perf: use a random pool

Author: ronag

lib/random-util.js

@@ -0,0 +1,38 @@
+'use strict';
+
+const RANDOM_POOL_SIZE = 8192;
+const RANDOM_POOL_REFRESH = 1024;
+
+let randomPool = Buffer.alloc(RANDOM_POOL_SIZE);
+let randomPoolIdx = RANDOM_POOL_SIZE;
+
+function onRandomBytes (err, buf) {
+  randomPending = false;
+  if (!err) {
+    randomPool = buf;
+    randomPoolIdx = 0;
+  }
+}
+
+let randomPending = true;
+crypto.randomBytes(RANDOM_POOL_SIZE, onRandomBytes);
+
+function randomFillMask (buffer) {
+  if (RANDOM_POOL_SIZE - randomPoolIdx < 4) {
+    return crypto.randomFillSync(buffer, offset, size);
+  }
+
+  buffer[0] = randomPool[randomPoolIdx++];
+  buffer[1] = randomPool[randomPoolIdx++];
+  buffer[2] = randomPool[randomPoolIdx++];
+  buffer[3] = randomPool[randomPoolIdx++];
+
+  if (!randomPending && RANDOM_POOL_SIZE - randomPoolIdx < RANDOM_POOL_REFRESH) {
+    randomPending = true;
+    crypto.randomBytes(RANDOM_POOL_SIZE, onRandomBytes);
+  }
+
+  return buffer;
+}
+
+module.exports = { randomFillMask };

lib/sender.js

@@ -4,7 +4,7 @@
 
 const net = require('net');
 const tls = require('tls');
-const { randomFillSync } = require('crypto');
+const { randomFillMask } = require('./random-util');
 
 const PerMessageDeflate = require('./permessage-deflate');
 const { EMPTY_BUFFER } = require('./constants');
@@ -81,7 +81,7 @@ class Sender {
 
     if (!options.mask) return [target, data];
 
-    randomFillSync(mask, 0, 4);
+    randomFillMask(mask);
 
     target[1] |= 0x80;
     target[offset - 4] = mask[0];