/*
* 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 org.apache.harmony.luni.util;
import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;
/**
* This class implements a password-protected input stream. The algorithm used
* for protection is a Vigenere (repeated-key) cipher. The encrypted data is the
* result of <original data> XOR KEYKEYKEY...
*/
public class PasswordProtectedInputStream extends FilterInputStream {
private byte[] password; // Password to use to decrypt the input bytes
private int pwdIndex; // Index into the password array.
/**
* Constructs a new instance of the receiver.
*
* @param in The actual input stream where to read the bytes from.
* @param password The password bytes to use to decrypt the input bytes
*/
public PasswordProtectedInputStream(InputStream in, byte[] password) {
super(in);
this.password = password.clone();
}
@Override
public int read() throws IOException {
int read = in.read();
if (read >= 0) {
read ^= password[pwdIndex];
pwdIndex = (pwdIndex + 1) % password.length;
}
return read;
}
@Override
public int read(byte b[], int off, int len) throws IOException {
int read = in.read(b, off, len);
if (read > 0) {
int lastIndex = off + read;
for (int i = off; i < lastIndex; i++) {
b[i] ^= password[pwdIndex];
pwdIndex = (pwdIndex + 1) % password.length;
}
}
return read;
}
@Override
public long skip(long n) throws IOException {
long skip = super.skip(n);
pwdIndex += skip;
return skip;
}
}