From ade6087b2fa99863b8b28cd73596c3b280510e38 Mon Sep 17 00:00:00 2001
From: Matt Joiner <anacrolix@gmail.com>
Date: Wed, 8 Apr 2015 02:20:01 +1000
Subject: [PATCH] Move torrentOffsetRequest and torrentRequestOffset, fixing a
 bug in former, and test it

---
 misc.go      | 29 +++++++++++++++++++++++++++++
 misc_test.go | 15 +++++++++++++++
 torrent.go   | 29 ++---------------------------
 3 files changed, 46 insertions(+), 27 deletions(-)
 create mode 100644 misc_test.go

diff --git a/misc.go b/misc.go
index 56d1f9c9..c567f68d 100644
--- a/misc.go
+++ b/misc.go
@@ -78,3 +78,32 @@ func super(child interface{}) (parent interface{}, ok bool) {
 	ok = parent != nil
 	return
 }
+
+// Return the request that would include the given offset into the torrent data.
+func torrentOffsetRequest(torrentLength, pieceSize, chunkSize, offset int64) (
+	r request, ok bool) {
+	if offset < 0 || offset >= torrentLength {
+		return
+	}
+	r.Index = pp.Integer(offset / pieceSize)
+	r.Begin = pp.Integer(offset % pieceSize / chunkSize * chunkSize)
+	r.Length = pp.Integer(chunkSize)
+	pieceLeft := pp.Integer(pieceSize - int64(r.Begin))
+	if r.Length > pieceLeft {
+		r.Length = pieceLeft
+	}
+	torrentLeft := torrentLength - int64(r.Index)*pieceSize - int64(r.Begin)
+	if int64(r.Length) > torrentLeft {
+		r.Length = pp.Integer(torrentLeft)
+	}
+	ok = true
+	return
+}
+
+func torrentRequestOffset(torrentLength, pieceSize int64, r request) (off int64) {
+	off = int64(r.Index)*pieceSize + int64(r.Begin)
+	if off < 0 || off >= torrentLength {
+		panic("invalid request")
+	}
+	return
+}
diff --git a/misc_test.go b/misc_test.go
new file mode 100644
index 00000000..a8bd10f4
--- /dev/null
+++ b/misc_test.go
@@ -0,0 +1,15 @@
+package torrent
+
+import . "gopkg.in/check.v1"
+
+func (suite) TestTorrentOffsetRequest(c *C) {
+	check := func(tl, ps, off int64, expected request, ok bool) {
+		req, _ok := torrentOffsetRequest(tl, ps, chunkSize, off)
+		c.Check(_ok, Equals, ok)
+		c.Check(req, Equals, expected)
+	}
+	check(13, 5, 0, newRequest(0, 0, 5), true)
+	check(13, 5, 3, newRequest(0, 0, 5), true)
+	check(13, 5, 11, newRequest(2, 0, 3), true)
+	check(13, 5, 13, request{}, false)
+}
diff --git a/torrent.go b/torrent.go
index 32fa54d7..8b5dbb71 100644
--- a/torrent.go
+++ b/torrent.go
@@ -630,37 +630,12 @@ func (t *torrent) close() (err error) {
 	return
 }
 
-// Return the request that would include the given offset into the torrent data.
-func torrentOffsetRequest(torrentLength, pieceSize, chunkSize, offset int64) (
-	r request, ok bool) {
-	if offset < 0 || offset >= torrentLength {
-		return
-	}
-	r.Index = pp.Integer(offset / pieceSize)
-	r.Begin = pp.Integer(offset % pieceSize / chunkSize * chunkSize)
-	left := torrentLength - int64(r.Index)*pieceSize - int64(r.Begin)
-	if chunkSize < left {
-		r.Length = pp.Integer(chunkSize)
-	} else {
-		r.Length = pp.Integer(left)
-	}
-	ok = true
-	return
-}
-
-func torrentRequestOffset(torrentLength, pieceSize int64, r request) (off int64) {
-	off = int64(r.Index)*pieceSize + int64(r.Begin)
-	if off < 0 || off >= torrentLength {
-		panic("invalid request")
-	}
-	return
-}
-
 func (t *torrent) requestOffset(r request) int64 {
 	return torrentRequestOffset(t.Length(), int64(t.usualPieceSize()), r)
 }
 
-// Return the request that would include the given offset into the torrent data.
+// Return the request that would include the given offset into the torrent
+// data. Returns !ok if there is no such request.
 func (t *torrent) offsetRequest(off int64) (req request, ok bool) {
 	return torrentOffsetRequest(t.Length(), t.Info.PieceLength, chunkSize, off)
 }