10 // Accesses torrent data via a client.
14 // Ensure operations that change the position are exclusive, like Read()
18 // Required when modifying pos and readahead, or reading them without
25 var _ io.ReadCloser = &Reader{}
27 // Don't wait for pieces to complete and be verified. Read calls return as
28 // soon as they can when the underlying chunks become available.
29 func (r *Reader) SetResponsive() {
33 // Configure the number of bytes ahead of a read that should also be
34 // prioritized in preparation for further reads.
35 func (r *Reader) SetReadahead(readahead int64) {
37 r.readahead = readahead
40 defer r.t.cl.mu.Unlock()
44 func (r *Reader) readable(off int64) (ret bool) {
45 if r.torrentClosed() {
48 req, ok := r.t.torrent.offsetRequest(off)
53 return r.t.torrent.haveChunk(req)
55 return r.t.torrent.pieceComplete(int(req.Index))
58 // How many bytes are available to read. Max is the most we could require.
59 func (r *Reader) available(off, max int64) (ret int64) {
61 req, ok := r.t.torrent.offsetRequest(off)
65 if !r.t.torrent.haveChunk(req) {
68 len1 := int64(req.Length) - (off - r.t.torrent.requestOffset(req))
73 // Ensure that ret hasn't exceeded our original max.
80 func (r *Reader) tickleClient() {
81 r.t.torrent.readersChanged()
84 func (r *Reader) waitReadable(off int64) {
85 // We may have been sent back here because we were told we could read but
91 func (r *Reader) Read(b []byte) (n int, err error) {
96 n1, err = r.readOnceAt(b, r.pos)
99 panic("expected error")
109 if r.pos >= r.t.torrent.length {
111 } else if err == io.EOF {
112 err = io.ErrUnexpectedEOF
117 // Safe to call with or without client lock.
118 func (r *Reader) torrentClosed() bool {
119 return r.t.torrent.isClosed()
122 // Wait until some data should be available to read. Tickles the client if it
123 // isn't. Returns how much should be readable without blocking.
124 func (r *Reader) waitAvailable(pos, wanted int64) (avail int64) {
126 defer r.t.cl.mu.Unlock()
127 for !r.readable(pos) {
130 return r.available(pos, wanted)
133 // Performs at most one successful read to torrent storage.
134 func (r *Reader) readOnceAt(b []byte, pos int64) (n int, err error) {
135 if pos >= r.t.torrent.length {
140 avail := r.waitAvailable(pos, int64(len(b)))
142 if r.torrentClosed() {
143 err = errors.New("torrent closed")
148 pi := int(pos / r.t.Info().PieceLength)
149 ip := r.t.Info().Piece(pi)
150 po := pos % ip.Length()
151 if int64(len(b1)) > ip.Length()-po {
152 b1 = b1[:ip.Length()-po]
154 n, err = r.t.torrent.readAt(b1, pos)
158 // log.Printf("%s: error reading from torrent storage pos=%d: %s", r.t, pos, err)
160 r.t.torrent.updateAllPieceCompletions()
161 r.t.torrent.updatePiecePriorities()
166 func (r *Reader) Close() error {
172 func (r *Reader) posChanged() {
174 defer r.t.cl.mu.Unlock()
175 r.t.torrent.readersChanged()
178 func (r *Reader) Seek(off int64, whence int) (ret int64, err error) {
180 defer r.opMu.Unlock()
189 r.pos = r.t.torrent.Info.TotalLength() + off
191 err = errors.New("bad whence")
200 func (r *Reader) Torrent() *Torrent {