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manager.go
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manager.go
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package chunk
import (
"fmt"
. "github.com/claudetech/loggo/default"
"math"
"github.com/dweidenfeld/plexdrive/drive"
)
// Manager manages chunks on disk
type Manager struct {
ChunkSize int64
LoadAhead int
downloader *Downloader
storage *Storage
queue chan *QueueEntry
}
type QueueEntry struct {
request *Request
response chan Response
}
// Request represents a chunk request
type Request struct {
id string
object *drive.APIObject
offsetStart int64
offsetEnd int64
chunkOffset int64
chunkOffsetEnd int64
preload bool
}
// Response represetns a chunk response
type Response struct {
Error error
Bytes []byte
}
// NewManager creates a new chunk manager
func NewManager(
chunkSize int64,
loadAhead,
checkThreads int,
loadThreads int,
client *drive.Client,
maxChunks int) (*Manager, error) {
if chunkSize < 4096 {
return nil, fmt.Errorf("Chunk size must not be < 4096")
}
if chunkSize%1024 != 0 {
return nil, fmt.Errorf("Chunk size must be divideable by 1024")
}
if maxChunks < 2 || maxChunks < loadAhead {
return nil, fmt.Errorf("max-chunks must be greater than 2 and bigger than the load ahead value")
}
downloader, err := NewDownloader(loadThreads, client)
if nil != err {
return nil, err
}
manager := Manager{
ChunkSize: chunkSize,
LoadAhead: loadAhead,
downloader: downloader,
storage: NewStorage(chunkSize, maxChunks),
queue: make(chan *QueueEntry, 100),
}
if err := manager.storage.Clear(); nil != err {
return nil, err
}
for i := 0; i < checkThreads; i++ {
go manager.thread()
}
return &manager, nil
}
// GetChunk loads one chunk and starts the preload for the next chunks
func (m *Manager) GetChunk(object *drive.APIObject, offset, size int64, response chan Response) {
chunkOffset := offset % m.ChunkSize
offsetStart := offset - chunkOffset
offsetEnd := offsetStart + m.ChunkSize
id := fmt.Sprintf("%v:%v", object.ObjectID, offsetStart)
request := &Request{
id: id,
object: object,
offsetStart: offsetStart,
offsetEnd: offsetEnd,
chunkOffset: chunkOffset,
chunkOffsetEnd: chunkOffset + size,
preload: false,
}
m.queue <- &QueueEntry{
request: request,
response: response,
}
for i := m.ChunkSize; i < (m.ChunkSize * int64(m.LoadAhead+1)); i += m.ChunkSize {
aheadOffsetStart := offsetStart + i
aheadOffsetEnd := aheadOffsetStart + m.ChunkSize
if uint64(aheadOffsetStart) < object.Size && uint64(aheadOffsetEnd) < object.Size {
id := fmt.Sprintf("%v:%v", object.ObjectID, aheadOffsetStart)
request := &Request{
id: id,
object: object,
offsetStart: aheadOffsetStart,
offsetEnd: aheadOffsetEnd,
preload: true,
}
m.queue <- &QueueEntry{
request: request,
}
}
}
}
func (m *Manager) thread() {
for {
queueEntry := <-m.queue
m.checkChunk(queueEntry.request, queueEntry.response)
}
}
func (m *Manager) checkChunk(req *Request, response chan Response) {
if bytes := m.storage.Load(req.id); nil != bytes {
if nil != response {
response <- Response{
Bytes: adjustResponseChunk(req, bytes),
}
close(response)
}
return
}
m.downloader.Download(req, func(err error, bytes []byte) {
if nil != err {
if nil != response {
response <- Response{
Error: err,
}
close(response)
}
return
}
if nil != response {
response <- Response{
Bytes: adjustResponseChunk(req, bytes),
}
close(response)
}
if err := m.storage.Store(req.id, bytes); nil != err {
Log.Warningf("Coult not store chunk %v", req.id)
}
})
}
func adjustResponseChunk(req *Request, bytes []byte) []byte {
sOffset := int64(math.Min(float64(req.chunkOffset), float64(len(bytes))))
eOffset := int64(math.Min(float64(req.chunkOffsetEnd), float64(len(bytes))))
return bytes[sOffset:eOffset]
}