (); return *thiz(); }
102 iter_t operator ++ () && { thiz()->__next__ (); return *thiz(); }
103 iter_t& operator -= (unsigned count) & { thiz()->__rewind__ (count); return *thiz(); }
104 iter_t operator -= (unsigned count) && { thiz()->__rewind__ (count); return *thiz(); }
105 iter_t& operator -- () & { thiz()->__prev__ (); return *thiz(); }
106 iter_t operator -- () && { thiz()->__prev__ (); return *thiz(); }
107 iter_t operator + (unsigned count) const { auto c = thiz()->iter (); c += count; return c; }
108 friend iter_t operator + (unsigned count, const iter_t &it) { return it + count; }
109 iter_t operator ++ (int) { iter_t c (*thiz()); ++*thiz(); return c; }
110 iter_t operator - (unsigned count) const { auto c = thiz()->iter (); c -= count; return c; }
111 iter_t operator -- (int) { iter_t c (*thiz()); --*thiz(); return c; }
112 template <typename T>
113 iter_t& operator >> (T &v) & { v = **thiz(); ++*thiz(); return *thiz(); }
114 template <typename T>
115 iter_t operator >> (T &v) && { v = **thiz(); ++*thiz(); return *thiz(); }
116 template <typename T>
117 iter_t& operator << (const T v) & { **thiz() = v; ++*thiz(); return *thiz(); }
118 template <typename T>
119 iter_t operator << (const T v) && { **thiz() = v; ++*thiz(); return *thiz(); }
120
121 protected:
122 hb_iter_t () = default;
123 hb_iter_t (const hb_iter_t &o HB_UNUSED) = default;
124 hb_iter_t (hb_iter_t &&o HB_UNUSED) = default;
125 hb_iter_t& operator = (const hb_iter_t &o HB_UNUSED) = default;
126 hb_iter_t& operator = (hb_iter_t &&o HB_UNUSED) = default;
127};
128
129#define HB_ITER_USING(Name) \
130 using item_t = typename Name::item_t; \
131 using Name::begin; \
132 using Name::end; \
133 using Name::get_item_size; \
134 using Name::is_iterator; \
135 using Name::iter; \
136 using Name::operator bool; \
137 using Name::len; \
138 using Name::operator ->; \
139 using Name::operator *; \
140 using Name::operator []; \
141 using Name::operator +=; \
142 using Name::operator ++; \
143 using Name::operator -=; \
144 using Name::operator --; \
145 using Name::operator +; \
146 using Name::operator -; \
147 using Name::operator >>; \
148 using Name::operator <<; \
149 static_assert (true, "")
150
151/* Returns iterator / item type of a type. */
152template <typename Iterable>
153using hb_iter_type = decltype (hb_deref (hb_declval (Iterable)).iter ());
154template <typename Iterable>
155using hb_item_type = decltype (*hb_deref (hb_declval (Iterable)).iter ());
156
157
158template <typename> struct hb_array_t;
159template <typename> struct hb_sorted_array_t;
160
161struct
162{
163 template <typename T> hb_iter_type<T>
164 operator () (T&& c) const
165 { return hb_deref (hb_forward<T> (c)).iter (); }
166
167 /* Specialization for C arrays. */
168
169 template <typename Type> inline hb_array_t<Type>
170 operator () (Type *array, unsigned int length) const
171 { return hb_array_t<Type> (array, length); }
172
173 template <typename Type, unsigned int length> hb_array_t<Type>
174 operator () (Type (&array)[length]) const
175 { return hb_array_t<Type> (array, length); }
176
177}
178HB_FUNCOBJ (hb_iter);
179struct
180{
181 template <typename T> unsigned
182 operator () (T&& c) const
183 { return c.len (); }
184
185}
186HB_FUNCOBJ (hb_len);
187
188/* Mixin to fill in what the subclass doesn't provide. */
