Name: vpR10011 Date: 06/04/2001



Specification of the class javax.imageio.stream.ImageOutputStreamImpl says:

"protected final void flushBits() throws IOException

If the bit offset is non-zero, forces the remaining bits in the current
byte to 0 and advances the stream position by one.
This method should be called by subclasses at the beginning of
the write(int) and write(byte[], int, int) methods.

Throws:
    IOException - if an I/O error occurs."


This method works incorrectly when the bit offset is non-zero and
the current stream position is equal to the stream length.
It happens when we use setBitOffset(int) before write(int).
In this case flushBits() reads byte from the stream and ignores
that read() returns -1 because the end of the stream is reached.

When the stream is empty, streamPos is equal to zero and bit offset isn't
zero flushBits() throws IndexOutOfBoundsException.

To reproduce this bug run the following test:
---------------------test.java--------------
import java.io.*;
import javax.imageio.stream.*;

public class test {
    public static void main(String[] argv) {
        OutputStream os = (OutputStream) new ByteArrayOutputStream();
        MemoryCacheImageOutputStream iosI =
                new MemoryCacheImageOutputStream(os);
        try {
            System.out.println("setBitOffset(7) when stream is empty:");
            iosI.seek(0);
            iosI.setBitOffset(7);
            iosI.write(1);
            System.out.println("Passed");

        } catch (Exception e) {
             System.out.println("Failed: unxepected xception: " + e);
        }
        try {
            System.out.println("setBitOffset(7) after write(1):");
            iosI.seek(0);
            iosI.write(1);
            iosI.setBitOffset(7);
            iosI.write(1);
            iosI.seek(0);
            int i = iosI.read();
            if (i == 1) {
                System.out.println("Passed: read() = " + i);
            } else {
                System.out.println("Failed: read() = " + i + " but expected 1");
            }
        } catch (Exception e) {
             System.out.println("Failed: unxepected xception: " + e);
        }
    }
}
-----------------------------------------
% javac test.java
% java -version
Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.0-beta_refresh-b66)
Java HotSpot(TM) Client VM (build 1.4.0-beta_refresh-b66, mixed mode)
% java test
setBitOffset(7) when stream is empty:
Failed: unxepected xception: java.lang.IndexOutOfBoundsException: pos < flushedPos!
setBitOffset(7) after write(1):
Failed: read() = 254 but expected 1
----------------------------------------


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