From eeb021b134137d2096f0ef899d5215ece8989ba0 Mon Sep 17 00:00:00 2001
From: Matt Joiner <anacrolix@gmail.com>
Date: Thu, 12 May 2022 13:47:12 +1000
Subject: [PATCH] Use Option for cached Torrent length

Fixes https://github.com/anacrolix/torrent/issues/630.
---
 client.go  |  4 ++--
 t.go       |  4 ++--
 torrent.go | 18 +++++++++++-------
 3 files changed, 15 insertions(+), 11 deletions(-)

diff --git a/client.go b/client.go
index d8b17064..28dbc8ed 100644
--- a/client.go
+++ b/client.go
@@ -166,8 +166,8 @@ func (cl *Client) WriteStatus(_w io.Writer) {
 				w,
 				"%f%% of %d bytes (%s)",
 				100*(1-float64(t.bytesMissingLocked())/float64(t.info.TotalLength())),
-				*t.length,
-				humanize.Bytes(uint64(*t.length)))
+				t.length(),
+				humanize.Bytes(uint64(t.length())))
 		} else {
 			w.WriteString("<missing metainfo>")
 		}
diff --git a/t.go b/t.go
index 324f761f..a20e02c8 100644
--- a/t.go
+++ b/t.go
@@ -32,7 +32,7 @@ func (t *Torrent) Info() (info *metainfo.Info) {
 // Returns a Reader bound to the torrent's data. All read calls block until the data requested is
 // actually available. Note that you probably want to ensure the Torrent Info is available first.
 func (t *Torrent) NewReader() Reader {
-	return t.newReader(0, *t.length)
+	return t.newReader(0, t.length())
 }
 
 func (t *Torrent) newReader(offset, length int64) Reader {
@@ -147,7 +147,7 @@ func (t *Torrent) Name() string {
 // The completed length of all the torrent data, in all its files. This is
 // derived from the torrent info, when it is available.
 func (t *Torrent) Length() int64 {
-	return *t.length
+	return t._length.Value()
 }
 
 // Returns a run-time generated metainfo for the torrent that includes the
diff --git a/torrent.go b/torrent.go
index bd7b7573..cc9458d1 100644
--- a/torrent.go
+++ b/torrent.go
@@ -74,7 +74,7 @@ type Torrent struct {
 	chunkPool sync.Pool
 	// Total length of the torrent in bytes. Stored because it's not O(1) to
 	// get this from the info dict.
-	length *int64
+	_length Option[int64]
 
 	// The storage to open when the info dict becomes available.
 	storageOpener *storage.Client
@@ -167,6 +167,10 @@ type Torrent struct {
 	requestIndexes     []RequestIndex
 }
 
+func (t *Torrent) length() int64 {
+	return t._length.Value()
+}
+
 func (t *Torrent) selectivePieceAvailabilityFromPeers(i pieceIndex) (count int) {
 	// This could be done with roaring.BitSliceIndexing.
 	t.iterPeers(func(peer *Peer) {
@@ -420,7 +424,7 @@ func (t *Torrent) cacheLength() {
 	for _, f := range t.info.UpvertedFiles() {
 		l += f.Length
 	}
-	t.length = &l
+	t._length = Some(l)
 }
 
 // TODO: This shouldn't fail for storage reasons. Instead we should handle storage failure
@@ -895,13 +899,13 @@ func (t *Torrent) close(wg *sync.WaitGroup) (err error) {
 }
 
 func (t *Torrent) requestOffset(r Request) int64 {
-	return torrentRequestOffset(*t.length, int64(t.usualPieceSize()), r)
+	return torrentRequestOffset(t.length(), int64(t.usualPieceSize()), r)
 }
 
 // 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, int64(t.chunkSize), off)
+	return torrentOffsetRequest(t.length(), t.info.PieceLength, int64(t.chunkSize), off)
 }
 
 func (t *Torrent) writeChunk(piece int, begin int64, data []byte) (err error) {
@@ -949,7 +953,7 @@ func (t *Torrent) pieceLength(piece pieceIndex) pp.Integer {
 		return 0
 	}
 	if piece == t.numPieces()-1 {
-		ret := pp.Integer(*t.length % t.info.PieceLength)
+		ret := pp.Integer(t.length() % t.info.PieceLength)
 		if ret != 0 {
 			return ret
 		}
@@ -1225,7 +1229,7 @@ func (t *Torrent) updatePiecePriorities(begin, end pieceIndex, reason string) {
 
 // Returns the range of pieces [begin, end) that contains the extent of bytes.
 func (t *Torrent) byteRegionPieces(off, size int64) (begin, end pieceIndex) {
-	if off >= *t.length {
+	if off >= t.length() {
 		return
 	}
 	if off < 0 {
@@ -1442,7 +1446,7 @@ func (t *Torrent) bytesCompleted() int64 {
 	if !t.haveInfo() {
 		return 0
 	}
-	return *t.length - t.bytesLeft()
+	return t.length() - t.bytesLeft()
 }
 
 func (t *Torrent) SetInfoBytes(b []byte) (err error) {
-- 
2.44.0