0
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1 /* Copyright (C) 1985, 1986, 1987, 1992, 1993, 1994
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2 Free Software Foundation, Inc.
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3
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4 This file is part of XEmacs.
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5
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6 XEmacs is free software; you can redistribute it and/or modify it
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7 under the terms of the GNU General Public License as published by the
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8 Free Software Foundation; either version 2, or (at your option) any
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9 later version.
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10
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11 XEmacs is distributed in the hope that it will be useful, but WITHOUT
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12 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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13 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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14 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 XEmacs; see the file COPYING. If not, write to
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18 the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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19 Boston, MA 02111-1307, USA. */
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20
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21 /* Synched up with: FSF 19.30. */
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22
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23 #include <config.h>
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24 #include "lisp.h"
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25
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26 #include "buffer.h"
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159
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27 #include <paths.h>
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0
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28
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29 #include "sysfile.h"
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30 #include "sysdir.h"
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31 #include "syspwd.h"
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32 #include "syssignal.h" /* for kill */
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33
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175
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34 #ifndef CLASH_DETECTION
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35 #error CLASH_DETECTION is not defined??
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36 #endif
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0
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37
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38 /* FSFmacs uses char *lock_dir and char *superlock_file instead of
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39 the Lisp variables we use. */
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40
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41 /* The name of the directory in which we keep lock files, with a '/'
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185
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42 appended. */
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0
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43 Lisp_Object Vlock_directory;
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44
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45 #if 0 /* FSFmacs */
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46 /* Look in startup.el */
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47 /* The name of the file in the lock directory which is used to
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48 arbitrate access to the entire directory. */
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49 #define SUPERLOCK_NAME "!!!SuperLock!!!"
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50 #endif
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51
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52 /* The name of the superlock file. This is SUPERLOCK_NAME appended to
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53 Vlock_directory. */
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54 Lisp_Object Vsuperlock_file;
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55
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56 Lisp_Object Qask_user_about_supersession_threat;
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57 Lisp_Object Qask_user_about_lock;
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58
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59 static void lock_superlock (CONST char *lfname);
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60 static int lock_file_1 (CONST char *lfname, int mode);
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61 static int lock_if_free (CONST char *lfname);
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62 static int current_lock_owner (CONST char *);
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63 static int current_lock_owner_1 (CONST char *);
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64
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65 /* Set LOCK to the name of the lock file for the filename FILE.
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66 char *LOCK; Lisp_Object FILE;
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67
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68 MAKE_LOCK_NAME assumes you have already verified that Vlock_directory
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69 is a string. */
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70
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71 #ifndef HAVE_LONG_FILE_NAMES
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72
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80
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73 #define MAKE_LOCK_NAME(lock, file) \
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74 (lock = (char *) alloca (14 + XSTRING_LENGTH (Vlock_directory) + 1), \
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0
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75 fill_in_lock_short_file_name (lock, (file)))
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76
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77 static void
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78 fill_in_lock_short_file_name (REGISTER char *lockfile, REGISTER Lisp_Object fn)
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79 {
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80 REGISTER union
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81 {
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82 unsigned int word [2];
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83 unsigned char byte [8];
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84 } crc;
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85 REGISTER unsigned char *p, new;
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86
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87 CHECK_STRING (Vlock_directory);
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185
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88
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0
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89 /* 7-bytes cyclic code for burst correction on byte-by-byte basis.
