func (world *World) lock() (err os.Error) {
if world.lockfd != nil {
panic("lock fd already exists... should never happen")
}
sessionLockPath := path.Join(world.dir, sessionlock)
world.lockfd, err = os.Open(sessionLockPath, os.O_RDWR|os.O_ASYNC, 0000)
if err != nil {
error.NewError(fmt.Sprint("could not open ", sessionlock), nil)
}
// minecraft's locking mechanism is peculiar.
// It writes the current system time in milliseconds since 1970 to the file.
// It then watches the file for changes. If a change is monitored, it aborts.
// This has strange implications, such as the LAST process to open the world owns it,
// not the first.
// but hey, when in rome...
sec, nsec, err := os.Time()
if err != nil {
err = error.NewError("couldn't get the current time..?!", err)
return
}
world.lockmsec = (sec * 1000) + (nsec / 1000000)
err = nbt.WriteInt64(world.lockfd, world.lockmsec)
if err != nil {
err = error.NewError("could not write timestamp to session lock", err)
return
}
return
}
func (world *World) LoadChunk(x int32, z int32) (err os.Error) {
if err = world.verifyLock(); err != nil {
return
}
xz := MakeXZ(x, z)
if _, ok := world.Chunks[xz]; ok {
return // nothing to do
}
var px, pz = posmod64(x), posmod64(z)
chunkPath := path.Join(
world.dir,
int32ToBase36String(px),
int32ToBase36String(pz),
fmt.Sprint(
"c.",
int32ToBase36String(x),
".",
int32ToBase36String(z),
".dat"))
_, chunkmap, err := nbt.Load(chunkPath)
if err != nil {
err = error.NewError(fmt.Sprintf("could not load chunk (%d, %d)", x, z), err)
return
}
world.Chunks[xz] = toChunk(chunkmap)
return
}
func (world *World) verifyLock() (err os.Error) {
_, err = world.lockfd.Seek(0, 0)
if err != nil {
err = error.NewError("could not seek to beginning of session lock", err)
return
}
msec, err := nbt.ReadInt64(world.lockfd)
if err != nil {
err = error.NewError("could not read timestamp from session lock", err)
return
}
if msec != world.lockmsec {
err = error.NewError("someone else has opened this world :(", nil)
return
}
return
}
func (world *World) verifyFormat() (err os.Error) {
// We don't want to go crazy vetting every byte, but we can at least do a sanity check
// for how the folder structure should look. It is important we don't touch any files,
// so if this world is in use by another process, things don't go terribly wrong.
fi, err := os.Stat(world.dir)
if err != nil {
err = error.NewError("could not stat world directory", err)
return
}
if !fi.IsDirectory() {
return error.NewError("expected a directory, didn't get one", nil)
}
var hasLevelDat, hasSessionLock bool
files, err := ioutil.ReadDir(world.dir)
if err != nil {
err = error.NewError("could not read world directory contents", nil)
return
}
for _, f := range files {
if f.IsRegular() {
switch f.Name {
case leveldat:
hasLevelDat = true
case sessionlock:
hasSessionLock = true
}
}
}
if !hasLevelDat {
err = error.NewError(fmt.Sprint("world is missing ", leveldat), nil)
return
}
if !hasSessionLock {
err = error.NewError(fmt.Sprint("world is missing ", sessionlock), nil)
return
}
return
}
func Open(worlddir string) (w *World, err os.Error) {
w = &World{dir: worlddir}
if err = w.verifyFormat(); err != nil {
err = error.NewError("could not verify world format", err)
return
}
if err = w.lock(); err != nil {
err = error.NewError("unable to obtain lock on world", err)
return
}
_, levelDat, err := nbt.Load(path.Join(w.dir, leveldat))
if err != nil {
err = error.NewError("could not read level", err)
return
}
w.Chunks = make(map[XZ]*Chunk)
w.loadLevelDat(levelDat)
return
}