/*
    * Licensed to the Apache Software Foundation (ASF) under one or more
    * contributor license agreements.  See the NOTICE file distributed with
    * this work for additional information regarding copyright ownership.
    * The ASF licenses this file to You under the Apache License, Version 2.0
    * (the "License"); you may not use this file except in compliance with
    * the License.  You may obtain a copy of the License at
    *
    *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.apache.commons.imaging.formats.bmp;
  
  import static org.apache.commons.imaging.common.BinaryFunctions.read2Bytes;
  import static org.apache.commons.imaging.common.BinaryFunctions.read3Bytes;
  import static org.apache.commons.imaging.common.BinaryFunctions.read4Bytes;
  import static org.apache.commons.imaging.common.BinaryFunctions.readByte;
  
  import java.io.IOException;
  import java.nio.ByteOrder;
  
  import org.apache.commons.imaging.ImagingException;
  
  final class PixelParserBitFields extends AbstractPixelParserSimple {
  
      private final int redShift;
      private final int greenShift;
      private final int blueShift;
      private final int alphaShift;
  
      private final int redMask;
      private final int greenMask;
      private final int blueMask;
      private final int alphaMask;
  
      private int byteCount;
  
      PixelParserBitFields(final BmpHeaderInfo bhi, final byte[] colorTable, final byte[] imageData) {
          super(bhi, colorTable, imageData);
  
          redMask = bhi.redMask;
          greenMask = bhi.greenMask;
          blueMask = bhi.blueMask;
          alphaMask = bhi.alphaMask;
  
          redShift = getMaskShift(redMask);
          greenShift = getMaskShift(greenMask);
          blueShift = getMaskShift(blueMask);
          alphaShift = alphaMask != 0 ? getMaskShift(alphaMask) : 0;
      }
  
      private int getMaskShift(int mask) {
          if (mask == 0) {
              return 0;
          }
  
          int trailingZeroes = 0;
  
          while ((0x1 & mask) == 0) {
              mask = 0x7fffffff & mask >> 1;
              trailingZeroes++;
          }
  
          int maskLength = 0;
  
          while ((0x1 & mask) == 1) {
              mask = 0x7fffffff & mask >> 1;
              maskLength++;
          }
  
          return trailingZeroes - (8 - maskLength);
      }
  
      @Override
      public int getNextRgb() throws ImagingException, IOException {
          int data;
  
          switch (bhi.bitsPerPixel) {
          case 8:
              data = 0xff & imageData[byteCount + 0];
              byteCount += 1;
              break;
          case 24:
              data = read3Bytes("Pixel", is, "BMP Image Data", ByteOrder.LITTLE_ENDIAN);
              byteCount += 3;
              break;
          case 32:
              data = read4Bytes("Pixel", is, "BMP Image Data", ByteOrder.LITTLE_ENDIAN);
              byteCount += 4;
              break;
          case 16:
              data = read2Bytes("Pixel", is, "BMP Image Data", ByteOrder.LITTLE_ENDIAN);
              byteCount += 2;
              break;
         default:
             throw new ImagingException("Unknown BitsPerPixel: " + bhi.bitsPerPixel);
         }
 
         int red = redMask & data;
         int green = greenMask & data;
         int blue = blueMask & data;
         int alpha = alphaMask != 0 ? alphaMask & data : 0xff;
 
         red = redShift >= 0 ? red >> redShift : red << -redShift;
         green = greenShift >= 0 ? green >> greenShift : green << -greenShift;
         blue = blueShift >= 0 ? blue >> blueShift : blue << -blueShift;
         alpha = alphaShift >= 0 ? alpha >> alphaShift : alpha << -alphaShift;
 
         return alpha << 24 | red << 16 | green << 8 | blue << 0;
     }
 
     @Override
     public void newline() throws ImagingException, IOException {
         while (byteCount % 4 != 0) {
             readByte("Pixel", is, "BMP Image Data");
             byteCount++;
         }
     }
 }