Add piece-per-resource storage

diff --git a/storage/piece_resource.go b/storage/piece_resource.go
new file mode 100644 (file)
index 0000000..2f6d6ee
--- /dev/null
+++ b/storage/piece_resource.go
@@ -0,0 +1,80 @@
+package storage
+
+import (
+       "io"
+       "path"
+
+       "github.com/anacrolix/missinggo"
+       "github.com/anacrolix/missinggo/uniform"
+
+       "github.com/anacrolix/torrent/metainfo"
+)
+
+type piecePerResource struct {
+       p uniform.Provider
+}
+
+func NewPiecePerResource(p uniform.Provider) I {
+       return &piecePerResource{
+               p: p,
+       }
+}
+
+func (s *piecePerResource) OpenTorrent(info *metainfo.InfoEx) (Torrent, error) {
+       return s, nil
+}
+
+func (s *piecePerResource) Close() error {
+       return nil
+}
+
+func (s *piecePerResource) Piece(p metainfo.Piece) Piece {
+       completed, err := s.p.NewResource(path.Join("completed", p.Hash().HexString()))
+       if err != nil {
+               panic(err)
+       }
+       incomplete, err := s.p.NewResource(path.Join("incomplete", p.Hash().HexString()))
+       if err != nil {
+               panic(err)
+       }
+       return piecePerResourcePiece{
+               p: p,
+               c: completed,
+               i: incomplete,
+       }
+}
+
+type piecePerResourcePiece struct {
+       p metainfo.Piece
+       c uniform.Resource
+       i uniform.Resource
+}
+
+func (s piecePerResourcePiece) GetIsComplete() bool {
+       fi, err := s.c.Stat()
+       return err == nil && fi.Size() == s.p.Length()
+}
+
+func (s piecePerResourcePiece) MarkComplete() error {
+       return uniform.Move(s.i, s.c)
+}
+
+func (s piecePerResourcePiece) ReadAt(b []byte, off int64) (n int, err error) {
+       missinggo.LimitLen(&b, s.p.Length()-off)
+       n, err = s.c.ReadAt(b, off)
+       if err != nil {
+               n, err = s.i.ReadAt(b, off)
+       }
+       off += int64(n)
+       if off >= s.p.Length() {
+               err = io.EOF
+       } else if err == io.EOF {
+               err = io.ErrUnexpectedEOF
+       }
+       return
+}
+
+func (s piecePerResourcePiece) WriteAt(b []byte, off int64) (n int, err error) {
+       missinggo.LimitLen(&b, s.p.Length()-off)
+       return s.i.WriteAt(b, off)
+}