A simple runtime assembler written in C++

Assembler.cpp

#include "Assembler.hpp"

Assembler::Assembler()
{
}

int Assembler::Run()
{
	if ( code.size() == 0 ) return -1;

	int reg_eax;

	unsigned char* func = (unsigned char*)VirtualAlloc( 0, code.size() + 1, 0x1000, 0x40 );

	memcpy( func, code.data(), code.size() );
	func[code.size()] = 0xC3;

	CallWindowProc( (WNDPROC)func, 0, 0, 0, 0 );

	_asm mov reg_eax, eax;

	VirtualFree( func, code.size() + 1, 0x4000 );

	return reg_eax;
}

void Assembler::Clear()
{
	code.clear();
}

void Assembler::INop()
{
	code.push_back( 0x90 );
}

void Assembler::IMov32( Register dst, int value )
{
	code.push_back( 0xC7 );
	code.push_back( 0xC0 | dst );
	PushInt32( value );
}

void Assembler::IMov32( Register dst, Register src )
{
	code.push_back( 0x8B );
	code.push_back( 0xC0 | ( dst << 3 ) | src );
}

void Assembler::IInc32( Register reg )
{
	code.push_back( 0xFF );
	code.push_back( 0xC0 | reg );
}

void Assembler::IAdd32( Register dst, Register src )
{
	code.push_back( 0x03 );
	code.push_back( 0xC0 | ( dst << 3 ) | src );
}

void Assembler::IPush32( int value )
{
	code.push_back( 0x68 );
	PushInt32( value );
}

void Assembler::IPop32( Register reg )
{
	code.push_back( 0x8F );
	code.push_back( 0xC0 | reg );
}

void Assembler::PushInt32( int i )
{
	char b[4];
	memcpy( b, &i, 4 );
	code.push_back( b[0] );
	code.push_back( b[1] );
	code.push_back( b[2] );
	code.push_back( b[3] );
}

Assembler.hpp

#include <Windows.h>
#include <vector>

// TODO:
// Preserve registers besides EAX (with naked function call?)
// Allow addressing beyond just registers (e.g. addresses in registers)

// Available registers for addressing
enum Register {
	REG_EAX = 0,
	REG_ECX = 1
};

// Class that allows programs to conveniently construct machine code at runtime
class Assembler
{
public:
	Assembler();

	int Run();
	void Clear();

	// Instructions
	void INop();
	void IMov32( Register dst, int value );
	void IMov32( Register dst, Register src );
	void IInc32( Register reg );
	void IAdd32( Register dst, Register src );
	void IPush32( int value );
	void IPop32( Register reg );

private:
	std::vector<unsigned char> code;

	void PushInt32( const int i );
};

main.cpp

#include <cstdio>
#include "Assembler.hpp"

int main()
{
	Assembler as;
		as.IMov32( REG_EAX, 2 );
		as.IMov32( REG_ECX, 4 );
		as.IAdd32( REG_EAX, REG_ECX );
	int eax = as.Run();

	printf( "EAX contains %d\n", eax );

	return 0;
}

clear and simple show how to assembler in windows platform, thanks