/*
* Licensed 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.
* under the License.
*/
package org.apache.sanselan.formats.jpeg.decoder;
import java.io.IOException;
import java.io.InputStream;
import org.apache.sanselan.ImageReadException;
import org.apache.sanselan.formats.jpeg.JpegConstants;
public class JpegInputStream
{
// Figure F.18, F.2.2.5, page 111 of ITU-T T.81
private final InputStream is;
private int cnt = 0;
private int b;
public JpegInputStream(InputStream is)
{
this.is = is;
}
public int nextBit()
throws IOException, ImageReadException
{
if (cnt == 0)
{
b = is.read();
if (b < 0)
throw new ImageReadException("Premature End of File");
cnt = 8;
if (b == 0xff)
{
int b2 = is.read();
if (b2 < 0)
throw new ImageReadException("Premature End of File");
if (b2 != 0)
{
if (b2 == (0xff & JpegConstants.DNLMarker))
throw new ImageReadException("DNL not yet supported");
else
throw new ImageReadException("Invalid marker found " +
"in entropy data");
}
}
}
int bit = (b >> 7) & 0x1;
cnt--;
b <<= 1;
return bit;
}
}