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283
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1 /* dirname.c -- return all but the last element in a file name
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2
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3 Copyright (C) 1990, 1998, 2000, 2001, 2003, 2004, 2005, 2006 Free Software
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4 Foundation, Inc.
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5
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6 This program is free software: you can redistribute it and/or modify
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7 it under the terms of the GNU General Public License as published by
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8 the Free Software Foundation; either version 3 of the License, or
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9 (at your option) any later version.
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10
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11 This program is distributed in the hope that it will be useful,
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12 but WITHOUT ANY WARRANTY; without even the implied warranty of
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13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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14 GNU General Public License for more details.
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15
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16 You should have received a copy of the GNU General Public License
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17 along with this program. If not, see <http://www.gnu.org/licenses/>. */
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18
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19 #include <config.h>
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20
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21 #include "dirname.h"
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22
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23 #include <string.h>
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24 #include "xalloc.h"
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25
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26 /* Return the length of the prefix of FILE that will be used by
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27 dir_name. If FILE is in the working directory, this returns zero
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28 even though `dir_name (FILE)' will return ".". Works properly even
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29 if there are trailing slashes (by effectively ignoring them). */
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30
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31 size_t
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32 dir_len (char const *file)
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33 {
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34 size_t prefix_length = FILE_SYSTEM_PREFIX_LEN (file);
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35 size_t length;
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36
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37 /* Advance prefix_length beyond important leading slashes. */
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38 prefix_length += (prefix_length != 0
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39 ? (FILE_SYSTEM_DRIVE_PREFIX_CAN_BE_RELATIVE
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40 && ISSLASH (file[prefix_length]))
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41 : (ISSLASH (file[0])
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42 ? ((DOUBLE_SLASH_IS_DISTINCT_ROOT
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43 && ISSLASH (file[1]) && ! ISSLASH (file[2])
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44 ? 2 : 1))
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45 : 0));
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46
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47 /* Strip the basename and any redundant slashes before it. */
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48 for (length = last_component (file) - file;
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49 prefix_length < length; length--)
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50 if (! ISSLASH (file[length - 1]))
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51 break;
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52 return length;
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53 }
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54
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55
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56 /* In general, we can't use the builtin `dirname' function if available,
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57 since it has different meanings in different environments.
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58 In some environments the builtin `dirname' modifies its argument.
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59
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60 Return the leading directories part of FILE, allocated with xmalloc.
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61 Works properly even if there are trailing slashes (by effectively
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62 ignoring them). Unlike POSIX dirname(), FILE cannot be NULL.
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63
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64 If lstat (FILE) would succeed, then { chdir (dir_name (FILE));
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65 lstat (base_name (FILE)); } will access the same file. Likewise,
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66 if the sequence { chdir (dir_name (FILE));
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67 rename (base_name (FILE), "foo"); } succeeds, you have renamed FILE
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68 to "foo" in the same directory FILE was in. */
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69
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70 char *
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71 dir_name (char const *file)
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72 {
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73 size_t length = dir_len (file);
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74 bool append_dot = (length == 0
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75 || (FILE_SYSTEM_DRIVE_PREFIX_CAN_BE_RELATIVE
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76 && length == FILE_SYSTEM_PREFIX_LEN (file)
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77 && file[2] != '\0' && ! ISSLASH (file[2])));
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78 char *dir = xmalloc (length + append_dot + 1);
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79 memcpy (dir, file, length);
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80 if (append_dot)
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81 dir[length++] = '.';
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82 dir[length] = '\0';
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83 return dir;
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84 }
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