/*
* @(#)$Id$
*
* Copyright 2006-2008 Makoto YUI
*
* 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.
*
* Contributors:
* Makoto YUI - initial implementation
*/
//package xbird.util.io;
import java.io.*;
/**
*
* <DIV lang="en"></DIV>
* <DIV lang="ja"></DIV>
*
* @author Makoto YUI ([email protected])
*/
public final class BitInputStream extends DataInputStream {
public static final int MAX_BITS = 31;
private int leftBits = 0;
private int byteBuf = 0;
public BitInputStream(InputStream in) {
super(in);
}
public final boolean readBit() throws IOException {
if(--leftBits >= 0) {
return ((byteBuf >>> leftBits) & 1) == 1;
}
leftBits = 7;
byteBuf = in.read();
if(byteBuf == -1) {
throw new EOFException("reached end of stream");
}
return ((byteBuf >>> 7) & 1) == 1;
}
public final int readBits(int n) throws IOException {
int x = 0;
while(n > leftBits) {
n -= leftBits;
x |= rightBits(leftBits, byteBuf) << n;
byteBuf = in.read();
if(byteBuf == -1) {
throw new EOFException("reached end of stream");
}
leftBits = 8;
}
leftBits -= n;
return x | rightBits(n, byteBuf >>> leftBits);
}
private static final int rightBits(int n, int x) {
return x & ((1 << n) - 1);
}
}
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