189template <typename iter_t, typename item_t = typename iter_t::__item_t__>
190struct hb_iter_fallback_mixin_t
191{
192 private:
193 /* https://en.wikipedia.org/wiki/Curiously_recurring_template_pattern */
194 const iter_t* thiz () const { return static_cast<const iter_t *> (this); }
195 iter_t* thiz () { return static_cast< iter_t *> (this); }
196 public:
197
198 /* Access: Implement __item__(), or __item_at__() if random-access. */
199 item_t __item__ () const { return (*thiz())[0]; }
200 item_t __item_at__ (unsigned i) const { return *(*thiz() + i); }
201
202 /* Termination: Implement __more__(), or __len__() if random-access. */
203 bool __more__ () const { return bool (thiz()->len ()); }
204 unsigned __len__ () const
205 { iter_t c (*thiz()); unsigned l = 0; while (c) { c++; l++; } return l; }
206
207 /* Advancing: Implement __next__(), or __forward__() if random-access. */
208 void __next__ () { *thiz() += 1; }
209 void __forward__ (unsigned n) { while (*thiz() && n--) ++*thiz(); }
210
211 /* Rewinding: Implement __prev__() or __rewind__() if bidirectional. */
212 void __prev__ () { *thiz() -= 1; }
213 void __rewind__ (unsigned n) { while (*thiz() && n--) --*thiz(); }
214
215 /* Range-based for: Implement __end__() if can be done faster,
216 * and operator!=. */
217 iter_t __end__ () const
218 {
219 if (thiz()->is_random_access_iterator)
220 return *thiz() + thiz()->len ();
221 /* Above expression loops twice. Following loops once. */
222 auto it = *thiz();
223 while (it) ++it;
224 return it;
225 }
226
227 protected:
228 hb_iter_fallback_mixin_t () = default;
229 hb_iter_fallback_mixin_t (const hb_iter_fallback_mixin_t &o HB_UNUSED) = default;
230 hb_iter_fallback_mixin_t (hb_iter_fallback_mixin_t &&o HB_UNUSED) = default;
231 hb_iter_fallback_mixin_t& operator = (const hb_iter_fallback_mixin_t &o HB_UNUSED) = default;
232 hb_iter_fallback_mixin_t& operator = (hb_iter_fallback_mixin_t &&o HB_UNUSED) = default;
233};
234
235template <typename iter_t, typename item_t = typename iter_t::__item_t__>
236struct hb_iter_with_fallback_t :
237 hb_iter_t<iter_t, item_t>,
238 hb_iter_fallback_mixin_t<iter_t, item_t>
239{
240 protected:
241 hb_iter_with_fallback_t () = default;
242 hb_iter_with_fallback_t (const hb_iter_with_fallback_t &o HB_UNUSED) = default;
243 hb_iter_with_fallback_t (hb_iter_with_fallback_t &&o HB_UNUSED) = default;
244 hb_iter_with_fallback_t& operator = (const hb_iter_with_fallback_t &o HB_UNUSED) = default;
245 hb_iter_with_fallback_t& operator = (hb_iter_with_fallback_t &&o HB_UNUSED) = default;
246};
247
248/*
249 * Meta-programming predicates.
250 */
251
252/* hb_is_iterator() / hb_is_iterator_of() */
253
254template<typename Iter, typename Item>
255struct hb_is_iterator_of
256{
257 template <typename Item2 = Item>
258 static hb_true_type impl (hb_priority<2>, hb_iter_t<Iter, hb_type_identity<Item2>> *);
259 static hb_false_type impl (hb_priority<0>, const void *);
260
261 public:
262 static constexpr bool value = decltype (impl (hb_prioritize, hb_declval (Iter*)))::value;
263};
264#define hb_is_iterator_of(Iter, Item) hb_is_iterator_of<Iter, Item>::value
265#define hb_is_iterator(Iter) hb_is_iterator_of (Iter, typename Iter::item_t)
266
267/* hb_is_iterable() */
268
269template <typename T>
270struct hb_is_iterable
271{
272 private:
273
