Cache with lru-cache.

Author: sandinmyjoints

lib/parsers/string.js

@@ -1,22 +1,34 @@
 'use strict';
 
 const Iconv = require('iconv-lite');
-const decoderCache = new Map();
+const LRU = require('lru-cache');
+
+const decoderCache = new LRU({
+  max: 500,
+});
 
 exports.decode = function (buffer, encoding, start, end, options) {
   if (Buffer.isEncoding(encoding)) {
     return buffer.toString(encoding, start, end);
   }
 
-  const decoderArgs = { encoding, options: options || {} };
-  const decoder =
-    decoderCache.get(decoderArgs) ||
-    decoderCache
-      .set(
-        decoderArgs,
-        Iconv.getDecoder(decoderArgs.encoding, decoderArgs.options),
-      )
-      .get(decoderArgs);
+  // Optimize for common case: encoding="short_string", options=undefined.
+  let decoder;
+  if (!options) {
+    decoder = decoderCache.get(encoding);
+    if (!decoder) {
+      decoder = Iconv.getDecoder(encoding);
+      decoderCache.set(encoding, decoder);
+    }
+  } else {
+    const decoderArgs = { encoding, options };
+    const decoderKey = JSON.stringify(decoderArgs);
+    decoder = decoderCache.get(decoderKey);
+    if (!decoder) {
+      decoder = Iconv.getDecoder(decoderArgs.encoding, decoderArgs.options);
+      decoderCache.set(decoderKey, decoder);
+    }
+  }
 
   const res = decoder.write(buffer.slice(start, end));
   const trail = decoder.end();