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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_test
import (
"context"
"fmt"
"log"
"sync"
"syscall"
"time"
"github.com/hanwen/go-fuse/v2/fs"
"github.com/hanwen/go-fuse/v2/fuse"
)
// bytesNode is a file that can be read and written
type bytesNode struct {
fs.Inode
// When file systems are mutable, all access must use
// synchronization.
mu sync.Mutex
content []byte
mtime time.Time
}
// Implement GetAttr to provide size and mtime
var _ = (fs.NodeGetattrer)((*bytesNode)(nil))
func (bn *bytesNode) Getattr(ctx context.Context, fh fs.FileHandle, out *fuse.AttrOut) syscall.Errno {
bn.mu.Lock()
defer bn.mu.Unlock()
bn.getattr(out)
return 0
}
func (bn *bytesNode) getattr(out *fuse.AttrOut) {
out.Size = uint64(len(bn.content))
out.SetTimes(nil, &bn.mtime, nil)
}
func (bn *bytesNode) resize(sz uint64) {
if sz > uint64(cap(bn.content)) {
n := make([]byte, sz)
copy(n, bn.content)
bn.content = n
} else {
bn.content = bn.content[:sz]
}
bn.mtime = time.Now()
}
// Implement Setattr to support truncation
var _ = (fs.NodeSetattrer)((*bytesNode)(nil))
func (bn *bytesNode) Setattr(ctx context.Context, fh fs.FileHandle, in *fuse.SetAttrIn, out *fuse.AttrOut) syscall.Errno {
bn.mu.Lock()
defer bn.mu.Unlock()
if sz, ok := in.GetSize(); ok {
bn.resize(sz)
}
bn.getattr(out)
return 0
}
// Implement handleless read.
var _ = (fs.NodeReader)((*bytesNode)(nil))
func (bn *bytesNode) Read(ctx context.Context, fh fs.FileHandle, dest []byte, off int64) (fuse.ReadResult, syscall.Errno) {
bn.mu.Lock()
defer bn.mu.Unlock()
end := off + int64(len(dest))
if end > int64(len(bn.content)) {
end = int64(len(bn.content))
}
// We could copy to the `dest` buffer, but since we have a
// []byte already, return that.
return fuse.ReadResultData(bn.content[off:end]), 0
}
// Implement handleless write.
var _ = (fs.NodeWriter)((*bytesNode)(nil))
func (bn *bytesNode) Write(ctx context.Context, fh fs.FileHandle, buf []byte, off int64) (uint32, syscall.Errno) {
bn.mu.Lock()
defer bn.mu.Unlock()
sz := int64(len(buf))
if off+sz > int64(len(bn.content)) {
bn.resize(uint64(off + sz))
}
copy(bn.content[off:], buf)
bn.mtime = time.Now()
return uint32(sz), 0
}
// Implement (handleless) Open
var _ = (fs.NodeOpener)((*bytesNode)(nil))
func (f *bytesNode) Open(ctx context.Context, openFlags uint32) (fh fs.FileHandle, fuseFlags uint32, errno syscall.Errno) {
return nil, 0, 0
}
// ExampleHandleLess shows how to create a file that can be read or written
// by implementing Read/Write directly on the nodes.
func Example_handleLess() {
mntDir := "/tmp/x"
root := &fs.Inode{}
// Mount the file system
server, err := fs.Mount(mntDir, root, &fs.Options{
MountOptions: fuse.MountOptions{Debug: false},
// Setup the file.
OnAdd: func(ctx context.Context) {
ch := root.NewPersistentInode(
ctx,
&bytesNode{},
fs.StableAttr{
Mode: syscall.S_IFREG,
// Make debug output readable.
Ino: 2,
})
root.AddChild("bytes", ch, true)
},
})
if err != nil {
log.Fatal(err)
}
fmt.Printf(`Try:
cd %s
ls -l bytes
echo hello > bytes
ls -l bytes
cat bytes
cd -
`, mntDir)
fmt.Printf("Unmount by calling 'fusermount -u %s'\n", mntDir)
// Serve the file system, until unmounted by calling fusermount -u
server.Wait()
}
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