274 template <typename U>
275 static auto impl (hb_priority<1>) -> decltype (hb_declval (U).iter (), hb_true_type ());
276
277 template <typename>
278 static hb_false_type impl (hb_priority<0>);
279
280 public:
281 static constexpr bool value = decltype (impl<T> (hb_prioritize))::value;
282};
283#define hb_is_iterable(Iterable) hb_is_iterable<Iterable>::value
284
285/* hb_is_source_of() / hb_is_sink_of() */
286
287template<typename Iter, typename Item>
288struct hb_is_source_of
289{
290 private:
291 template <typename Iter2 = Iter,
292 hb_enable_if (hb_is_convertible (typename Iter2::item_t, hb_add_lvalue_reference<hb_add_const<Item>>))>
293 static hb_true_type impl (hb_priority<2>);
294 template <typename Iter2 = Iter>
295 static auto impl (hb_priority<1>) -> decltype (hb_declval (Iter2) >> hb_declval (Item &), hb_true_type ());
296 static hb_false_type impl (hb_priority<0>);
297
298 public:
299 static constexpr bool value = decltype (impl (hb_prioritize))::value;
300};
301#define hb_is_source_of(Iter, Item) hb_is_source_of<Iter, Item>::value
302
303template<typename Iter, typename Item>
304struct hb_is_sink_of
305{
306 private:
307 template <typename Iter2 = Iter,
308 hb_enable_if (hb_is_convertible (typename Iter2::item_t, hb_add_lvalue_reference<Item>))>
309 static hb_true_type impl (hb_priority<2>);
310 template <typename Iter2 = Iter>
311 static auto impl (hb_priority<1>) -> decltype (hb_declval (Iter2) << hb_declval (Item), hb_true_type ());
312 static hb_false_type impl (hb_priority<0>);
313
314 public:
315 static constexpr bool value = decltype (impl (hb_prioritize))::value;
316};
317#define hb_is_sink_of(Iter, Item) hb_is_sink_of<Iter, Item>::value
318
319/* This is commonly used, so define: */
320#define hb_is_sorted_source_of(Iter, Item) \
321 (hb_is_source_of(Iter, Item) && Iter::is_sorted_iterator)
322
323
324/* Range-based 'for' for iterables. */
325
326template <typename Iterable,
327 hb_requires (hb_is_iterable (Iterable))>
328static inline auto begin (Iterable&& iterable) HB_AUTO_RETURN (hb_iter (iterable).begin ())
329
330template <typename Iterable,
331 hb_requires (hb_is_iterable (Iterable))>
332static inline auto end (Iterable&& iterable) HB_AUTO_RETURN (hb_iter (iterable).end ())
333
334/* begin()/end() are NOT looked up non-ADL. So each namespace must declare them.
335 * Do it for namespace OT. */
336namespace OT {
337
338template <typename Iterable,
339 hb_requires (hb_is_iterable (Iterable))>
340static inline auto begin (Iterable&& iterable) HB_AUTO_RETURN (hb_iter (iterable).begin ())
341
342template <typename Iterable,
343 hb_requires (hb_is_iterable (Iterable))>
344static inline auto end (Iterable&& iterable) HB_AUTO_RETURN (hb_iter (iterable).end ())
345
346}
347
348
349/*
350 * Adaptors, combiners, etc.
351 */
352
353template <typename Lhs, typename Rhs,
354 hb_requires (hb_is_iterator (Lhs))>
355static inline auto
356operator | (Lhs&& lhs, Rhs&& rhs) HB_AUTO_RETURN (hb_forward<Rhs> (rhs) (hb_forward<Lhs> (lhs)))
357
358/* hb_map(), hb_filter(), hb_reduce() */
359
360enum class hb_function_sortedness_t {
361 NOT_SORTED,
362 RETAINS_SORTING,
363 SORTED,
364};
365
366template <typename Iter, typename Proj, hb_function_sortedness_t Sorted,
367 hb_requires (hb_is_iterator (Iter))>
368struct hb_map_iter_t :
369 hb_iter_t<hb_map_iter_t<Iter, Proj, Sorted>,
