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