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README.md

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Introduction

This is readme file for xnode - variant-like data type container for dynamic-type variables in C++.

License

Software is published under BSD license, see LICENSE.txt for details.

Project home

https://github.com/vpiotr/xnode

Purpose

  • for support of variables with dynamic type
  • for on-the-fly conversion between string-int-long etc.
  • for support of dynamic tuples (as arguments or return values)
  • for support of optional named parameters with default values
  • for processing of dynamic structures like JSON, XML or INI files with values where type information can be missing

Features

  • handles the following value types: null, scalar, pointer, owned object
  • size of object is minimal (2x pointers inside)
  • scalar types are stored without dynamic allocation
  • supports storing of value for any struct, class or scalar without changing single line in library
  • supports polymorphism

Benefits

  • dynamic typing

      xnode value;
  Assert(value.is_null()); 
  
  value.set_as(5);
  Assert(value.type() == typeid(int));

  value.set_as(false);
  Assert(value.is<bool>()));

  • perform on-fly transparent conversion & type checking

      xnode ivalue;
  std::string s("123");

  ivalue.set_as(s);
  Assert(ivalue.is<std::string>());

  cout << "int value: " << ivalue.get_as<int>() << endl;
  Assert(ivalue.is_convertable_to<int>());

  • handle optional named parameters without builder pattern

      std::string printInFont(const xnode &font, const std::string &text) {
  	std::ostringstream out;

  	const xnode_named_list &list = font.get_ref<xnode_named_list>();

  	out << "text in font [";
  	out << "color:" << list.get_def("color", xnode::value_of(0x00ff00)).get_as<int>();
  	out << ", font_name:" << list.get_def("font_name", xnode::value_of("courier")).get_as<std::string>();
  	out << ", size:" << list.get_def("size", xnode::value_of(10)).get_as<int>();
  	out << ", bold:" << list.get_def("bold", xnode::value_of(false)).get_as<bool>();
  	out << "] = " << text;

  	return(out.str());  
  }

  • acquire ownership of & auto-delete objects

      void TestHoldObj() {
  	struct TestStr {
  		int a;
  		int b;
  	};
  
  	std::auto_ptr<TestStr> holder(new TestStr());
  	holder->a = 12;
  	holder->b = 21;
  
  	xnode value;
  	TestStr *ptr = holder.get();
  	value.hold(holder.release());
  
  	Assert(value.get_ptr<TestStr>() == ptr);
  	Assert(value.get_ptr<TestStr>()->a == 12);
  	Assert(value.get_ptr<TestStr>()->b == 21);
  	Assert(value.is<TestStr>());
  }

  • store pointers (non-owned blocks of memory)

      void TestReleaseNonOwned() {
  	xnode svalue;
  
  	char test[] = "Test";
  	svalue.set_as(&test[0]);
  	Assert(svalue.release<char *>() == nullptr);
  
  	svalue.set_as(5);
  	Assert(svalue.release<int>() == nullptr);
  }

Conversion

Example conversion matrix defined in xnode_builtins.h specify conversion between types:

  • bool
  • float, double
  • char, short, int, long, long long
  • unsigned: char, short, int, long, long long
  • std::string

Conversion between types can be user-defined (see xnode_long_double.h & TestLongDoubleWithPolicy).

Supported environments

  • compiler: any compiler with C++11 support
  • tested with:
    • VS 2015 C++ compiler
    • GCC 4.8.1 (under MinGW)

External dependencies

  • just C++ standard library, including std::string

Other similar efforts

  • boost::any
  • boost::variant

Building

In order to build the test application just add all *.cpp files to your project from directory "\test" and add "\include" to include path.

Contact information

Documentation

To build documentation, use Code::Blocks 13 and command:

DoxyBlocks \ Extract documentation

Output will be generated into: "./help/html/" directory in html format.

Release History

See the CHANGELOG.