// Create creates the file name within the file system fs
func Create(fs fs.FS, name string) (File, error) {
f, err := fs.Create(name)
if err != nil {
return nil, err
}
return &file{name: name, file: f}, nil
}
// Open opens the file name within the file system fs
func Open(fs fs.FS, name string) (File, error) {
f, err := fs.OpenFile(name, os.O_RDWR, 0600) // perm = u+rw
if err != nil {
return nil, err
}
if _, err = f.Seek(0, os.SEEK_SET); err != nil {
return nil, err
}
return &file{name: name, file: f}, nil
}
// Mount opens a write-ahead log file system
func Mount(disk fs.FS) (*Disk, error) {
dir, err := disk.Open("/")
if err != nil {
return nil, err
}
defer dir.Close()
sfi, err := dir.Readdir(0)
if err != nil {
return nil, err
}
var m string
for _, fi := range sfi {
n := fi.Name()
if !strings.HasPrefix(n, "master") {
continue
}
if n > m {
m = n
}
}
d := &Disk{disk: disk}
var mf File
if m == "" {
m = d.makeName()
mf, err = Create(disk, m)
} else {
if d.seqno, err = parseMasterName(m); err != nil {
return nil, errors.New("foreign files on disk: " + m)
}
mf, err = Open(disk, m)
}
if err != nil {
return nil, err
}
d.master = mf
return d, nil
}