370 decltype (hb_get (hb_declval (Proj), *hb_declval (Iter)))>
371{
372 hb_map_iter_t (const Iter& it, Proj f_) : it (it), f (f_) {}
373
374 typedef decltype (hb_get (hb_declval (Proj), *hb_declval (Iter))) __item_t__;
375 static constexpr bool is_random_access_iterator = Iter::is_random_access_iterator;
376 static constexpr bool is_sorted_iterator =
377 Sorted == hb_function_sortedness_t::SORTED ? true :
378 Sorted == hb_function_sortedness_t::RETAINS_SORTING ? Iter::is_sorted_iterator :
379 false;
380 __item_t__ __item__ () const { return hb_get (f.get (), *it); }
381 __item_t__ __item_at__ (unsigned i) const { return hb_get (f.get (), it[i]); }
382 bool __more__ () const { return bool (it); }
383 unsigned __len__ () const { return it.len (); }
384 void __next__ () { ++it; }
385 void __forward__ (unsigned n) { it += n; }
386 void __prev__ () { --it; }
387 void __rewind__ (unsigned n) { it -= n; }
388 hb_map_iter_t __end__ () const { return hb_map_iter_t (it.end (), f); }
389 bool operator != (const hb_map_iter_t& o) const
390 { return it != o.it; }
391
392 private:
393 Iter it;
394 hb_reference_wrapper<Proj> f;
395};
396
397template <typename Proj, hb_function_sortedness_t Sorted>
398struct hb_map_iter_factory_t
399{
400 hb_map_iter_factory_t (Proj f) : f (f) {}
401
402 template <typename Iter,
403 hb_requires (hb_is_iterator (Iter))>
404 hb_map_iter_t<Iter, Proj, Sorted>
405 operator () (Iter it)
406 { return hb_map_iter_t<Iter, Proj, Sorted> (it, f); }
407
408 private:
409 Proj f;
410};
411struct
412{
413 template <typename Proj>
414 hb_map_iter_factory_t<Proj, hb_function_sortedness_t::NOT_SORTED>
415 operator () (Proj&& f) const
416 { return hb_map_iter_factory_t<Proj, hb_function_sortedness_t::NOT_SORTED> (f); }
417}
418HB_FUNCOBJ (hb_map);
419struct
420{
421 template <typename Proj>
422 hb_map_iter_factory_t<Proj, hb_function_sortedness_t::RETAINS_SORTING>
423 operator () (Proj&& f) const
424 { return hb_map_iter_factory_t<Proj, hb_function_sortedness_t::RETAINS_SORTING> (f); }
425}
426HB_FUNCOBJ (hb_map_retains_sorting);
427struct
428{
429 template <typename Proj>
430 hb_map_iter_factory_t<Proj, hb_function_sortedness_t::SORTED>
431 operator () (Proj&& f) const
432 { return hb_map_iter_factory_t<Proj, hb_function_sortedness_t::SORTED> (f); }
433}
434HB_FUNCOBJ (hb_map_sorted);
435
436template <typename Iter, typename Pred, typename Proj,
437 hb_requires (hb_is_iterator (Iter))>
438struct hb_filter_iter_t :
439 hb_iter_with_fallback_t<hb_filter_iter_t<Iter, Pred, Proj>,
440 typename Iter::item_t>
441{
442 hb_filter_iter_t (const Iter& it_, Pred p_, Proj f_) : it (it_), p (p_), f (f_)
443 { while (it && !hb_has (p.get (), hb_get (f.get (), *it))) ++it; }
444
445 typedef typename Iter::item_t __item_t__;
446 static constexpr bool is_sorted_iterator = Iter::is_sorted_iterator;
447 __item_t__ __item__ () const { return *it; }
448 bool __more__ () const { return bool (it); }
449 void __next__ () { do ++it; while (it && !hb_has (p.get (), hb_get (f.get (), *it))); }
450 void __prev__ () { do --it; while (it && !hb_has (p.get (), hb_get (f.get (), *it))); }
451 hb_filter_iter_t __end__ () const { return hb_filter_iter_t (it.end (), p, f); }
452 bool operator != (const hb_filter_iter_t& o) const
453 { return it != o.it; }
454
455 private:
456 Iter it;
