Name: ipR10067 Date: 09/27/2001




Specification of the
method javax.imageio.stream.ImageOutputStreamImpl.writeBits
says:

"public void writeBits(long bits, int numBits) throws IOException

  ... The bit offset is advanced by numBits and reduced modulo 8.
  

"
The implementation (JDK 1.4.0beta3, build b80) of the method
sets current bit offset to numBits instead of advancing by numBits.

To reproduce the bug run the following test:
------------ test.java ------------------------
import javax.imageio.stream.MemoryCacheImageOutputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;

public class test {

    public static void main(String argv[]) {
       ByteArrayOutputStream ostream = new ByteArrayOutputStream();
       MemoryCacheImageOutputStream mcios = new MemoryCacheImageOutputStream(ostream);
       try {
           for (int i=0; i < 8; i+=2) {
               mcios.writeBits(3, 2);
               System.out.println(mcios.getBitOffset());
           }
       } catch (IOException e) {
             System.out.println("Unexpected IOException: " + e);
       }
   }

}

------------ Logs -----------------------------
$ java -version
java version "1.4.0-beta3"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.0-beta3-b80)
Java HotSpot(TM) Client VM (build 1.4.0-beta3-b80, mixed mode)

$ javac -d . test.java

$ java test
2
2
2
2
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This bug affects new JCK test:
api/javax_imageio/stream/ImageOutputStreamImpl/index.html#WriteBits[WriteBits001]
api/javax_imageio/stream/ImageOutputStreamImpl/index.html#WriteBits[WriteBits002]
api/javax_imageio/stream/ImageOutputStreamImpl/index.html#WriteBits[WriteBits003]
api/javax_imageio/stream/ImageOutputStreamImpl/index.html#WriteBits[WriteBits004]
api/javax_imageio/stream/ImageOutputStreamImpl/index.html#WriteBits[WriteBits005]
api/javax_imageio/stream/ImageOutputStreamImpl/index.html#WriteBits[WriteBits006]
api/javax_imageio/stream/ImageOutputStreamImpl/index.html#WriteBits[WriteBits007]
api/javax_imageio/stream/ImageOutputStreamImpl/index.html#WriteBits[WriteBits009]

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