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1 <?php |
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2 /** |
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3 * Class used internally by Text_Diff to actually compute the diffs. |
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4 * |
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5 * This class is implemented using native PHP code. |
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6 * |
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7 * The algorithm used here is mostly lifted from the perl module |
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8 * Algorithm::Diff (version 1.06) by Ned Konz, which is available at: |
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9 * http://www.perl.com/CPAN/authors/id/N/NE/NEDKONZ/Algorithm-Diff-1.06.zip |
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10 * |
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11 * More ideas are taken from: http://www.ics.uci.edu/~eppstein/161/960229.html |
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12 * |
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13 * Some ideas (and a bit of code) are taken from analyze.c, of GNU |
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14 * diffutils-2.7, which can be found at: |
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15 * ftp://gnudist.gnu.org/pub/gnu/diffutils/diffutils-2.7.tar.gz |
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16 * |
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17 * Some ideas (subdivision by NCHUNKS > 2, and some optimizations) are from |
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18 * Geoffrey T. Dairiki <dairiki@dairiki.org>. The original PHP version of this |
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19 * code was written by him, and is used/adapted with his permission. |
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20 * |
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21 * Copyright 2004-2010 The Horde Project (http://www.horde.org/) |
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22 * |
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23 * See the enclosed file COPYING for license information (LGPL). If you did |
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24 * not receive this file, see http://opensource.org/licenses/lgpl-license.php. |
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25 * |
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26 * @author Geoffrey T. Dairiki <dairiki@dairiki.org> |
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27 * @package Text_Diff |
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28 */ |
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29 class Text_Diff_Engine_native { |
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30 |
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31 function diff($from_lines, $to_lines) |
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32 { |
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33 array_walk($from_lines, array('Text_Diff', 'trimNewlines')); |
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34 array_walk($to_lines, array('Text_Diff', 'trimNewlines')); |
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35 |
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36 $n_from = count($from_lines); |
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37 $n_to = count($to_lines); |
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38 |
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39 $this->xchanged = $this->ychanged = array(); |
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40 $this->xv = $this->yv = array(); |
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41 $this->xind = $this->yind = array(); |
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42 unset($this->seq); |
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43 unset($this->in_seq); |
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44 unset($this->lcs); |
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45 |
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46 // Skip leading common lines. |
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47 for ($skip = 0; $skip < $n_from && $skip < $n_to; $skip++) { |
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48 if ($from_lines[$skip] !== $to_lines[$skip]) { |
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49 break; |
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50 } |
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51 $this->xchanged[$skip] = $this->ychanged[$skip] = false; |
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52 } |
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53 |
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54 // Skip trailing common lines. |
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55 $xi = $n_from; $yi = $n_to; |
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56 for ($endskip = 0; --$xi > $skip && --$yi > $skip; $endskip++) { |
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57 if ($from_lines[$xi] !== $to_lines[$yi]) { |
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58 break; |
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59 } |
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60 $this->xchanged[$xi] = $this->ychanged[$yi] = false; |
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61 } |
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62 |
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63 // Ignore lines which do not exist in both files. |
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64 for ($xi = $skip; $xi < $n_from - $endskip; $xi++) { |
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65 $xhash[$from_lines[$xi]] = 1; |
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66 } |
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67 for ($yi = $skip; $yi < $n_to - $endskip; $yi++) { |
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68 $line = $to_lines[$yi]; |
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69 if (($this->ychanged[$yi] = empty($xhash[$line]))) { |
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70 continue; |
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71 } |
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72 $yhash[$line] = 1; |
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73 $this->yv[] = $line; |
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74 $this->yind[] = $yi; |
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75 } |
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76 for ($xi = $skip; $xi < $n_from - $endskip; $xi++) { |
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77 $line = $from_lines[$xi]; |
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78 if (($this->xchanged[$xi] = empty($yhash[$line]))) { |
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79 continue; |
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80 } |
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81 $this->xv[] = $line; |
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82 $this->xind[] = $xi; |
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83 } |
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84 |
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85 // Find the LCS. |
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86 $this->_compareseq(0, count($this->xv), 0, count($this->yv)); |
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87 |
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88 // Merge edits when possible. |
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89 $this->_shiftBoundaries($from_lines, $this->xchanged, $this->ychanged); |
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90 $this->_shiftBoundaries($to_lines, $this->ychanged, $this->xchanged); |
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91 |
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92 // Compute the edit operations. |
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93 $edits = array(); |
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94 $xi = $yi = 0; |
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95 while ($xi < $n_from || $yi < $n_to) { |
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96 assert($yi < $n_to || $this->xchanged[$xi]); |
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97 assert($xi < $n_from || $this->ychanged[$yi]); |
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98 |
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99 // Skip matching "snake". |
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100 $copy = array(); |
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101 while ($xi < $n_from && $yi < $n_to |
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102 && !$this->xchanged[$xi] && !$this->ychanged[$yi]) { |
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103 $copy[] = $from_lines[$xi++]; |
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104 ++$yi; |
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105 } |
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106 if ($copy) { |
