1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one
3 * or more contributor license agreements. See the NOTICE file
4 * distributed with this work for additional information
5 * regarding copyright ownership. The ASF licenses this file
6 * to you under the Apache License, Version 2.0 (the
7 * "License"); you may not use this file except in compliance
8 * with the License. You may obtain a copy of the License at
9 *
10 * http://www.apache.org/licenses/LICENSE-2.0
11 *
12 * Unless required by applicable law or agreed to in writing,
13 * software distributed under the License is distributed on an
14 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15 * KIND, either express or implied. See the License for the
16 * specific language governing permissions and limitations
17 * under the License.
18 */
19
20 package org.apache.commons.compress.archivers.zip;
21
22 import java.io.IOException;
23 import java.io.InputStream;
24 import java.nio.ByteOrder;
25
26 import org.apache.commons.compress.utils.BitInputStream;
27
28 /**
29 * Iterates over the bits of an InputStream. For each byte the bits are read from the right to the left.
30 *
31 * @since 1.7
32 */
33 final class BitStream extends BitInputStream {
34
35 BitStream(final InputStream in) {
36 super(in, ByteOrder.LITTLE_ENDIAN);
37 }
38
39 /**
40 * Returns the next bit.
41 *
42 * @return The next bit (0 or 1) or -1 if the end of the stream has been reached
43 * @throws IOException on error.
44 */
45 int nextBit() throws IOException {
46 return (int) readBits(1);
47 }
48
49 /**
50 * Returns the integer value formed by the n next bits (up to 8 bits).
51 *
52 * @param n the number of bits read (up to 8)
53 * @return The value formed by the n bits, or -1 if the end of the stream has been reached
54 * @throws IOException on error.
55 */
56 long nextBits(final int n) throws IOException {
57 if (n < 0 || n > 8) {
58 throw new IOException("Trying to read " + n + " bits, at most 8 are allowed");
59 }
60 return readBits(n);
61 }
62
63 int nextByte() throws IOException {
64 return (int) readBits(8);
65 }
66 }