Add support for constructors in nested parsers

README.md

@@ -220,6 +220,24 @@ Nest a parser in this position. Parse result of the nested parser is stored in t
 
 - `type` - (Required) A `Parser` object.
 
+If a constructor is required for a nested parser, then the constructor function should be a selector
+for the corresponding constructor (none, `main` or nested Parser variable name).
+
+```javascript
+new Parser()
+        .create(function(param) {
+          if (!param) {
+            return {};
+          } else if (param == 'main') {
+            //replace mainConstructorFn with main parser constructor function
+            return new mainConstructorFn();
+          } else if (param === 'nested1') {
+            //replace nestedConstructorFn with nested parser constructor function
+            //nested1 is the varName of the nested parser
+            return new nestedConstructorFn();//call;
+          }
+        })
+```
 ### skip(length)
 Skip parsing for `length` bytes.
 

lib/binary_parser.js

@@ -203,7 +203,7 @@ Parser.prototype.getCode = function() {
     var ctx = new Context();
 
     if (this.constructorFn) {
-        ctx.pushCode('var vars = new constructorFn();');
+        ctx.pushCode('var vars = new constructorFn("main");');
     } else {
         ctx.pushCode('var vars = {};');
     }
@@ -539,7 +539,11 @@ Parser.prototype.generateChoice = function(ctx) {
 
 Parser.prototype.generateNest = function(ctx) {
     var nestVar = ctx.generateVariable(this.varName);
-    ctx.pushCode('{0} = {};', nestVar);
+    if(this.options.type.constructorFn) {
+      ctx.pushCode('{0} = new constructorFn("' + this.varName + '");', nestVar);
+    } else {
+      ctx.pushCode('{0} = {};', nestVar);
+    }
     ctx.pushPath(this.varName);
     this.options.type.generate(ctx);
     ctx.popPath();