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/*
* 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 javax.crypto;
import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;
import javax.crypto.NullCipher;
import java.security.GeneralSecurityException;
/**
* This class wraps an {@code InputStream} and a cipher so that {@code read()}
* methods return data that are read from the underlying {@code InputStream} and
* processed by the cipher.
* <p>
* The cipher must be initialized for the requested operation before being used
* by a {@code CipherInputStream}. For example, if a cipher initialized for
* decryption is used with a {@code CipherInputStream}, the {@code
* CipherInputStream} tries to read the data an decrypt them before returning.
*/
public class CipherInputStream extends FilterInputStream {
private final Cipher cipher;
private final int I_BUFFER_SIZE = 20;
private final byte[] i_buffer = new byte[I_BUFFER_SIZE];
private int index; // index of the bytes to return from o_buffer
private byte[] o_buffer;
private boolean finished;
/**
* Creates a new {@code CipherInputStream} instance for an {@code
* InputStream} and a cipher.
*
* @param is
* the input stream to read data from.
* @param c
* the cipher to process the data with.
*/
public CipherInputStream(InputStream is, Cipher c) {
super(is);
this.cipher = c;
}
/**
* Creates a new {@code CipherInputStream} instance for an {@code
* InputStream} without a cipher.
* <p>
* A {@code NullCipher} is created and used to process the data.
*
* @param is
* the input stream to read data from.
*/
protected CipherInputStream(InputStream is) {
this(is, new NullCipher());
}
/**
* Reads the next byte from this cipher input stream.
*
* @return the next byte, or {@code -1} if the end of the stream is reached.
* @throws IOException
* if an error occurs.
*/
@Override
public int read() throws IOException {
if (finished) {
return ((o_buffer == null) || (index == o_buffer.length))
? -1
: o_buffer[index++] & 0xFF;
}
if ((o_buffer != null) && (index < o_buffer.length)) {
return o_buffer[index++] & 0xFF;
}
index = 0;
o_buffer = null;
int num_read;
while (o_buffer == null) {
if ((num_read = in.read(i_buffer)) == -1) {
try {
o_buffer = cipher.doFinal();
} catch (Exception e) {
throw new IOException(e.getMessage());
}
finished = true;
break;
}
o_buffer = cipher.update(i_buffer, 0, num_read);
}
return read();
}
/**
* Reads the next {@code b.length} bytes from this input stream into buffer
* {@code b}.
*
* @param b
* the buffer to be filled with data.
* @return the number of bytes filled into buffer {@code b}, or {@code -1}
* if the end of the stream is reached.
* @throws IOException
* if an error occurs.
*/
@Override
public int read(byte[] b) throws IOException {
return read(b, 0, b.length);
}
/**
* Reads the next {@code len} bytes from this input stream into buffer
* {@code b} starting at offset {@code off}.
* <p>
* if {@code b} is {@code null}, the next {@code len} bytes are read and
* discarded.
*
* @param b
* the buffer to be filled with data.
* @param off
* the offset to start in the buffer.
* @param len
* the maximum number of bytes to read.
* @return the number of bytes filled into buffer {@code b}, or {@code -1}
* of the of the stream is reached.
* @throws IOException
* if an error occurs.
* @throws NullPointerException
* if the underlying input stream is {@code null}.
*/
@Override
public int read(byte[] b, int off, int len) throws IOException {
if (in == null) {
throw new NullPointerException("Underlying input stream is null");
}
int read_b;
int i;
for (i=0; i<len; i++) {
if ((read_b = read()) == -1) {
return (i == 0) ? -1 : i;
}
if (b != null) {
b[off+i] = (byte) read_b;
}
}
return i;
}
/**
* Skips up to n bytes from this input stream.
* <p>
* The number of bytes skipped depends on the result of a call to
* {@link CipherInputStream#available() available}. The smaller of n and the
* result are the number of bytes being skipped.
*
* @param n
* the number of bytes that should be skipped.
* @return the number of bytes actually skipped.
* @throws IOException
* if an error occurs
*/
@Override
public long skip(long n) throws IOException {
long i = 0;
int available = available();
if (available < n) {
n = available;
}
while ((i < n) && (read() != -1)) {
i++;
}
return i;
}
@Override
public int available() throws IOException {
return 0;
}
/**
* Closes this {@code CipherInputStream}, also closes the underlying input
* stream and call {@code doFinal} on the cipher object.
*
* @throws IOException
* if an error occurs.
*/
@Override
public void close() throws IOException {
in.close();
try {
cipher.doFinal();
} catch (GeneralSecurityException ignore) {
//do like RI does
}
}
/**
* Returns whether this input stream supports {@code mark} and
* {@code reset}, which it does not.
*
* @return false, since this input stream does not support {@code mark} and
* {@code reset}.
*/
@Override
public boolean markSupported() {
return false;
}
}
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