1 | #pragma once |
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2 | |
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3 | #include <memory> |
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4 | |
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5 | namespace ast { |
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6 | |
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7 | class Node { |
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8 | public: |
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9 | virtual ~Node() = default; |
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10 | |
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11 | enum class ref_type { |
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12 | strong, |
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13 | weak |
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14 | }; |
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15 | |
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16 | void increment(ref_type ref) { |
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17 | switch (ref) { |
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18 | case ref_type::strong: strong_ref++; break; |
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19 | case ref_type::weak : weak_ref ++; break; |
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20 | } |
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21 | } |
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22 | |
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23 | void decrement(ref_type ref) { |
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24 | switch (ref) { |
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25 | case ref_type::strong: strong_ref--; break; |
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26 | case ref_type::weak : weak_ref --; break; |
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27 | } |
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28 | |
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29 | if(!strong_ref && !weak_ref) { |
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30 | delete this; |
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31 | } |
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32 | } |
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33 | |
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34 | template<typename node_t> |
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35 | friend auto mutate(const node_t * node); |
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36 | |
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37 | private: |
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38 | size_t strong_ref = 0; |
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39 | size_t weak_ref = 0; |
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40 | }; |
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41 | |
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42 | // Mutate a node, non-member function to avoid static type |
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43 | // problems and be able to use auto return |
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44 | template<typename node_t> |
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45 | auto mutate(const node_t * node) { |
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46 | assertf( |
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47 | node->strong_count >= 1, |
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48 | "Error: attempting to mutate a node that appears to have been linked" |
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49 | ); |
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50 | if (node->strong_count == 1) { |
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51 | return const_cast<node_t *>(node); |
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52 | } |
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53 | |
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54 | assertf( |
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55 | node->weak_count == 0, |
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56 | "Error: mutating node with weak references to it will invalided some references" |
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57 | ); |
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58 | return node->clone(); |
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59 | } |
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60 | |
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61 | // All accept routines should look as follows : |
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62 | // virtual void accept( Visitor &v ) override { |
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63 | // return v.visit(this); |
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64 | // } |
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65 | // Using the following wrapper to handle the node type |
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66 | template< typename node_t > |
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67 | auto visit_this( visitor & v, node_t * node ) { |
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68 | ptr<node_t> p; |
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69 | p.node = node; |
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70 | auto r = v.visit(p); |
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71 | p.node = nullptr; |
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72 | return r; |
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73 | } |
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74 | |
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75 | // Base class for the smart pointer types |
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76 | // should never really be used. |
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77 | template< typename node_t, enum Node::ref_type ref_t> |
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78 | class ptr_base { |
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79 | public: |
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80 | ptr_base() : node(nullptr) {} |
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81 | ptr_base( node_t * n ) : node(n) { if( !node ) node->increment(ref_t); } |
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82 | ~ptr_base() { if( node ) node->decrement(ref_t); } |
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83 | |
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84 | template< enum Node::ref_type o_ref_t > |
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85 | ptr_base( const ptr_base<node_t, o_ref_t> & o ) : node(o.node) { |
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86 | if( !node ) return; |
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87 | node->increment(ref_t); |
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88 | } |
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89 | |
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90 | template< enum Node::ref_type o_ref_t > |
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91 | ptr_base( ptr_base<node_t, o_ref_t> && o ) : node(o.node) { |
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92 | if( node ) node->increment(ref_t); |
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93 | if( node ) node->decrement(o_ref_t); |
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94 | } |
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95 | |
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96 | template< enum Node::ref_type o_ref_t > |
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97 | ptr_base & operator=( const ptr_base<node_t, o_ref_t> & o ) { |
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98 | assign(o.node); |
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99 | return *this; |
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100 | } |
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101 | |
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102 | template< enum Node::ref_type o_ref_t > |
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103 | ptr_base & operator=( ptr_base<node_t, o_ref_t> && o ) { |
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104 | if(o.node == node) return *this; |
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105 | assign(o.node); |
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106 | if( node ) node->decrement(o_ref_t); |
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107 | return *this; |
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108 | } |
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109 | |
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110 | const node_t * get() const { return node; } |
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111 | const node_t * operator->() const { return node; } |
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112 | const node_t & operator* () const { return *node; } |
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113 | operator bool() const { return node; } |
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114 | |
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115 | private: |
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116 | void assign(node_t * other ) { |
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117 | if( other ) other->increment(ref_t); |
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118 | if( node ) node ->decrement(ref_t); |
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119 | node = other; |
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120 | } |
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121 | |
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122 | protected: |
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123 | node_t * node; |
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124 | }; |
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125 | |
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126 | template< typename node_t > |
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127 | using ptr = ptr_base< node_t, Node::ref_type::strong >; |
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128 | |
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129 | template< typename node_t > |
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130 | using readonly = ptr_base< node_t, Node::ref_type::weak >; |
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131 | } |
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