diff options
Diffstat (limited to 'stdlib/canonicalize.c')
| -rw-r--r-- | stdlib/canonicalize.c | 196 |
1 files changed, 196 insertions, 0 deletions
diff --git a/stdlib/canonicalize.c b/stdlib/canonicalize.c new file mode 100644 index 0000000000..55ac1bcf1d --- /dev/null +++ b/stdlib/canonicalize.c @@ -0,0 +1,196 @@ +/* Return the canonical absolute name of a given file. +Copyright (C) 1996 Free Software Foundation, Inc. +This file is part of the GNU C Library. + +The GNU C Library is free software; you can redistribute it and/or +modify it under the terms of the GNU Library General Public License as +published by the Free Software Foundation; either version 2 of the +License, or (at your option) any later version. + +The GNU C Library is distributed in the hope that it will be useful, +but WITHOUT ANY WARRANTY; without even the implied warranty of +MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU +Library General Public License for more details. + +You should have received a copy of the GNU Library General Public +License along with the GNU C Library; see the file COPYING.LIB. If +not, write to the Free Software Foundation, Inc., 675 Mass Ave, +Cambridge, MA 02139, USA. */ + +#include <stdlib.h> +#include <string.h> +#include <unistd.h> +#include <limits.h> +#include <sys/stat.h> +#include <errno.h> + +/* Return the canonical absolute name of file NAME. The last file name + component need not exist, and may be a symlink to a nonexistent file. + If RESOLVED is null, the result is malloc'd; otherwise, if the canonical + name is PATH_MAX chars or more, returns null with `errno' set to + ENAMETOOLONG; if the name fits in fewer than PATH_MAX chars, returns the + name in RESOLVED. */ + +static char * +canonicalize (const char *name, char *resolved) +{ + struct stat st; + const char *p; + long int path_max; + char *result, *dir, *end; + size_t namelen; + + if (! resolved) + path_max = 0; + else + { +#ifdef PATH_MAX + path_max = PATH_MAX; +#else + path_max = sysconf (_SC_PATH_MAX); + if (path_max <= 0) + path_max = 1024; +#endif + } + + p = strrchr (name, '/'); + if (!p) + { + dir = (char *) "."; + p = name; + } + else + { + if (p++ == name) + dir = (char *) "/"; + else + { + dir = __alloca (p - name); + memcpy (dir, name, p - name - 1); + dir[p - name] = '\0'; + } + } + + result = __canonicalize_directory_name_internal (dir, resolved, path_max); + if (!result) + return NULL; + + /* Reconstruct the file name in the canonicalized directory. */ + namelen = strlen (name); + end = strchr (result, '\0'); + if (resolved) + { + /* Make sure the name is not too long. */ + if (end - result + namelen > path_max) + { + errno = ENAMETOOLONG; + return NULL; + } + } + else + { + /* The name is dynamically allocated. Extend it. */ + char *new = realloc (result, end - result + namelen + 1); + if (! new) + { + free (result); + return NULL; + } + end = new + (end - result); + result = new; + } + memcpy (end, name, namelen + 1); + + while (__lstat (result, &st) == 0 && S_ISLNK (st.st_mode)) + { + /* The file is a symlink. Read its contents. */ + ssize_t n; + read_link_contents: + n = readlink (result, end, + resolved ? result + path_max - end : namelen + 1); + if (n < 0) + /* Error reading the link contents. */ + return NULL; + + if (end[0] == '/') + { + /* Absolute symlink. */ + if (resolved ? (end + n < result + path_max) : (n < namelen + 1)) + { + /* It fit in our buffer, so we have the whole thing. */ + memcpy (result, end, n); + result[n] = '\0'; + } + else if (resolved) + { + /* It didn't fit in the remainder of the buffer. Either it + fits in the entire buffer, or it doesn't. Copy back the + unresolved name onto the canonical directory and try once + more. */ + memcpy (end, name, namelen + 1); + n = readlink (result, result, path_max); + if (n < 0) + return NULL; + if (n == path_max) + { + errno = ENAMETOOLONG; + return NULL; + } + result[n] = '\0'; + } + else + /* Try again with a bigger buffer. */ + goto extend_buffer; + + /* Check the resolved name for being a symlink too. */ + continue; + } + + if (resolved) + { + if (end + n == result + path_max) + { + /* The link contents we read fill the buffer completely. + There may be even more to read, and there is certainly no + space for the null terminator. */ + errno = ENAMETOOLONG; + return NULL; + } + } + else if (n == namelen + 1) + extend_buffer: + { + /* The name buffer is dynamically allocated. Extend it. */ + char *new; + + /* Copy back the unresolved name onto the canonical directory. */ + memcpy (end, name, namelen + 1); + + /* Make more space for readlink. */ + namelen *= 2; + new = realloc (result, end - result + namelen + 1); + if (! new) + { + free (result); + return NULL; + } + end = new + (end - result); + result = new; + + goto read_link_contents; + } + + /* Terminate the string; readlink does not. */ + end[n] = '\0'; + } + + return result; +} + +weak_alias (canonicalize, realpath) + +char * +canonicalize_file_name (const char *name) +{ + return canonicalize (name, NULL); +} |