1 | |
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2 | /* |
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3 | * Chain.cpp -- |
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4 | * |
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5 | * The module implements a generic linked list package. |
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6 | * |
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7 | * Copyright 1991-2004 George A Howlett. |
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8 | * |
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9 | * Permission is hereby granted, free of charge, to any person obtaining |
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10 | * a copy of this software and associated documentation files (the |
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11 | * "Software"), to deal in the Software without restriction, including |
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12 | * without limitation the rights to use, copy, modify, merge, publish, |
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13 | * distribute, sublicense, and/or sell copies of the Software, and to |
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14 | * permit persons to whom the Software is furnished to do so, subject to |
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15 | * the following conditions: |
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16 | * |
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17 | * The above copyright notice and this permission notice shall be |
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18 | * included in all copies or substantial portions of the Software. |
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19 | * |
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20 | * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, |
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21 | * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF |
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22 | * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND |
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23 | * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE |
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24 | * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION |
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25 | * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION |
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26 | * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. |
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27 | */ |
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28 | |
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29 | #include <stdlib.h> |
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30 | #include <stdio.h> |
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31 | #include "Chain.h" |
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32 | |
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33 | typedef int (QSortCompareProc) (const void *, const void *); |
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34 | |
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35 | /* |
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36 | *---------------------------------------------------------------------- |
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37 | * |
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38 | * Reset -- |
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39 | * |
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40 | * Removes all the links from the chain, freeing the memory for each |
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41 | * link. Memory pointed to by the link (clientData) is not freed. It's |
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42 | * the caller's responsibility to deallocate it. |
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43 | * |
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44 | * Results: |
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45 | * None. |
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46 | * |
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47 | *---------------------------------------------------------------------- |
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48 | */ |
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49 | void |
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50 | Chain::Reset() /* Chain to clear */ |
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51 | { |
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52 | ChainLink *oldPtr; |
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53 | ChainLink *linkPtr = _head; |
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54 | |
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55 | while (linkPtr != NULL) { |
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56 | oldPtr = linkPtr; |
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57 | linkPtr = linkPtr->Next(); |
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58 | delete oldPtr; |
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59 | } |
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60 | Init(); |
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61 | } |
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62 | |
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63 | /* |
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64 | *---------------------------------------------------------------------- |
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65 | * |
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66 | * LinkAfter -- |
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67 | * |
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68 | * Inserts a link after another link. If afterPtr is NULL, then the new |
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69 | * link is prepended to the beginning of the chain. |
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70 | * |
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71 | * Results: |
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72 | * None. |
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73 | * |
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74 | *---------------------------------------------------------------------- |
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75 | */ |
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76 | void |
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77 | Chain::LinkAfter(ChainLink *linkPtr, ChainLink *afterPtr) |
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78 | { |
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79 | if (_head == NULL) { |
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80 | _tail = _head = linkPtr; |
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81 | } else { |
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82 | if (afterPtr == NULL) { |
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83 | /* Prepend to the front of the chain */ |
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84 | linkPtr->_next = _head; |
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85 | linkPtr->_prev = NULL; |
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86 | _head->_prev = linkPtr; |
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87 | _head = linkPtr; |
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88 | } else { |
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89 | linkPtr->_next = afterPtr->Next(); |
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90 | linkPtr->_prev = afterPtr; |
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91 | if (afterPtr == _tail) { |
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92 | _tail = linkPtr; |
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93 | } else { |
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94 | afterPtr->Next()->_prev = linkPtr; |
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95 | } |
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96 | afterPtr->_next = linkPtr; |
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97 | } |
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98 | } |
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99 | _nLinks++; |
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100 | } |
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101 | |
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102 | /* |
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103 | *---------------------------------------------------------------------- |
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104 | * |
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105 | * LinkBefore -- |
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106 | * |
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107 | * Inserts a new link preceding a given link in a chain. If beforePtr is |
