1 | /**************************************************************************
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2 | *
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3 | * sptree.c -- Splay tree code
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4 | * Copyright (C) 1994 Gary Eddy, Alistair Moffat and Neil Sharman
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5 | *
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6 | * This program is free software; you can redistribute it and/or modify
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7 | * it under the terms of the GNU General Public License as published by
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8 | * the Free Software Foundation; either version 2 of the License, or
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9 | * (at your option) any later version.
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10 | *
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11 | * This program is distributed in the hope that it will be useful,
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12 | * but WITHOUT ANY WARRANTY; without even the implied warranty of
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13 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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14 | * GNU General Public License for more details.
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15 | *
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16 | * You should have received a copy of the GNU General Public License
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17 | * along with this program; if not, write to the Free Software
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18 | * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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19 | *
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20 | **************************************************************************/
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21 |
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22 |
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23 | #include "sysfuncs.h"
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24 | #include "sptree.h"
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25 |
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26 | #define TRACE(w)
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27 |
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28 | #define POOL_SIZE 1024
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29 |
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30 |
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31 | typedef struct node_rec node;
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32 |
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33 | struct node_rec
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34 | {
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35 | node *left, *rght;
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36 | node *par;
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37 | char *datsun;
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38 | };
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39 |
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40 | struct pool
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41 | {
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42 | int length, pos;
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43 | struct pool *next;
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44 | node nodes[POOL_SIZE];
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45 | };
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46 |
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47 | static node *SP_splay ();
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48 |
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49 | #define CNULL ((char *) NULL)
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50 | #define NNULL ((node *) NULL)
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51 | #define SNULL ((Splay_Tree *) NULL)
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52 |
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53 |
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54 | /*
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55 | * createset():
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56 | * allocates memory for and initialises a set.
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57 | *
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58 | * Accesses outside variables: none
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59 | *
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60 | * Return value...: none
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61 | */
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62 |
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63 | Splay_Tree *
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64 | SP_createset (int (*cmp) (void *, void *))
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65 | {
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66 | Splay_Tree *S;
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67 |
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68 | if (!(S = (Splay_Tree *) malloc (sizeof (Splay_Tree))))
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69 | return (SNULL);
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70 | S->cmp = cmp;
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71 | S->root = CNULL;
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72 | S->no_of_items = 0;
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73 | S->mem_in_use = sizeof (Splay_Tree);
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74 | S->pool = NULL;
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75 | S->pool_chunks = 1024;
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76 | return S;
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77 | } /* createset() */
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78 |
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79 |
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80 |
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81 | static node *
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82 | SP_get_node (Splay_Tree * S)
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83 | {
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84 | struct pool *p = S->pool;
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85 | if (!p || p->pos == p->length)
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86 | {
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87 | p = malloc (sizeof (struct pool));
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88 | if (!p)
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89 | return NULL;
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90 | S->mem_in_use += sizeof (struct pool);
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91 | p->length = POOL_SIZE;
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92 | p->pos = 0;
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93 | p->next = S->pool;
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94 | S->pool = p;
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95 | }
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96 | return &(p->nodes[p->pos++]);
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97 | }
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98 |
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99 |
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100 |
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101 | /*
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102 | * SP_freeset():
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103 | * free the memory allocated to a splay tree. Note this Does not
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104 | * free the data in the tree you must do this yourself.
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105 | *
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106 | * Accesses outside variables: none
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107 | *
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108 | * Return value...: none
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109 | */
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110 |
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111 | void
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112 | SP_freeset (Splay_Tree * S)
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113 | {
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114 | while (S->pool)
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115 | {
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116 | struct pool *p = S->pool;
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117 | S->pool = p->next;
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118 | free (p);
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119 | }
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120 | free (S);
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121 | }
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122 |
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123 |
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124 | /*
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125 | * insert():
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126 | * inserts the item given into the set given in the order
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127 | * specified by the comparison function in the set
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128 | * definition.
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129 | *
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130 | * Accesses outside variables: none
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131 | *
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132 | * Return value...: none
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133 | */
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134 |
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135 |
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136 | void *
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137 | SP_insert (void *item, Splay_Tree * S)
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138 | {
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139 | int dir = 0;
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140 | register node *curr, *prev;
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141 | node *tmp;
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142 |
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143 | prev = NNULL;
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144 | curr = (node *) S->root;
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145 | for (; curr;)
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146 | {
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147 | prev = curr;
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148 | dir = S->cmp (item, curr->datsun);
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149 | if (dir < 0)
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150 | curr = curr->left;
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151 | else
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152 | curr = curr->rght;
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153 | }
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154 | if (!(tmp = SP_get_node (S)))
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155 | return NULL;
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156 | tmp->datsun = item;
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157 |
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158 | if (prev == NNULL)
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159 | S->root = (char *) tmp;
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160 | else if (dir < 0)
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161 | prev->left = tmp;
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162 | else
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163 | prev->rght = tmp;
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164 |
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165 | tmp->par = prev;
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166 | tmp->left = NNULL;
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167 | tmp->rght = NNULL;
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168 | S->no_of_items++;
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169 | S->root = (char *) SP_splay (tmp);
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170 | return (tmp->datsun);
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171 | } /* insert() */
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172 |
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173 | /*
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174 | * get_first():
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175 | * returns a pointer to the first item in the set. If the set
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176 | * is empty a NULL pointer is returned.
