feat: fromBase58check never returns pooled non-Buffers

This is also slightly faster, as subarray is slower than slice on
Uint8Array instances allocated in heap (length <= 64)

Author: ChALkeR

fallback/base58check.js

@@ -10,15 +10,15 @@ function encodeWithChecksum(arr, checksum) {
   // arr type in already validated in input
   const res = new Uint8Array(arr.length + 4)
   res.set(arr, 0)
-  res.set(checksum.subarray(0, 4), arr.length)
+  res.set(checksum.slice(0, 4), arr.length)
   return toBase58(res)
 }
 
 function decodeWithChecksum(str) {
   const arr = fromBase58(str) // checks input
   const payloadSize = arr.length - 4
   if (payloadSize < 0) throw new Error(E_CHECKSUM)
-  return [arr.subarray(0, payloadSize), arr.subarray(payloadSize)]
+  return [arr.slice(0, payloadSize), arr.slice(payloadSize)]
 }
 
 function assertChecksum(c, r) {

tests/base58check.test.js

@@ -1,4 +1,4 @@
-import { fromBase58checkSync, toBase58checkSync } from '@exodus/bytes/base58check.js'
+import { fromBase58checkSync as fromBase58c, toBase58checkSync } from '@exodus/bytes/base58check.js'
 import { randomValues } from '@exodus/crypto/randomBytes'
 import { test } from 'node:test'
 import bs58check from 'bs58check'
@@ -10,6 +10,14 @@ const toShared = (u8) => {
   return res
 }
 
+const tracked = []
+
+function fromBase58checkSync(...args) {
+  const res = fromBase58c(...args)
+  tracked.push(res)
+  return res
+}
+
 test('zeros', (t) => {
   for (let size = 0; size <= 1024; size++) {
     const zeros = new Uint8Array(size)
@@ -91,3 +99,12 @@ test('sizes roundtrip, random data', (t) => {
     t.assert.deepStrictEqual(fromBase58checkSync(toBase58checkSync(arr)), arr, `random x${size}`)
   }
 })
+
+test('fromBase58check returns non-pooled Uint8Array instances', (t) => {
+  t.assert.ok(tracked.length > 1000)
+
+  for (const u8 of tracked) {
+    if (Buffer.isBuffer(u8)) continue
+    t.assert.strictEqual(u8.byteLength, u8.buffer.byteLength)
+  }
+})