crypto: refactor ArrayBuffer to bigint conversion utils

PR-URL: nodejs#45567
Refs: nodejs/performance#16
Reviewed-By: Yagiz Nizipli <yagiz@nizipli.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

lib/internal/crypto/random.js

@@ -2,17 +2,22 @@
 
 const {
   Array,
+  ArrayBufferPrototypeGetByteLength,
   ArrayPrototypeForEach,
   ArrayPrototypePush,
   ArrayPrototypeShift,
   ArrayPrototypeSplice,
   BigInt,
+  BigIntPrototypeToString,
+  DataView,
+  DataViewPrototypeGetUint8,
   FunctionPrototypeBind,
   FunctionPrototypeCall,
   MathMin,
   NumberIsNaN,
   NumberIsSafeInteger,
   NumberPrototypeToString,
+  StringFromCharCodeApply,
   StringPrototypePadStart,
 } = primordials;
 
@@ -493,17 +498,39 @@ function generatePrimeSync(size, options = kEmptyObject) {
   return job.result(prime);
 }
 
-function arrayBufferToUnsignedBigInt(arrayBuffer) {
-  return BigInt(`0x${Buffer.from(arrayBuffer).toString('hex')}`);
+/**
+ * 48 is the ASCII code for '0', 97 is the ASCII code for 'a'.
+ * @param {number} number An integer between 0 and 15.
+ * @returns {number} corresponding to the ASCII code of the hex representation
+ *                   of the parameter.
+ */
+const numberToHexCharCode = (number) => (number < 10 ? 48 : 87) + number;
+
+/**
+ * @param {ArrayBuffer} buf An ArrayBuffer.
+ * @return {bigint}
+ */
+function arrayBufferToUnsignedBigInt(buf) {
+  const length = ArrayBufferPrototypeGetByteLength(buf);
+  const chars = Array(length * 2);
+  const view = new DataView(buf);
+
+  for (let i = 0; i < length; i++) {
+    const val = DataViewPrototypeGetUint8(view, i);
+    chars[2 * i] = numberToHexCharCode(val >> 4);
+    chars[2 * i + 1] = numberToHexCharCode(val & 0xf);
+  }
+
+  return BigInt(`0x${StringFromCharCodeApply(chars)}`);
 }
 
 function unsignedBigIntToBuffer(bigint, name) {
   if (bigint < 0) {
     throw new ERR_OUT_OF_RANGE(name, '>= 0', bigint);
   }
 
-  const hex = bigint.toString(16);
-  const padded = hex.padStart(hex.length + (hex.length % 2), 0);
+  const hex = BigIntPrototypeToString(bigint, 16);
+  const padded = StringPrototypePadStart(hex, hex.length + (hex.length % 2), 0);
   return Buffer.from(padded, 'hex');
 }
 

lib/internal/per_context/primordials.js

@@ -45,6 +45,8 @@ const varargsMethods = [
   'MathHypot',
   'MathMax',
   'MathMin',
+  'StringFromCharCode',
+  'StringFromCodePoint',
   'StringPrototypeConcat',
   'TypedArrayOf',
 ];

typings/primordials.d.ts

@@ -422,7 +422,9 @@ declare namespace primordials {
   export const StringName: typeof String.name
   export const StringPrototype: typeof String.prototype
   export const StringFromCharCode: typeof String.fromCharCode
+  export const StringFromCharCodeApply: StaticApply<typeof String.fromCharCode>
   export const StringFromCodePoint: typeof String.fromCodePoint
+  export const StringFromCodePointApply: StaticApply<typeof String.fromCodePoint>
   export const StringRaw: typeof String.raw
   export const StringPrototypeAnchor: UncurryThis<typeof String.prototype.anchor>
   export const StringPrototypeBig: UncurryThis<typeof String.prototype.big>