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272
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1 /* basename.c -- return the last element in a file name
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2
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3 Copyright (C) 1990, 1998, 1999, 2000, 2001, 2003, 2004, 2005, 2006 Free
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4 Software 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 #include "xstrndup.h"
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26
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27 /* Return the address of the last file name component of NAME. If
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28 NAME has no relative file name components because it is a file
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29 system root, return the empty string. */
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30
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31 char *
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32 last_component (char const *name)
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33 {
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34 char const *base = name + FILE_SYSTEM_PREFIX_LEN (name);
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35 char const *p;
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36 bool saw_slash = false;
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37
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38 while (ISSLASH (*base))
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39 base++;
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40
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41 for (p = base; *p; p++)
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42 {
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43 if (ISSLASH (*p))
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44 saw_slash = true;
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45 else if (saw_slash)
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46 {
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47 base = p;
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48 saw_slash = false;
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49 }
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50 }
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51
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52 return (char *) base;
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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 `basename' 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 `basename' modifies its argument.
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59
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60 Return the last file name component of NAME, allocated with
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61 xmalloc. On systems with drive letters, a leading "./"
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62 distinguishes relative names that would otherwise look like a drive
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63 letter. Unlike POSIX basename(), NAME cannot be NULL,
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64 base_name("") returns "", and the first trailing slash is not
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65 stripped.
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66
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67 If lstat (NAME) would succeed, then { chdir (dir_name (NAME));
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68 lstat (base_name (NAME)); } will access the same file. Likewise,
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69 if the sequence { chdir (dir_name (NAME));
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70 rename (base_name (NAME), "foo"); } succeeds, you have renamed NAME
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71 to "foo" in the same directory NAME was in. */
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72
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73 char *
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74 base_name (char const *name)
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75 {
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76 char const *base = last_component (name);
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77 size_t length;
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78
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79 /* If there is no last component, then name is a file system root or the
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80 empty string. */
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81 if (! *base)
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82 return xstrndup (name, base_len (name));
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83
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84 /* Collapse a sequence of trailing slashes into one. */
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85 length = base_len (base);
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86 if (ISSLASH (base[length]))
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87 length++;
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88
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89 /* On systems with drive letters, `a/b:c' must return `./b:c' rather
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90 than `b:c' to avoid confusion with a drive letter. On systems
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91 with pure POSIX semantics, this is not an issue. */
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92 if (FILE_SYSTEM_PREFIX_LEN (base))
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93 {
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94 char *p = xmalloc (length + 3);
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95 p[0] = '.';
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96 p[1] = '/';
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97 memcpy (p + 2, base, length);
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98 p[length + 2] = '\0';
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99 return p;
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100 }
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101
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102 /* Finally, copy the basename. */
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103 return xstrndup (base, length);
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104 }
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105
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106 /* Return the length of the basename NAME. Typically NAME is the
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107 value returned by base_name or last_component. Act like strlen
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108 (NAME), except omit all trailing slashes. */
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109
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110 size_t
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111 base_len (char const *name)
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112 {
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113 size_t len;
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114 size_t prefix_len = FILE_SYSTEM_PREFIX_LEN (name);
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115
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116 for (len = strlen (name); 1 < len && ISSLASH (name[len - 1]); len--)
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117 continue;
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118
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119 if (DOUBLE_SLASH_IS_DISTINCT_ROOT && len == 1
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120 && ISSLASH (name[0]) && ISSLASH (name[1]) && ! name[2])
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121 return 2;
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122
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123 if (FILE_SYSTEM_DRIVE_PREFIX_CAN_BE_RELATIVE && prefix_len
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124 && len == prefix_len && ISSLASH (name[prefix_len]))
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125 return prefix_len + 1;
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126
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127 return len;
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128 }
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