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90 the used polynomial is D^7 + D^6 + D^3 +1. pot@cnuce.cnr.it */
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91
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92 crc.word[0] = crc.word[1] = 0;
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93
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14
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94 for (p = XSTRING_DATA (fn); new = *p++; )
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0
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95 {
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96 new += crc.byte[6];
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97 crc.byte[6] = crc.byte[5] + new;
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98 crc.byte[5] = crc.byte[4];
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99 crc.byte[4] = crc.byte[3];
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100 crc.byte[3] = crc.byte[2] + new;
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101 crc.byte[2] = crc.byte[1];
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102 crc.byte[1] = crc.byte[0];
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103 crc.byte[0] = new;
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104 }
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105
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106 {
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107 int need_slash = 0;
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108
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109 /* in case lock-directory doesn't end in / */
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80
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110 if (XSTRING_BYTE (Vlock_directory,
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14
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111 XSTRING_LENGTH (Vlock_directory) - 1) != '/')
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0
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112 need_slash = 1;
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113
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114 sprintf (lockfile, "%s%s%.2x%.2x%.2x%.2x%.2x%.2x%.2x",
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14
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115 (char *) XSTRING_DATA (Vlock_directory),
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0
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116 need_slash ? "/" : "",
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117 crc.byte[0], crc.byte[1], crc.byte[2], crc.byte[3],
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118 crc.byte[4], crc.byte[5], crc.byte[6]);
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119 }
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120 }
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121
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122 #else /* defined HAVE_LONG_FILE_NAMES */
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123
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124 /* +2 for terminating null and possible extra slash */
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80
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125 #define MAKE_LOCK_NAME(lock, file) \
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126 (lock = (char *) alloca (XSTRING_LENGTH (file) + \
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127 XSTRING_LENGTH (Vlock_directory) + 2), \
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0
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128 fill_in_lock_file_name (lock, (file)))
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129
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130 static void
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131 fill_in_lock_file_name (REGISTER char *lockfile, REGISTER Lisp_Object fn)
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132 /* fn must be a Lisp_String! */
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133 {
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134 REGISTER char *p;
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135
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136 CHECK_STRING (Vlock_directory);
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137
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14
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138 strcpy (lockfile, (char *) XSTRING_DATA (Vlock_directory));
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0
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139
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140 p = lockfile + strlen (lockfile);
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141
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142 if (p == lockfile /* lock-directory is empty?? */
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143 || *(p - 1) != '/') /* in case lock-directory doesn't end in / */
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144 {
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145 *p = '/';
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146 p++;
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147 }
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148
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14
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149 strcpy (p, (char *) XSTRING_DATA (fn));
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0
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150
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151 for (; *p; p++)
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152 {
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153 if (*p == '/')
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154 *p = '!';
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155 }
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156 }
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157 #endif /* !defined HAVE_LONG_FILE_NAMES */
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158
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159 static Lisp_Object
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160 lock_file_owner_name (CONST char *lfname)
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161 {
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162 struct stat s;
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163 struct passwd *the_pw = 0;
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164
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165 if (lstat (lfname, &s) == 0)
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166 the_pw = getpwuid (s.st_uid);
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167 return (the_pw == 0 ? Qnil : build_string (the_pw->pw_name));
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168 }
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169
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170
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171 /* lock_file locks file fn,
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172 meaning it serves notice on the world that you intend to edit that file.
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173 This should be done only when about to modify a file-visiting
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174 buffer previously unmodified.
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175 Do not (normally) call lock_buffer for a buffer already modified,
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176 as either the file is already locked, or the user has already
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177 decided to go ahead without locking.
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178
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179 When lock_buffer returns, either the lock is locked for us,
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180 or the user has said to go ahead without locking.
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181
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182 If the file is locked by someone else, lock_buffer calls
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183 ask-user-about-lock (a Lisp function) with two arguments,
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184 the file name and the name of the user who did the locking.
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185 This function can signal an error, or return t meaning
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186 take away the lock, or return nil meaning ignore the lock. */
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187
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188 /* The lock file name is the file name with "/" replaced by "!"
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189 and put in the Emacs lock directory. */
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190 /* (ie., /ka/king/junk.tex -> /!/!ka!king!junk.tex). */
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191
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192 /* If HAVE_LONG_FILE_NAMES is not defined, the lock file name is the hex
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193 representation of a 14-bytes CRC generated from the file name
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194 and put in the Emacs lock directory (not very nice, but it works).
