Michal Iskierko
319
vendor/github.com/anacrolix/torrent/reader.go
generated
vendored
Normal file
319
vendor/github.com/anacrolix/torrent/reader.go
generated
vendored
Normal file
@@ -0,0 +1,319 @@
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package torrent
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import (
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"context"
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"errors"
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"fmt"
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"io"
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"sync"
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"github.com/anacrolix/log"
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"github.com/anacrolix/missinggo/v2"
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)
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// Accesses Torrent data via a Client. Reads block until the data is available. Seeks and readahead
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// also drive Client behaviour.
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type Reader interface {
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io.ReadSeekCloser
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missinggo.ReadContexter
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// Configure the number of bytes ahead of a read that should also be prioritized in preparation
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// for further reads. Overridden by non-nil readahead func, see SetReadaheadFunc.
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SetReadahead(int64)
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// If non-nil, the provided function is called when the implementation needs to know the
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// readahead for the current reader. Calls occur during Reads and Seeks, and while the Client is
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// locked.
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SetReadaheadFunc(ReadaheadFunc)
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// Don't wait for pieces to complete and be verified. Read calls return as soon as they can when
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// the underlying chunks become available.
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SetResponsive()
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}
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// Piece range by piece index, [begin, end).
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type pieceRange struct {
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begin, end pieceIndex
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}
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type ReadaheadContext struct {
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ContiguousReadStartPos int64
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CurrentPos int64
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}
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// Returns the desired readahead for a Reader.
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type ReadaheadFunc func(ReadaheadContext) int64
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type reader struct {
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t *Torrent
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// Adjust the read/seek window to handle Readers locked to File extents and the like.
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offset, length int64
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// Function to dynamically calculate readahead. If nil, readahead is static.
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readaheadFunc ReadaheadFunc
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// Required when modifying pos and readahead.
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mu sync.Locker
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readahead, pos int64
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// Position that reads have continued contiguously from.
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contiguousReadStartPos int64
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// The cached piece range this reader wants downloaded. The zero value corresponds to nothing.
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// We cache this so that changes can be detected, and bubbled up to the Torrent only as
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// required.
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pieces pieceRange
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// Reads have been initiated since the last seek. This is used to prevent readaheads occurring
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// after a seek or with a new reader at the starting position.
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reading bool
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responsive bool
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}
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var _ io.ReadSeekCloser = (*reader)(nil)
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func (r *reader) SetResponsive() {
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r.responsive = true
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r.t.cl.event.Broadcast()
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}
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// Disable responsive mode. TODO: Remove?
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func (r *reader) SetNonResponsive() {
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r.responsive = false
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r.t.cl.event.Broadcast()
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}
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func (r *reader) SetReadahead(readahead int64) {
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r.mu.Lock()
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r.readahead = readahead
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r.readaheadFunc = nil
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r.posChanged()
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r.mu.Unlock()
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}
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func (r *reader) SetReadaheadFunc(f ReadaheadFunc) {
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r.mu.Lock()
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r.readaheadFunc = f
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r.posChanged()
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r.mu.Unlock()
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}
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// How many bytes are available to read. Max is the most we could require.
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func (r *reader) available(off, max int64) (ret int64) {
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off += r.offset
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for max > 0 {
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req, ok := r.t.offsetRequest(off)
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if !ok {
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break
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}
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if !r.responsive && !r.t.pieceComplete(pieceIndex(req.Index)) {
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break
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}
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if !r.t.haveChunk(req) {
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break
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}
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len1 := int64(req.Length) - (off - r.t.requestOffset(req))
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max -= len1
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ret += len1
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off += len1
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}
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// Ensure that ret hasn't exceeded our original max.
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if max < 0 {
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ret += max
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}
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return
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}
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// Calculates the pieces this reader wants downloaded, ignoring the cached value at r.pieces.
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func (r *reader) piecesUncached() (ret pieceRange) {
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ra := r.readahead
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if r.readaheadFunc != nil {
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ra = r.readaheadFunc(ReadaheadContext{
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ContiguousReadStartPos: r.contiguousReadStartPos,
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CurrentPos: r.pos,
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})
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}
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if ra < 1 {
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// Needs to be at least 1, because [x, x) means we don't want
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// anything.
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ra = 1
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}
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if !r.reading {
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ra = 0
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}
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if ra > r.length-r.pos {
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ra = r.length - r.pos
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}
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ret.begin, ret.end = r.t.byteRegionPieces(r.torrentOffset(r.pos), ra)
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return
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}
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func (r *reader) Read(b []byte) (n int, err error) {
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return r.ReadContext(context.Background(), b)
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}
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func (r *reader) ReadContext(ctx context.Context, b []byte) (n int, err error) {
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if len(b) > 0 {
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r.reading = true
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// TODO: Rework reader piece priorities so we don't have to push updates in to the Client
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// and take the lock here.