457 hb_reference_wrapper<Pred> p;
458 hb_reference_wrapper<Proj> f;
459};
460template <typename Pred, typename Proj>
461struct hb_filter_iter_factory_t
462{
463 hb_filter_iter_factory_t (Pred p, Proj f) : p (p), f (f) {}
464
465 template <typename Iter,
466 hb_requires (hb_is_iterator (Iter))>
467 hb_filter_iter_t<Iter, Pred, Proj>
468 operator () (Iter it)
469 { return hb_filter_iter_t<Iter, Pred, Proj> (it, p, f); }
470
471 private:
472 Pred p;
473 Proj f;
474};
475struct
476{
477 template <typename Pred = decltype ((hb_identity)),
478 typename Proj = decltype ((hb_identity))>
479 hb_filter_iter_factory_t<Pred, Proj>
480 operator () (Pred&& p = hb_identity, Proj&& f = hb_identity) const
481 { return hb_filter_iter_factory_t<Pred, Proj> (p, f); }
482}
483HB_FUNCOBJ (hb_filter);
484
485template <typename Redu, typename InitT>
486struct hb_reduce_t
487{
488 hb_reduce_t (Redu r, InitT init_value) : r (r), init_value (init_value) {}
489
490 template <typename Iter,
491 hb_requires (hb_is_iterator (Iter)),
492 typename AccuT = hb_decay<decltype (hb_declval (Redu) (hb_declval (InitT), hb_declval (typename Iter::item_t)))>>
493 AccuT
494 operator () (Iter it)
495 {
496 AccuT value = init_value;
497 for (; it; ++it)
498 value = r (value, *it);
499 return value;
500 }
501
502 private:
503 Redu r;
504 InitT init_value;
505};
506struct
507{
508 template <typename Redu, typename InitT>
509 hb_reduce_t<Redu, InitT>
510 operator () (Redu&& r, InitT init_value) const
511 { return hb_reduce_t<Redu, InitT> (r, init_value); }
512}
513HB_FUNCOBJ (hb_reduce);
514
515
516/* hb_zip() */
517
518template <typename A, typename B>
519struct hb_zip_iter_t :
520 hb_iter_t<hb_zip_iter_t<A, B>,
521 hb_pair_t<typename A::item_t, typename B::item_t>>
522{
523 hb_zip_iter_t () {}
524 hb_zip_iter_t (const A& a, const B& b) : a (a), b (b) {}
525
526 typedef hb_pair_t<typename A::item_t, typename B::item_t> __item_t__;
527 static constexpr bool is_random_access_iterator =
528 A::is_random_access_iterator &&
529 B::is_random_access_iterator;
530 /* Note. The following categorization is only valid if A is strictly sorted,
531 * ie. does NOT have duplicates. Previously I tried to categorize sortedness
532 * more granularly, see commits:
533 *
534 * 513762849a683914fc266a17ddf38f133cccf072
535 * 4d3cf2adb669c345cc43832d11689271995e160a
536 *
537 * However, that was not enough, since hb_sorted_array_t, hb_sorted_vector_t,
538 * SortedArrayOf, etc all needed to be updated to add more variants. At that
539 * point I saw it not worth the effort, and instead we now deem all sorted
540 * collections as essentially strictly-sorted for the purposes of zip.
541 *
542 * The above assumption is not as bad as it sounds. Our "sorted" comes with
543 * no guarantees. It's just a contract, put in place to help you remember,
544 * and think about, whether an iterator you receive is expected to be
545 * sorted or not. As such, it's not perfect by definition, and should not
546 * be treated so. The inaccuracy here just errs in the direction of being
547 * more permissive, so your code compiles instead of erring on the side of
548 * marking your zipped iterator unsorted in which case your code won't
549 * compile.
550 *
551 * This semantical limitation does NOT affect logic in any other place I
552 * know of as of this writing.
