vendor: add github.com/hanwen/go-fuse/v2@master for mount2

vendor/github.com/hanwen/go-fuse/v2/fs/dirstream_linux.go

@@ -0,0 +1,93 @@
+// Copyright 2019 the Go-FUSE 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 fs
+
+import (
+	"sync"
+	"syscall"
+	"unsafe"
+
+	"github.com/hanwen/go-fuse/v2/fuse"
+)
+
+type loopbackDirStream struct {
+	buf  []byte
+	todo []byte
+
+	// Protects fd so we can guard against double close
+	mu sync.Mutex
+	fd int
+}
+
+// NewLoopbackDirStream open a directory for reading as a DirStream
+func NewLoopbackDirStream(name string) (DirStream, syscall.Errno) {
+	fd, err := syscall.Open(name, syscall.O_DIRECTORY, 0755)
+	if err != nil {
+		return nil, ToErrno(err)
+	}
+
+	ds := &loopbackDirStream{
+		buf: make([]byte, 4096),
+		fd:  fd,
+	}
+
+	if err := ds.load(); err != 0 {
+		ds.Close()
+		return nil, err
+	}
+	return ds, OK
+}
+
+func (ds *loopbackDirStream) Close() {
+	ds.mu.Lock()
+	defer ds.mu.Unlock()
+	if ds.fd != -1 {
+		syscall.Close(ds.fd)
+		ds.fd = -1
+	}
+}
+
+func (ds *loopbackDirStream) HasNext() bool {
+	ds.mu.Lock()
+	defer ds.mu.Unlock()
+	return len(ds.todo) > 0
+}
+
+func (ds *loopbackDirStream) Next() (fuse.DirEntry, syscall.Errno) {
+	ds.mu.Lock()
+	defer ds.mu.Unlock()
+	de := (*syscall.Dirent)(unsafe.Pointer(&ds.todo[0]))
+
+	nameBytes := ds.todo[unsafe.Offsetof(syscall.Dirent{}.Name):de.Reclen]
+	ds.todo = ds.todo[de.Reclen:]
+
+	// After the loop, l contains the index of the first '\0'.
+	l := 0
+	for l = range nameBytes {
+		if nameBytes[l] == 0 {
+			break
+		}
+	}
+	nameBytes = nameBytes[:l]
+	result := fuse.DirEntry{
+		Ino:  de.Ino,
+		Mode: (uint32(de.Type) << 12),
+		Name: string(nameBytes),
+	}
+	return result, ds.load()
+}
+
+func (ds *loopbackDirStream) load() syscall.Errno {
+	if len(ds.todo) > 0 {
+		return OK
+	}
+
+	n, err := syscall.Getdents(ds.fd, ds.buf)
+	if err != nil {
+		return ToErrno(err)
+	}
+	ds.todo = ds.buf[:n]
+	return OK
+}