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1
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2 /*
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3 * Copyright (C) Igor Sysoev
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660
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4 * Copyright (C) Nginx, Inc.
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5 */
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6
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7
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8 #include <ngx_config.h>
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9 #include <ngx_core.h>
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10
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11
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12 /*
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108
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13 * The red-black tree code is based on the algorithm described in
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14 * the "Introduction to Algorithms" by Cormen, Leiserson and Rivest.
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0
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15 */
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16
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17
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108
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18 static ngx_inline void ngx_rbtree_left_rotate(ngx_rbtree_node_t **root,
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19 ngx_rbtree_node_t *sentinel, ngx_rbtree_node_t *node);
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20 static ngx_inline void ngx_rbtree_right_rotate(ngx_rbtree_node_t **root,
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21 ngx_rbtree_node_t *sentinel, ngx_rbtree_node_t *node);
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22
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23
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42
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24 void
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108
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25 ngx_rbtree_insert(ngx_thread_volatile ngx_rbtree_t *tree,
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26 ngx_rbtree_node_t *node)
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27 {
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108
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28 ngx_rbtree_node_t **root, *temp, *sentinel;
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29
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30 /* a binary tree insert */
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31
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108
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32 root = (ngx_rbtree_node_t **) &tree->root;
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33 sentinel = tree->sentinel;
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34
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35 if (*root == sentinel) {
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36 node->parent = NULL;
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37 node->left = sentinel;
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38 node->right = sentinel;
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39 ngx_rbt_black(node);
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40 *root = node;
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41
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42 return;
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43 }
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44
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258
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45 tree->insert(*root, node, sentinel);
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46
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47 /* re-balance tree */
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48
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49 while (node != *root && ngx_rbt_is_red(node->parent)) {
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50
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51 if (node->parent == node->parent->parent->left) {
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52 temp = node->parent->parent->right;
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53
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54 if (ngx_rbt_is_red(temp)) {
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55 ngx_rbt_black(node->parent);
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56 ngx_rbt_black(temp);
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57 ngx_rbt_red(node->parent->parent);
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58 node = node->parent->parent;
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59
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60 } else {
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61 if (node == node->parent->right) {
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62 node = node->parent;
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63 ngx_rbtree_left_rotate(root, sentinel, node);
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64 }
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65
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66 ngx_rbt_black(node->parent);
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67 ngx_rbt_red(node->parent->parent);
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68 ngx_rbtree_right_rotate(root, sentinel, node->parent->parent);
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69 }
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70
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71 } else {
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72 temp = node->parent->parent->left;
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73
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74 if (ngx_rbt_is_red(temp)) {
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75 ngx_rbt_black(node->parent);
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76 ngx_rbt_black(temp);
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77 ngx_rbt_red(node->parent->parent);
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78 node = node->parent->parent;
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79
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80 } else {
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81 if (node == node->parent->left) {
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82 node = node->parent;
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83 ngx_rbtree_right_rotate(root, sentinel, node);
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84 }
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85
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86 ngx_rbt_black(node->parent);
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87 ngx_rbt_red(node->parent->parent);
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88 ngx_rbtree_left_rotate(root, sentinel, node->parent->parent);
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89 }
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90 }
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91 }
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92
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93 ngx_rbt_black(*root);
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94 }
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95
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96
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42
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97 void
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258
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98 ngx_rbtree_insert_value(ngx_rbtree_node_t *temp, ngx_rbtree_node_t *node,
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99 ngx_rbtree_node_t *sentinel)
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100 {
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356
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101 ngx_rbtree_node_t **p;
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102
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258
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103 for ( ;; ) {
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104
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356
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105 p = (node->key < temp->key) ? &temp->left : &temp->right;
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258
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106
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356
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107 if (*p == sentinel) {
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108 break;
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109 }
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258
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110
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356
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111 temp = *p;
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258
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112 }
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113
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356
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114 *p = node;
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258
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115 node->parent = temp;
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116 node->left = sentinel;
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117 node->right = sentinel;
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118 ngx_rbt_red(node);
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119 }
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120
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121
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122 void
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123 ngx_rbtree_insert_timer_value(ngx_rbtree_node_t *temp, ngx_rbtree_node_t *node,
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124 ngx_rbtree_node_t *sentinel)
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125 {
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356
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126 ngx_rbtree_node_t **p;
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127
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258
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128 for ( ;; ) {
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129
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130 /*
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131 * Timer values
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132 * 1) are spread in small range, usually several minutes,
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133 * 2) and overflow each 49 days, if milliseconds are stored in 32 bits.