553 */
554 static constexpr bool is_sorted_iterator = A::is_sorted_iterator;
555
556 __item_t__ __item__ () const { return __item_t__ (*a, *b); }
557 __item_t__ __item_at__ (unsigned i) const { return __item_t__ (a[i], b[i]); }
558 bool __more__ () const { return bool (a) && bool (b); }
559 unsigned __len__ () const { return hb_min (a.len (), b.len ()); }
560 void __next__ () { ++a; ++b; }
561 void __forward__ (unsigned n) { a += n; b += n; }
562 void __prev__ () { --a; --b; }
563 void __rewind__ (unsigned n) { a -= n; b -= n; }
564 hb_zip_iter_t __end__ () const { return hb_zip_iter_t (a.end (), b.end ()); }
565 /* Note, we should stop if ANY of the iters reaches end. As such two compare
566 * unequal if both items are unequal, NOT if either is unequal. */
567 bool operator != (const hb_zip_iter_t& o) const
568 { return a != o.a && b != o.b; }
569
570 private:
571 A a;
572 B b;
573};
574struct
575{ HB_PARTIALIZE(2);
576 template <typename A, typename B,
577 hb_requires (hb_is_iterable (A) && hb_is_iterable (B))>
578 hb_zip_iter_t<hb_iter_type<A>, hb_iter_type<B>>
579 operator () (A&& a, B&& b) const
580 { return hb_zip_iter_t<hb_iter_type<A>, hb_iter_type<B>> (hb_iter (a), hb_iter (b)); }
581}
582HB_FUNCOBJ (hb_zip);
583
584/* hb_apply() */
585
586template <typename Appl>
587struct hb_apply_t
588{
589 hb_apply_t (Appl a) : a (a) {}
590
591 template <typename Iter,
592 hb_requires (hb_is_iterator (Iter))>
593 void operator () (Iter it)
594 {
595 for (; it; ++it)
596 (void) hb_invoke (a, *it);
597 }
598
599 private:
600 Appl a;
601};
602struct
603{
604 template <typename Appl> hb_apply_t<Appl>
605 operator () (Appl&& a) const
606 { return hb_apply_t<Appl> (a); }
607
608 template <typename Appl> hb_apply_t<Appl&>
609 operator () (Appl *a) const
610 { return hb_apply_t<Appl&> (*a); }
611}
612HB_FUNCOBJ (hb_apply);
613
614/* hb_range()/hb_iota()/hb_repeat() */
615
616template <typename T, typename S>
617struct hb_range_iter_t :
618 hb_iter_t<hb_range_iter_t<T, S>, T>
619{
620 hb_range_iter_t (T start, T end_, S step) : v (start), end_ (end_for (start, end_, step)), step (step) {}
621
622 typedef T __item_t__;
623 static constexpr bool is_random_access_iterator = true;
624 static constexpr bool is_sorted_iterator = true;
625 __item_t__ __item__ () const { return hb_ridentity (v); }
626 __item_t__ __item_at__ (unsigned j) const { return v + j * step; }
627 bool __more__ () const { return v != end_; }
628 unsigned __len__ () const { return !step ? UINT_MAX : (end_ - v) / step; }
629 void __next__ () { v += step; }
630 void __forward__ (unsigned n) { v += n * step; }
631 void __prev__ () { v -= step; }
632 void __rewind__ (unsigned n) { v -= n * step; }
633 hb_range_iter_t __end__ () const { return hb_range_iter_t (end_, end_, step); }
634 bool operator != (const hb_range_iter_t& o) const
635 { return v != o.v; }
636
637 private:
638 static inline T end_for (T start, T end_, S step)
639 {
640 if (!step)
641 return end_;
642 auto res = (end_ - start) % step;
643 if (!res)
644 return end_;
645 end_ += step - res;
646 return end_;
647 }
648
649 private:
650 T v;
651 T end_;
652 S step;
653};
654struct
655{
656 template <typename T = unsigned> hb_range_iter_t<T, unsigned>
657 operator () (T end = (unsigned) -1) const
658 { return hb_range_iter_t<T, unsigned> (0, end, 1u); }
659
660 template <typename T, typename S = unsigned> hb_range_iter_t<T, S>
661 operator () (T start, T end, S step = 1u) const
662 { return hb_range_iter_t<T, S> (start, end, step); }
663}
664HB_FUNCOBJ (hb_range);
665
