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0
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1 /* A splay-tree datatype.
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2 Copyright (C) 1998, 1999, 2000, 2001 Free Software Foundation, Inc.
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3 Contributed by Mark Mitchell (mark@markmitchell.com).
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4
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5 This file is part of GNU CC.
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6
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7 GNU CC is free software; you can redistribute it and/or modify it
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8 under the terms of the GNU General Public License as published by
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9 the Free Software Foundation; either version 2, or (at your option)
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10 any later version.
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11
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12 GNU CC is distributed in the hope that it will be useful, but
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13 WITHOUT ANY WARRANTY; without even the implied warranty of
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14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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15 General Public License for more details.
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16
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17 You should have received a copy of the GNU General Public License
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18 along with GNU CC; see the file COPYING. If not, write to
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19 the Free Software Foundation, 51 Franklin Street - Fifth Floor,
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20 Boston, MA 02110-1301, USA. */
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21
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22 /* For an easily readable description of splay-trees, see:
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23
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24 Lewis, Harry R. and Denenberg, Larry. Data Structures and Their
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25 Algorithms. Harper-Collins, Inc. 1991. */
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26
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27 #ifdef HAVE_CONFIG_H
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28 #include "config.h"
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29 #endif
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30
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31 #ifdef HAVE_STDLIB_H
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32 #include <stdlib.h>
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33 #endif
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34
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35 #include <stdio.h>
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36
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37 #include "libiberty.h"
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38 #include "splay-tree.h"
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39
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40 static void splay_tree_delete_helper (splay_tree, splay_tree_node);
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41 static inline void rotate_left (splay_tree_node *,
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42 splay_tree_node, splay_tree_node);
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43 static inline void rotate_right (splay_tree_node *,
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44 splay_tree_node, splay_tree_node);
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45 static void splay_tree_splay (splay_tree, splay_tree_key);
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46 static int splay_tree_foreach_helper (splay_tree, splay_tree_node,
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47 splay_tree_foreach_fn, void*);
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48
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49 /* Deallocate NODE (a member of SP), and all its sub-trees. */
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50
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51 static void
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52 splay_tree_delete_helper (splay_tree sp, splay_tree_node node)
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53 {
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54 splay_tree_node pending = 0;
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55 splay_tree_node active = 0;
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56
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57 if (!node)
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58 return;
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59
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60 #define KDEL(x) if (sp->delete_key) (*sp->delete_key)(x);
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61 #define VDEL(x) if (sp->delete_value) (*sp->delete_value)(x);
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62
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63 KDEL (node->key);
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64 VDEL (node->value);
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65
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66 /* We use the "key" field to hold the "next" pointer. */
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67 node->key = (splay_tree_key)pending;
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68 pending = (splay_tree_node)node;
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69
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70 /* Now, keep processing the pending list until there aren't any
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71 more. This is a little more complicated than just recursing, but
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72 it doesn't toast the stack for large trees. */
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73
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74 while (pending)
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75 {
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76 active = pending;
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77 pending = 0;
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78 while (active)
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79 {
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80 splay_tree_node temp;
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81
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82 /* active points to a node which has its key and value
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83 deallocated, we just need to process left and right. */
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84
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85 if (active->left)
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86 {
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87 KDEL (active->left->key);
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88 VDEL (active->left->value);
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89 active->left->key = (splay_tree_key)pending;
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90 pending = (splay_tree_node)(active->left);
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91 }
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92 if (active->right)
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93 {
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94 KDEL (active->right->key);
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95 VDEL (active->right->value);
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96 active->right->key = (splay_tree_key)pending;
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97 pending = (splay_tree_node)(active->right);
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98 }
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99
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100 temp = active;
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101 active = (splay_tree_node)(temp->key);
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102 (*sp->deallocate) ((char*) temp, sp->allocate_data);
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103 }
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104 }
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105 #undef KDEL
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106 #undef VDEL
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107 }
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108
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109 /* Rotate the edge joining the left child N with its parent P. PP is the
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110 grandparents' pointer to P. */
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111
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112 static inline void
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113 rotate_left (splay_tree_node *pp, splay_tree_node p, splay_tree_node n)
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114 {
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115 splay_tree_node tmp;
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116 tmp = n->right;
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117 n->right = p;
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118 p->left = tmp;
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119 *pp = n;
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120 }
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121
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122 /* Rotate the edge joining the right child N with its parent P. PP is the
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123 grandparents' pointer to P. */
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124
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125 static inline void
