Add SubmountFileSystem.

This is a file system that will composite multiple FUSE
filesystems, so you can have for example

 /dir1   -> one simple FUSE filesystem
 /dir2   -> another simple FUSE filesystem
 /config -> a FS interface to daemon configuration

Each of these directories should be RawFileSystem instances.  This
class takes care of the mapping between global inode ids and inode ids
of each sub-FUSE filesystem.

No files or directories may be created in the toplevel dir. Instead,
the daemon should issue AddFileSystem() and RemoveFileSystem()
methods internally.  This could be done in response to writes in a
/config directory.

examplelib/Makefile

@@ -7,6 +7,7 @@ DEPS=../fuse
 
 GOFILES=dummyfuse.go\
 	passthrough.go\
+	stackfs.go
 
 include $(GOROOT)/src/Make.pkg
 

examplelib/stackfs_test.go

+package examplelib
+
+import (
+	"github.com/hanwen/go-fuse/fuse"
+	"fmt"
+	"log"
+	"os"
+	"path"
+	"strings"
+	"testing"
+)
+
+var _ = strings.Join
+var _ = log.Println
+
+////////////////
+
+func IsDir(name string) bool {
+	fi, _ := os.Lstat(name)
+	return fi != nil && fi.IsDirectory()
+}
+
+func IsFile(name string) bool {
+	fi, _ := os.Lstat(name)
+	return fi != nil && fi.IsRegular()
+}
+
+func FileExists(name string) bool {
+	_, err := os.Lstat(name)
+	return err == nil
+}
+
+// Create and mount filesystem.
+const magicMode uint32 = 0753
+
+type testCase struct {
+	origDir1      string
+	origDir2      string
+	mountDir      string
+	testDir      string
+	tester *testing.T
+
+	fs           *SubmountFileSystem	
+	state        *fuse.MountState
+}
+
+func (self *testCase) Setup(t *testing.T) {
+	self.tester = t
+
+	self.testDir = fuse.MakeTempDir()
+	self.origDir1 = path.Join(self.testDir, "orig1")
+	self.origDir2 = path.Join(self.testDir, "orig2")
+	self.mountDir = path.Join(self.testDir, "mount")
+
+	os.Mkdir(self.origDir1, 0700)
+	os.Mkdir(self.origDir2, 0700)
+	os.Mkdir(self.mountDir, 0700)
+	
+	fs1 := fuse.NewPathFileSystemConnector(NewPassThroughFuse(self.origDir1))
+	fs2 := fuse.NewPathFileSystemConnector(NewPassThroughFuse(self.origDir2))
+
+	self.fs = NewSubmountFileSystem()
+
+	attr := fuse.Attr{
+	Mode: uint32(magicMode),
+	}
+
+	self.fs.AddFileSystem("sub1", fs1, attr)
+	self.fs.AddFileSystem("sub2", fs2, attr)
+	
+	self.state = fuse.NewMountState(self.fs)
+	self.state.Mount(self.mountDir)
+
+	self.state.Debug = true
+
+	fmt.Println("tempdir: ", self.testDir)
+
+	// Unthreaded, but in background.
+	go self.state.Loop(false)
+}
+
+// Unmount and del.
+func (self *testCase) Cleanup() {
+	fmt.Println("Unmounting.")
+	err := self.state.Unmount()
+	if err != nil {
+		self.tester.Errorf("Can't unmount a dir, err: %v", err)
+	}
+	os.RemoveAll(self.testDir)
+}
+
+////////////////
+
+func (self *testCase) testReaddir() {
+	fmt.Println("testReaddir... ")
+	dir, err := os.Open(self.mountDir, os.O_RDONLY, 0)
+	if err != nil {
+		self.tester.Errorf("opendir err %v", err)
+		return
+	}
+	infos, err := dir.Readdir(10)
+	if err != nil {
+		self.tester.Errorf("readdir err %v", err)
+	}
+	
+	wanted := map[string]bool{
+		"sub1": true,