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r.mu.Lock()
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r.posChanged()
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r.mu.Unlock()
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}
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n, err = r.readOnceAt(ctx, b, r.pos)
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if n == 0 {
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if err == nil && len(b) > 0 {
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panic("expected error")
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} else {
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return
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}
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}
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r.mu.Lock()
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r.pos += int64(n)
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r.posChanged()
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r.mu.Unlock()
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if r.pos >= r.length {
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err = io.EOF
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} else if err == io.EOF {
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err = io.ErrUnexpectedEOF
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}
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return
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}
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var closedChan = make(chan struct{})
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func init() {
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close(closedChan)
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}
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// Wait until some data should be available to read. Tickles the client if it isn't. Returns how
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// much should be readable without blocking.
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func (r *reader) waitAvailable(ctx context.Context, pos, wanted int64, wait bool) (avail int64, err error) {
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t := r.t
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for {
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r.t.cl.rLock()
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avail = r.available(pos, wanted)
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readerCond := t.piece(int((r.offset + pos) / t.info.PieceLength)).readerCond.Signaled()
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r.t.cl.rUnlock()
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if avail != 0 {
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return
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}
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var dontWait <-chan struct{}
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if !wait || wanted == 0 {
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dontWait = closedChan
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}
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select {
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case <-r.t.closed.Done():
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err = errors.New("torrent closed")
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return
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case <-ctx.Done():
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err = ctx.Err()
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return
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case <-r.t.dataDownloadDisallowed.On():
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err = errors.New("torrent data downloading disabled")
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case <-r.t.networkingEnabled.Off():
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err = errors.New("torrent networking disabled")
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return
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case <-dontWait:
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return
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case <-readerCond:
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}
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}
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}
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// Adds the reader's torrent offset to the reader object offset (for example the reader might be
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// constrainted to a particular file within the torrent).
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func (r *reader) torrentOffset(readerPos int64) int64 {
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return r.offset + readerPos
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}
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// Performs at most one successful read to torrent storage.
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func (r *reader) readOnceAt(ctx context.Context, b []byte, pos int64) (n int, err error) {
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if pos >= r.length {
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err = io.EOF
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return
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}
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for {
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var avail int64
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avail, err = r.waitAvailable(ctx, pos, int64(len(b)), n == 0)
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if avail == 0 {
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return
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}
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firstPieceIndex := pieceIndex(r.torrentOffset(pos) / r.t.info.PieceLength)
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firstPieceOffset := r.torrentOffset(pos) % r.t.info.PieceLength
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b1 := missinggo.LimitLen(b, avail)
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n, err = r.t.readAt(b1, r.torrentOffset(pos))
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if n != 0 {
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err = nil
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return
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}
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r.t.cl.lock()
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// TODO: Just reset pieces in the readahead window. This might help
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// prevent thrashing with small caches and file and piece priorities.
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r.log(log.Fstr("error reading torrent %s piece %d offset %d, %d bytes: %v",
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r.t.infoHash.HexString(), firstPieceIndex, firstPieceOffset, len(b1), err))
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if !r.t.updatePieceCompletion(firstPieceIndex) {
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r.log(log.Fstr("piece %d completion unchanged", firstPieceIndex))
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}
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// Update the rest of the piece completions in the readahead window, without alerting to
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// changes (since only the first piece, the one above, could have generated the read error
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// we're currently handling).
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if r.pieces.begin != firstPieceIndex {
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panic(fmt.Sprint(r.pieces.begin, firstPieceIndex))
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}
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for index := r.pieces.begin + 1; index < r.pieces.end; index++ {
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r.t.updatePieceCompletion(index)
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}
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r.t.cl.unlock()
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}
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}
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// Hodor
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func (r *reader) Close() error {
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r.t.cl.lock()
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r.t.deleteReader(r)
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r.t.cl.unlock()
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return nil
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}
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func (r *reader) posChanged() {
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to := r.piecesUncached()
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from := r.pieces
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if to == from {
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return
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}
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r.pieces = to
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// log.Printf("reader pos changed %v->%v", from, to)
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r.t.readerPosChanged(from, to)
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}
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func (r *reader) Seek(off int64, whence int) (newPos int64, err error) {
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switch whence {
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case io.SeekStart:
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newPos = off
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r.mu.Lock()
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case io.SeekCurrent:
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r.mu.Lock()
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newPos = r.pos + off
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case io.SeekEnd:
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newPos = r.length + off
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r.mu.Lock()
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default:
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return 0, errors.New("bad whence")
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}
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if newPos != r.pos {
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r.reading = false
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||||
r.pos = newPos
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r.contiguousReadStartPos = newPos
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r.posChanged()
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}
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||||
r.mu.Unlock()
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||||
return
|
||||
}
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||||
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||||
func (r *reader) log(m log.Msg) {
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||||
r.t.logger.LogLevel(log.Debug, m.Skip(1))
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||||
}
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||||
// Implementation inspired by https://news.ycombinator.com/item?id=27019613.
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||||
func defaultReadaheadFunc(r ReadaheadContext) int64 {
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return r.CurrentPos - r.ContiguousReadStartPos
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||||
}
|
||||
Reference in New Issue
Block a user