perf: optimize decoding on byteLength <= 64

Author: ChALkeR

fallback/_utils.js

@@ -128,3 +128,9 @@ export function decode2string(arr, start, end, m) {
 export function assert(condition, msg) {
   if (!condition) throw new Error(msg)
 }
+
+// On arrays in heap (<= 64) it's cheaper to copy into a pooled buffer than lazy-create the ArrayBuffer storage
+export const toBuf = (x) =>
+  x.byteLength <= 64 && x.BYTES_PER_ELEMENT === 1
+    ? Buffer.from(x)
+    : Buffer.from(x.buffer, x.byteOffset, x.byteLength)

multi-byte.node.js

@@ -1,10 +1,8 @@
 import { assertUint8 } from './assert.js'
-import { isDeno } from './fallback/_utils.js'
+import { isDeno, toBuf } from './fallback/_utils.js'
 import { isAsciiSuperset, multibyteDecoder } from './fallback/multi-byte.js'
 import { isAscii } from 'node:buffer'
 
-const toBuf = (x) => Buffer.from(x.buffer, x.byteOffset, x.byteLength)
-
 export function createMultibyteDecoder(encoding, loose = false) {
   const jsDecoder = multibyteDecoder(encoding, loose) // asserts
   let streaming = false

single-byte.node.js

@@ -1,11 +1,9 @@
 import { assertUint8 } from './assert.js'
 import { isAscii } from 'node:buffer'
-import { isDeno, isLE } from './fallback/_utils.js'
+import { isDeno, isLE, toBuf } from './fallback/_utils.js'
 import { asciiPrefix } from './fallback/latin1.js'
 import { encodingMapper, encodingDecoder, E_STRICT } from './fallback/single-byte.js'
 
-const toBuf = (x) => Buffer.from(x.buffer, x.byteOffset, x.byteLength)
-
 function latin1Prefix(arr, start) {
   let p = start | 0
   const length = arr.length