From d540058ebd7f32e613d26c33e8a99b16d39a13d8 Mon Sep 17 00:00:00 2001
From: John Hiesey <john@hiesey.com>
Date: Wed, 30 Jun 2021 13:19:18 -0700
Subject: feat: Use a cache on the chunk store (#2095)

---
 lib/torrent.js | 21 +++++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

(limited to 'lib')

diff --git a/lib/torrent.js b/lib/torrent.js
index 1f0be5b..b46cde3 100644
--- a/lib/torrent.js
+++ b/lib/torrent.js
@@ -2,6 +2,7 @@
 
 const addrToIPPort = require('addr-to-ip-port')
 const BitField = require('bitfield').default
+const CacheChunkStore = require('cache-chunk-store')
 const ChunkStoreWriteStream = require('chunk-store-stream/write')
 const cpus = require('cpus')
 const debug = require('debug')('webtorrent:torrent')
@@ -12,6 +13,7 @@ const FSChunkStore = require('fs-chunk-store') // browser: `memory-chunk-store`
 const get = require('simple-get')
 const ImmediateChunkStore = require('immediate-chunk-store')
 const ltDontHave = require('lt_donthave')
+const MemoryChunkStore = require('memory-chunk-store')
 const MultiStream = require('multistream')
 const net = require('net') // browser exclude
 const os = require('os') // browser exclude
@@ -75,6 +77,7 @@ class Torrent extends EventEmitter {
     this.skipVerify = !!opts.skipVerify
     this._store = opts.store || FSChunkStore
     this._preloadedStore = opts.preloadedStore || null
+    this._storeCacheSlots = opts.storeCacheSlots !== undefined ? opts.storeCacheSlots : 20
     this._destroyStoreOnDestroy = opts.destroyStoreOnDestroy || false
     this._getAnnounceOpts = opts.getAnnounceOpts
 
@@ -470,8 +473,11 @@ class Torrent extends EventEmitter {
 
     this._rarityMap = new RarityMap(this)
 
-    this.store = new ImmediateChunkStore(
-      this._preloadedStore || new this._store(this.pieceLength, {
+    let rawStore = this._preloadedStore
+    if (!rawStore) {
+      rawStore = new this._store(this.pieceLength, {
+        // opts.torrent is deprecated (replaced by the name property).
+        // it doesn't appear to be used by current versions of any stores on npm.
         torrent: {
           infoHash: this.infoHash
         },
@@ -483,6 +489,17 @@ class Torrent extends EventEmitter {
         length: this.length,
         name: this.infoHash
       })
+    }
+
+    // don't use the cache if the store is already in memory
+    if (this._storeCacheSlots > 0 && !(rawStore instanceof MemoryChunkStore)) {
+      rawStore = new CacheChunkStore(rawStore, {
+        max: this._storeCacheSlots
+      })
+    }
+
+    this.store = new ImmediateChunkStore(
+      rawStore
     )
 
     this.files = this.files.map(file => new File(this, file))
-- 
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