From 97ae59dfaf977ca0cad2e4c057ff853fa25c723a Mon Sep 17 00:00:00 2001
From: Matt Joiner <anacrolix@gmail.com>
Date: Sun, 14 Sep 2014 03:50:15 +1000
Subject: [PATCH] Improve the data waiter system

---
 client.go  | 74 +++++++++++++++++++++++++++++++++++++++++-------------
 torrent.go | 13 ++++++++++
 2 files changed, 69 insertions(+), 18 deletions(-)

diff --git a/client.go b/client.go
index 1ad69cab..5b161293 100644
--- a/client.go
+++ b/client.go
@@ -29,6 +29,7 @@ import (
 	mathRand "math/rand"
 	"net"
 	"os"
+	"strings"
 	"sync"
 	"syscall"
 	"time"
@@ -77,6 +78,14 @@ func (cl *Client) queuePieceCheck(t *torrent, pieceIndex pp.Integer) {
 	go cl.verifyPiece(t, pieceIndex)
 }
 
+func (cl *Client) queueFirstHash(t *torrent, piece int) {
+	p := t.Pieces[piece]
+	if p.EverHashed || p.Hashing || p.QueuedForHash {
+		return
+	}
+	cl.queuePieceCheck(t, pp.Integer(piece))
+}
+
 // Queues the torrent data for the given region for download. The beginning of
 // the region is given highest priority to allow a subsequent read at the same
 // offset to return data ASAP.
@@ -97,9 +106,9 @@ func (me *Client) PrioritizeDataRegion(ih InfoHash, off, len_ int64) error {
 	return nil
 }
 
-type dataSpec struct {
-	InfoHash
-	request
+type dataWait struct {
+	offset int64
+	ready  chan struct{}
 }
 
 type Client struct {
@@ -120,8 +129,7 @@ type Client struct {
 	handshaking int
 	torrents    map[InfoHash]*torrent
 
-	dataWaiterMutex sync.Mutex
-	dataWaiter      chan struct{}
+	dataWaits map[*torrent][]dataWait
 }
 
 func (me *Client) ListenAddr() net.Addr {
@@ -153,6 +161,11 @@ func (cl *Client) WriteStatus(w io.Writer) {
 				return 100 * (1 - float32(t.BytesLeft())/float32(t.Length()))
 			}
 		}())
+		fmt.Fprint(w, "Blocked reads:")
+		for _, dw := range cl.dataWaits[t] {
+			fmt.Fprintf(w, " %d", dw.offset)
+		}
+		fmt.Fprintln(w)
 		t.WriteStatus(w)
 		fmt.Fprintln(w)
 	}
@@ -223,6 +236,8 @@ func NewClient(cfg *Config) (cl *Client, err error) {
 
 		quit:     make(chan struct{}),
 		torrents: make(map[InfoHash]*torrent),
+
+		dataWaits: make(map[*torrent][]dataWait),
 	}
 	cl.event.L = &cl.mu
 	cl.mu.Init(2)
@@ -1128,6 +1143,10 @@ func (me *Client) DropTorrent(infoHash InfoHash) (err error) {
 	}
 	delete(me.torrents, infoHash)
 	me.downloadStrategy.TorrentStopped(t)
+	for _, dw := range me.dataWaits[t] {
+		close(dw.ready)
+	}
+	delete(me.dataWaits, t)
 	return
 }
 
@@ -1369,7 +1388,7 @@ func (me *Client) downloadedChunk(t *torrent, c *connection, msg *pp.Message) er
 
 	// Record that we have the chunk.
 	delete(t.Pieces[req.Index].PendingChunkSpecs, req.chunkSpec)
-	me.dataReady(dataSpec{t.InfoHash, req})
+	me.dataReady(t, req)
 	if len(t.Pieces[req.Index].PendingChunkSpecs) == 0 {
 		me.queuePieceCheck(t, req.Index)
 	}
@@ -1390,24 +1409,43 @@ func (me *Client) downloadedChunk(t *torrent, c *connection, msg *pp.Message) er
 	return nil
 }
 
-func (cl *Client) dataReady(ds dataSpec) {
-	cl.dataWaiterMutex.Lock()
-	if cl.dataWaiter != nil {
-		close(cl.dataWaiter)
+func (cl *Client) dataReady(t *torrent, r request) {
+	dws := cl.dataWaits[t]
+	begin := t.requestOffset(r)
+	end := begin + int64(r.Length)
+	for i := 0; i < len(dws); {
+		dw := dws[i]
+		if begin <= dw.offset && dw.offset < end {
+			close(dw.ready)
+			dws[i] = dws[len(dws)-1]
+			dws = dws[:len(dws)-1]
+		} else {
+			i++
+		}
 	}
-	cl.dataWaiter = nil
-	cl.dataWaiterMutex.Unlock()
+	cl.dataWaits[t] = dws
 }
 
 // Returns a channel that is closed when new data has become available in the
 // client.
-func (me *Client) DataWaiter() (ret <-chan struct{}) {
-	me.dataWaiterMutex.Lock()
-	if me.dataWaiter == nil {
-		me.dataWaiter = make(chan struct{})
+func (me *Client) DataWaiter(ih InfoHash, off int64) (ret <-chan struct{}) {
+	me.mu.Lock()
+	defer me.mu.Unlock()
+	ch := make(chan struct{})
+	ret = ch
+	t := me.torrents[ih]
+	if t == nil {
+		close(ch)
+		return
+	}
+	if r, ok := t.offsetRequest(off); !ok || t.haveChunk(r) {
+		close(ch)
+		return
 	}
-	ret = me.dataWaiter
-	me.dataWaiterMutex.Unlock()
+	me.dataWaits[t] = append(me.dataWaits[t], dataWait{
+		offset: off,
+		ready:  ch,
+	})
 	return
 }
 
diff --git a/torrent.go b/torrent.go
index 6ac23114..19b5f053 100644
--- a/torrent.go
+++ b/torrent.go
@@ -533,6 +533,19 @@ func (me *torrent) haveAnyPieces() bool {
 	return false
 }
 
+func (t *torrent) havePiece(index int) bool {
+	return t.haveInfo() && t.Pieces[index].Complete()
+}
+
+func (t *torrent) haveChunk(r request) bool {
+	p := t.Pieces[r.Index]
+	if !p.EverHashed {
+		return false
+	}
+	_, ok := p.PendingChunkSpecs[r.chunkSpec]
+	return !ok
+}
+
 func (t *torrent) wantChunk(r request) bool {
 	if !t.wantPiece(int(r.Index)) {
 		return false
-- 
2.48.1