cephfs: add ReadDir implementing ceph_readdir_r function

Adds a method to ReadDir that implements ceph_readdir_r returning
a single dir entry at at time.

Signed-off-by: John Mulligan <jmulligan@redhat.com>

cephfs/directory.go

@@ -47,3 +47,48 @@ func (mount *MountInfo) OpenDir(path string) (*Directory, error) {
 func (dir *Directory) Close() error {
 	return getError(C.ceph_closedir(dir.mount.mount, dir.dir))
 }
+
+// Inode represents an inode number in the file system.
+type Inode uint64
+
+// DirEntry represents an entry within a directory.
+type DirEntry struct {
+	inode Inode
+	name  string
+}
+
+// Name returns the directory entry's name.
+func (d *DirEntry) Name() string {
+	return d.name
+}
+
+// Inode returns the directory entry's inode number.
+func (d *DirEntry) Inode() Inode {
+	return d.inode
+}
+
+// toDirEntry converts a c struct dirent to our go wrapper.
+func toDirEntry(de *C.struct_dirent) *DirEntry {
+	return &DirEntry{
+		inode: Inode(de.d_ino),
+		name:  C.GoString(&de.d_name[0]),
+	}
+}
+
+// ReadDir reads a single directory entry from the open Directory.
+// A nil DirEntry pointer will be returned when the Directory stream has been
+// exhausted.
+//
+// Implements:
+//  int ceph_readdir_r(struct ceph_mount_info *cmount, struct ceph_dir_result *dirp, struct dirent *de);
+func (dir *Directory) ReadDir() (*DirEntry, error) {
+	var de C.struct_dirent
+	ret := C.ceph_readdir_r(dir.mount.mount, dir.dir, &de)
+	if ret < 0 {
+		return nil, getError(ret)
+	}
+	if ret == 0 {
+		return nil, nil // End-of-stream
+	}
+	return toDirEntry(&de), nil
+}

cephfs/directory_test.go

@@ -36,3 +36,62 @@ func TestOpenCloseDir(t *testing.T) {
 	assert.Error(t, err)
 	assert.Nil(t, dir)
 }
+
+func TestReadDir(t *testing.T) {
+	mount := fsConnect(t)
+	defer fsDisconnect(t, mount)
+
+	dir1 := "/base"
+	err := mount.MakeDir(dir1, 0755)
+	assert.NoError(t, err)
+	defer func() { assert.NoError(t, mount.RemoveDir(dir1)) }()
+
+	subdirs := []string{"a", "bb", "ccc", "dddd"}
+	for _, s := range subdirs {
+		spath := dir1 + "/" + s
+		err = mount.MakeDir(spath, 0755)
+		assert.NoError(t, err)
+		defer func(d string) {
+			assert.NoError(t, mount.RemoveDir(d))
+		}(spath)
+	}
+
+	t.Run("root", func(t *testing.T) {
+		dir, err := mount.OpenDir("/")
+		assert.NoError(t, err)
+		assert.NotNil(t, dir)
+		defer func() { assert.NoError(t, dir.Close()) }()
+
+		found := []string{}
+		for {
+			entry, err := dir.ReadDir()
+			assert.NoError(t, err)
+			if entry == nil {
+				break
+			}
+			assert.NotEqual(t, Inode(0), entry.Inode())
+			assert.NotEqual(t, "", entry.Name())
+			found = append(found, entry.Name())
+		}
+		assert.Contains(t, found, "base")
+	})
+	t.Run("dir1", func(t *testing.T) {
+		dir, err := mount.OpenDir(dir1)
+		assert.NoError(t, err)
+		assert.NotNil(t, dir)
+		defer func() { assert.NoError(t, dir.Close()) }()
+
+		found := []string{}
+		for {
+			entry, err := dir.ReadDir()
+			assert.NoError(t, err)
+			if entry == nil {
+				break
+			}
+			assert.NotEqual(t, Inode(0), entry.Inode())
+			assert.NotEqual(t, "", entry.Name())
+			found = append(found, entry.Name())
+		}
+		assert.Subset(t, found, subdirs)
+	})
+}