666template <typename T, typename S>
667struct hb_iota_iter_t :
668 hb_iter_with_fallback_t<hb_iota_iter_t<T, S>, T>
669{
670 hb_iota_iter_t (T start, S step) : v (start), step (step) {}
671
672 private:
673
674 template <typename S2 = S>
675 auto
676 inc (hb_type_identity<S2> s, hb_priority<1>)
677 -> hb_void_t<decltype (hb_invoke (hb_forward<S2> (s), hb_declval<T&> ()))>
678 { v = hb_invoke (hb_forward<S2> (s), v); }
679
680 void
681 inc (S s, hb_priority<0>)
682 { v += s; }
683
684 public:
685
686 typedef T __item_t__;
687 static constexpr bool is_random_access_iterator = true;
688 static constexpr bool is_sorted_iterator = true;
689 __item_t__ __item__ () const { return hb_ridentity (v); }
690 bool __more__ () const { return true; }
691 unsigned __len__ () const { return UINT_MAX; }
692 void __next__ () { inc (step, hb_prioritize); }
693 void __prev__ () { v -= step; }
694 hb_iota_iter_t __end__ () const { return *this; }
695 bool operator != (const hb_iota_iter_t& o) const { return true; }
696
697 private:
698 T v;
699 S step;
700};
701struct
702{
703 template <typename T = unsigned, typename S = unsigned> hb_iota_iter_t<T, S>
704 operator () (T start = 0u, S step = 1u) const
705 { return hb_iota_iter_t<T, S> (start, step); }
706}
707HB_FUNCOBJ (hb_iota);
708
709template <typename T>
710struct hb_repeat_iter_t :
711 hb_iter_t<hb_repeat_iter_t<T>, T>
712{
713 hb_repeat_iter_t (T value) : v (value) {}
714
715 typedef T __item_t__;
716 static constexpr bool is_random_access_iterator = true;
717 static constexpr bool is_sorted_iterator = true;
718 __item_t__ __item__ () const { return v; }
719 __item_t__ __item_at__ (unsigned j) const { return v; }
720 bool __more__ () const { return true; }
721 unsigned __len__ () const { return UINT_MAX; }
722 void __next__ () {}
723 void __forward__ (unsigned) {}
724 void __prev__ () {}
725 void __rewind__ (unsigned) {}
726 hb_repeat_iter_t __end__ () const { return *this; }
727 bool operator != (const hb_repeat_iter_t& o) const { return true; }
728
729 private:
730 T v;
731};
732struct
733{
734 template <typename T> hb_repeat_iter_t<T>
735 operator () (T value) const
736 { return hb_repeat_iter_t<T> (value); }
737}
738HB_FUNCOBJ (hb_repeat);
739
740/* hb_enumerate()/hb_take() */
741
742struct
743{
744 template <typename Iterable,
745 typename Index = unsigned,
746 hb_requires (hb_is_iterable (Iterable))>
747 auto operator () (Iterable&& it, Index start = 0u) const HB_AUTO_RETURN
748 ( hb_zip (hb_iota (start), it) )
749}
750HB_FUNCOBJ (hb_enumerate);
751
752struct
753{ HB_PARTIALIZE(2);
754 template <typename Iterable,
755 hb_requires (hb_is_iterable (Iterable))>
756 auto operator () (Iterable&& it, unsigned count) const HB_AUTO_RETURN
757 ( hb_zip (hb_range (count), it) | hb_map (hb_second) )
758
759 /* Specialization arrays. */
760
761 template <typename Type> inline hb_array_t<Type>
762 operator () (hb_array_t<Type> array, unsigned count) const
763 { return array.sub_array (0, count); }
764
765 template <typename Type> inline hb_sorted_array_t<Type>
766 operator () (hb_sorted_array_t<Type> array, unsigned count) const
767 { return array.sub_array (0, count); }
768}
769HB_FUNCOBJ (hb_take);
770
771struct
772{ HB_PARTIALIZE(2);
773 template <typename Iter,
774 hb_requires (hb_is_iterator (Iter))>
775 auto operator () (Iter it, unsigned count) const HB_AUTO_RETURN
776 (
777 + hb_iota (it, hb_add (count))
778 | hb_map (hb_take (count))
779 | hb_take ((hb_len (it) + count - 1) / count)
780 )
781}
782HB_FUNCOBJ (hb_chop);
783
784/* hb_sink() */
785