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134 * The comparison takes into account that overflow.
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135 */
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136
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356
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137 /* node->key < temp->key */
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258
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138
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356
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139 p = ((ngx_rbtree_key_int_t) node->key - (ngx_rbtree_key_int_t) temp->key
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140 < 0)
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141 ? &temp->left : &temp->right;
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258
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142
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356
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143 if (*p == sentinel) {
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144 break;
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145 }
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258
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146
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356
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147 temp = *p;
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258
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148 }
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149
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356
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150 *p = node;
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258
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151 node->parent = temp;
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152 node->left = sentinel;
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153 node->right = sentinel;
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154 ngx_rbt_red(node);
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155 }
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156
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157
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158 void
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108
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159 ngx_rbtree_delete(ngx_thread_volatile ngx_rbtree_t *tree,
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160 ngx_rbtree_node_t *node)
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161 {
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258
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162 ngx_uint_t red;
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108
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163 ngx_rbtree_node_t **root, *sentinel, *subst, *temp, *w;
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0
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164
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165 /* a binary tree delete */
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166
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108
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167 root = (ngx_rbtree_node_t **) &tree->root;
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168 sentinel = tree->sentinel;
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169
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0
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170 if (node->left == sentinel) {
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171 temp = node->right;
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172 subst = node;
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173
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174 } else if (node->right == sentinel) {
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175 temp = node->left;
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176 subst = node;
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177
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178 } else {
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179 subst = ngx_rbtree_min(node->right, sentinel);
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180
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181 if (subst->left != sentinel) {
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182 temp = subst->left;
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183 } else {
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184 temp = subst->right;
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185 }
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186 }
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187
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188 if (subst == *root) {
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189 *root = temp;
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190 ngx_rbt_black(temp);
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191
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192 /* DEBUG stuff */
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193 node->left = NULL;
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194 node->right = NULL;
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195 node->parent = NULL;
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196 node->key = 0;
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197
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198 return;
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199 }
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200
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258
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201 red = ngx_rbt_is_red(subst);
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202
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203 if (subst == subst->parent->left) {
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204 subst->parent->left = temp;
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205
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206 } else {
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207 subst->parent->right = temp;
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208 }
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209
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210 if (subst == node) {
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211
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212 temp->parent = subst->parent;
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213
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214 } else {
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215
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216 if (subst->parent == node) {
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217 temp->parent = subst;
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218
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219 } else {
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220 temp->parent = subst->parent;
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221 }
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222
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223 subst->left = node->left;
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224 subst->right = node->right;
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225 subst->parent = node->parent;
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226 ngx_rbt_copy_color(subst, node);
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227
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228 if (node == *root) {
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229 *root = subst;
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230
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231 } else {
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232 if (node == node->parent->left) {
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233 node->parent->left = subst;
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234 } else {
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235 node->parent->right = subst;
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236 }
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237 }
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238
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239 if (subst->left != sentinel) {
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240 subst->left->parent = subst;
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241 }
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242
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243 if (subst->right != sentinel) {
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244 subst->right->parent = subst;
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245 }
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358
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246 }
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0
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247
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358
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248 /* DEBUG stuff */
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249 node->left = NULL;
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250 node->right = NULL;
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251 node->parent = NULL;
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252 node->key = 0;
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0
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253
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258
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254 if (red) {
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255 return;
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256 }
