1 files changed, 94 insertions, 0 deletions
diff --git a/src/lib/os/getwd.go b/src/lib/os/getwd.go
new file mode 100644
index 000000000..2d7b754b5
--- /dev/null
+++ b/src/lib/os/getwd.go
@@ -0,0 +1,94 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package os
+
+import (
+	"os";
+	"syscall"
+)
+
+// Getwd returns a rooted path name corresponding to the
+// current directory.  If the current directory can be
+// reached via multiple paths (due to symbolic links),
+// Getwd may return any one of them.
+func Getwd() (string, Error) {
+	// If the operating system provides a Getwd call, use it.
+	if syscall.ImplementsGetwd {
+		s, e := syscall.Getwd();
+		return s, ErrnoToError(e);
+	}
+
+	// Otherwise, we're trying to find our way back to ".".
+	dot, err := Stat(".");
+	if err != nil {
+		return "", err;
+	}
+
+	// Clumsy but widespread kludge:
+	// if $PWD is set and matches ".", use it.
+	pwd, _ := Getenv("PWD");
+	if len(pwd) > 0 && pwd[0] == '/' {
+		d, err := Stat(pwd);
+		if err == nil && d.Dev == dot.Dev && d.Ino == dot.Ino {
+			return pwd, nil
+		}
+	}
+
+	// Root is a special case because it has no parent
+	// and ends in a slash.
+	root, err := Stat("/");
+	if err != nil {
+		// Can't stat root - no hope.
+		return "", err;
+	}
+	if root.Dev == dot.Dev && root.Ino == dot.Ino {
+		return "/", nil
+	}
+
+	// General algorithm: find name in parent
+	// and then find name of parent.  Each iteration
+	// adds /name to the beginning of pwd.
+	elem := make([]string, 0, 16);
+	pwd = "";
+	for parent := "..";; parent = "../" + parent {
+		if len(parent) >= 1024 {	// Sanity check
+			return "", ENAMETOOLONG;
+		}
+		fd, err := Open(parent, O_RDONLY, 0);
+		if err != nil {
+			return "", err;
+		}
+
+		for {
+			names, err := fd.Readdirnames(100);
+			if err != nil {
+				fd.Close();
+				return "", err;
+			}
+			for i, name := range names {
+				d, err := Lstat(parent + "/" + name);
+				if d.Dev == dot.Dev && d.Ino == dot.Ino {
+					pwd = "/" + name + pwd;
+					goto Found;
+				}
+			}
+		}
+		fd.Close();
+		return "", ENOENT;
+
+	Found:
+		pd, err := fd.Stat();
+		if err != nil {
+			return "", err;
+		}
+		fd.Close();
+		if pd.Dev == root.Dev && pd.Ino == root.Ino {
+			break;
+		}
+		// Set up for next round.
+		dot = pd;
+	}
+	return pwd, nil
+}