+# By John Bazik
+#
+# Usage: $cwd = &fastcwd;
+#
+# This is a faster version of getcwd. It's also more dangerous because
+# you might chdir out of a directory that you can't chdir back into.
+
+sub fastcwd_ {
+ my($odev, $oino, $cdev, $cino, $tdev, $tino);
+ my(@path, $path);
+ local(*DIR);
+
+ my($orig_cdev, $orig_cino) = stat('.');
+ ($cdev, $cino) = ($orig_cdev, $orig_cino);
+ for (;;) {
+ my $direntry;
+ ($odev, $oino) = ($cdev, $cino);
+ CORE::chdir('..') || return undef;
+ ($cdev, $cino) = stat('.');
+ last if $odev == $cdev && $oino == $cino;
+ opendir(DIR, '.') || return undef;
+ for (;;) {
+ $direntry = readdir(DIR);
+ last unless defined $direntry;
+ next if $direntry eq '.';
+ next if $direntry eq '..';
+
+ ($tdev, $tino) = lstat($direntry);
+ last unless $tdev != $odev || $tino != $oino;
+ }
+ closedir(DIR);
+ return undef unless defined $direntry; # should never happen
+ unshift(@path, $direntry);
+ }
+ $path = '/' . join('/', @path);
+ if ($^O eq 'apollo') { $path = "/".$path; }
+ # At this point $path may be tainted (if tainting) and chdir would fail.
+ # Untaint it then check that we landed where we started.
+ $path =~ /^(.*)\z/s # untaint
+ && CORE::chdir($1) or return undef;
+ ($cdev, $cino) = stat('.');
+ die "Unstable directory path, current directory changed unexpectedly"
+ if $cdev != $orig_cdev || $cino != $orig_cino;
+ $path;
+}
+if (not defined &fastcwd) { *fastcwd = \&fastcwd_ }
+
+