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195 (ie., /ka/king/junk.tex -> /!/12a82c62f1c6da). */
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196
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197 void
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198 lock_file (Lisp_Object fn)
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199 {
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114
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200 /* This function can GC. */
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201 /* dmoore - and can destroy current_buffer and all sorts of other
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202 mean nasty things with pointy teeth. If you call this make sure
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203 you protect things right. */
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204
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0
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205 REGISTER Lisp_Object attack, orig_fn;
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206 REGISTER char *lfname;
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207 struct gcpro gcpro1, gcpro2;
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208 Lisp_Object subject_buf = Qnil;
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209
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210 if (NILP (Vlock_directory) || NILP (Vsuperlock_file))
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211 return;
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212 CHECK_STRING (fn);
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213 CHECK_STRING (Vlock_directory);
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214
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215 GCPRO2 (fn, subject_buf);
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216 orig_fn = fn;
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217 fn = Fexpand_file_name (fn, Qnil);
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218
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219 /* Create the name of the lock-file for file fn */
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220 MAKE_LOCK_NAME (lfname, fn);
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221
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222 /* See if this file is visited and has changed on disk since it was
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223 visited. */
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224 subject_buf = Fget_file_buffer (fn);
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225 if (!NILP (subject_buf)
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226 && NILP (Fverify_visited_file_modtime (subject_buf))
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227 && !NILP (Ffile_exists_p (fn)))
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228 call1_in_buffer (XBUFFER (subject_buf),
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229 Qask_user_about_supersession_threat, fn);
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230
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231 /* Try to lock the lock. */
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232 if (lock_if_free (lfname) <= 0)
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233 /* Return now if we have locked it, or if lock dir does not exist */
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234 goto done;
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235
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236 /* Else consider breaking the lock */
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237 attack = call2_in_buffer (BUFFERP (subject_buf) ? XBUFFER (subject_buf) :
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238 current_buffer, Qask_user_about_lock, fn,
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239 lock_file_owner_name (lfname));
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240 if (!NILP (attack))
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241 /* User says take the lock */
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242 {
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243 CHECK_STRING (Vsuperlock_file);
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244 lock_superlock (lfname);
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245 lock_file_1 (lfname, O_WRONLY);
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14
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246 unlink ((char *) XSTRING_DATA (Vsuperlock_file));
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0
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247 goto done;
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248 }
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249 /* User says ignore the lock */
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250 done:
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251 UNGCPRO;
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252 }
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253
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254
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255 /* Lock the lock file named LFNAME.
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256 If MODE is O_WRONLY, we do so even if it is already locked.
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257 If MODE is O_WRONLY | O_EXCL | O_CREAT, we do so only if it is free.
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258 Return 1 if successful, 0 if not. */
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259
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260 static int
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261 lock_file_1 (CONST char *lfname, int mode)
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262 {
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263 REGISTER int fd;
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264 char buf[20];
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265
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266 if ((fd = open (lfname, mode, 0666)) >= 0)
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267 {
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100
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268 #if defined(WINDOWSNT)
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269 chmod(lfname, _S_IREAD|_S_IWRITE);
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270 #elif defined(USG)
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0
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271 chmod (lfname, 0666);
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272 #else
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273 fchmod (fd, 0666);
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274 #endif
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275 sprintf (buf, "%ld ", (long) getpid ());
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276 write (fd, buf, strlen (buf));
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277 close (fd);
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278 return 1;
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279 }
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280 else
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281 return 0;
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282 }
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283
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284 /* Lock the lock named LFNAME if possible.
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285 Return 0 in that case.
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286 Return positive if lock is really locked by someone else.
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287 Return -1 if cannot lock for any other reason. */
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288
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289 static int
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290 lock_if_free (CONST char *lfname)
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291 {
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292 REGISTER int clasher;
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293
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294 while (lock_file_1 (lfname, O_WRONLY | O_EXCL | O_CREAT) == 0)
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295 {
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296 if (errno != EEXIST)
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297 return -1;
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298 clasher = current_lock_owner (lfname);
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299 if (clasher != 0)
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300 if (clasher != getpid ())
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301 return (clasher);
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302 else return (0);
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303 /* Try again to lock it */
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304 }
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305 return 0;
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306 }
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307
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308 /* Return the pid of the process that claims to own the lock file LFNAME,
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309 or 0 if nobody does or the lock is obsolete,
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310 or -1 if something is wrong with the locking mechanism. */
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311
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312 static int
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313 current_lock_owner (CONST char *lfname)
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314 {
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315 int owner = current_lock_owner_1 (lfname);
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316 if (owner == 0 && errno == ENOENT)
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317 return (0);
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318 /* Is it locked by a process that exists? */
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319 if (owner != 0 && (kill (owner, 0) >= 0 || errno == EPERM))
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320 return (owner);
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321 if (unlink (lfname) < 0)
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322 return (-1);
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323 return (0);
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324 }
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325
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326 static int
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327 current_lock_owner_1 (CONST char *lfname)
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328 {
