feat: CoreReplicationState (#288)

* feat: CoreReplicationState

Add a new CoreReplicationState implementation, see
#287

* cleanup and simplify

* derive state

* Add missing and connected & cleanup

* Move exported class to top

* cache derived state

* Add code comments

* add benchmarks

* entries -> for index, 4,150ms -> 2,500ms

Use `for(let j = 0; j < peers.length ...` instead of `peers.entries()`

* re-used haves/wants arrays, 2500ms -> 2300ms

* Remove wants array, 2300ms -> 2180ms

* deriveState unit tests

* bitwise operations, 1500ms -> ~90ms

* increase benchmark iterations for better accuracy

* Update src/core-manager/core-replication-state.js

Co-authored-by: Andrew Chou <andrewchou@fastmail.com>

* fixes

* wip tests

* fix prehave test

* fix failing test

* bitcount test

* add some additional code comments

---------

Co-authored-by: Andrew Chou <andrewchou@fastmail.com>

benchmarks/core-replication-state.js

@@ -0,0 +1,46 @@
+import bench from 'nanobench'
+import {
+  PeerState,
+  deriveState,
+} from '../src/core-manager/core-replication-state.js'
+import RemoteBitfield from '../src/core-manager/remote-bitfield.js'
+import createRandom from 'math-random-seed'
+
+bench('deriveState x 10,000; 10 peers; 10,000 blocks', function (b) {
+  const length = 10000
+  const remotePeers = new Map()
+  for (let i = 0; i < 10; i++) {
+    remotePeers.set(i, createPeer(length, i + ''))
+  }
+  const localPeer = createPeer(length, 'local')
+
+  const state = {
+    length,
+    localState: localPeer,
+    remoteStates: remotePeers,
+  }
+
+  b.start()
+  for (let i = 0; i < 10000; i++) {
+    deriveState(state)
+  }
+  b.end()
+})
+
+function createPeer(length, seed) {
+  const peer = new PeerState()
+  peer.setHavesBitfield(createBitfield(length, seed))
+  return peer
+}
+
+function createBitfield(length, seed) {
+  const random = createRandom(seed)
+  const b = new RemoteBitfield()
+  let i = random() < 0.5 ? 0 : Math.ceil(random() * 200)
+  while (i < length) {
+    const length = Math.ceil(random() * 200)
+    b.setRange(i, length, true)
+    i += length + Math.ceil(random() * 200)
+  }
+  return b
+}

package.json

@@ -79,6 +79,7 @@
     "eslint": "^8.39.0",
     "fastify": "^4.20.0",
     "light-my-request": "^5.10.0",
+    "math-random-seed": "^2.0.0",
     "nanobench": "^3.0.0",
     "npm-run-all": "^4.1.5",
     "prettier": "^2.8.8",