[perf] Reduce the amount of crypto.randomFillSync() calls

Use a pool of random bytes to reduce the amount of
`crypto.randomFillSync()` calls.

Refs: nodejs/undici#3204

lib/sender.js

@@ -12,6 +12,9 @@ const { mask: applyMask, toBuffer } = require('./buffer-util');
 
 const kByteLength = Symbol('kByteLength');
 const maskBuffer = Buffer.alloc(4);
+const RANDOM_POOL_SIZE = 8 * 1024;
+let randomPool;
+let randomPoolPointer = RANDOM_POOL_SIZE;
 
 /**
  * HyBi Sender implementation.
@@ -76,7 +79,19 @@ class Sender {
  if (options.generateMask) {
  options.generateMask(mask);
  } else {
- randomFillSync(mask, 0, 4);
+ if (randomPoolPointer === RANDOM_POOL_SIZE) {
+ if (randomPool === undefined) {
+ randomPool = Buffer.alloc(RANDOM_POOL_SIZE);
+ }
+
+ randomFillSync(randomPool, 0, RANDOM_POOL_SIZE);
+ randomPoolPointer = 0;
+ }
+
+ mask[0] = randomPool[randomPoolPointer++];
+ mask[1] = randomPool[randomPoolPointer++];
+ mask[2] = randomPool[randomPoolPointer++];
+ mask[3] = randomPool[randomPoolPointer++];
  }
 
  skipMasking = (mask[0] | mask[1] | mask[2] | mask[3]) === 0;