forked from anacrolix/torrent
/
piece_resource.go
271 lines (239 loc) · 6.28 KB
/
piece_resource.go
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package storage
import (
"bytes"
"fmt"
"io"
"io/ioutil"
"path"
"sort"
"strconv"
"sync"
"github.com/anacrolix/missinggo/v2/resource"
"github.com/anacrolix/torrent/metainfo"
)
type piecePerResource struct {
rp PieceProvider
opts ResourcePiecesOpts
}
type ResourcePiecesOpts struct {
LeaveIncompleteChunks bool
NoSizedPuts bool
}
func NewResourcePieces(p PieceProvider) ClientImpl {
return NewResourcePiecesOpts(p, ResourcePiecesOpts{})
}
func NewResourcePiecesOpts(p PieceProvider, opts ResourcePiecesOpts) ClientImpl {
return &piecePerResource{
rp: p,
opts: opts,
}
}
type piecePerResourceTorrentImpl struct {
piecePerResource
locks []sync.RWMutex
}
func (piecePerResourceTorrentImpl) Close() error {
return nil
}
func (s piecePerResource) OpenTorrent(info *metainfo.Info, infoHash metainfo.Hash) (TorrentImpl, error) {
return piecePerResourceTorrentImpl{
s,
make([]sync.RWMutex, info.NumPieces()),
}, nil
}
func (s piecePerResourceTorrentImpl) Piece(p metainfo.Piece) PieceImpl {
return piecePerResourcePiece{
mp: p,
piecePerResource: s.piecePerResource,
mu: &s.locks[p.Index()],
}
}
type PieceProvider interface {
resource.Provider
}
type ConsecutiveChunkReader interface {
ReadConsecutiveChunks(prefix string) (io.ReadCloser, error)
}
type piecePerResourcePiece struct {
mp metainfo.Piece
piecePerResource
// This protects operations that move complete/incomplete pieces around, which can trigger read
// errors that may cause callers to do more drastic things.
mu *sync.RWMutex
}
var _ io.WriterTo = piecePerResourcePiece{}
func (s piecePerResourcePiece) WriteTo(w io.Writer) (int64, error) {
s.mu.RLock()
defer s.mu.RUnlock()
if s.mustIsComplete() {
r, err := s.completed().Get()
if err != nil {
return 0, fmt.Errorf("getting complete instance: %w", err)
}
defer r.Close()
return io.Copy(w, r)
}
if ccr, ok := s.rp.(ConsecutiveChunkReader); ok {
return s.writeConsecutiveIncompleteChunks(ccr, w)
}
return io.Copy(w, io.NewSectionReader(s, 0, s.mp.Length()))
}
func (s piecePerResourcePiece) writeConsecutiveIncompleteChunks(ccw ConsecutiveChunkReader, w io.Writer) (int64, error) {
r, err := ccw.ReadConsecutiveChunks(s.incompleteDirPath() + "/")
if err != nil {
return 0, err
}
defer r.Close()
return io.Copy(w, r)
}
// Returns if the piece is complete. Ok should be true, because we are the definitive source of
// truth here.
func (s piecePerResourcePiece) mustIsComplete() bool {
completion := s.Completion()
if !completion.Ok {
panic("must know complete definitively")
}
return completion.Complete
}
func (s piecePerResourcePiece) Completion() Completion {
s.mu.RLock()
defer s.mu.RUnlock()
fi, err := s.completed().Stat()
return Completion{
Complete: err == nil && fi.Size() == s.mp.Length(),
Ok: true,
}
}
type SizedPutter interface {
PutSized(io.Reader, int64) error
}
func (s piecePerResourcePiece) MarkComplete() error {
s.mu.Lock()
defer s.mu.Unlock()
incompleteChunks := s.getChunks()
r, err := func() (io.ReadCloser, error) {
if ccr, ok := s.rp.(ConsecutiveChunkReader); ok {
return ccr.ReadConsecutiveChunks(s.incompleteDirPath() + "/")
}
return ioutil.NopCloser(io.NewSectionReader(incompleteChunks, 0, s.mp.Length())), nil
}()
if err != nil {
return fmt.Errorf("getting incomplete chunks reader: %w", err)
}
defer r.Close()
completedInstance := s.completed()
err = func() error {
if sp, ok := completedInstance.(SizedPutter); ok && !s.opts.NoSizedPuts {
return sp.PutSized(r, s.mp.Length())
} else {
return completedInstance.Put(r)
}
}()
if err == nil && !s.opts.LeaveIncompleteChunks {
// I think we do this synchronously here since we don't want callers to act on the completed
// piece if we're concurrently still deleting chunks. The caller may decide to start
// downloading chunks again and won't expect us to delete them. It seems to be much faster
// to let the resource provider do this if possible.
var wg sync.WaitGroup
for _, c := range incompleteChunks {
wg.Add(1)
go func(c chunk) {
defer wg.Done()
c.instance.Delete()
}(c)
}
wg.Wait()
}
return err
}
func (s piecePerResourcePiece) MarkNotComplete() error {
s.mu.Lock()
defer s.mu.Unlock()
return s.completed().Delete()
}
func (s piecePerResourcePiece) ReadAt(b []byte, off int64) (int, error) {
s.mu.RLock()
defer s.mu.RUnlock()
if s.mustIsComplete() {
return s.completed().ReadAt(b, off)
}
return s.getChunks().ReadAt(b, off)
}
func (s piecePerResourcePiece) WriteAt(b []byte, off int64) (n int, err error) {
s.mu.RLock()
defer s.mu.RUnlock()
i, err := s.rp.NewInstance(path.Join(s.incompleteDirPath(), strconv.FormatInt(off, 10)))
if err != nil {
panic(err)
}
r := bytes.NewReader(b)
err = i.Put(r)
n = len(b) - r.Len()
return
}
type chunk struct {
offset int64
instance resource.Instance
}
type chunks []chunk
func (me chunks) ReadAt(b []byte, off int64) (int, error) {
for {
if len(me) == 0 {
return 0, io.EOF
}
if me[0].offset <= off {
break
}
me = me[1:]
}
n, err := me[0].instance.ReadAt(b, off-me[0].offset)
if n == len(b) {
return n, nil
}
if err == nil || err == io.EOF {
n_, err := me[1:].ReadAt(b[n:], off+int64(n))
return n + n_, err
}
return n, err
}
func (s piecePerResourcePiece) getChunks() (chunks chunks) {
names, err := s.incompleteDir().Readdirnames()
if err != nil {
return
}
for _, n := range names {
offset, err := strconv.ParseInt(n, 10, 64)
if err != nil {
panic(err)
}
i, err := s.rp.NewInstance(path.Join(s.incompleteDirPath(), n))
if err != nil {
panic(err)
}
chunks = append(chunks, chunk{offset, i})
}
sort.Slice(chunks, func(i, j int) bool {
return chunks[i].offset < chunks[j].offset
})
return
}
func (s piecePerResourcePiece) completedInstancePath() string {
return path.Join("completed", s.mp.Hash().HexString())
}
func (s piecePerResourcePiece) completed() resource.Instance {
i, err := s.rp.NewInstance(s.completedInstancePath())
if err != nil {
panic(err)
}
return i
}
func (s piecePerResourcePiece) incompleteDirPath() string {
return path.Join("incompleted", s.mp.Hash().HexString())
}
func (s piecePerResourcePiece) incompleteDir() resource.DirInstance {
i, err := s.rp.NewInstance(s.incompleteDirPath())
if err != nil {
panic(err)
}
return i.(resource.DirInstance)
}