1 /* Concatenate two arbitrary file names. 2 3 Copyright (C) 1996-2007, 2009-2021 Free Software Foundation, Inc. 4 5 This file is free software: you can redistribute it and/or modify 6 it under the terms of the GNU Lesser General Public License as 7 published by the Free Software Foundation; either version 2.1 of the 8 License, or (at your option) any later version. 9 10 This file is distributed in the hope that it will be useful, 11 but WITHOUT ANY WARRANTY; without even the implied warranty of 12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 13 GNU Lesser General Public License for more details. 14 15 You should have received a copy of the GNU Lesser General Public License 16 along with this program. If not, see <https://www.gnu.org/licenses/>. */ 17 18 /* Written by Jim Meyering. */ 19 20 #include <config.h> 21 22 /* Specification. */ 23 #include "filenamecat.h" 24 25 #include <stdlib.h> 26 #include <string.h> 27 28 #include "basename-lgpl.h" 29 #include "filename.h" 30 31 #if ! HAVE_MEMPCPY && ! defined mempcpy 32 # define mempcpy(D, S, N) ((void *) ((char *) memcpy (D, S, N) + (N))) 33 #endif 34 35 /* Concatenate two file name components, DIR and BASE, in 36 newly-allocated storage and return the result. 37 The resulting file name F is such that the commands "ls F" and "(cd 38 DIR; ls ./BASE)" refer to the same file. If necessary, put 39 a separator between DIR and BASE in the result. Typically this 40 separator is "/", but in rare cases it might be ".". 41 In any case, if BASE_IN_RESULT is non-NULL, set 42 *BASE_IN_RESULT to point to the copy of BASE at the end of the 43 returned concatenation. 44 45 If malloc fails, return NULL with errno set. */ 46 47 char * 48 mfile_name_concat (char const *dir, char const *base, char **base_in_result) /* */ 49 { 50 char const *dirbase = last_component (dir); 51 size_t dirbaselen = base_len (dirbase); 52 size_t dirlen = dirbase - dir + dirbaselen; 53 size_t baselen = strlen (base); 54 char sep = '\0'; 55 if (dirbaselen) 56 { 57 /* DIR is not a file system root, so separate with / if needed. */ 58 if (! ISSLASH (dir[dirlen - 1]) && ! ISSLASH (*base)) 59 sep = '/'; 60 } 61 else if (ISSLASH (*base)) 62 { 63 /* DIR is a file system root and BASE begins with a slash, so 64 separate with ".". For example, if DIR is "/" and BASE is 65 "/foo" then return "/./foo", as "//foo" would be wrong on 66 some POSIX systems. A fancier algorithm could omit "." in 67 some cases but is not worth the trouble. */ 68 sep = '.'; 69 } 70 71 char *p_concat = malloc (dirlen + (sep != '\0') + baselen + 1); 72 if (p_concat == NULL) 73 return NULL; 74 75 { 76 char *p; 77 78 p = mempcpy (p_concat, dir, dirlen); 79 *p = sep; 80 p += sep != '\0'; 81 82 if (base_in_result) 83 *base_in_result = p; 84 85 p = mempcpy (p, base, baselen); 86 *p = '\0'; 87 } 88 89 return p_concat; 90 }