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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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100 for ( ;; ) {
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101
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102 if (node->key < temp->key) {
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103
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104 if (temp->left == sentinel) {
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105 temp->left = node;
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106 break;
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107 }
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108
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109 temp = temp->left;
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110
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111 } else {
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112
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113 if (temp->right == sentinel) {
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114 temp->right = node;
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115 break;
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116 }
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117
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118 temp = temp->right;
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119 }
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120 }
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121
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122 node->parent = temp;
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123 node->left = sentinel;
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124 node->right = sentinel;
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125 ngx_rbt_red(node);
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126 }
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127
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128
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129 void
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130 ngx_rbtree_insert_timer_value(ngx_rbtree_node_t *temp, ngx_rbtree_node_t *node,
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131 ngx_rbtree_node_t *sentinel)
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132 {
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133 for ( ;; ) {
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134
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135 /*
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136 * Timer values
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137 * 1) are spread in small range, usually several minutes,
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138 * 2) and overflow each 49 days, if milliseconds are stored in 32 bits.
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139 * The comparison takes into account that overflow.
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140 */
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141
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142 if ((ngx_rbtree_key_int_t) node->key - (ngx_rbtree_key_int_t) temp->key
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143 < 0)
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144 {
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145 /* node->key < temp->key */
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146
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147 if (temp->left == sentinel) {
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148 temp->left = node;
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149 break;
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150 }
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151
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152 temp = temp->left;
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153
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154 } else {
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155
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156 if (temp->right == sentinel) {
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157 temp->right = node;
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158 break;
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159 }
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160
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161 temp = temp->right;
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162 }
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163 }
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164
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165 node->parent = temp;
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166 node->left = sentinel;
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167 node->right = sentinel;
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168 ngx_rbt_red(node);
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169 }
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170
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171
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172 void
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173 ngx_rbtree_delete(ngx_thread_volatile ngx_rbtree_t *tree,
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174 ngx_rbtree_node_t *node)
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175 {
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176 ngx_uint_t red;
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177 ngx_rbtree_node_t **root, *sentinel, *subst, *temp, *w;
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178
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179 /* a binary tree delete */
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180
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108
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181 root = (ngx_rbtree_node_t **) &tree->root;
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182 sentinel = tree->sentinel;
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183
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184 if (node->left == sentinel) {
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185 temp = node->right;
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186 subst = node;
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187
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188 } else if (node->right == sentinel) {
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189 temp = node->left;
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190 subst = node;
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191
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192 } else {
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193 subst = ngx_rbtree_min(node->right, sentinel);
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194
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195 if (subst->left != sentinel) {
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196 temp = subst->left;
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197 } else {
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198 temp = subst->right;
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199 }
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200 }
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201
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202 if (subst == *root) {
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203 *root = temp;
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204 ngx_rbt_black(temp);
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205
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206 /* DEBUG stuff */
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207 node->left = NULL;
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208 node->right = NULL;
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209 node->parent = NULL;
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210 node->key = 0;
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211
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212 return;
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213 }
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214
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215 red = ngx_rbt_is_red(subst);
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216
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217 if (subst == subst->parent->left) {
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218 subst->parent->left = temp;
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219
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220 } else {
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221 subst->parent->right = temp;
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222 }
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223
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224 if (subst == node) {
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225
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226 temp->parent = subst->parent;
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227
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228 } else {
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229
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230 if (subst->parent == node) {
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231 temp->parent = subst;
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232
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233 } else {
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234 temp->parent = subst->parent;
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235 }
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236
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237 subst->left = node->left;
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238 subst->right = node->right;
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239 subst->parent = node->parent;
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240 ngx_rbt_copy_color(subst, node);
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241
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242 if (node == *root) {
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243 *root = subst;
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244
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245 } else {
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246 if (node == node->parent->left) {
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247 node->parent->left = subst;
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248 } else {
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249 node->parent->right = subst;
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250 }
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251 }
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252
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253 if (subst->left != sentinel) {
