remove new Function calls

src/Pointer.js

@@ -10,9 +10,14 @@ class Pointer {
     if (this.options.allowNull == null) { this.options.allowNull = true; }
     if (this.options.nullValue == null) { this.options.nullValue = 0; }
     if (this.options.lazy == null) { this.options.lazy = false; }
-    if (this.options.relativeTo) {
-      this.relativeToGetter = new Function('ctx', `return ctx.${this.options.relativeTo}`);
-    }
+  }
+
+  // this.options.relativeTo may be a string of properties
+  //   'foo'
+  //   'foo.bar'
+  // this property chain will be executed against `ctx`
+  relativeToGetter(ctx) {
+    return utils.getPropertyChain(ctx, this.options.relativeTo);
   }
 
   decode(stream, ctx) {

src/VersionedStruct.js

@@ -1,4 +1,5 @@
 const Struct = require('./Struct');
+const utils = require('./utils');
 
 class VersionedStruct extends Struct {
   constructor(type, versions = {}) {
@@ -11,6 +12,22 @@ class VersionedStruct extends Struct {
     }
   }
 
+  versionGetter(parent) {
+    if (typeof this.type === 'string') {
+      // this.type may be a string of properties
+      //   'foo'
+      //   'foo.bar'
+      // this property chain will be executed against `parent`
+      return utils.getPropertyChain(parent, this.type);
+    } else {
+      return null;
+    }
+  }
+
+  versionSetter(parent, version) {
+    return utils.setPropertyChain(parent, this.type, version);
+  }
+
   decode(stream, parent, length = 0) {    
     const res = this._setup(stream, parent, length);
 

src/utils.js

@@ -22,6 +22,26 @@ exports.resolveLength = function(length, stream, parent) {
   return res;
 };
 
+// 'chain' may be a string of properties
+//   'foo'
+//   'foo.bar'
+// this property chain will be executed against `ref`
+exports.getPropertyChain = function(ref, chain) {
+  return chain.split('.').reduce(function(obj, prop) {
+    return obj[prop];
+  }, ref);
+}
+
+exports.setPropertyChain = function(ref, chain, newValue) {
+  let props = chain.split('.');
+  let lastProp = props.pop();
+  let ref1 = props.reduce(function(obj, prop) {
+    return obj[prop];
+  }, ref);
+  ref1[lastProp] = newValue;
+  return newValue;
+}
+
 class PropertyDescriptor {
   constructor(opts = {}) {    
     this.enumerable = true;