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1
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2 /*
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3 * Copyright (C) Igor Sysoev
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4 */
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5
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6
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7 #include <ngx_config.h>
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8 #include <ngx_core.h>
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9
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10
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11 /*
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108
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12 * The red-black tree code is based on the algorithm described in
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13 * the "Introduction to Algorithms" by Cormen, Leiserson and Rivest.
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14 */
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15
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16
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108
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17 static ngx_inline void ngx_rbtree_left_rotate(ngx_rbtree_node_t **root,
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18 ngx_rbtree_node_t *sentinel, ngx_rbtree_node_t *node);
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19 static ngx_inline void ngx_rbtree_right_rotate(ngx_rbtree_node_t **root,
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20 ngx_rbtree_node_t *sentinel, ngx_rbtree_node_t *node);
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21
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22
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42
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23 void
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108
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24 ngx_rbtree_insert(ngx_thread_volatile ngx_rbtree_t *tree,
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25 ngx_rbtree_node_t *node)
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26 {
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108
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27 ngx_rbtree_node_t **root, *temp, *sentinel;
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28
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29 /* a binary tree insert */
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30
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108
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31 root = (ngx_rbtree_node_t **) &tree->root;
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32 sentinel = tree->sentinel;
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33
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34 if (*root == sentinel) {
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35 node->parent = NULL;
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36 node->left = sentinel;
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37 node->right = sentinel;
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38 ngx_rbt_black(node);
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39 *root = node;
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40
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41 return;
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42 }
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43
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258
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44 tree->insert(*root, node, sentinel);
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45
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46 /* re-balance tree */
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47
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48 while (node != *root && ngx_rbt_is_red(node->parent)) {
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49
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50 if (node->parent == node->parent->parent->left) {
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51 temp = node->parent->parent->right;
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52
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53 if (ngx_rbt_is_red(temp)) {
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54 ngx_rbt_black(node->parent);
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55 ngx_rbt_black(temp);
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56 ngx_rbt_red(node->parent->parent);
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57 node = node->parent->parent;
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58
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59 } else {
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60 if (node == node->parent->right) {
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61 node = node->parent;
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62 ngx_rbtree_left_rotate(root, sentinel, node);
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63 }
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64
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65 ngx_rbt_black(node->parent);
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66 ngx_rbt_red(node->parent->parent);
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67 ngx_rbtree_right_rotate(root, sentinel, node->parent->parent);
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68 }
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69
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70 } else {
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71 temp = node->parent->parent->left;
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72
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73 if (ngx_rbt_is_red(temp)) {
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74 ngx_rbt_black(node->parent);
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75 ngx_rbt_black(temp);
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76 ngx_rbt_red(node->parent->parent);
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77 node = node->parent->parent;
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78
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79 } else {
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80 if (node == node->parent->left) {
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81 node = node->parent;
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82 ngx_rbtree_right_rotate(root, sentinel, node);
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83 }
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84
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85 ngx_rbt_black(node->parent);
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86 ngx_rbt_red(node->parent->parent);
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87 ngx_rbtree_left_rotate(root, sentinel, node->parent->parent);
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88 }
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89 }
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90 }
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91
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92 ngx_rbt_black(*root);
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93 }
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94
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95
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42
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96 void
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258
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97 ngx_rbtree_insert_value(ngx_rbtree_node_t *temp, ngx_rbtree_node_t *node,
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98 ngx_rbtree_node_t *sentinel)
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99 {
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356
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100 ngx_rbtree_node_t **p;
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101
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258
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102 for ( ;; ) {
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103
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356
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104 p = (node->key < temp->key) ? &temp->left : &temp->right;
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258
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105
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356
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106 if (*p == sentinel) {
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107 break;
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108 }
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258
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109
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356
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110 temp = *p;
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258
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111 }
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112
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356
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113 *p = node;
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258
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114 node->parent = temp;
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115 node->left = sentinel;
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116 node->right = sentinel;
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117 ngx_rbt_red(node);
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118 }
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119
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120
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121 void
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122 ngx_rbtree_insert_timer_value(ngx_rbtree_node_t *temp, ngx_rbtree_node_t *node,
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123 ngx_rbtree_node_t *sentinel)
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124 {
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356
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125 ngx_rbtree_node_t **p;
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126
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258
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127 for ( ;; ) {
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128
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129 /*
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130 * Timer values
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131 * 1) are spread in small range, usually several minutes,
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132 * 2) and overflow each 49 days, if milliseconds are stored in 32 bits.
