From 8f065e473f0dfa474356d0758889fd79c3ee294c Mon Sep 17 00:00:00 2001
From: Matt Joiner <anacrolix@gmail.com>
Date: Sun, 24 Aug 2014 06:54:14 +1000
Subject: [PATCH] Add some checks to TorrentReadAt for 0 byte reads

---
 client.go | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/client.go b/client.go
index 2a20b263..86f90881 100644
--- a/client.go
+++ b/client.go
@@ -161,10 +161,14 @@ func (cl *Client) TorrentReadAt(ih InfoHash, off int64, p []byte) (n int, err er
 		return
 	}
 	piece := t.Pieces[index]
-	pieceOff := pp.Integer(off % int64(t.PieceLength(0)))
-	high := int(t.PieceLength(index) - pieceOff)
-	if high < len(p) {
-		p = p[:high]
+	pieceOff := pp.Integer(off % int64(t.UsualPieceSize()))
+	pieceLeft := int(t.PieceLength(index) - pieceOff)
+	if pieceLeft <= 0 {
+		err = io.EOF
+		return
+	}
+	if len(p) > pieceLeft {
+		p = p[:pieceLeft]
 	}
 	for cs, _ := range piece.PendingChunkSpecs {
 		chunkOff := int64(pieceOff) - int64(cs.Begin)
@@ -181,6 +185,9 @@ func (cl *Client) TorrentReadAt(ih InfoHash, off int64, p []byte) (n int, err er
 			p = p[:-chunkOff]
 		}
 	}
+	if len(p) == 0 {
+		panic(len(p))
+	}
 	return t.Data.ReadAt(p, off)
 }