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329 REGISTER int fd;
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330 char buf[20];
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331 int tem;
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332
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333 fd = open (lfname, O_RDONLY, 0666);
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334 if (fd < 0)
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335 return 0;
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336 tem = read (fd, buf, sizeof buf);
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337 close (fd);
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338 return (tem <= 0 ? 0 : atoi (buf));
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339 }
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340
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341
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342 void
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343 unlock_file (Lisp_Object fn)
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344 {
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114
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345 /* This function can GC. */
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346 /* dmoore - and can destroy current_buffer and all sorts of other
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347 mean nasty things with pointy teeth. If you call this make sure
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348 you protect things right. */
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349
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0
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350 REGISTER char *lfname;
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351 if (NILP (Vlock_directory) || NILP (Vsuperlock_file)) return;
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352 CHECK_STRING (fn);
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353 CHECK_STRING (Vlock_directory);
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354 CHECK_STRING (Vsuperlock_file);
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355
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356 fn = Fexpand_file_name (fn, Qnil);
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357
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358 MAKE_LOCK_NAME (lfname, fn);
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359
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360 lock_superlock (lfname);
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361
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362 if (current_lock_owner_1 (lfname) == getpid ())
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363 unlink (lfname);
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364
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14
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365 unlink ((char *) XSTRING_DATA (Vsuperlock_file));
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0
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366 }
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367
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368 static void
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369 lock_superlock (CONST char *lfname)
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370 {
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371 REGISTER int i, fd;
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372 DIR *lockdir;
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373
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374 for (i = -20; i < 0 &&
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14
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375 (fd = open ((char *) XSTRING_DATA (Vsuperlock_file),
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0
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376 O_WRONLY | O_EXCL | O_CREAT, 0666)) < 0;
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377 i++)
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378 {
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379 if (errno != EEXIST)
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380 return;
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381
|
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382 /* This seems to be necessary to prevent Emacs from hanging when the
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383 competing process has already deleted the superlock, but it's still
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384 in the NFS cache. So we force NFS to synchronize the cache. */
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14
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385 lockdir = opendir ((char *) XSTRING_DATA (Vlock_directory));
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0
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386 if (lockdir)
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387 closedir (lockdir);
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388
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389 emacs_sleep (1);
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390 }
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391 if (fd >= 0)
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392 {
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100
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393 #if defined(WINDOWSNT)
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394 chmod(lfname, _S_IREAD|_S_IWRITE);
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395 #elif defined(USG)
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14
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396 chmod ((char *) XSTRING_DATA (Vsuperlock_file), 0666);
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0
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397 #else
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398 fchmod (fd, 0666);
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399 #endif
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400 write (fd, lfname, strlen (lfname));
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401 close (fd);
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402 }
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403 }
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404
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405 void
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406 unlock_all_files (void)
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407 {
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114
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408 /* This function can GC. */
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409
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410 Lisp_Object tail;
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0
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411 REGISTER struct buffer *b;
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114
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412 struct gcpro gcpro1;
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0
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413
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114
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414 GCPRO1 (tail);
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0
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415 for (tail = Vbuffer_alist; GC_CONSP (tail);
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416 tail = XCDR (tail))
|
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417 {
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418 b = XBUFFER (XCDR (XCAR (tail)));
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419 if (STRINGP (b->file_truename) &&
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420 BUF_SAVE_MODIFF (b) < BUF_MODIFF (b))
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421 unlock_file (b->file_truename);
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422 }
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114
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423 UNGCPRO;
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0
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424 }
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425
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426
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20
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427 DEFUN ("lock-buffer", Flock_buffer, 0, 1, 0, /*
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0
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428 Lock FILE, if current buffer is modified.
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429 FILE defaults to current buffer's visited file,
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430 or else nothing is done if current buffer isn't visiting a file.
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20
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431 */
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432 (fn))
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0
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433 {
|
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434 /* This function can GC */
|
114
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435 /* dmoore - and can destroy current_buffer and all sorts of other
|
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436 mean nasty things with pointy teeth. If you call this make sure
|
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437 you protect things right. */
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438
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0
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439 if (NILP (fn))
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440 fn = current_buffer->file_truename;
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441 CHECK_STRING (fn);
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442 if (BUF_SAVE_MODIFF (current_buffer) < BUF_MODIFF (current_buffer)
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443 && !NILP (fn))
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444 lock_file (fn);
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185
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445 return Qnil;
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0
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446 }
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447
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20
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448 DEFUN ("unlock-buffer", Funlock_buffer, 0, 0, 0, /*
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0
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449 Unlock the file visited in the current buffer,
|
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450 if it should normally be locked.
