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1 ;;; compare-w.el --- compare text between windows for Emacs.
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2
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3 ;; Copyright (C) 1986, 1989, 1993 Free Software Foundation, Inc.
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4
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5 ;; Maintainer: FSF
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6
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7 ;; This file is part of XEmacs.
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8
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9 ;; XEmacs is free software; you can redistribute it and/or modify it
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10 ;; under the terms of the GNU General Public License as published by
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11 ;; the Free Software Foundation; either version 2, or (at your option)
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12 ;; any later version.
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13
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14 ;; XEmacs is distributed in the hope that it will be useful, but
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15 ;; WITHOUT ANY WARRANTY; without even the implied warranty of
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16 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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17 ;; General Public License for more details.
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18
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19 ;; You should have received a copy of the GNU General Public License
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20 ;; along with XEmacs; see the file COPYING. If not, write to the Free
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21 ;; Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
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22
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23 ;;; Synched up with: FSF 19.30.
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24
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25 ;;; Whatever was here before didn't look any more correct than the
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26 ;;; FSF version, so I've junked it and replaced it with the FSF version.
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27 ;;; If you really don't like this, dig out the previous version from
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28 ;;; 19.13. --ben
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29
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30 ;;; Commentary:
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31
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32 ;; This package provides one entry point, compare-windows. It compares
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33 ;; text starting from point in two adjacent windows, advancing point
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34 ;; until it finds a difference. Option variables permit you to ignore
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35 ;; whitespace differences, or case differences, or both.
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36
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37 ;;; Code:
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38
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39 (defvar compare-windows-whitespace "[ \t\n]+"
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40 "*Regexp that defines whitespace sequences for \\[compare-windows].
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41 Changes in whitespace are optionally ignored.
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42
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43 The value of `compare-windows-whitespace' may instead be a function; this
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44 function is called in each buffer, with point at the current scanning point.
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45 The function's job is to categorize any whitespace around (including before)
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46 point; it should also advance past any whitespace.
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47
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48 The function is passed one argument, the point where `compare-windows'
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49 was originally called; it should not consider any text before that point.
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50 If the function returns the same value for both buffers, then the
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51 whitespace is considered to match, and is skipped.")
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52
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53 (defvar compare-ignore-case nil
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54 "*Non-nil means \\[compare-windows] ignores case differences.")
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55
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56 ;;;###autoload
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57 (defun compare-windows (ignore-whitespace)
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58 "Compare text in current window with text in next window.
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59 Compares the text starting at point in each window,
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60 moving over text in each one as far as they match.
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61
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62 This command pushes the mark in each window
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63 at the prior location of point in that window.
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64 If both windows display the same buffer,
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65 the mark is pushed twice in that buffer:
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66 first in the other window, then in the selected window.
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67
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68 A prefix arg means ignore changes in whitespace.
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69 The variable `compare-windows-whitespace' controls how whitespace is skipped.
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70 If `compare-ignore-case' is non-nil, changes in case are also ignored."
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71 (interactive "P")
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72 (let* (p1 p2 maxp1 maxp2 b1 b2 w2
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73 success size
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74 (opoint1 (point))
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75 opoint2
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76 (skip-whitespace (if ignore-whitespace
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77 compare-windows-whitespace)))
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78 (setq p1 (point) b1 (current-buffer))
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79 (setq w2 (next-window (selected-window)))
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80 (if (eq w2 (selected-window))
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81 (error "No other window"))
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82 (setq p2 (window-point w2)
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83 b2 (window-buffer w2))
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84 (setq opoint2 p2)
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85 (setq maxp1 (point-max))
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86 (save-excursion
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87 (set-buffer b2)
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88 (push-mark p2 t)
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89 (setq maxp2 (point-max)))
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90 (push-mark)
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91
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92 (setq success t)
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93 (while success
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94 (setq success nil)
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95 ;; if interrupted, show how far we've gotten
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96 (goto-char p1)
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97 (set-window-point w2 p2)
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98
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99 ;; If both buffers have whitespace next to point,
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100 ;; optionally skip over it.
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101
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102 (and skip-whitespace
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103 (save-excursion
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104 (let (p1a p2a w1 w2 result1 result2)
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105 (setq result1
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106 (if (stringp skip-whitespace)
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107 (compare-windows-skip-whitespace opoint1)
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108 (funcall skip-whitespace opoint1)))
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109 (setq p1a (point))
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110 (set-buffer b2)
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111 (goto-char p2)
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112 (setq result2
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113 (if (stringp skip-whitespace)
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114 (compare-windows-skip-whitespace opoint2)
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115 (funcall skip-whitespace opoint2)))
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116 (setq p2a (point))
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117 (if (or (stringp skip-whitespace)
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118 (and result1 result2 (eq result1 result2)))
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119 (setq p1 p1a
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120 p2 p2a)))))
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121
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122 ;; Try advancing comparing 1000 chars at a time.
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123 ;; When that fails, go 500 chars at a time, and so on.
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124 (let ((size 1000)
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125 success-1
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126 (case-fold-search compare-ignore-case))
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127 (while (> size 0)
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128 (setq success-1 t)
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129 ;; Try comparing SIZE chars at a time, repeatedly, till that fails.
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130 (while success-1
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131 (setq size (min size (- maxp1 p1) (- maxp2 p2)))
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132 (setq success-1
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133 (and (> size 0)
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134 (= 0 (compare-buffer-substrings b2 p2 (+ size p2)
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135 b1 p1 (+ size p1)))))
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136 (if success-1
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137 (setq p1 (+ p1 size) p2 (+ p2 size)
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138 success t)))
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139 ;; If SIZE chars don't match, try fewer.
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140 (setq size (/ size 2)))))
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141
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142 (goto-char p1)
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143 (set-window-point w2 p2)
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144 (if (= (point) opoint1)
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145 (ding))))
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146
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147 ;; Move forward over whatever might be called whitespace.
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148 ;; compare-windows-whitespace is a regexp that matches whitespace.
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149 ;; Match it at various starting points before the original point
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150 ;; and find the latest point at which a match ends.
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151 ;; Don't try starting points before START, though.
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152 ;; Value is non-nil if whitespace is found.
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153
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154 ;; If there is whitespace before point, but none after,
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155 ;; then return t, but don't advance point.
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156 (defun compare-windows-skip-whitespace (start)
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157 (let ((end (point))
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158 (beg (point))
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159 (opoint (point)))
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160 (while (or (and (looking-at compare-windows-whitespace)
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161 (<= end (match-end 0))
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162 ;; This match goes past END, so advance END.
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163 (progn (setq end (match-end 0))
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164 (> (point) start)))
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165 (and (/= (point) start)
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166 ;; Consider at least the char before point,
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167 ;; unless it is also before START.
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168 (= (point) opoint)))
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169 ;; keep going back until whitespace
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170 ;; doesn't extend to or past end
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171 (forward-char -1))
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172 (setq beg (point))
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173 (goto-char end)
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174 (or (/= beg opoint)
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175 (/= end opoint))))
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176
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177 (provide 'compare-w)
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178
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179 ;;; compare-w.el ends here
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