How to build an in-memory state engine at runtime

//	Copyright � 2007, solosTec
//  All rights reserved.
//---------------------------------------------------------------------
//	License for redistribution is the GNU General Public License v2.
//	See the included readme.txt for details.
//---------------------------------------------------------------------
//	developed by solosTec
//	http://www.solostec.de
//---------------------------------------------------------------------
//
//	$Author: $
//	$Revision: $
/*	$Log: $
*/
//---------------------------------------------------------------------

#include "main.h"


int main(int argc, char* argv[])
{
	Source	source_;
	Scanner	scanner_;
	scanner_.run( source_ );

	return 0;
}

Source::Source()
	: content_ ( "This string contains some keywords that we have to find fast and in a reliable manner. The keywords are: keyword, string and and." )
	, pos_( const_cast<char*> (content_ ))
{}

char Source::next()
{
	const char c ( *pos_ );
	if (c == '\0')
	{
		return EOF;	//	-1
	}
	pos_++;
//	std::cout << "next: " << c << std::endl;
	return c;
}

size_t Source::position() const
{
	return pos_ - content_;
}

Scanner::Scanner()
{
	tagTree_.insertKeyWord( "keyword", KEY_KEYWORD );
	tagTree_.insertKeyWord( "string", KEY_STRING );
	tagTree_.insertKeyWord( "and", KEY_AND );
}

void Scanner::run( Source& source )
{
	for (;;)
	{
		switch( consume( source ))
		{
		case Scanner::KEY_KEYWORD:
			std::cout 
				<< "KEYWORD at " 
				<< source.position() 
				<< std::endl;
			break;
		case Scanner::KEY_STRING:
			std::cout 
				<< "STRING at " 
				<< source.position() 
				<< std::endl;
			break;
		case Scanner::KEY_AND:
			std::cout 
				<< "AND at " 
				<< source.position() 
				<< std::endl;
			break;
		case Scanner::KEY_EOS:
			std::cout 
				<< "End of String at " 
				<< source.position() 
				<< std::endl;
			return;
		default:
			break;
		}
	}

}

Scanner::KEY Scanner::consume( Source& source )
{
	TagTreePtr_ prev = &tagTree_;
	for (;;)
	{
		const char c( source.next());
		if (c == EOF)
		{
			return KEY_EOS;
		}
		TagTreePtr_ p = prev->findNode( c );
		if (p == NULL)
		{
			break;
		}
		prev = p;
	}
	return (prev != NULL)
		? prev->getValue()
		: KEY_UNKNOWN;
}