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126 rotate_right (splay_tree_node *pp, splay_tree_node p, splay_tree_node n)
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127 {
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128 splay_tree_node tmp;
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129 tmp = n->left;
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130 n->left = p;
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131 p->right = tmp;
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132 *pp = n;
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133 }
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134
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135 /* Bottom up splay of key. */
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136
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137 static void
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138 splay_tree_splay (splay_tree sp, splay_tree_key key)
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139 {
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140 if (sp->root == 0)
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141 return;
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142
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143 do {
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144 int cmp1, cmp2;
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145 splay_tree_node n, c;
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146
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147 n = sp->root;
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148 cmp1 = (*sp->comp) (key, n->key);
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149
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150 /* Found. */
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151 if (cmp1 == 0)
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152 return;
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153
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154 /* Left or right? If no child, then we're done. */
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155 if (cmp1 < 0)
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156 c = n->left;
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157 else
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158 c = n->right;
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159 if (!c)
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160 return;
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161
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162 /* Next one left or right? If found or no child, we're done
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163 after one rotation. */
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164 cmp2 = (*sp->comp) (key, c->key);
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165 if (cmp2 == 0
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166 || (cmp2 < 0 && !c->left)
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167 || (cmp2 > 0 && !c->right))
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168 {
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169 if (cmp1 < 0)
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170 rotate_left (&sp->root, n, c);
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171 else
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172 rotate_right (&sp->root, n, c);
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173 return;
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174 }
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175
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176 /* Now we have the four cases of double-rotation. */
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177 if (cmp1 < 0 && cmp2 < 0)
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178 {
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179 rotate_left (&n->left, c, c->left);
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180 rotate_left (&sp->root, n, n->left);
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181 }
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182 else if (cmp1 > 0 && cmp2 > 0)
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183 {
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184 rotate_right (&n->right, c, c->right);
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185 rotate_right (&sp->root, n, n->right);
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186 }
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187 else if (cmp1 < 0 && cmp2 > 0)
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188 {
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189 rotate_right (&n->left, c, c->right);
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190 rotate_left (&sp->root, n, n->left);
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191 }
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192 else if (cmp1 > 0 && cmp2 < 0)
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193 {
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194 rotate_left (&n->right, c, c->left);
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195 rotate_right (&sp->root, n, n->right);
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196 }
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197 } while (1);
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198 }
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199
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200 /* Call FN, passing it the DATA, for every node below NODE, all of
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201 which are from SP, following an in-order traversal. If FN every
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202 returns a non-zero value, the iteration ceases immediately, and the
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203 value is returned. Otherwise, this function returns 0. */
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204
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205 static int
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206 splay_tree_foreach_helper (splay_tree sp, splay_tree_node node,
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207 splay_tree_foreach_fn fn, void *data)
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208 {
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209 int val;
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210
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211 if (!node)
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212 return 0;
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213
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214 val = splay_tree_foreach_helper (sp, node->left, fn, data);
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215 if (val)
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216 return val;
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217
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218 val = (*fn)(node, data);
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219 if (val)
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220 return val;
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221
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222 return splay_tree_foreach_helper (sp, node->right, fn, data);
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223 }
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224
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225
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226 /* An allocator and deallocator based on xmalloc. */
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227 static void *
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228 splay_tree_xmalloc_allocate (int size, void *data ATTRIBUTE_UNUSED)
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229 {
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230 return (void *) xmalloc (size);
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231 }
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232
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233 static void
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234 splay_tree_xmalloc_deallocate (void *object, void *data ATTRIBUTE_UNUSED)
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235 {
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236 free (object);
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237 }
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238
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239
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240 /* Allocate a new splay tree, using COMPARE_FN to compare nodes,
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241 DELETE_KEY_FN to deallocate keys, and DELETE_VALUE_FN to deallocate
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242 values. Use xmalloc to allocate the splay tree structure, and any
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243 nodes added. */
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244
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245 splay_tree
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246 splay_tree_new (splay_tree_compare_fn compare_fn,
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247 splay_tree_delete_key_fn delete_key_fn,
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248 splay_tree_delete_value_fn delete_value_fn)
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249 {
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250 return (splay_tree_new_with_allocator
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251 (compare_fn, delete_key_fn, delete_value_fn,
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252 splay_tree_xmalloc_allocate, splay_tree_xmalloc_deallocate, 0));
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253 }
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254
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255
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256 /* Allocate a new splay tree, using COMPARE_FN to compare nodes,
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257 DELETE_KEY_FN to deallocate keys, and DELETE_VALUE_FN to deallocate
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258 values. */
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259
