From 6c8f277d3471e4cd36a8fdeeb056cc78535c48b2 Mon Sep 17 00:00:00 2001
From: Matt Joiner <anacrolix@gmail.com>
Date: Fri, 18 Jul 2025 23:08:15 +1000
Subject: [PATCH] Allocate Torrent file segments index just once

---
 piece.go          |  2 +-
 torrent.go        | 10 +++++++---
 webseed-peer.go   |  2 +-
 webseed/client.go |  7 +++----
 4 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/piece.go b/piece.go
index 597cd190..fc17714b 100644
--- a/piece.go
+++ b/piece.go
@@ -451,7 +451,7 @@ func (p *Piece) publishStateChange() {
 }
 
 func (p *Piece) fileExtents(offsetIntoPiece int64) iter.Seq2[int, segments.Extent] {
-	return p.t.info.FileSegmentsIndex().LocateIter(segments.Extent{
+	return p.t.fileSegmentsIndex.Unwrap().LocateIter(segments.Extent{
 		p.torrentBeginOffset() + offsetIntoPiece,
 		int64(p.length()) - offsetIntoPiece,
 	})
diff --git a/torrent.go b/torrent.go
index aab918a8..104733f9 100644
--- a/torrent.go
+++ b/torrent.go
@@ -35,6 +35,7 @@ import (
 	"github.com/anacrolix/missinggo/v2/pubsub"
 	"github.com/anacrolix/multiless"
 	"github.com/anacrolix/sync"
+	"github.com/anacrolix/torrent/segments"
 	"github.com/pion/webrtc/v4"
 	"golang.org/x/sync/errgroup"
 	"golang.org/x/time/rate"
@@ -115,8 +116,9 @@ type Torrent struct {
 	// routines. Cancelled when the Torrent is Closed too.
 	getInfoCtx context.Context
 	// Put a nice reason in :)
-	getInfoCtxCancel context.CancelCauseFunc
-	files            *[]*File
+	getInfoCtxCancel  context.CancelCauseFunc
+	files             *[]*File
+	fileSegmentsIndex g.Option[segments.Index]
 
 	_chunksPerRegularPiece chunkIndexType
 
@@ -380,7 +382,8 @@ func (t *Torrent) invalidateMetadata() {
 		t.metadataCompletedChunks[i] = false
 	}
 	t.nameMu.Lock()
-	t.info = nil
+	// Why the fuck would info be set?
+	panicif.NotNil(t.info)
 	t.nameMu.Unlock()
 }
 
@@ -538,6 +541,7 @@ func (t *Torrent) setInfo(info *metainfo.Info) error {
 	}
 	t.nameMu.Lock()
 	t.info = info
+	panicif.True(t.fileSegmentsIndex.Set(info.FileSegmentsIndex()).Ok)
 	t.getInfoCtxCancel(errors.New("got info"))
 	t.nameMu.Unlock()
 	t._chunksPerRegularPiece = chunkIndexType(intCeilDiv(pp.Integer(t.usualPieceSize()), t.chunkSize))
diff --git a/webseed-peer.go b/webseed-peer.go
index 1a131f12..b7c7a54f 100644
--- a/webseed-peer.go
+++ b/webseed-peer.go
@@ -90,7 +90,7 @@ func (ws *webseedPeer) String() string {
 }
 
 func (ws *webseedPeer) onGotInfo(info *metainfo.Info) {
-	ws.client.SetInfo(info)
+	ws.client.SetInfo(info, ws.peer.t.fileSegmentsIndex.UnwrapPtr())
 	// There should be probably be a callback in Client instead, so it can remove pieces at its whim
 	// too.
 	ws.client.Pieces.Iterate(func(x uint32) bool {
diff --git a/webseed/client.go b/webseed/client.go
index f6e03da5..a4d43274 100644
--- a/webseed/client.go
+++ b/webseed/client.go
@@ -67,8 +67,7 @@ type Client struct {
 	// Max concurrent requests to a WebSeed for a given torrent.
 	MaxRequests int
 
-	// TODO: Share this with Torrent.
-	fileIndex segments.Index
+	fileIndex *segments.Index
 	info      *metainfo.Info
 	// The pieces we can request with the Url. We're more likely to ban/block at the file-level
 	// given that's how requests are mapped to webseeds, but the torrent.Client works at the piece
@@ -84,13 +83,13 @@ type Client struct {
 
 type ResponseBodyWrapper func(io.Reader) io.Reader
 
-func (me *Client) SetInfo(info *metainfo.Info) {
+func (me *Client) SetInfo(info *metainfo.Info, fileIndex *segments.Index) {
 	if !strings.HasSuffix(me.Url, "/") && info.IsDir() {
 		// In my experience, this is a non-conforming webseed. For example the
 		// http://ia600500.us.archive.org/1/items URLs in archive.org torrents.
 		return
 	}
-	me.fileIndex = info.FileSegmentsIndex()
+	me.fileIndex = fileIndex
 	me.info = info
 	me.Pieces.AddRange(0, uint64(info.NumPieces()))
 }
-- 
2.51.0