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257
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258 /* a delete fixup */
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259
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260 while (temp != *root && ngx_rbt_is_black(temp)) {
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261
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262 if (temp == temp->parent->left) {
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263 w = temp->parent->right;
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264
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265 if (ngx_rbt_is_red(w)) {
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266 ngx_rbt_black(w);
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267 ngx_rbt_red(temp->parent);
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268 ngx_rbtree_left_rotate(root, sentinel, temp->parent);
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269 w = temp->parent->right;
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270 }
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271
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272 if (ngx_rbt_is_black(w->left) && ngx_rbt_is_black(w->right)) {
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273 ngx_rbt_red(w);
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274 temp = temp->parent;
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275
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276 } else {
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277 if (ngx_rbt_is_black(w->right)) {
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278 ngx_rbt_black(w->left);
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279 ngx_rbt_red(w);
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280 ngx_rbtree_right_rotate(root, sentinel, w);
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281 w = temp->parent->right;
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282 }
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283
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284 ngx_rbt_copy_color(w, temp->parent);
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285 ngx_rbt_black(temp->parent);
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286 ngx_rbt_black(w->right);
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287 ngx_rbtree_left_rotate(root, sentinel, temp->parent);
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288 temp = *root;
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289 }
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290
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291 } else {
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292 w = temp->parent->left;
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293
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294 if (ngx_rbt_is_red(w)) {
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295 ngx_rbt_black(w);
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296 ngx_rbt_red(temp->parent);
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297 ngx_rbtree_right_rotate(root, sentinel, temp->parent);
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298 w = temp->parent->left;
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299 }
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300
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301 if (ngx_rbt_is_black(w->left) && ngx_rbt_is_black(w->right)) {
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302 ngx_rbt_red(w);
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303 temp = temp->parent;
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304
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305 } else {
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306 if (ngx_rbt_is_black(w->left)) {
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307 ngx_rbt_black(w->right);
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308 ngx_rbt_red(w);
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309 ngx_rbtree_left_rotate(root, sentinel, w);
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310 w = temp->parent->left;
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311 }
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312
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313 ngx_rbt_copy_color(w, temp->parent);
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314 ngx_rbt_black(temp->parent);
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315 ngx_rbt_black(w->left);
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316 ngx_rbtree_right_rotate(root, sentinel, temp->parent);
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317 temp = *root;
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318 }
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319 }
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320 }
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321
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322 ngx_rbt_black(temp);
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323 }
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324
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325
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42
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326 static ngx_inline void
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108
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327 ngx_rbtree_left_rotate(ngx_rbtree_node_t **root, ngx_rbtree_node_t *sentinel,
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328 ngx_rbtree_node_t *node)
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0
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329 {
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108
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330 ngx_rbtree_node_t *temp;
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0
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331
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332 temp = node->right;
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333 node->right = temp->left;
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334
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335 if (temp->left != sentinel) {
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336 temp->left->parent = node;
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337 }
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338
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339 temp->parent = node->parent;
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340
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341 if (node == *root) {
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342 *root = temp;
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343
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344 } else if (node == node->parent->left) {
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345 node->parent->left = temp;
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346
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347 } else {
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348 node->parent->right = temp;
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349 }
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350
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351 temp->left = node;
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352 node->parent = temp;
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353 }
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354
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355
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42
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356 static ngx_inline void
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108
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357 ngx_rbtree_right_rotate(ngx_rbtree_node_t **root, ngx_rbtree_node_t *sentinel,
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358 ngx_rbtree_node_t *node)
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0
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359 {
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108
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360 ngx_rbtree_node_t *temp;
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0
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361
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362 temp = node->left;
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363 node->left = temp->right;
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364
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365 if (temp->right != sentinel) {
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366 temp->right->parent = node;
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367 }
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368
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369 temp->parent = node->parent;
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370
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371 if (node == *root) {
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372 *root = temp;
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373
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374 } else if (node == node->parent->right) {
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375 node->parent->right = temp;
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376
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377 } else {
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378 node->parent->left = temp;
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379 }
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380
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381 temp->right = node;
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382 node->parent = temp;
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383 }
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