flow like the river

BACK_BACK/node_modules/pbkdf2/lib/precondition.js

@@ -0,0 +1,19 @@
+var MAX_ALLOC = Math.pow(2, 30) - 1 // default in iojs
+
+module.exports = function (iterations, keylen) {
+  if (typeof iterations !== 'number') {
+    throw new TypeError('Iterations not a number')
+  }
+
+  if (iterations < 0) {
+    throw new TypeError('Bad iterations')
+  }
+
+  if (typeof keylen !== 'number') {
+    throw new TypeError('Key length not a number')
+  }
+
+  if (keylen < 0 || keylen > MAX_ALLOC || keylen !== keylen) { /* eslint no-self-compare: 0 */
+    throw new TypeError('Bad key length')
+  }
+}