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133 * The comparison takes into account that overflow.
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134 */
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135
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356
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136 /* node->key < temp->key */
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258
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137
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356
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138 p = ((ngx_rbtree_key_int_t) node->key - (ngx_rbtree_key_int_t) temp->key
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139 < 0)
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140 ? &temp->left : &temp->right;
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258
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141
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356
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142 if (*p == sentinel) {
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143 break;
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144 }
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258
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145
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356
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146 temp = *p;
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258
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147 }
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148
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356
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149 *p = node;
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258
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150 node->parent = temp;
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151 node->left = sentinel;
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152 node->right = sentinel;
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153 ngx_rbt_red(node);
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154 }
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155
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156
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157 void
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108
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158 ngx_rbtree_delete(ngx_thread_volatile ngx_rbtree_t *tree,
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159 ngx_rbtree_node_t *node)
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160 {
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258
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161 ngx_uint_t red;
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108
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162 ngx_rbtree_node_t **root, *sentinel, *subst, *temp, *w;
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163
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164 /* a binary tree delete */
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165
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108
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166 root = (ngx_rbtree_node_t **) &tree->root;
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167 sentinel = tree->sentinel;
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168
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169 if (node->left == sentinel) {
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170 temp = node->right;
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171 subst = node;
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172
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173 } else if (node->right == sentinel) {
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174 temp = node->left;
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175 subst = node;
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176
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177 } else {
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178 subst = ngx_rbtree_min(node->right, sentinel);
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179
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180 if (subst->left != sentinel) {
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181 temp = subst->left;
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182 } else {
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183 temp = subst->right;
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184 }
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185 }
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186
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187 if (subst == *root) {
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188 *root = temp;
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189 ngx_rbt_black(temp);
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190
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191 /* DEBUG stuff */
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192 node->left = NULL;
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193 node->right = NULL;
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194 node->parent = NULL;
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195 node->key = 0;
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196
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197 return;
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198 }
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199
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200 red = ngx_rbt_is_red(subst);
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201
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202 if (subst == subst->parent->left) {
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203 subst->parent->left = temp;
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204
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205 } else {
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206 subst->parent->right = temp;
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207 }
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208
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209 if (subst == node) {
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210
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211 temp->parent = subst->parent;
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212
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213 } else {
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214
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215 if (subst->parent == node) {
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216 temp->parent = subst;
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217
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218 } else {
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219 temp->parent = subst->parent;
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220 }
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221
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222 subst->left = node->left;
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223 subst->right = node->right;
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224 subst->parent = node->parent;
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225 ngx_rbt_copy_color(subst, node);
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226
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227 if (node == *root) {
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228 *root = subst;
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229
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230 } else {
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231 if (node == node->parent->left) {
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232 node->parent->left = subst;
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233 } else {
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234 node->parent->right = subst;
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235 }
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236 }
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237
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238 if (subst->left != sentinel) {
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239 subst->left->parent = subst;
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240 }
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241
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242 if (subst->right != sentinel) {
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243 subst->right->parent = subst;
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244 }
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358
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245 }
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0
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246
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358
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247 /* DEBUG stuff */
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248 node->left = NULL;
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249 node->right = NULL;
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250 node->parent = NULL;
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251 node->key = 0;
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252
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258
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253 if (red) {
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254 return;
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255 }
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256
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257 /* a delete fixup */