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107 $edits[] = new Text_Diff_Op_copy($copy); |
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108 } |
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109 |
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110 // Find deletes & adds. |
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111 $delete = array(); |
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112 while ($xi < $n_from && $this->xchanged[$xi]) { |
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113 $delete[] = $from_lines[$xi++]; |
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114 } |
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115 |
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116 $add = array(); |
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117 while ($yi < $n_to && $this->ychanged[$yi]) { |
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118 $add[] = $to_lines[$yi++]; |
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119 } |
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120 |
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121 if ($delete && $add) { |
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122 $edits[] = new Text_Diff_Op_change($delete, $add); |
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123 } elseif ($delete) { |
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124 $edits[] = new Text_Diff_Op_delete($delete); |
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125 } elseif ($add) { |
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126 $edits[] = new Text_Diff_Op_add($add); |
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127 } |
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128 } |
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129 |
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130 return $edits; |
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131 } |
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132 |
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133 /** |
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134 * Divides the Largest Common Subsequence (LCS) of the sequences (XOFF, |
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135 * XLIM) and (YOFF, YLIM) into NCHUNKS approximately equally sized |
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136 * segments. |
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137 * |
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138 * Returns (LCS, PTS). LCS is the length of the LCS. PTS is an array of |
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139 * NCHUNKS+1 (X, Y) indexes giving the diving points between sub |
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140 * sequences. The first sub-sequence is contained in (X0, X1), (Y0, Y1), |
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141 * the second in (X1, X2), (Y1, Y2) and so on. Note that (X0, Y0) == |
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142 * (XOFF, YOFF) and (X[NCHUNKS], Y[NCHUNKS]) == (XLIM, YLIM). |
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143 * |
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144 * This function assumes that the first lines of the specified portions of |
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145 * the two files do not match, and likewise that the last lines do not |
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146 * match. The caller must trim matching lines from the beginning and end |
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147 * of the portions it is going to specify. |
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148 */ |
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149 function _diag ($xoff, $xlim, $yoff, $ylim, $nchunks) |
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150 { |
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151 $flip = false; |
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152 |
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153 if ($xlim - $xoff > $ylim - $yoff) { |
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154 /* Things seems faster (I'm not sure I understand why) when the |
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155 * shortest sequence is in X. */ |
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156 $flip = true; |
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157 list ($xoff, $xlim, $yoff, $ylim) |
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158 = array($yoff, $ylim, $xoff, $xlim); |
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159 } |
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160 |
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161 if ($flip) { |
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162 for ($i = $ylim - 1; $i >= $yoff; $i--) { |
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163 $ymatches[$this->xv[$i]][] = $i; |
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164 } |
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165 } else { |
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166 for ($i = $ylim - 1; $i >= $yoff; $i--) { |
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167 $ymatches[$this->yv[$i]][] = $i; |
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168 } |
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169 } |
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170 |
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171 $this->lcs = 0; |
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172 $this->seq[0]= $yoff - 1; |
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173 $this->in_seq = array(); |
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174 $ymids[0] = array(); |
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175 |
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176 $numer = $xlim - $xoff + $nchunks - 1; |
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177 $x = $xoff; |
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178 for ($chunk = 0; $chunk < $nchunks; $chunk++) { |
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179 if ($chunk > 0) { |
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180 for ($i = 0; $i <= $this->lcs; $i++) { |
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181 $ymids[$i][$chunk - 1] = $this->seq[$i]; |
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182 } |
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183 } |
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184 |
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185 $x1 = $xoff + (int)(($numer + ($xlim - $xoff) * $chunk) / $nchunks); |
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186 for (; $x < $x1; $x++) { |
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187 $line = $flip ? $this->yv[$x] : $this->xv[$x]; |
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188 if (empty($ymatches[$line])) { |
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189 continue; |
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190 } |
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191 $matches = $ymatches[$line]; |
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192 reset($matches); |
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193 while (list(, $y) = each($matches)) { |
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194 if (empty($this->in_seq[$y])) { |
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195 $k = $this->_lcsPos($y); |
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196 assert($k > 0); |
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197 $ymids[$k] = $ymids[$k - 1]; |
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198 break; |
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199 } |
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200 } |
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201 while (list(, $y) = each($matches)) { |
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202 if ($y > $this->seq[$k - 1]) { |
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203 assert($y <= $this->seq[$k]); |
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204 /* Optimization: this is a common case: next match is |
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205 * just replacing previous match. */ |
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206 $this->in_seq[$this->seq[$k]] = false; |
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207 $this->seq[$k] = $y; |
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208 $this->in_seq[$y] = 1; |
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209 } elseif (empty($this->in_seq[$y])) { |
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210 $k = $this->_lcsPos($y); |
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211 assert($k > 0); |
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212 $ymids[$k] = $ymids[$k - 1]; |
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213 } |
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214 } |
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215 } |
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216 } |
