refactor the whole damn thing

src/Struct/ItemString.js

@@ -0,0 +1,24 @@
+import Item from './Item'
+
+export default class ItemString extends Item {
+  constructor () {
+    super()
+    this._content = null
+  }
+  get _length () {
+    return this._content.length
+  }
+  _fromBinary (y, decoder) {
+    let missing = super._fromBinary(y, decoder)
+    this._content = decoder.readVarString()
+    return missing
+  }
+  _toBinary (y, encoder) {
+    super._toBinary(y, encoder)
+    encoder.writeVarString(this._content)
+  }
+  _logString () {
+    let s = super._logString()
+    return 'ItemString: ' + s
+  }
+}