Cache verified remote contiguous length

lib/replicator.js

@@ -585,7 +585,10 @@ class Peer {
   }
 
   get remoteContiguousLength() {
-    return this.remoteBitfield.findFirst(false, this._remoteContiguousLength)
+    const length = this.remoteBitfield.findFirst(false, this._remoteContiguousLength)
+    // Cache the verified extent so repeated reads do not rescan the same bitfield run.
+    if (length > this._remoteContiguousLength) this._remoteContiguousLength = length
+    return length
   }
 
   getMaxInflight() {
@@ -1411,12 +1414,13 @@ class Peer {
     if (start === 0 && drop === false) {
       if (length > this._remoteContiguousLength) {
         this._remoteContiguousLength = length
-        if (
-          this.remoteFork === this.core.state.fork &&
-          length > this.core.header.hints.remoteContiguousLength
-        ) {
-          this.core.updateRemoteContiguousLength(length)
-        }
+      }
+
+      if (
+        this.remoteFork === this.core.state.fork &&
+        length > this.core.header.hints.remoteContiguousLength
+      ) {
+        this.core.updateRemoteContiguousLength(length)
       }
     } else if (length === 1) {
       const bitfield = this.core.skipBitfield === null ? this.core.bitfield : this.core.skipBitfield

test/remote-bitfield.js

@@ -1,7 +1,7 @@
 const test = require('brittle')
 const b4a = require('b4a')
 const RemoteBitfield = require('../lib/remote-bitfield')
-const { create, replicate } = require('./helpers')
+const { create, replicate, eventFlush } = require('./helpers')
 
 test('remote bitfield - findFirst', function (t) {
   const b = new RemoteBitfield()
@@ -66,6 +66,43 @@ test('remote congituous length consistency (remote-bitfield findFirst edge case)
   )
 })
 
+test('remote contiguous length caches verified bitfield extent', async function (t) {
+  const a = await create(t)
+  const b = await create(t, a.key)
+
+  replicate(a, b, t)
+  await eventFlush()
+
+  const peer = getPeer(b, a)
+
+  peer.remoteBitfield.setRange(0, 1024, true)
+  peer._remoteContiguousLength = 0
+
+  t.is(peer.remoteContiguousLength, 1024)
+  t.is(peer._remoteContiguousLength, 1024)
+})
+
+test('range updates core remote contiguous length after getter advances peer cache', async function (t) {
+  const a = await create(t)
+  const b = await create(t, a.key)
+
+  replicate(a, b, t)
+  await eventFlush()
+
+  const peer = getPeer(b, a)
+
+  peer.remoteFork = b.core.state.fork
+  peer.remoteBitfield.setRange(0, 1024, true)
+  peer._remoteContiguousLength = 0
+
+  t.is(peer.remoteContiguousLength, 1024)
+  t.is(b.core.header.hints.remoteContiguousLength, 0)
+
+  await peer.onrange({ start: 0, length: 1024, drop: false })
+
+  t.is(b.core.header.hints.remoteContiguousLength, 1024)
+})
+
 test('bitfield messages sent on cache miss', async function (t) {
   const original = await create(t)
   const sparse = await create(t, original.key)