feat(memo): added memoization lib

lib/memoization.js

@@ -0,0 +1,31 @@
+'use strict'
+
+let MEMOIZED = {}
+
+module.exports.clearMemoized = clearMemoized
+function clearMemoized () {
+  var old = MEMOIZED
+  MEMOIZED = {}
+  return old
+}
+
+module.exports.put = put
+function put (cache, entry, data) {
+  MEMOIZED[`key:${cache}:${entry.key}`] = { entry, data }
+  putDigest(cache, entry.digest, entry.hashAlgorithm, data)
+}
+
+module.exports.put.byDigest = putDigest
+function putDigest (cache, digest, algo, data) {
+  MEMOIZED[`digest:${cache}:${algo}:${digest}`] = data
+}
+
+module.exports.get = get
+function get (cache, key) {
+  return MEMOIZED[`key:${cache}:${key}`]
+}
+
+module.exports.get.byDigest = getDigest
+function getDigest (cache, digest, algo) {
+  return MEMOIZED[`digest:${cache}:${algo}:${digest}`]
+}