+		"sub2": true,
+	}
+	if len(wanted) != len(infos) {
+		self.tester.Errorf("Length mismatch %v", infos)
+	} else {
+		for _, v := range infos {
+			_, ok := wanted[v.Name]
+			if !ok {
+				self.tester.Errorf("Unexpected name %v", v.Name)
+			}
+
+			if v.Mode & 0777 != magicMode {
+				self.tester.Errorf("Unexpected mode %o, %v", v.Mode, v)
+			}
+		}
+	}
+
+	dir.Close()
+}
+
+
+func (self *testCase) testSubFs() {
+	fmt.Println("testSubFs... ")
+	for i := 1; i <= 2; i++ {
+		// orig := path.Join(self.testDir, fmt.Sprintf("orig%d", i))
+		mount := path.Join(self.mountDir, fmt.Sprintf("sub%d", i))
+
+		name := "testFile"
+		
+		mountFile := path.Join(mount, name)
+
+		f, err := os.Open(mountFile, os.O_WRONLY, 0)
+		if err == nil {
+			self.tester.Errorf("Expected error for open write %v", name)
+			continue
+		}
+		content1 := "booh!"
+		f, err = os.Open(mountFile, os.O_WRONLY | os.O_CREATE, magicMode)
+		if err != nil {
+			self.tester.Errorf("Create %v", err)	
+		}
+
+		f.Write([]byte(content1))
+		f.Close()
+
+		err = os.Chmod(mountFile, magicMode)
+		if err != nil {
+			self.tester.Errorf("chmod %v", err)	
+		}
+		
+		fi, err := os.Lstat(mountFile)
+		if err != nil {
+			self.tester.Errorf("Lstat %v", err)	
+		} else {
+			if fi.Mode & 0777 != magicMode {
+				self.tester.Errorf("Mode %o", fi.Mode)	
+			}
+		}
+		
+		g, err := os.Open(mountFile, os.O_RDONLY, 0)
+		if err != nil {
+			self.tester.Errorf("Open %v", err)	
+		} else {
+			buf := make([]byte, 1024)
+			n, err := g.Read(buf)
+			if err != nil {
+				self.tester.Errorf("read err %v", err)
+			}
+			if string(buf[:n]) != content1 {
+				self.tester.Errorf("content %v", buf[:n])
+			}
+			g.Close()
+		}
+	}
+}
+
+func (self *testCase) testAddRemove() {
+	self.tester.Log("testAddRemove")
+	attr := fuse.Attr{
+	Mode:0755,
+	}
+
+	conn := fuse.NewPathFileSystemConnector(NewPassThroughFuse(self.origDir1))
+	ok := self.fs.AddFileSystem("sub1", conn, attr)
+	if ok {
+		self.tester.Errorf("AddFileSystem should fail")
+		return
+	}
+	ok = self.fs.AddFileSystem("third", conn, attr)
+	if !ok {
+		self.tester.Errorf("AddFileSystem fail")
+	}
+	conn.Init(new(fuse.InHeader), new(fuse.InitIn)) 
+	
+	fi, err := os.Lstat(path.Join(self.mountDir, "third"))
+	if err != nil {
+		self.tester.Errorf("third lstat err %v", err)
+	} else {
+		if !fi.IsDirectory() {
+			self.tester.Errorf("not a directory %v", fi)
+		}
+	}
+
+	fs := self.fs.RemoveFileSystem("third")
+	if fs == nil {
+		self.tester.Errorf("remove fail")
+	}
+	dir, err := os.Open(self.mountDir, os.O_RDONLY, 0)
+	if err != nil {
+		self.tester.Errorf("opendir err %v", err)
+		return
+	}
+	infos, err := dir.Readdir(10)
+	if len(infos) != 2 {
+		self.tester.Errorf("lstat expect 2 infos %v", infos)
+	}
+	dir.Close()
+
+	_, err = os.Open(path.Join(self.mountDir, "third"), os.O_RDONLY, 0)
+	if err == nil {
+		self.tester.Errorf("expect enoent %v", err)
+	}
+}
+
+
+// Test driver.
+func TestMount(t *testing.T) {
+	ts := new(testCase)
+	ts.Setup(t)
+
+	ts.testReaddir()
+	ts.testSubFs()
+	ts.testAddRemove()
+
+	ts.Cleanup()
+}