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217 |
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218 $seps[] = $flip ? array($yoff, $xoff) : array($xoff, $yoff); |
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219 $ymid = $ymids[$this->lcs]; |
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220 for ($n = 0; $n < $nchunks - 1; $n++) { |
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221 $x1 = $xoff + (int)(($numer + ($xlim - $xoff) * $n) / $nchunks); |
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222 $y1 = $ymid[$n] + 1; |
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223 $seps[] = $flip ? array($y1, $x1) : array($x1, $y1); |
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224 } |
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225 $seps[] = $flip ? array($ylim, $xlim) : array($xlim, $ylim); |
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226 |
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227 return array($this->lcs, $seps); |
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228 } |
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229 |
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230 function _lcsPos($ypos) |
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231 { |
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232 $end = $this->lcs; |
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233 if ($end == 0 || $ypos > $this->seq[$end]) { |
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234 $this->seq[++$this->lcs] = $ypos; |
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235 $this->in_seq[$ypos] = 1; |
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236 return $this->lcs; |
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237 } |
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238 |
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239 $beg = 1; |
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240 while ($beg < $end) { |
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241 $mid = (int)(($beg + $end) / 2); |
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242 if ($ypos > $this->seq[$mid]) { |
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243 $beg = $mid + 1; |
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244 } else { |
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245 $end = $mid; |
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246 } |
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247 } |
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248 |
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249 assert($ypos != $this->seq[$end]); |
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250 |
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251 $this->in_seq[$this->seq[$end]] = false; |
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252 $this->seq[$end] = $ypos; |
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253 $this->in_seq[$ypos] = 1; |
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254 return $end; |
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255 } |
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256 |
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257 /** |
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258 * Finds LCS of two sequences. |
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259 * |
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260 * The results are recorded in the vectors $this->{x,y}changed[], by |
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261 * storing a 1 in the element for each line that is an insertion or |
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262 * deletion (ie. is not in the LCS). |
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263 * |
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264 * The subsequence of file 0 is (XOFF, XLIM) and likewise for file 1. |
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265 * |
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266 * Note that XLIM, YLIM are exclusive bounds. All line numbers are |
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267 * origin-0 and discarded lines are not counted. |
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268 */ |
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269 function _compareseq ($xoff, $xlim, $yoff, $ylim) |
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270 { |
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271 /* Slide down the bottom initial diagonal. */ |
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272 while ($xoff < $xlim && $yoff < $ylim |
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273 && $this->xv[$xoff] == $this->yv[$yoff]) { |
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274 ++$xoff; |
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275 ++$yoff; |
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276 } |
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277 |
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278 /* Slide up the top initial diagonal. */ |
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279 while ($xlim > $xoff && $ylim > $yoff |
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280 && $this->xv[$xlim - 1] == $this->yv[$ylim - 1]) { |
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281 --$xlim; |
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282 --$ylim; |
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283 } |
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284 |
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285 if ($xoff == $xlim || $yoff == $ylim) { |
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286 $lcs = 0; |
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287 } else { |
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288 /* This is ad hoc but seems to work well. $nchunks = |
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289 * sqrt(min($xlim - $xoff, $ylim - $yoff) / 2.5); $nchunks = |
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290 * max(2,min(8,(int)$nchunks)); */ |
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291 $nchunks = min(7, $xlim - $xoff, $ylim - $yoff) + 1; |
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292 list($lcs, $seps) |
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293 = $this->_diag($xoff, $xlim, $yoff, $ylim, $nchunks); |
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294 } |
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295 |
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296 if ($lcs == 0) { |
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297 /* X and Y sequences have no common subsequence: mark all |
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298 * changed. */ |
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299 while ($yoff < $ylim) { |
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300 $this->ychanged[$this->yind[$yoff++]] = 1; |
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301 } |
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302 while ($xoff < $xlim) { |
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303 $this->xchanged[$this->xind[$xoff++]] = 1; |
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304 } |
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305 } else { |
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306 /* Use the partitions to split this problem into subproblems. */ |
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307 reset($seps); |
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308 $pt1 = $seps[0]; |
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309 while ($pt2 = next($seps)) { |
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310 $this->_compareseq ($pt1[0], $pt2[0], $pt1[1], $pt2[1]); |
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311 $pt1 = $pt2; |
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312 } |
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313 } |
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314 } |
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315 |
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316 /** |
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317 * Adjusts inserts/deletes of identical lines to join changes as much as |
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318 * possible. |
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319 * |
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320 * We do something when a run of changed lines include a line at one end |
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321 * and has an excluded, identical line at the other. We are free to |
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322 * choose which identical line is included. `compareseq' usually chooses |
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323 * the one at the beginning, but usually it is cleaner to consider the |
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324 * following identical line to be the "change". |
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325 * |
