piece.go                 | 30 ------------------------------
 undirtied-chunks-iter.go | 34 ++++++++++++++++++++++++++++++++++

diff --git a/piece.go b/piece.go
index 44f2dd9d623410844a2769f952130aa1886e3163..d892a406e809843af1eee379f28c5171724e2e25 100644
--- a/piece.go
+++ b/piece.go
@@ -10,7 +10,6 @@ 	"github.com/anacrolix/missinggo/v2/bitmap"
 	"github.com/anacrolix/torrent/metainfo"
 	pp "github.com/anacrolix/torrent/peer_protocol"
 	"github.com/anacrolix/torrent/storage"
-	"github.com/anacrolix/torrent/typed-roaring"
 )
 
 type Piece struct {
@@ -247,35 +246,6 @@ }
 
 func init() {
 	gob.Register(undirtiedChunksIter{})
-}
-
-// Use an iterator to jump between dirty bits.
-type undirtiedChunksIter struct {
-	TorrentDirtyChunks *typedRoaring.Bitmap[RequestIndex]
-	StartRequestIndex  RequestIndex
-	EndRequestIndex    RequestIndex
-}
-
-func (me *undirtiedChunksIter) Iter(f func(chunkIndexType)) {
-	it := me.TorrentDirtyChunks.Iterator()
-	startIndex := me.StartRequestIndex
-	endIndex := me.EndRequestIndex
-	it.AdvanceIfNeeded(startIndex)
-	lastDirty := startIndex - 1
-	for it.HasNext() {
-		next := it.Next()
-		if next >= endIndex {
-			break
-		}
-		for index := lastDirty + 1; index < next; index++ {
-			f(index - startIndex)
-		}
-		lastDirty = next
-	}
-	for index := lastDirty + 1; index < endIndex; index++ {
-		f(index - startIndex)
-	}
-	return
 }
 
 func (p *Piece) requestIndexOffset() RequestIndex {
diff --git a/undirtied-chunks-iter.go b/undirtied-chunks-iter.go
new file mode 100644
index 0000000000000000000000000000000000000000..14f88a24f922ee966d7315263f716b41c77130b2
--- /dev/null
+++ b/undirtied-chunks-iter.go
@@ -0,0 +1,34 @@
+package torrent
+
+import (
+	"github.com/anacrolix/torrent/typed-roaring"
+)
+
+// Use an iterator to jump between dirty bits.
+type undirtiedChunksIter struct {
+	TorrentDirtyChunks *typedRoaring.Bitmap[RequestIndex]
+	StartRequestIndex  RequestIndex
+	EndRequestIndex    RequestIndex
+}
+
+func (me *undirtiedChunksIter) Iter(f func(chunkIndexType)) {
+	it := me.TorrentDirtyChunks.Iterator()
+	startIndex := me.StartRequestIndex
+	endIndex := me.EndRequestIndex
+	it.AdvanceIfNeeded(startIndex)
+	lastDirty := startIndex - 1
+	for it.HasNext() {
+		next := it.Next()
+		if next >= endIndex {
+			break
+		}
+		for index := lastDirty + 1; index < next; index++ {
+			f(index - startIndex)
+		}
+		lastDirty = next
+	}
+	for index := lastDirty + 1; index < endIndex; index++ {
+		f(index - startIndex)
+	}
+	return
+}