#include <dos.h>
#include <stdlib.h>

/*************************************************************************
 * Screen Macros
 *************************************************************************/
#define SCR_WIDTH 80
#define SCR_HEIGHT 25

char far *ScrPtr=(char far *) 0xB8000000L;
#define ScrChar(row,col) *(ScrPtr + ((row) * SCR_WIDTH * 2) + ((col) * 2))
#define ScrClr(row,col) *(ScrPtr + ((row) * SCR_WIDTH * 2) + ((col) * 2) + 1)

/*************************************************************************
 * Color Streams Definition
 *************************************************************************/
#define COLOR_BACKGROUND 0x00
#define COLOR_FIRST_CHAR 0x0A
#define COLOR_STREAM 0x02
#define COLOR_NORMAL 0x07

/*************************************************************************
 * Stream Macros
 *************************************************************************/
#define MaxStreams 80
#define MAX_STREAM_LEN SCR_HEIGHT
#define MIN_SPEED 5
#define DELAY_INTERVAL 100
#define ERASE_ODDS 3

#define StreamWrite 1
#define StreamErase 0

typedef struct
{
	char Active;
	int Row, Pos;
	int Length;
	char Type;
	char Data[MAX_STREAM_LEN];
} Stream;

static Stream MatrixStreams[SCR_WIDTH];
static unsigned char StreamCount;

/*************************************************************************
 * Matrix Streams Macro Shorthands
 *************************************************************************/
#define StreamActive		MatrixStreams[StreamID].Active
#define StreamRow			MatrixStreams[StreamID].Row
#define StreamPos			MatrixStreams[StreamID].Pos
#define StreamLength		MatrixStreams[StreamID].Length
#define StreamData			MatrixStreams[StreamID].Data
#define StreamType			MatrixStreams[StreamID].Type

void InitializeStream (unsigned char StreamID)
{
	int i;

	if (StreamID < SCR_WIDTH)
	{
		StreamActive = 0;

		StreamRow = 0;
		StreamPos = 0;
		StreamLength = 0;

		StreamType = StreamErase;

		for (i=0; i<MAX_STREAM_LEN; i++)
		{
			StreamData[i] = 0;
		}
	}
}

void DisplayStream (unsigned char StreamID)
{
	if ((StreamID < SCR_WIDTH) && (StreamActive == 1))
	{
		if (StreamType == StreamWrite)
		{
			if (StreamPos > 0)
			{
				ScrClr(StreamRow-1, StreamID) = COLOR_STREAM;
			}

			if (StreamPos < StreamLength)
			{
				ScrChar(StreamRow, StreamID) = StreamData[StreamPos];
				ScrClr(StreamRow, StreamID) = COLOR_FIRST_CHAR;
			}
			else
			{
				StreamRow = SCR_HEIGHT;
			}
		}
		else
		{
			ScrClr(StreamRow - 1, StreamID) = COLOR_BACKGROUND;
		}
	}
}

void DeleteStream (unsigned char StreamID)
{
	if ((StreamID < SCR_WIDTH) && (StreamActive == 1))
	{
		StreamCount--;
		InitializeStream(StreamID);
	}
}

void UpdateStream (unsigned char StreamID)
{
	if ((StreamID < SCR_WIDTH) && (StreamActive == 1))
	{
		StreamRow++;

		if (StreamRow <= SCR_HEIGHT)
		{
			StreamPos++;
		}
		else
		{
			DeleteStream(StreamID);
		}
	}
}

void CreateStream (unsigned char StreamID)
{
	int i;

	if ((StreamID < SCR_WIDTH) & (StreamActive == 0))
	{
		StreamCount++;
		InitializeStream(StreamID);
		StreamActive=1;
		StreamRow = random(SCR_HEIGHT);
		StreamLength = random(MAX_STREAM_LEN - StreamRow) + 1;

		StreamType = (rand() % ERASE_ODDS == 0) ? StreamErase : StreamWrite;

		for (i=0; i<StreamLength; i++)
		{
			StreamData[i] = random(94) + 32;
		}
	}
}

void ClearScreen (int Color)
{
	int i,j;

	for (i=0; i<SCR_HEIGHT; i++)
	{
		for (j=0; j<SCR_WIDTH; j++)
		{
			ScrChar(i,j) = 0;
			ScrClr(i,j) = Color;
		}
	}
}

int main(int argc, char *argv[])
{
	unsigned char MaxStreamCount;
	unsigned int i,j;

	MaxStreamCount = 0;

	if (argc == 2)
	{
		MaxStreamCount = atoi(argv[1]);
	}

	if ((MaxStreamCount == 0) || (MaxStreamCount > SCR_WIDTH))
	{
		MaxStreamCount = MaxStreams;
	}

	/* Initialize Streams */
	StreamCount = 0;
	for (i=0; i<SCR_WIDTH; i++)
	{
		InitializeStream(i);
	}

	/* Initialize Randomizer */
	randomize();

	/* Clear Screen */
	ClearScreen(COLOR_BACKGROUND);

	/* Start Loop */
	while (!kbhit())
	{
	/* Create Streams */
	while (StreamCount < MaxStreamCount)
	{
		i = random(SCR_WIDTH);
		CreateStream(i);
	}

	/* Display Streams */
	for (i=0; i<SCR_WIDTH; i++)
	{
		DisplayStream(i);
		UpdateStream(i);
	}

	/* Delay */
	delay(DELAY_INTERVAL);
	} /* End Loop */

	getch();

	/* Clear Screen */
	ClearScreen(COLOR_NORMAL);

	return 0;
}