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260 splay_tree
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261 splay_tree_new_with_allocator (splay_tree_compare_fn compare_fn,
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262 splay_tree_delete_key_fn delete_key_fn,
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263 splay_tree_delete_value_fn delete_value_fn,
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264 splay_tree_allocate_fn allocate_fn,
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265 splay_tree_deallocate_fn deallocate_fn,
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266 void *allocate_data)
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267 {
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268 splay_tree sp = (splay_tree) (*allocate_fn) (sizeof (struct splay_tree_s),
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269 allocate_data);
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270 sp->root = 0;
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271 sp->comp = compare_fn;
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272 sp->delete_key = delete_key_fn;
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273 sp->delete_value = delete_value_fn;
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274 sp->allocate = allocate_fn;
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275 sp->deallocate = deallocate_fn;
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276 sp->allocate_data = allocate_data;
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277
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278 return sp;
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279 }
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280
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281 /* Deallocate SP. */
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282
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283 void
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284 splay_tree_delete (splay_tree sp)
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285 {
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286 splay_tree_delete_helper (sp, sp->root);
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287 (*sp->deallocate) ((char*) sp, sp->allocate_data);
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288 }
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289
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290 /* Insert a new node (associating KEY with DATA) into SP. If a
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291 previous node with the indicated KEY exists, its data is replaced
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292 with the new value. Returns the new node. */
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293
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294 splay_tree_node
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295 splay_tree_insert (splay_tree sp, splay_tree_key key, splay_tree_value value)
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296 {
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297 int comparison = 0;
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298
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299 splay_tree_splay (sp, key);
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300
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301 if (sp->root)
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302 comparison = (*sp->comp)(sp->root->key, key);
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303
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304 if (sp->root && comparison == 0)
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305 {
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306 /* If the root of the tree already has the indicated KEY, just
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307 replace the value with VALUE. */
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308 if (sp->delete_value)
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309 (*sp->delete_value)(sp->root->value);
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310 sp->root->value = value;
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311 }
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312 else
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313 {
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314 /* Create a new node, and insert it at the root. */
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315 splay_tree_node node;
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316
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317 node = ((splay_tree_node)
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318 (*sp->allocate) (sizeof (struct splay_tree_node_s),
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319 sp->allocate_data));
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320 node->key = key;
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321 node->value = value;
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322
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323 if (!sp->root)
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324 node->left = node->right = 0;
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325 else if (comparison < 0)
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326 {
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327 node->left = sp->root;
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328 node->right = node->left->right;
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329 node->left->right = 0;
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330 }
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331 else
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332 {
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333 node->right = sp->root;
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334 node->left = node->right->left;
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335 node->right->left = 0;
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336 }
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337
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338 sp->root = node;
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339 }
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340
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341 return sp->root;
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342 }
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343
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344 /* Remove KEY from SP. It is not an error if it did not exist. */
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345
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346 void
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347 splay_tree_remove (splay_tree sp, splay_tree_key key)
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348 {
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349 splay_tree_splay (sp, key);
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350
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351 if (sp->root && (*sp->comp) (sp->root->key, key) == 0)
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352 {
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353 splay_tree_node left, right;
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354
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355 left = sp->root->left;
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356 right = sp->root->right;
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357
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358 /* Delete the root node itself. */
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359 if (sp->delete_value)
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360 (*sp->delete_value) (sp->root->value);
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361 (*sp->deallocate) (sp->root, sp->allocate_data);
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362
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363 /* One of the children is now the root. Doesn't matter much
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364 which, so long as we preserve the properties of the tree. */
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365 if (left)
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366 {
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367 sp->root = left;
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368
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369 /* If there was a right child as well, hang it off the
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370 right-most leaf of the left child. */
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371 if (right)
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372 {
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373 while (left->right)
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374 left = left->right;
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375 left->right = right;
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376 }
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377 }
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378 else
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379 sp->root = right;
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380 }
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381 }
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382
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383 /* Lookup KEY in SP, returning VALUE if present, and NULL
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384 otherwise. */
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385
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386 splay_tree_node
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387 splay_tree_lookup (splay_tree sp, splay_tree_key key)
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388 {
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389 splay_tree_splay (sp, key);
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390
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391 if (sp->root && (*sp->comp)(sp->root->key, key) == 0)
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392 return sp->root;