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326 * This is extracted verbatim from analyze.c (GNU diffutils-2.7). |
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327 */ |
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328 function _shiftBoundaries($lines, &$changed, $other_changed) |
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329 { |
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330 $i = 0; |
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331 $j = 0; |
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332 |
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333 assert('count($lines) == count($changed)'); |
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334 $len = count($lines); |
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335 $other_len = count($other_changed); |
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336 |
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337 while (1) { |
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338 /* Scan forward to find the beginning of another run of |
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339 * changes. Also keep track of the corresponding point in the |
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340 * other file. |
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341 * |
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342 * Throughout this code, $i and $j are adjusted together so that |
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343 * the first $i elements of $changed and the first $j elements of |
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344 * $other_changed both contain the same number of zeros (unchanged |
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345 * lines). |
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346 * |
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347 * Furthermore, $j is always kept so that $j == $other_len or |
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348 * $other_changed[$j] == false. */ |
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349 while ($j < $other_len && $other_changed[$j]) { |
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350 $j++; |
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351 } |
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352 |
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353 while ($i < $len && ! $changed[$i]) { |
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354 assert('$j < $other_len && ! $other_changed[$j]'); |
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355 $i++; $j++; |
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356 while ($j < $other_len && $other_changed[$j]) { |
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357 $j++; |
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358 } |
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359 } |
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360 |
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361 if ($i == $len) { |
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362 break; |
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363 } |
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364 |
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365 $start = $i; |
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366 |
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367 /* Find the end of this run of changes. */ |
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368 while (++$i < $len && $changed[$i]) { |
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369 continue; |
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370 } |
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371 |
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372 do { |
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373 /* Record the length of this run of changes, so that we can |
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374 * later determine whether the run has grown. */ |
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375 $runlength = $i - $start; |
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376 |
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377 /* Move the changed region back, so long as the previous |
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378 * unchanged line matches the last changed one. This merges |
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379 * with previous changed regions. */ |
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380 while ($start > 0 && $lines[$start - 1] == $lines[$i - 1]) { |
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381 $changed[--$start] = 1; |
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382 $changed[--$i] = false; |
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383 while ($start > 0 && $changed[$start - 1]) { |
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384 $start--; |
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385 } |
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386 assert('$j > 0'); |
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387 while ($other_changed[--$j]) { |
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388 continue; |
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389 } |
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390 assert('$j >= 0 && !$other_changed[$j]'); |
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391 } |
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392 |
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393 /* Set CORRESPONDING to the end of the changed run, at the |
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394 * last point where it corresponds to a changed run in the |
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395 * other file. CORRESPONDING == LEN means no such point has |
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396 * been found. */ |
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397 $corresponding = $j < $other_len ? $i : $len; |
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398 |
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399 /* Move the changed region forward, so long as the first |
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400 * changed line matches the following unchanged one. This |
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401 * merges with following changed regions. Do this second, so |
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402 * that if there are no merges, the changed region is moved |
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403 * forward as far as possible. */ |
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404 while ($i < $len && $lines[$start] == $lines[$i]) { |
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405 $changed[$start++] = false; |
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406 $changed[$i++] = 1; |
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407 while ($i < $len && $changed[$i]) { |
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408 $i++; |
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409 } |
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410 |
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411 assert('$j < $other_len && ! $other_changed[$j]'); |
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412 $j++; |
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413 if ($j < $other_len && $other_changed[$j]) { |
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414 $corresponding = $i; |
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415 while ($j < $other_len && $other_changed[$j]) { |
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416 $j++; |
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417 } |
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418 } |
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419 } |
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420 } while ($runlength != $i - $start); |
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421 |
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422 /* If possible, move the fully-merged run of changes back to a |
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423 * corresponding run in the other file. */ |
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424 while ($corresponding < $i) { |
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425 $changed[--$start] = 1; |
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426 $changed[--$i] = 0; |
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427 assert('$j > 0'); |
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428 while ($other_changed[--$j]) { |
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429 continue; |
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430 } |
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431 assert('$j >= 0 && !$other_changed[$j]'); |
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432 } |
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433 } |
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434 } |
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435 |
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436 } |