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108 | * NULL, then the new link is placed at the beginning of the list. |
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109 | * |
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110 | * Results: |
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111 | * None. |
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112 | * |
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113 | *---------------------------------------------------------------------- |
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114 | */ |
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115 | void |
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116 | Chain::LinkBefore( |
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117 | ChainLink *linkPtr, /* New entry to be inserted */ |
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118 | ChainLink *beforePtr) /* Entry to link before */ |
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119 | { |
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120 | if (_head == NULL) { |
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121 | _tail = _head = linkPtr; |
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122 | } else { |
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123 | if (beforePtr == NULL) { |
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124 | /* Append to the end of the chain. */ |
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125 | linkPtr->_next = NULL; |
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126 | linkPtr->_prev = _tail; |
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127 | _tail->_next = linkPtr; |
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128 | _tail = linkPtr; |
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129 | } else { |
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130 | linkPtr->_prev = beforePtr->Prev(); |
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131 | linkPtr->_next = beforePtr; |
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132 | if (beforePtr == _head) { |
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133 | _head = linkPtr; |
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134 | } else { |
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135 | beforePtr->Prev()->_next = linkPtr; |
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136 | } |
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137 | beforePtr->_prev = linkPtr; |
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138 | } |
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139 | } |
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140 | _nLinks++; |
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141 | } |
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142 | |
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143 | /* |
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144 | *---------------------------------------------------------------------- |
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145 | * |
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146 | * Unlink -- |
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147 | * |
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148 | * Unlinks a link from the chain. The link is not deallocated, |
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149 | * but only removed from the chain. |
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150 | * |
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151 | * Results: |
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152 | * None. |
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153 | * |
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154 | *---------------------------------------------------------------------- |
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155 | */ |
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156 | void |
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157 | Chain::Unlink(ChainLink *linkPtr) |
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158 | { |
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159 | bool unlinked; /* Indicates if the link is actually removed |
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160 | * from the chain. */ |
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161 | |
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162 | unlinked = false; |
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163 | if (_head == linkPtr) { |
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164 | _head = linkPtr->Next(); |
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165 | unlinked = true; |
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166 | } |
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167 | if (_tail == linkPtr) { |
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168 | _tail = linkPtr->Prev(); |
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169 | unlinked = true; |
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170 | } |
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171 | if (linkPtr->Next() != NULL) { |
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172 | linkPtr->Next()->_prev = linkPtr->Prev(); |
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173 | unlinked = true; |
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174 | } |
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175 | if (linkPtr->Prev() != NULL) { |
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176 | linkPtr->Prev()->_next = linkPtr->Next(); |
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177 | unlinked = true; |
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178 | } |
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179 | if (unlinked) { |
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180 | _nLinks--; |
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181 | } |
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182 | linkPtr->_prev = linkPtr->_next = NULL; |
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183 | } |
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184 | |
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185 | /* |
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186 | *---------------------------------------------------------------------- |
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187 | * |
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188 | * DeleteLink -- |
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189 | * |
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190 | * Unlinks and frees the given link from the chain. It's assumed that |
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191 | * the link belong to the chain. No error checking is performed to verify |
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192 | * this. |
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193 | * |
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194 | * Results: |
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195 | * None. |
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196 | * |
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197 | *---------------------------------------------------------------------- |
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198 | */ |
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199 | void |
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200 | Chain::DeleteLink(ChainLink *linkPtr) |
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201 | { |
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202 | Unlink(linkPtr); |
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203 | delete linkPtr; |
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204 | } |
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205 | |
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206 | /* |
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207 | *---------------------------------------------------------------------- |
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208 | * |
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209 | * Append -- |
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210 | * |
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211 | * Creates and new link with the given data and appends it to the end of |
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212 | * the chain. |
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213 | * |
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214 | * Results: |
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215 | * Returns a pointer to the link created. |
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216 | * |
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217 | *---------------------------------------------------------------------- |
