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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"
"log"
"os"
"strconv"
"syscall"
"github.com/hanwen/go-fuse/v2/fs"
"github.com/hanwen/go-fuse/v2/fuse"
)
// numberNode is a filesystem node representing an integer. Prime
// numbers are regular files, while composite numbers are directories
// containing all smaller numbers, eg.
//
// $ ls -F /tmp/x/6
// 2 3 4/ 5
//
// the file system nodes are deduplicated using inode numbers. The
// number 2 appears in many directories, but it is actually the represented
// by the same numberNode{} object, with inode number 2.
//
// $ ls -i1 /tmp/x/2 /tmp/x/8/6/4/2
// 2 /tmp/x/2
// 2 /tmp/x/8/6/4/2
type numberNode struct {
// Must embed an Inode for the struct to work as a node.
fs.Inode
// num is the integer represented in this file/directory
num int
}
// isPrime returns whether n is prime
func isPrime(n int) bool {
for i := 2; i*i <= n; i++ {
if n%i == 0 {
return false
}
}
return true
}
func numberToMode(n int) uint32 {
// prime numbers are files
if isPrime(n) {
return fuse.S_IFREG
}
// composite numbers are directories
return fuse.S_IFDIR
}
// Ensure we are implementing the NodeReaddirer interface
var _ = (fs.NodeReaddirer)((*numberNode)(nil))
// Readdir is part of the NodeReaddirer interface
func (n *numberNode) Readdir(ctx context.Context) (fs.DirStream, syscall.Errno) {
r := make([]fuse.DirEntry, 0, n.num)
for i := 2; i < n.num; i++ {
d := fuse.DirEntry{
Name: strconv.Itoa(i),
Ino: uint64(i),
Mode: numberToMode(i),
}
r = append(r, d)
}
return fs.NewListDirStream(r), 0
}
// Ensure we are implementing the NodeLookuper interface
var _ = (fs.NodeLookuper)((*numberNode)(nil))
// Lookup is part of the NodeLookuper interface
func (n *numberNode) Lookup(ctx context.Context, name string, out *fuse.EntryOut) (*fs.Inode, syscall.Errno) {
i, err := strconv.Atoi(name)
if err != nil {
return nil, syscall.ENOENT
}
if i >= n.num || i <= 1 {
return nil, syscall.ENOENT
}
stable := fs.StableAttr{
Mode: numberToMode(i),
// The child inode is identified by its Inode number.
// If multiple concurrent lookups try to find the same
// inode, they are deduplicated on this key.
Ino: uint64(i),
}
operations := &numberNode{num: i}
// The NewInode call wraps the `operations` object into an Inode.
child := n.NewInode(ctx, operations, stable)
// In case of concurrent lookup requests, it can happen that operations !=
// child.Operations().
return child, 0
}
// ExampleDynamic is a whimsical example of a dynamically discovered
// file system.
func Example_dynamic() {
// This is where we'll mount the FS
mntDir := "/tmp/x"
os.Mkdir(mntDir, 0755)
root := &numberNode{num: 10}
server, err := fs.Mount(mntDir, root, &fs.Options{
MountOptions: fuse.MountOptions{
// Set to true to see how the file system works.
Debug: true,
},
})
if err != nil {
log.Panic(err)
}
log.Printf("Mounted on %s", mntDir)
log.Printf("Unmount by calling 'fusermount -u %s'", mntDir)
// Wait until unmount before exiting
server.Wait()
}
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