import java.lang.*;
import java.io.*;
import java.awt.*;
import java.awt.image.*;

final public class BitmapInputStream extends FilterInputStream
{  int _cx, _cy;
   int _cBitCount, _cBytesPerLine;
   int _aiPalettes[] = null;
   byte _abBuffer[] = null;

   final static String strInvalidFile = "BitmapInputStream: invalid file format";


   // little endian functions;

   final static short readShort(byte ab[], int iIndex)
   {  return (short)(((int)ab[iIndex] & 255) | (((int)ab[iIndex + 1] & 255) << 8));
   }

   final static int readInt(byte ab[], int iIndex)
   {  return ((int)ab[iIndex] & 255) | (((int)ab[iIndex + 1] & 255) << 8)
	 | (((int)ab[iIndex + 2] & 255) << 16) | (((int)ab[iIndex + 3] & 255) << 24);
   }

   final static int readRGB(byte ab[], int iIndex)
   {  return ((int)ab[iIndex] & 255) | (((int)ab[iIndex + 1] & 255) << 8)
	 | (((int)ab[iIndex + 2] & 255) << 16);
   }

   final boolean readHeader(InputStream in) throws IOException
   {  byte abFileHeader[] = new byte[Bitmap.FILE_HEADER_SIZE];

      if (in.read(abFileHeader) != Bitmap.FILE_HEADER_SIZE
	  && readShort(abFileHeader, Bitmap.USTYPE) != Bitmap.BITMAP_TYPE)
      {	 return false;
      }

      int infoHeaderSize = readInt(abFileHeader, Bitmap.OFFBITS) - Bitmap.FILE_HEADER_SIZE;
      byte abInfoHeader[] = new byte[infoHeaderSize];

      if (in.read(abInfoHeader) != infoHeaderSize)
      {	 return false;
      }

      int cbFix;

      if ((cbFix = readInt(abInfoHeader, Bitmap.CBFIX)) == Bitmap.VER1_HEADER_SIZE)
      {	 if (readShort(abInfoHeader, Bitmap.CPLANES_1) != 1)
	 {  return false;
	 }

	 _cx = (int)readShort(abInfoHeader, Bitmap.CX_1);
	 _cy = (int)readShort(abInfoHeader, Bitmap.CY_1);
	 _cBitCount = (int)readShort(abInfoHeader, Bitmap.CBITCOUNT_1);

	 if (_cBitCount == 1 || _cBitCount == 4 || _cBitCount == 8)
	 {  int cPalettes = 1 << _cBitCount;
	    _aiPalettes = new int[cPalettes];
	    for (int iIndex = 0; iIndex < cPalettes; iIndex++)
	    {  _aiPalettes[iIndex] = readRGB(abInfoHeader, Bitmap.VER1_HEADER_SIZE + iIndex * 3);
	    }
	 }
	 else if (_cBitCount != 24)
	 {  return false;
	 }
      }
      else
      {	 if (readShort(abInfoHeader, Bitmap.CPLANES_2) != 1
	     || (cbFix >= (Bitmap.ULCOMPRESSION + 4)
		 && readInt(abInfoHeader, Bitmap.ULCOMPRESSION) != 0))
	 {  return false;
	 }

	 _cx = readInt(abInfoHeader, Bitmap.CX_2);
	 _cy = readInt(abInfoHeader, Bitmap.CY_2);
	 _cBitCount = (int)readShort(abInfoHeader, Bitmap.CBITCOUNT_2);

	 if (_cBitCount == 1 || _cBitCount == 4 || _cBitCount == 8)
	 {  int cPalettes;

	    if (cbFix < (Bitmap.CCLRUSED + 4)
		|| (cPalettes = readInt(abInfoHeader, Bitmap.CCLRUSED)) == 0)
	    {  cPalettes = 1 << _cBitCount;
	    }

	    _aiPalettes = new int[cPalettes];
	    for (int iIndex = 0; iIndex < cPalettes; iIndex++)
	    {  _aiPalettes[iIndex] = readInt(abInfoHeader, cbFix + iIndex * 4);
	    }
	 }
	 else if (_cBitCount != 24)
	 {  return false;
	 }
      }

      _cBytesPerLine = ((_cx * _cBitCount + 31) & ~31) / 8;
      _abBuffer = new byte[_cBytesPerLine];
      return true;
   }

   BitmapInputStream(InputStream in) throws IOException
   {  super(in);

      if (!readHeader(in))
      {	 throw new IOException(strInvalidFile);
      }
   }

   final public int xSize()
   {  return _cx;
   }

   final public int ySize()
   {  return _cy;
   }

   final public int bytesPerLine()
   {  return _cBytesPerLine;
   }

   final public int[] readLine() throws IOException
   {  int aiLine[] = new int[_cx];
      in.read(_abBuffer);

      switch (_cBitCount)
      {	 case 1:
	 {  byte bPalette = 0;
	    for (int x = 0; x < _cx; x++)
	    {  if ((x & 7) == 0)
	       {  bPalette = _abBuffer[x >>> 3];
	       }
	       else
	       {  bPalette <<= 1;
	       }

	       aiLine[x] = _aiPalettes[(bPalette >>> 7) & 1];
	    }
	    break;
	 }
	 case 4:
	 {  byte bPalette = 0;
	    for (int x = 0; x < _cx; x++)
	    {  if ((x & 1) == 0)
	       {  bPalette = _abBuffer[x >>> 1];
	       }
	       else
	       {  bPalette <<= 4;
	       }

	       aiLine[x] = _aiPalettes[(bPalette >>> 4) & 15];
	    }
	    break;
	 }
	 case 8:
	    for (int x = 0; x < _cx; x++)
	    {  aiLine[x] = _aiPalettes[(int)_abBuffer[x] & 255];
	    }
	    break;
	 default:
	    for (int x = 0, iOffset = 0; x < _cx; x++)
	    {  aiLine[x] = (((int)_abBuffer[iOffset++] & 255)
			    | (((int)_abBuffer[iOffset++] & 255) << 8)
			    | (((int)_abBuffer[iOffset++] & 255) << 16));
	    }
	    break;
      }

      return aiLine;
   }
}