State distance function (#540)

* state: remove custom distance function

* state: compare distance function using xor

* remove distance export

* state: change distance test to xor

* state: change distance import in routingTable

packages/portalnetwork/src/index.ts

@@ -1,7 +1,7 @@
 export { PortalNetwork } from './client/client.js'
 export * from './client/index.js'
 export * from './networks/index.js'
-export { distance, StateNetworkRoutingTable } from './networks/state/index.js'
+export { StateNetworkRoutingTable } from './networks/state/index.js'
 export * from './transports/index.js'
 export * from './util/index.js'
 export * from './wire/index.js'

packages/portalnetwork/src/networks/state/routingTable.ts

@@ -1,6 +1,6 @@
-import { PortalNetworkRoutingTable } from '../../client/routingTable.js'
+import { distance } from '@chainsafe/discv5'
 
-import { distance } from './util.js'
+import { PortalNetworkRoutingTable } from '../../client/routingTable.js'
 
 import type { ENR, NodeId } from '@chainsafe/discv5'
 
@@ -17,7 +17,7 @@ export class StateNetworkRoutingTable extends PortalNetworkRoutingTable {
       results.push(...bucket.values())
     }
     results.sort((a, b) => {
-      const diff = distance(BigInt(id), BigInt(a.nodeId)) - distance(BigInt(id), BigInt(b.nodeId))
+      const diff = distance(id, a.nodeId) - distance(id, b.nodeId)
       if (diff < 0) return -1
       if (diff === 0n) return 0
       return 1

packages/portalnetwork/src/networks/state/util.ts

@@ -1,4 +1,6 @@
 import { digest as sha256 } from '@chainsafe/as-sha256'
+import { distance } from '@chainsafe/discv5'
+import { equalsBytes } from '@ethereumjs/util'
 
 import {
   AccountTrieNodeKey,
@@ -16,23 +18,6 @@ import type {
   TStorageTrieNodeKey,
 } from './types.js'
 
-export const MODULO = 2n ** 256n
-const MID = 2n ** 255n
-
-/**
- * Calculates the distance between two ids using the distance function defined here
- * https://github.com/ethereum/portal-network-specs/blob/master/state-network.md#distance-function
- */
-export const distance = (id1: bigint, id2: bigint): bigint => {
-  if (id1 >= MODULO || id2 >= MODULO) {
-    throw new Error('numeric representation of node id cannot be greater than 2^256')
-  }
-  let diff: bigint
-  id1 > id2 ? (diff = id1 - id2) : (diff = id2 - id1)
-  diff > MID ? (diff = MODULO - diff) : diff
-  return diff
-}
-
 /* ContentKeys */
 
 export const keyType = (contentKey: Uint8Array): StateNetworkContentType => {
@@ -146,3 +131,12 @@ export const tightlyPackNibbles = (nibbles: TNibble[]): TNibbles => {
   })
   return { isOddLength, packedNibbles: Uint8Array.from(packedBytes) }
 }
+
+export const compareDistance = (nodeId: string, nodeA: Uint8Array, nodeB: Uint8Array) => {
+  if (equalsBytes(nodeA, nodeB)) {
+    return nodeA
+  }
+  const distanceA = distance(nodeId, nodeA.toString())
+  const distanceB = distance(nodeId, nodeB.toString())
+  return distanceA < distanceB ? nodeA : nodeB
+}

packages/portalnetwork/test/networks/state/utils.spec.ts

@@ -1,23 +1,21 @@
+import { distance } from '@chainsafe/discv5'
 import { randomBytes } from '@ethereumjs/util'
 import { assert, describe, it } from 'vitest'
 
 import { StateNetworkContentType } from '../../../src/networks/state/types.js'
-import {
-  MODULO,
-  calculateAddressRange,
-  distance,
-  keyType,
-} from '../../../src/networks/state/util.js'
+import { calculateAddressRange, keyType } from '../../../src/networks/state/util.js'
 
 describe('distance()', () => {
   it('should calculate distance between two values', () => {
-    assert.ok(distance(10n, 10n) === 0n, 'calculates correct distance')
-    assert.ok(distance(5n, MODULO - 1n) === 6n, 'calculates correct distance')
-    assert.ok(distance(MODULO - 1n, 6n) === 7n, 'calculates correct distance')
-    assert.ok(distance(5n, 1n) === 4n, 'calculates correct distance')
-    assert.ok(distance(1n, 5n) === 4n, 'calculates correct distance')
-    assert.ok(distance(0n, 2n ** 255n) === 2n ** 255n, 'calculates correct distance')
-    assert.ok(distance(0n, 2n ** 255n + 1n) === 2n ** 255n - 1n, 'calculates correct distance')
+    assert.equal(distance('00', '08'), 8n, 'calculates correct distance')
+    assert.equal(distance('00', '09'), 9n, 'calculates correct distance')
+    assert.equal(distance('00', '0a'), 10n, 'calculates correct distance')
+    assert.equal(distance('01', '0a'), 11n, 'calculates correct distance')
+    assert.equal(distance('02', '0a'), 8n, 'calculates correct distance')
+    assert.equal(distance('03', '0a'), 9n, 'calculates correct distance')
+    assert.equal(distance('0a', '00'), 10n, 'calculates correct distance')
+    assert.equal(distance('0a', '01'), 11n, 'calculates correct distance')
+    assert.equal(distance('0a', '0a'), 0n, 'calculates correct distance')
   })
 })