ladder.cpp

barcode readers [ from Image]

//
// Ladder
//   A pipeline that consists of two parallel pipelines that are combined by a "Join" function.
//   Any image input is passed down both pipelines and the results of each are combined in the
//   join function, giving the result. Unlike a real ladder, the two pipelines do not have to
//   be the same length, but they must both give exactly one result for one input. The input
//   image is replicated so that both pipelines can modify it if they wish.
//
// Copyright (C) 2003, 2006 by Jon A. Webb (Contact via GMail; username is jonawebb)
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
// 
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// Lesser General Public License for more details.
// 
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
//


#include "Ladder.h"
#include "Replicate.h"

namespace Core
{
	//
	// Lifecycle
	//
	EXPORT_C CLadder* CLadder::NewL(MPipelineStage* pPipe1, MPipelineStage* pPipe2, MJoin* pJoin) {
		return new (ELeave) CLadder(pPipe1, pPipe2, pJoin);
	}

	CLadder::~CLadder(void) {
		delete iPipe1;
		delete iPipe2;
		delete iJoin;
	}

	CLadder::CLadder(MPipelineStage* pPipe1, MPipelineStage* pPipe2, MJoin* pJoin) :
		ibEmpty(true), iPipe1(pPipe1), iPipe2(pPipe2), iJoin(pJoin)
	{}

	//
	// Overrides
	//
	CImage CLadder::FrontL() 
	{
		if (ibEmpty) {
			User::Leave(KErrGeneral);
			return CImage();
		}
		ibEmpty = true;
		return iResult;
	}

	void CLadder::PushL(CImage image) {
		// make a copy of the input image for the second pipeline,
		// in case either one alters it.
		IReplicate rRepl(image);
		rRepl.CopyL(iImage);
		iPipe1->PushL(image);
		iPipe2->PushL(iImage);
		// make sure we can legally do the join
		if (iPipe1->Empty() || iPipe2->Empty()) {
			User::Leave(KErrGeneral);
		}
		// do the join
		iResult = iJoin->DoJoinL(iPipe1->FrontL(), iPipe2->FrontL());
		ibEmpty = false;
	}

	bool CLadder::Empty() const {
		return ibEmpty;
	}
};