786template <typename Sink>
787struct hb_sink_t
788{
789 hb_sink_t (Sink s) : s (s) {}
790
791 template <typename Iter,
792 hb_requires (hb_is_iterator (Iter))>
793 void operator () (Iter it)
794 {
795 for (; it; ++it)
796 s << *it;
797 }
798
799 private:
800 Sink s;
801};
802struct
803{
804 template <typename Sink> hb_sink_t<Sink>
805 operator () (Sink&& s) const
806 { return hb_sink_t<Sink> (s); }
807
808 template <typename Sink> hb_sink_t<Sink&>
809 operator () (Sink *s) const
810 { return hb_sink_t<Sink&> (*s); }
811}
812HB_FUNCOBJ (hb_sink);
813
814/* hb-drain: hb_sink to void / blackhole / /dev/null. */
815
816struct
817{
818 template <typename Iter,
819 hb_requires (hb_is_iterator (Iter))>
820 void operator () (Iter it) const
821 {
822 for (; it; ++it)
823 (void) *it;
824 }
825}
826HB_FUNCOBJ (hb_drain);
827
828/* hb_unzip(): unzip and sink to two sinks. */
829
830template <typename Sink1, typename Sink2>
831struct hb_unzip_t
832{
833 hb_unzip_t (Sink1 s1, Sink2 s2) : s1 (s1), s2 (s2) {}
834
835 template <typename Iter,
836 hb_requires (hb_is_iterator (Iter))>
837 void operator () (Iter it)
838 {
839 for (; it; ++it)
840 {
841 const auto &v = *it;
842 s1 << v.first;
843 s2 << v.second;
844 }
845 }
846
847 private:
848 Sink1 s1;
849 Sink2 s2;
850};
851struct
852{
853 template <typename Sink1, typename Sink2> hb_unzip_t<Sink1, Sink2>
854 operator () (Sink1&& s1, Sink2&& s2) const
855 { return hb_unzip_t<Sink1, Sink2> (s1, s2); }
856
857 template <typename Sink1, typename Sink2> hb_unzip_t<Sink1&, Sink2&>
858 operator () (Sink1 *s1, Sink2 *s2) const
859 { return hb_unzip_t<Sink1&, Sink2&> (*s1, *s2); }
860}
861HB_FUNCOBJ (hb_unzip);
862
863
864/* hb-all, hb-any, hb-none. */
865
866struct
867{
868 template <typename Iterable,
869 typename Pred = decltype ((hb_identity)),
870 typename Proj = decltype ((hb_identity)),
871 hb_requires (hb_is_iterable (Iterable))>
872 bool operator () (Iterable&& c,
873 Pred&& p = hb_identity,
874 Proj&& f = hb_identity) const
875 {
876 for (auto it = hb_iter (c); it; ++it)
877 if (!hb_match (hb_forward<Pred> (p), hb_get (hb_forward<Proj> (f), *it)))
878 return false;
879 return true;
880 }
881}
882HB_FUNCOBJ (hb_all);
883struct
884{
885 template <typename Iterable,
886 typename Pred = decltype ((hb_identity)),
887 typename Proj = decltype ((hb_identity)),
888 hb_requires (hb_is_iterable (Iterable))>
889 bool operator () (Iterable&& c,
890 Pred&& p = hb_identity,
891 Proj&& f = hb_identity) const
892 {
893 for (auto it = hb_iter (c); it; ++it)
894 if (hb_match (hb_forward<Pred> (p), hb_get (hb_forward<Proj> (f), *it)))
895 return true;
896 return false;
897 }
898}
899HB_FUNCOBJ (hb_any);
900struct
901{
902 template <typename Iterable,
903 typename Pred = decltype ((hb_identity)),
904 typename Proj = decltype ((hb_identity)),
905 hb_requires (hb_is_iterable (Iterable))>
906 bool operator () (Iterable&& c,
907 Pred&& p = hb_identity,
908 Proj&& f = hb_identity) const
909 {
910 for (auto it = hb_iter (c); it; ++it)
911 if (hb_match (hb_forward<Pred> (p), hb_get (hb_forward<Proj> (f), *it)))
912 return false;
913 return true;
914 }
915}
916HB_FUNCOBJ (hb_none);
917
918/*
919 * Algorithms operating on iterators.
920 */
921
922template <typename C, typename V,
923 hb_requires (hb_is_iterable (C))>
924inline void
925hb_fill (C& c, const V &v)
926{
927 for (auto i = hb_iter (c); i; i++)
928 *i = v;
929}
930
931template <typename S, typename D>
932inline void
933hb_copy (S&& is, D&& id)
934{
935 hb_iter (is) | hb_sink (id);
936}
937
938
939#endif /* HB_ITER_HH */
940