| /* |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You 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. |
| */ |
| |
| package java.util.zip; |
| |
| import java.io.IOException; |
| import java.io.InputStream; |
| |
| /** |
| * The {@code CheckedInputStream} class is used to maintain a checksum at the |
| * same time as the data, on which the checksum is computed, is read from a |
| * stream. The purpose of this checksum is to establish data integrity, |
| * comparing the computed checksum against a published checksum value. |
| */ |
| public class CheckedInputStream extends java.io.FilterInputStream { |
| |
| private final Checksum check; |
| |
| /** |
| * Constructs a new {@code CheckedInputStream} on {@code InputStream} |
| * {@code is}. The checksum will be calculated using the algorithm |
| * implemented by {@code csum}. |
| * |
| * @param is |
| * the input stream to calculate checksum from. |
| * @param csum |
| * an entity implementing the checksum algorithm. |
| */ |
| public CheckedInputStream(InputStream is, Checksum csum) { |
| super(is); |
| check = csum; |
| } |
| |
| /** |
| * Reads one byte of data from the underlying input stream and updates the |
| * checksum with the byte data. |
| * |
| * @return {@code -1} at the end of the stream, a single byte value |
| * otherwise. |
| * @throws IOException |
| * if an {@code IOException} occurs. |
| */ |
| @Override |
| public int read() throws IOException { |
| int x = in.read(); |
| if (x != -1) { |
| check.update(x); |
| } |
| return x; |
| } |
| |
| /** |
| * Reads up to n bytes of data from the underlying input stream, storing it |
| * into {@code buf}, starting at offset {@code off}. The checksum is |
| * updated with the bytes read. |
| * |
| * @param buf |
| * the byte array in which to store the bytes read. |
| * @param off |
| * the initial position in {@code buf} to store the bytes read |
| * from this stream. |
| * @param nbytes |
| * the maximum number of bytes to store in {@code buf}. |
| * @return the number of bytes actually read or {@code -1} if arrived at the |
| * end of the filtered stream while reading the data. |
| * @throws IOException |
| * if this stream is closed or some I/O error occurs. |
| */ |
| @Override |
| public int read(byte[] buf, int off, int nbytes) throws IOException { |
| int x = in.read(buf, off, nbytes); |
| if (x != -1) { |
| check.update(buf, off, x); |
| } |
| return x; |
| } |
| |
| /** |
| * Returns the checksum calculated on the stream read so far. |
| * |
| * @return the updated checksum. |
| */ |
| public Checksum getChecksum() { |
| return check; |
| } |
| |
| /** |
| * Skip up to n bytes of data on the underlying input stream. Any skipped |
| * bytes are added to the running checksum value. |
| * |
| * @param nbytes |
| * the number of bytes to skip. |
| * @throws IOException |
| * if this stream is closed or another I/O error occurs. |
| * @return the number of bytes skipped. |
| */ |
| @Override |
| public long skip(long nbytes) throws IOException { |
| if (nbytes < 1) { |
| return 0; |
| } |
| long skipped = 0; |
| byte[] b = new byte[2048]; |
| int x, v; |
| while (skipped != nbytes) { |
| x = in.read(b, 0, |
| (v = (int) (nbytes - skipped)) > b.length ? b.length : v); |
| if (x == -1) { |
| return skipped; |
| } |
| check.update(b, 0, x); |
| skipped += x; |
| } |
| return skipped; |
| } |
| } |