// Read is thread-safe
func (sr *StorageReader) Read(p []byte) (n int, err error) {
sr.mutex.Lock()
defer sr.mutex.Unlock()
if !sr.parent.alive {
return -1, errors.New("EOF")
}
chunkId := sr.Offset / CHUNK_SIZE
internalMsgId := uint64(sr.Offset % CHUNK_SIZE)
sr.parent.dataCond.L.Lock()
for sr.currentSub == nil ||
chunkId >= uint64(len(sr.parent.stores)) ||
internalMsgId >= sr.parent.stores[chunkId].Size {
// Block for new data
sr.parent.dataCond.Wait()
sr.handleRollover()
}
sr.parent.dataCond.L.Unlock()
// We have a valid reader, and can read from it
nextMsgSize, err := sr.parent.stores[chunkId].SizeOf(internalMsgId)
if err != nil {
return 0, err
}
if nextMsgSize > uint64(len(p)) {
return 0, fmt.Errorf("Message, of size %d, does not fit into available buffer", nextMsgSize)
}
target := p[0:nextMsgSize]
_, err = sr.currentSub.Read(target)
utils.Check(err)
sr.Offset++
sr.handleRollover()
return int(nextMsgSize), nil
}
func (t *Track) startWriter(startId uint64) {
t.writeChan = make(chan []byte, CHUNK_SIZE/100) // Buffer 1% of a chunk
go func() {
msgId := startId
for {
msg, more := <-t.writeChan
if !more {
t.alive = false
return
}
chunkId := msgId / CHUNK_SIZE
if chunkId == uint64(len(t.stores)) {
if chunkId > 0 {
t.stores[chunkId-1].switchToReadOnly() // Migrate the old chunk to readonly
}
storeId := fmt.Sprintf("%s%d", t.Id, chunkId)
t.stores = append(t.stores, NewFileStorage(t.RootPath, storeId, CHUNK_SIZE))
}
internalMsgId := int(msgId % CHUNK_SIZE)
err := t.stores[chunkId].WriteMessage(internalMsgId, msg)
utils.Check(err)
msgId++
// Tell any waiting routines that there's new data
t.dataCond.Broadcast()
}
}()
}
func (t *Track) ReaderAt(offset uint64) (io.ReadCloser, error) {
if offset < 0 {
return nil, fmt.Errorf("Offset out of bounds: %d", offset)
}
r := &StorageReader{
parent: t,
Offset: offset,
mutex: &sync.Mutex{},
}
chunkIndex := offset / CHUNK_SIZE
msgIndex := offset % CHUNK_SIZE
if chunkIndex < uint64(len(t.stores)) && uint64(msgIndex) < t.stores[chunkIndex].Size {
var err error
r.currentSub, err = t.stores[chunkIndex].ReaderAt(msgIndex)
utils.Check(err)
}
return r, nil
}