1 /*
2 * Copyright © 2018 Google, Inc.
3 *
4 * This is part of HarfBuzz, a text shaping library.
5 *
6 * Permission is hereby granted, without written agreement and without
7 * license or royalty fees, to use, copy, modify, and distribute this
8 * software and its documentation for any purpose, provided that the
9 * above copyright notice and the following two paragraphs appear in
10 * all copies of this software.
11 *
12 * IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
13 * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
14 * ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
15 * IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
16 * DAMAGE.
17 *
18 * THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
19 * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
20 * FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS
21 * ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
22 * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
23 *
24 * Google Author(s): Behdad Esfahbod
25 */
26
27 #ifndef HB_ITER_HH
28 #define HB_ITER_HH
29
30 #include "hb.hh"
31 #include "hb-null.hh"
32
33
34 /* Unified iterator object.
35 *
36 * The goal of this template is to make the same iterator interface
37 * available to all types, and make it very easy and compact to use.
38 * hb_iter_tator objects are small, light-weight, objects that can be
39 * copied by value. If the collection / object being iterated on
40 * is writable, then the iterator returns lvalues, otherwise it
41 * returns rvalues.
42 */
43
44 /* Base class for all iterators. */
45 template <typename Iter, typename Item = typename Iter::__item_type__>
46 struct hb_iter_t
47 {
48 typedef Iter iter_t;
49 typedef iter_t const_iter_t;
50 typedef Item item_t;
51 static constexpr unsigned item_size = hb_static_size (Item);
52
53 private:
54 /* https://en.wikipedia.org/wiki/Curiously_recurring_template_pattern */
55 const iter_t* thiz () const { return static_cast<const iter_t *> (this); }
56 iter_t* thiz () { return static_cast< iter_t *> (this); }
57 public:
58
59 /* Operators. */
60 operator iter_t () { return iter(); }
61 explicit_operator bool () const { return more (); }
62 item_t& operator * () const { return item (); }
63 item_t& operator [] (signed i) const { return item_at ((unsigned) i); }
64 iter_t& operator += (unsigned count) { forward (count); return *thiz(); }
65 iter_t& operator ++ () { next (); return *thiz(); }
66 iter_t& operator -= (unsigned count) { rewind (count); return *thiz(); }
67 iter_t& operator -- () { prev (); return *thiz(); }
68 iter_t operator + (unsigned count) { iter_t c (*thiz()); c += count; return c; }
69 iter_t operator ++ (int) { iter_t c (*thiz()); ++*thiz(); return c; }
70 iter_t operator - (unsigned count) { iter_t c (*thiz()); c -= count; return c; }
71 iter_t operator -- (int) { iter_t c (*thiz()); --*thiz(); return c; }
72
73 /* Methods. */
74 iter_t iter () const { return *thiz(); }
75 const_iter_t const_iter () const { return iter (); }
76 item_t& item () const { return thiz()->__item__ (); }
77 item_t& item_at (unsigned i) const { return thiz()->__item_at__ (i); }
78 bool more () const { return thiz()->__more__ (); }
79 unsigned len () const { return thiz()->__len__ (); }
80 void next () { thiz()->__next__ (); }
81 void forward (unsigned n) { thiz()->__forward__ (n); }
82 void prev () { thiz()->__prev__ (); }
83 void rewind (unsigned n) { thiz()->__rewind__ (n); }
84 bool random_access () const { return thiz()->__random_access__ (); }
85
86 protected:
87 hb_iter_t () {}
88 hb_iter_t (const hb_iter_t &o HB_UNUSED) {}
89 void operator = (const hb_iter_t &o HB_UNUSED) {}
90 };
91
92 /* Base class for sorted iterators. Does not enforce anything.
93 * Just for class taxonomy and requirements. */
94 template <typename Iter, typename Item = typename Iter::__item_type__>
95 struct hb_sorted_iter_t : hb_iter_t<Iter, Item>
96 {
97 protected:
98 hb_sorted_iter_t () {}
99 hb_sorted_iter_t (const hb_sorted_iter_t &o) : hb_iter_t<Iter, Item> (o) {}
100 void operator = (const hb_sorted_iter_t &o HB_UNUSED) {}
101 };
102
103 /* Mixin to fill in what the subclass doesn't provide. */
104 template <typename iter_t, typename item_t = typename iter_t::__item_type__>
105 struct hb_iter_mixin_t
106 {
107 private:
108 /* https://en.wikipedia.org/wiki/Curiously_recurring_template_pattern */
109 const iter_t* thiz () const { return static_cast<const iter_t *> (this); }
110 iter_t* thiz () { return static_cast< iter_t *> (this); }
111 public:
112
113 /* Access: Implement __item__(), or __item_at__() if random-access. */
114 item_t& __item__ () const { return thiz()->item_at (0); }
115 item_t& __item_at__ (unsigned i) const { return *(thiz() + i); }
116
117 /* Termination: Implement __more__(), or __len__() if random-access. */
118 bool __more__ () const { return thiz()->__len__ (); }
119 unsigned __len__ () const
120 { iter_t c (*thiz()); unsigned l = 0; while (c) { c++; l++; }; return l; }
121
122 /* Advancing: Implement __next__(), or __forward__() if random-access. */
123 void __next__ () { thiz()->forward (1); }
124 void __forward__ (unsigned n) { while (n--) thiz()->next (); }
125
126 /* Rewinding: Implement __prev__() or __rewind__() if bidirectional. */
127 void __prev__ () { thiz()->rewind (1); }
128 void __rewind__ (unsigned n) { while (n--) thiz()->prev (); }
129
130 /* Random access: Return true if item_at(), len(), forward() are fast. */
131 bool __random_access__ () const { return false; }
132 };
133
134
135 /* Functions operating on iterators or iteratables. */
136
137 template <typename C, typename V> inline void
138 hb_fill (const C& c, const V &v)
139 {
140 for (typename C::iter_t i (c); i; i++)
141 hb_assign (*i, v);
142 }
143
144 template <typename S, typename D> inline bool
145 hb_copy (hb_iter_t<D> &id, hb_iter_t<S> &is)
146 {
147 for (; id && is; ++id, ++is)
148 *id = *is;
149 return !is;
150 }
151
152
153 #endif /* HB_ITER_HH */