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254 subst->left->parent = subst;
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255 }
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256
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257 if (subst->right != sentinel) {
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258 subst->right->parent = subst;
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259 }
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260
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261 /* DEBUG stuff */
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262 node->left = NULL;
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263 node->right = NULL;
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264 node->parent = NULL;
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265 node->key = 0;
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266 }
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267
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258
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268 if (red) {
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269 return;
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270 }
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271
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272 /* a delete fixup */
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273
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274 while (temp != *root && ngx_rbt_is_black(temp)) {
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275
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276 if (temp == temp->parent->left) {
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277 w = temp->parent->right;
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278
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279 if (ngx_rbt_is_red(w)) {
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280 ngx_rbt_black(w);
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281 ngx_rbt_red(temp->parent);
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282 ngx_rbtree_left_rotate(root, sentinel, temp->parent);
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283 w = temp->parent->right;
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284 }
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285
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286 if (ngx_rbt_is_black(w->left) && ngx_rbt_is_black(w->right)) {
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287 ngx_rbt_red(w);
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288 temp = temp->parent;
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289
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290 } else {
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291 if (ngx_rbt_is_black(w->right)) {
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292 ngx_rbt_black(w->left);
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293 ngx_rbt_red(w);
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294 ngx_rbtree_right_rotate(root, sentinel, w);
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295 w = temp->parent->right;
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296 }
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297
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298 ngx_rbt_copy_color(w, temp->parent);
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299 ngx_rbt_black(temp->parent);
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300 ngx_rbt_black(w->right);
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301 ngx_rbtree_left_rotate(root, sentinel, temp->parent);
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302 temp = *root;
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303 }
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304
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305 } else {
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306 w = temp->parent->left;
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307
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308 if (ngx_rbt_is_red(w)) {
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309 ngx_rbt_black(w);
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310 ngx_rbt_red(temp->parent);
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311 ngx_rbtree_right_rotate(root, sentinel, temp->parent);
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312 w = temp->parent->left;
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313 }
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314
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315 if (ngx_rbt_is_black(w->left) && ngx_rbt_is_black(w->right)) {
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316 ngx_rbt_red(w);
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317 temp = temp->parent;
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318
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319 } else {
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320 if (ngx_rbt_is_black(w->left)) {
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321 ngx_rbt_black(w->right);
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322 ngx_rbt_red(w);
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323 ngx_rbtree_left_rotate(root, sentinel, w);
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324 w = temp->parent->left;
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325 }
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326
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327 ngx_rbt_copy_color(w, temp->parent);
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328 ngx_rbt_black(temp->parent);
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329 ngx_rbt_black(w->left);
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330 ngx_rbtree_right_rotate(root, sentinel, temp->parent);
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331 temp = *root;
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332 }
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333 }
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334 }
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335
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336 ngx_rbt_black(temp);
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337 }
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338
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339
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340 static ngx_inline void
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108
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341 ngx_rbtree_left_rotate(ngx_rbtree_node_t **root, ngx_rbtree_node_t *sentinel,
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342 ngx_rbtree_node_t *node)
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0
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343 {
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108
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344 ngx_rbtree_node_t *temp;
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0
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345
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346 temp = node->right;
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347 node->right = temp->left;
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348
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349 if (temp->left != sentinel) {
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350 temp->left->parent = node;
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351 }
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352
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353 temp->parent = node->parent;
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354
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355 if (node == *root) {
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356 *root = temp;
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357
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358 } else if (node == node->parent->left) {
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359 node->parent->left = temp;
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360
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361 } else {
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362 node->parent->right = temp;
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363 }
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364
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365 temp->left = node;
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366 node->parent = temp;
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367 }
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368
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369
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42
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370 static ngx_inline void
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108
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371 ngx_rbtree_right_rotate(ngx_rbtree_node_t **root, ngx_rbtree_node_t *sentinel,
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372 ngx_rbtree_node_t *node)
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0
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373 {
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108
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374 ngx_rbtree_node_t *temp;
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0
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375
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376 temp = node->left;
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377 node->left = temp->right;
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378
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379 if (temp->right != sentinel) {
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380 temp->right->parent = node;
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381 }
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382
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383 temp->parent = node->parent;
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384
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385 if (node == *root) {
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386 *root = temp;
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387
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388 } else if (node == node->parent->right) {
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389 node->parent->right = temp;
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390
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391 } else {
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392 node->parent->left = temp;
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393 }
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394
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395 temp->right = node;
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396 node->parent = temp;
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397 }
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