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393 else
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394 return 0;
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395 }
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396
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397 /* Return the node in SP with the greatest key. */
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398
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399 splay_tree_node
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400 splay_tree_max (splay_tree sp)
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401 {
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402 splay_tree_node n = sp->root;
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403
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404 if (!n)
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405 return NULL;
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406
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407 while (n->right)
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408 n = n->right;
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409
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410 return n;
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411 }
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412
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413 /* Return the node in SP with the smallest key. */
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414
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415 splay_tree_node
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416 splay_tree_min (splay_tree sp)
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417 {
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418 splay_tree_node n = sp->root;
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419
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420 if (!n)
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421 return NULL;
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422
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423 while (n->left)
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424 n = n->left;
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425
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426 return n;
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427 }
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428
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429 /* Return the immediate predecessor KEY, or NULL if there is no
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430 predecessor. KEY need not be present in the tree. */
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431
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432 splay_tree_node
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433 splay_tree_predecessor (splay_tree sp, splay_tree_key key)
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434 {
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435 int comparison;
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436 splay_tree_node node;
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437
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438 /* If the tree is empty, there is certainly no predecessor. */
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439 if (!sp->root)
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440 return NULL;
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441
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442 /* Splay the tree around KEY. That will leave either the KEY
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443 itself, its predecessor, or its successor at the root. */
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444 splay_tree_splay (sp, key);
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445 comparison = (*sp->comp)(sp->root->key, key);
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446
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447 /* If the predecessor is at the root, just return it. */
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448 if (comparison < 0)
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449 return sp->root;
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450
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451 /* Otherwise, find the rightmost element of the left subtree. */
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452 node = sp->root->left;
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453 if (node)
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454 while (node->right)
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455 node = node->right;
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456
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457 return node;
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458 }
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459
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460 /* Return the immediate successor KEY, or NULL if there is no
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461 successor. KEY need not be present in the tree. */
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462
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463 splay_tree_node
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464 splay_tree_successor (splay_tree sp, splay_tree_key key)
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465 {
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466 int comparison;
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467 splay_tree_node node;
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468
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469 /* If the tree is empty, there is certainly no successor. */
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470 if (!sp->root)
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471 return NULL;
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472
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473 /* Splay the tree around KEY. That will leave either the KEY
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474 itself, its predecessor, or its successor at the root. */
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475 splay_tree_splay (sp, key);
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476 comparison = (*sp->comp)(sp->root->key, key);
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477
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478 /* If the successor is at the root, just return it. */
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479 if (comparison > 0)
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480 return sp->root;
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481
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482 /* Otherwise, find the leftmost element of the right subtree. */
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483 node = sp->root->right;
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484 if (node)
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485 while (node->left)
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486 node = node->left;
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487
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488 return node;
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489 }
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490
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491 /* Call FN, passing it the DATA, for every node in SP, following an
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492 in-order traversal. If FN every returns a non-zero value, the
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493 iteration ceases immediately, and the value is returned.
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494 Otherwise, this function returns 0. */
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495
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496 int
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497 splay_tree_foreach (splay_tree sp, splay_tree_foreach_fn fn, void *data)
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498 {
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499 return splay_tree_foreach_helper (sp, sp->root, fn, data);
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500 }
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501
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502 /* Splay-tree comparison function, treating the keys as ints. */
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503
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504 int
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505 splay_tree_compare_ints (splay_tree_key k1, splay_tree_key k2)
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506 {
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507 if ((int) k1 < (int) k2)
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508 return -1;
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509 else if ((int) k1 > (int) k2)
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510 return 1;
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511 else
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512 return 0;
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513 }
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514
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515 /* Splay-tree comparison function, treating the keys as pointers. */
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516
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517 int
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518 splay_tree_compare_pointers (splay_tree_key k1, splay_tree_key k2)
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519 {
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520 if ((char*) k1 < (char*) k2)
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521 return -1;
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522 else if ((char*) k1 > (char*) k2)
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523 return 1;
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524 else
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525 return 0;
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526 }
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