|
20
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451 */
|
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452 ())
|
0
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453 {
|
114
|
454 /* This function can GC */
|
|
455 /* dmoore - and can destroy current_buffer and all sorts of other
|
|
456 mean nasty things with pointy teeth. If you call this make sure
|
|
457 you protect things right. */
|
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458
|
0
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459 if (BUF_SAVE_MODIFF (current_buffer) < BUF_MODIFF (current_buffer)
|
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460 && STRINGP (current_buffer->file_truename))
|
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461 unlock_file (current_buffer->file_truename);
|
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462 return Qnil;
|
|
463 }
|
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464
|
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465
|
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466 /* Unlock the file visited in buffer BUFFER. */
|
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467
|
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468 void
|
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469 unlock_buffer (struct buffer *buffer)
|
|
470 {
|
114
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471 /* This function can GC */
|
|
472 /* dmoore - and can destroy current_buffer and all sorts of other
|
|
473 mean nasty things with pointy teeth. If you call this make sure
|
|
474 you protect things right. */
|
0
|
475 if (BUF_SAVE_MODIFF (buffer) < BUF_MODIFF (buffer)
|
|
476 && STRINGP (buffer->file_truename))
|
|
477 unlock_file (buffer->file_truename);
|
|
478 }
|
|
479
|
20
|
480 DEFUN ("file-locked-p", Ffile_locked_p, 0, 1, 0, /*
|
0
|
481 Return nil if the FILENAME is not locked,
|
|
482 t if it is locked by you, else a string of the name of the locker.
|
20
|
483 */
|
|
484 (fn))
|
0
|
485 {
|
|
486 /* This function can GC */
|
|
487 REGISTER char *lfname;
|
|
488 int owner;
|
|
489
|
|
490 if (NILP (Vlock_directory) || NILP (Vsuperlock_file))
|
|
491 return Qnil;
|
|
492 CHECK_STRING (Vlock_directory);
|
|
493
|
|
494 fn = Fexpand_file_name (fn, Qnil);
|
|
495
|
|
496 MAKE_LOCK_NAME (lfname, fn);
|
|
497
|
|
498 owner = current_lock_owner (lfname);
|
|
499 if (owner <= 0)
|
|
500 return (Qnil);
|
|
501 else if (owner == getpid ())
|
|
502 return (Qt);
|
185
|
503
|
0
|
504 return (lock_file_owner_name (lfname));
|
|
505 }
|
|
506
|
|
507 void
|
|
508 syms_of_filelock (void)
|
|
509 {
|
|
510 /* This function can GC */
|
20
|
511 DEFSUBR (Funlock_buffer);
|
|
512 DEFSUBR (Flock_buffer);
|
|
513 DEFSUBR (Ffile_locked_p);
|
0
|
514
|
|
515 defsymbol (&Qask_user_about_supersession_threat,
|
|
516 "ask-user-about-supersession-threat");
|
|
517 defsymbol (&Qask_user_about_lock, "ask-user-about-lock");
|
|
518 }
|
|
519
|
|
520 void
|
|
521 vars_of_filelock (void)
|
|
522 {
|
|
523 DEFVAR_LISP ("lock-directory", &Vlock_directory /*
|
|
524 Don't change this
|
|
525 */ );
|
|
526 DEFVAR_LISP ("superlock-file", &Vsuperlock_file /*
|
|
527 Don't change this
|
|
528 */ );
|
|
529 }
|
|
530
|
|
531 void
|
|
532 complex_vars_of_filelock (void)
|
|
533 {
|
|
534 #ifdef PATH_LOCK
|
|
535 Vlock_directory =
|
|
536 Ffile_name_as_directory (build_string (PATH_LOCK));
|
|
537 #else
|
|
538 Vlock_directory = Qnil;
|
|
539 #endif
|
|
540 #ifdef PATH_SUPERLOCK
|
|
541 Vsuperlock_file =
|
|
542 Ffile_name_as_directory (build_string (PATH_SUPERLOCK));
|
|
543 #else
|
|
544 Vsuperlock_file = Qnil;
|
|
545 #endif
|
|
546 /* All the rest done dynamically by startup.el */
|
|
547 }
|