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177 | *
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178 | * Accesses outside variables: none
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179 | */
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180 |
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181 | void *
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182 | SP_get_first (Splay_Tree * S)
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183 | {
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184 | node *curr, *prev;
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185 |
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186 | for (curr = (node *) S->root, prev = NNULL; curr;
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187 | prev = curr, curr = curr->left)
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188 | ; /* NULLBODY */
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189 |
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190 | if (prev)
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191 | S->root = (char *) SP_splay (prev);
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192 | return (prev ? prev->datsun : CNULL);
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193 | } /* get_first() */
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194 |
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195 | /*
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196 | * get_next():
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197 | * returns the in-order successor of the currently fingered
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198 | * item of the set. If no item is fingered or if there is
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199 | * no in-order successor a NULL pointer is returned.
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200 | *
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201 | * Accesses outside variables: none
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202 | */
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203 |
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204 | void *
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205 | SP_get_next (Splay_Tree * S)
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206 | {
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207 | node *curr, *prev;
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208 |
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209 | curr = (node *) S->root;
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210 | if (!curr || !curr->rght)
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211 | return (CNULL);
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212 |
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213 | for (prev = curr, curr = curr->rght; curr;
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214 | prev = curr, curr = curr->left)
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215 | ; /* NULLBODY */
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216 |
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217 | if (prev)
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218 | S->root = (char *) SP_splay (prev);
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219 | return (prev ? prev->datsun : CNULL);
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220 | } /* get_next() */
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221 |
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222 | /*
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223 | * deletemin():
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224 | * removes the first element in the set and returns a
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225 | * pointer to it. If the set is empty a NULL pointer
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226 | * is returned.
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227 | *
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228 | * Accesses outside variables: none
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229 | */
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230 |
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231 | void *
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232 | SP_deletemin (Splay_Tree * S)
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233 | {
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234 | node *tmp;
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235 | char *dat;
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236 |
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237 | dat = SP_get_first (S);
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238 | if (dat)
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239 | {
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240 | tmp = (node *) S->root;
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241 | S->root = (char *) tmp->rght;
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242 | if (S->root)
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243 | ((node *) S->root)->par = NULL;
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244 | }
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245 | S->no_of_items--;
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246 | return dat;
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247 | } /* deletemin() */
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248 |
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249 |
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250 | /*
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251 | * member():
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252 | * searches the given set for an item which matches (has
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253 | * the same key) and returns a pointer to a copy of that item.
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254 | * If no matching item is found a NULL pointer is
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255 | * returned.
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256 | *
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257 | * Accesses outside variables: none
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258 | */
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259 |
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260 | void *
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261 | SP_member (void *dat, Splay_Tree * S)
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262 | {
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263 | register node *curr;
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264 | register int dir;
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265 | static int calls = 0;
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266 |
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267 | TRACE ("in member");
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268 | for (curr = (node *) S->root; curr;)
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269 | {
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270 | TRACE ("call to cmp");
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271 | dir = S->cmp (dat, curr->datsun);
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272 | TRACE ("out of cmp");
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273 | if (dir < 0)
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274 | curr = curr->left;
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275 | else if (dir > 0)
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276 | curr = curr->rght;
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277 | else
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278 | {
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279 | /* splay occasionaly to speed up execution */
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280 | if ((calls++ % 4) == 0 && curr)
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281 | S->root = (char *) SP_splay (curr);
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282 | TRACE ("out of member");
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283 | return (curr->datsun);
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284 | }
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285 | }
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286 | TRACE ("out of member");
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287 | return (CNULL);
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288 | } /* member() */
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289 |
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290 | #define ROTATEL(p,q) \
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291 | do{ \
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292 | p->par = q->par; \
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293 | q->par = p; \
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294 | q->rght = p->left; \
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295 | if(q->rght) \
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296 | q->rght->par = q; \
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297 | p->left = q; \
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298 | if(p->par) \
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299 | if(q == p->par->left) \
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300 | p->par->left = p; \
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301 | else \
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302 | p->par->rght = p; \
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303 | }while(0)
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304 |
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305 | #define ROTATER(p,q) \
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306 | do{ \
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307 | p->par = q->par; \
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308 | q->par = p; \
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309 | q->left = p->rght; \
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310 | if(q->left) \
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311 | q->left->par = q; \
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312 | p->rght = q; \
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313 | if(p->par) \
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314 | if(q == p->par->left) \
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315 | p->par->left = p; \
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316 | else \
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317 | p->par->rght = p; \
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318 | }while(0)
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319 |
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320 |
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321 | /*
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322 | * splay():
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323 | * i
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324 | *
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325 | * Accesses outside variables: i
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326 | *
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327 | * Return value...: i
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328 | */
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329 |
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330 | static node *
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331 | SP_splay (p)
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332 | register node *p;
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333 | {
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334 | register node *q, *g;
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335 |
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336 | q = p->par;
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337 | /* splay the tree about p */
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338 | while (q != NNULL)
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339 | {
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340 | g = q->par;
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341 | if (p == q->left)
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342 | {
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343 | if (g == NNULL)
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344 | ROTATER (p, q);
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345 | else if (q == g->left)
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346 | {
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347 | ROTATER (q, g);
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348 | ROTATER (p, q);
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349 | }
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350 | else
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351 | {
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352 | ROTATER (p, q);
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353 | ROTATEL (p, g);
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354 | }
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355 | }
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356 | else
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357 | {
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358 | if (g == NNULL)
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359 | ROTATEL (p, q);
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360 | else if (q == g->rght)
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361 | {
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362 | ROTATEL (q, g);
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363 | ROTATEL (p, q);
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364 | }
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365 | else
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366 | {
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367 | ROTATEL (p, q);
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368 | ROTATER (p, g);
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369 | }
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370 | }
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371 | q = p->par;
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372 | }
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373 | return (p);
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374 | }
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