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258
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259 while (temp != *root && ngx_rbt_is_black(temp)) {
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260
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261 if (temp == temp->parent->left) {
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262 w = temp->parent->right;
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263
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264 if (ngx_rbt_is_red(w)) {
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265 ngx_rbt_black(w);
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266 ngx_rbt_red(temp->parent);
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267 ngx_rbtree_left_rotate(root, sentinel, temp->parent);
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268 w = temp->parent->right;
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269 }
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270
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271 if (ngx_rbt_is_black(w->left) && ngx_rbt_is_black(w->right)) {
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272 ngx_rbt_red(w);
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273 temp = temp->parent;
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274
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275 } else {
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276 if (ngx_rbt_is_black(w->right)) {
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277 ngx_rbt_black(w->left);
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278 ngx_rbt_red(w);
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279 ngx_rbtree_right_rotate(root, sentinel, w);
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280 w = temp->parent->right;
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281 }
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282
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283 ngx_rbt_copy_color(w, temp->parent);
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284 ngx_rbt_black(temp->parent);
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285 ngx_rbt_black(w->right);
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286 ngx_rbtree_left_rotate(root, sentinel, temp->parent);
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287 temp = *root;
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288 }
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289
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290 } else {
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291 w = temp->parent->left;
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292
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293 if (ngx_rbt_is_red(w)) {
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294 ngx_rbt_black(w);
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295 ngx_rbt_red(temp->parent);
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296 ngx_rbtree_right_rotate(root, sentinel, temp->parent);
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297 w = temp->parent->left;
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298 }
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299
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300 if (ngx_rbt_is_black(w->left) && ngx_rbt_is_black(w->right)) {
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301 ngx_rbt_red(w);
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302 temp = temp->parent;
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303
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304 } else {
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305 if (ngx_rbt_is_black(w->left)) {
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306 ngx_rbt_black(w->right);
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307 ngx_rbt_red(w);
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308 ngx_rbtree_left_rotate(root, sentinel, w);
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309 w = temp->parent->left;
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310 }
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311
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312 ngx_rbt_copy_color(w, temp->parent);
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313 ngx_rbt_black(temp->parent);
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314 ngx_rbt_black(w->left);
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315 ngx_rbtree_right_rotate(root, sentinel, temp->parent);
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316 temp = *root;
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317 }
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318 }
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319 }
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320
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321 ngx_rbt_black(temp);
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322 }
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323
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324
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42
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325 static ngx_inline void
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108
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326 ngx_rbtree_left_rotate(ngx_rbtree_node_t **root, ngx_rbtree_node_t *sentinel,
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327 ngx_rbtree_node_t *node)
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0
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328 {
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108
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329 ngx_rbtree_node_t *temp;
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0
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330
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331 temp = node->right;
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332 node->right = temp->left;
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333
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334 if (temp->left != sentinel) {
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335 temp->left->parent = node;
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336 }
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337
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338 temp->parent = node->parent;
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339
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340 if (node == *root) {
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341 *root = temp;
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342
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343 } else if (node == node->parent->left) {
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344 node->parent->left = temp;
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345
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346 } else {
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347 node->parent->right = temp;
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348 }
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349
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350 temp->left = node;
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351 node->parent = temp;
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352 }
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353
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354
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42
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355 static ngx_inline void
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108
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356 ngx_rbtree_right_rotate(ngx_rbtree_node_t **root, ngx_rbtree_node_t *sentinel,
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357 ngx_rbtree_node_t *node)
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0
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358 {
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108
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359 ngx_rbtree_node_t *temp;
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0
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360
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361 temp = node->left;
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362 node->left = temp->right;
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363
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364 if (temp->right != sentinel) {
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365 temp->right->parent = node;
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366 }
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367
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368 temp->parent = node->parent;
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369
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370 if (node == *root) {
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371 *root = temp;
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372
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373 } else if (node == node->parent->right) {
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374 node->parent->right = temp;
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375
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376 } else {
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377 node->parent->left = temp;
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378 }
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379
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380 temp->right = node;
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381 node->parent = temp;
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382 }
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