// Copyright (C) 2002-2009 Nikolaus Gebhardt
// This file is part of the "Irrlicht Engine".
// For conditions of distribution and use, see copyright notice in irrlicht.h

#include "CLimitReadFile.h"
#include "irrString.h"

namespace irr
{
namespace io
{


CLimitReadFile::CLimitReadFile(IReadFile* alreadyOpenedFile, long pos, long areaSize,
							   const core::string<c16>& name)
: Filename(name), AreaStart(0), AreaEnd(0), Pos(0), File(alreadyOpenedFile)
{
	#ifdef _DEBUG
	setDebugName("CLimitReadFile");
	#endif

	if (File)
	{
		File->grab();
		AreaStart = pos;
		AreaEnd = AreaStart + areaSize;
	}
}


CLimitReadFile::~CLimitReadFile()
{
	if (File)
		File->drop();
}



//! returns how much was read
s32 CLimitReadFile::read(void* buffer, u32 sizeToRead)
{
#if 1
	if ( 0 == File )
		return 0;

	s32 r = AreaStart + Pos;
	s32 toRead = core::s32_min( AreaEnd, r + sizeToRead ) - core::s32_max( AreaStart, r );
	if ( toRead < 0 )
		return 0;
	File->seek ( r );
	r = File->read(buffer, toRead);
	Pos += r;
	return r;
#else
	const long pos = File->getPos();

	if (pos >= AreaEnd)
		return 0;

	if (pos + (long)sizeToRead >= AreaEnd)
		sizeToRead = AreaEnd - pos;

	return File->read(buffer, sizeToRead);
#endif
}



//! changes position in file, returns true if successful
//! if relativeMovement==true, the pos is changed relative to current pos,
//! otherwise from begin of file
bool CLimitReadFile::seek(long finalPos, bool relativeMovement)
{
#if 1
	Pos = core::s32_clamp ( finalPos + (relativeMovement ? Pos : 0 ), 0, AreaEnd - AreaStart );
	return true;
#else
	const long pos = File->getPos();

	if (relativeMovement)
	{
		if (pos + finalPos > AreaEnd)
			finalPos = AreaEnd - pos;
	}
	else
	{
		finalPos += AreaStart;
		if (finalPos > AreaEnd)
			return false;
	}

	return File->seek(finalPos, relativeMovement);	
#endif
}


//! returns size of file
long CLimitReadFile::getSize() const
{
	return AreaEnd - AreaStart;
}



//! returns where in the file we are.
long CLimitReadFile::getPos() const
{
#if 1
	return Pos;
#else
	return File->getPos() - AreaStart;
#endif
}



//! returns name of file
const core::string<c16>& CLimitReadFile::getFileName() const
{
	return Filename;
}


IReadFile* createLimitReadFile(const core::string<c16>& fileName, IReadFile* alreadyOpenedFile, long pos, long areaSize)
{
	return new CLimitReadFile(alreadyOpenedFile, pos, areaSize, fileName);
}


} // end namespace io
} // end namespace irr