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// 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
}
// Like syscall.Dirent, but without the [256]byte name.
type dirent struct {
Ino uint64
Off int64
Reclen uint16
Type uint8
Name [1]uint8 // align to 4 bytes for 32 bits.
}
func (ds *loopbackDirStream) Next() (fuse.DirEntry, syscall.Errno) {
ds.mu.Lock()
defer ds.mu.Unlock()
// We can't use syscall.Dirent here, because it declares a
// [256]byte name, which may run beyond the end of ds.todo.
// when that happens in the race detector, it causes a panic
// "converted pointer straddles multiple allocations"
de := (*dirent)(unsafe.Pointer(&ds.todo[0]))
nameBytes := ds.todo[unsafe.Offsetof(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
}
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