#include <gif/istream.hpp>

IStream::IStream(void)
: mFileDescriptor(-1), mCurrentWord(0), mCurrentChar(0), mhGlobalBuffer(0),
	mlpBuffer(0), mBufferIndex(0), mlpBufferPointer(0)
{
}

IStream::IStream(const char *pathFileName)
: mFileDescriptor(-1), mCurrentWord(0), mCurrentChar(0), mhGlobalBuffer(0),
	mlpBuffer(0), mBufferIndex(0), mlpBufferPointer(0)
{
  open(pathFileName);
}

IStream::~IStream()
{
  close();
}

BOOL IStream::open(const char *pathFileName)
{
  close();
	if(-1==(mFileDescriptor=::open(pathFileName,O_RDONLY|O_BINARY,0,SH_DENYWR)))return FALSE;
	mhGlobalBuffer=::GlobalAlloc(GMEM_FIXED,MaxInputBuffer);
	if(!mhGlobalBuffer){close();return FALSE;}
	mlpBuffer=(UCHAR FAR *)::GlobalLock(mhGlobalBuffer);
	mlpBufferPointer=0;
	mBufferIndex=0;
	mCurrentChar=0;
	mCurrentWord=0;
	return TRUE;
}

void IStream::close(void)
{
	if(-1!=mFileDescriptor)::close(mFileDescriptor);
	mFileDescriptor=-1;
	if(mhGlobalBuffer)
	{
		::GlobalUnlock(mhGlobalBuffer);
		::GlobalFree(mhGlobalBuffer);
		mhGlobalBuffer=0;
  }
}

WORD IStream::getChar(void)
{
	if(-1==mFileDescriptor)return FALSE;
	if(!mBufferIndex)
	{
		mBufferIndex=::read(mFileDescriptor,(VPTR)mlpBuffer,MaxInputBuffer);
		if(!mBufferIndex)return FALSE;
		mlpBufferPointer=mlpBuffer;
	}
	mCurrentChar=*(mlpBufferPointer);
	mlpBufferPointer++;
	mBufferIndex--;
	return TRUE;
}

WORD IStream::getWord(void)
{
	if(-1==mFileDescriptor)return FALSE;
	mCurrentWord=0;
	if(!getChar())return FALSE;
	mCurrentWord=mCurrentChar;
	if(!getChar())return FALSE;
	mCurrentWord|=((short)mCurrentChar)<<8;
	return TRUE;
}