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218 | */ |
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219 | ChainLink * |
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220 | Chain::Append(void *clientData) |
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221 | { |
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222 | ChainLink *linkPtr; |
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223 | |
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224 | linkPtr = new ChainLink(clientData); |
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225 | LinkBefore(linkPtr, (ChainLink *)NULL); |
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226 | return linkPtr; |
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227 | } |
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228 | |
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229 | /* |
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230 | *---------------------------------------------------------------------- |
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231 | * |
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232 | * Prepend -- |
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233 | * |
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234 | * Creates and new link with the given data and prepends it to beginning |
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235 | * of the chain. |
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236 | * |
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237 | * Results: |
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238 | * Returns a pointer to the link created. |
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239 | * |
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240 | *---------------------------------------------------------------------- |
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241 | */ |
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242 | ChainLink * |
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243 | Chain::Prepend(void *clientData) |
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244 | { |
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245 | ChainLink *linkPtr; |
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246 | |
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247 | linkPtr = new ChainLink(clientData); |
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248 | LinkAfter(linkPtr, (ChainLink *)NULL); |
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249 | return linkPtr; |
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250 | } |
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251 | |
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252 | /* |
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253 | *---------------------------------------------------------------------- |
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254 | * |
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255 | * GetNthLink -- |
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256 | * |
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257 | * Find the link at the given position in the chain. |
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258 | * |
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259 | * Results: |
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260 | * Returns the pointer to the link, if that numbered link |
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261 | * exists. Otherwise NULL. |
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262 | * |
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263 | *---------------------------------------------------------------------- |
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264 | */ |
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265 | ChainLink * |
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266 | Chain::GetNthLink(long position) /* Index of link to select from front or back |
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267 | * of the chain. */ |
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268 | { |
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269 | ChainLink *linkPtr; |
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270 | |
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271 | for (linkPtr = _head; linkPtr != NULL; linkPtr = linkPtr->Next()) { |
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272 | if (position == 0) { |
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273 | return linkPtr; |
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274 | } |
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275 | position--; |
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276 | } |
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277 | return NULL; |
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278 | } |
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279 | |
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280 | /* |
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281 | *---------------------------------------------------------------------- |
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282 | * |
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283 | * Sort -- |
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284 | * |
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285 | * Sorts the chain according to the given comparison routine. |
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286 | * |
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287 | * Results: |
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288 | * None. |
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289 | * |
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290 | * Side Effects: |
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291 | * The chain is reordered. |
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292 | * |
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293 | *---------------------------------------------------------------------- |
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294 | */ |
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295 | |
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296 | void |
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297 | Chain::Sort(ChainCompareProc *proc) |
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298 | { |
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299 | ChainLink *linkPtr; |
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300 | long i; |
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301 | |
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302 | if (_nLinks < 2) { |
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303 | return; |
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304 | } |
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305 | ChainLink **linkArr = new ChainLink *[_nLinks + 1]; |
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306 | if (linkArr == NULL) { |
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307 | return; /* Out of memory. */ |
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308 | } |
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309 | i = 0; |
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310 | for (linkPtr = _head; linkPtr != NULL; linkPtr = linkPtr->Next()) { |
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311 | linkArr[i++] = linkPtr; |
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312 | } |
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313 | qsort((char *)linkArr, _nLinks, sizeof(ChainLink *), |
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314 | (QSortCompareProc *)proc); |
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315 | |
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316 | /* Rethread the chain. */ |
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317 | linkPtr = linkArr[0]; |
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318 | _head = linkPtr; |
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319 | linkPtr->_prev = NULL; |
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320 | for (i = 1; i < _nLinks; i++) { |
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321 | linkPtr->_next = linkArr[i]; |
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322 | linkPtr->Next()->_prev = linkPtr; |
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323 | linkPtr = linkPtr->Next(); |
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324 | } |
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325 | _tail = linkPtr; |
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326 | linkPtr->_next = NULL; |
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327 | delete [] linkArr; |
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328 | } |
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329 | |
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