func readFile(fs vfs.Filesystem, name string) ([]byte, error) {
f, err := fs.OpenFile(name, os.O_RDONLY, 0)
if err != nil {
return nil, err
}
return ioutil.ReadAll(f)
}
func writeFile(fs vfs.Filesystem, name string, flags int, mode os.FileMode, b []byte) (int, error) {
f, err := fs.OpenFile(name, flags, mode)
if err != nil {
return 0, err
}
return f.Write(b)
}
// port of ioutil.Writefile for vfs
func writeFile(fs vfs.Filesystem, filename string, data []byte, perm os.FileMode) error {
f, err := fs.OpenFile(filename, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, perm)
if err != nil {
return err
}
n, err := f.Write(data)
if err == nil && n < len(data) {
err = io.ErrShortWrite
}
if err1 := f.Close(); err == nil {
err = err1
}
return err
}
func Example() {
// Create a vfs accessing the filesystem of the underlying OS
var osfs vfs.Filesystem = vfs.OS()
osfs.Mkdir("/tmp", 0777)
// Make the filesystem read-only:
osfs = vfs.ReadOnly(osfs) // Simply wrap filesystems to change its behaviour
// os.O_CREATE will fail and return vfs.ErrReadOnly
// os.O_RDWR is supported but Write(..) on the file is disabled
f, _ := osfs.OpenFile("/tmp/example.txt", os.O_RDWR, 0)
// Return vfs.ErrReadOnly
_, err := f.Write([]byte("Write on readonly fs?"))
if err != nil {
fmt.Errorf("Filesystem is read only!\n")
}
// Create a fully writable filesystem in memory
mfs := memfs.Create()
mfs.Mkdir("/root", 0777)
// Create a vfs supporting mounts
// The root fs is accessing the filesystem of the underlying OS
fs := mountfs.Create(osfs)
// Mount a memfs inside /memfs
// /memfs may not exist
fs.Mount(mfs, "/memfs")
// This will create /testdir inside the memfs
fs.Mkdir("/memfs/testdir", 0777)
// This would create /tmp/testdir inside your OS fs
// But the rootfs `osfs` is read-only
fs.Mkdir("/tmp/testdir", 0777)
}