ProxyInputStream.java
/*
* 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.commons.io.input;
import static org.apache.commons.io.IOUtils.EOF;
import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;
import org.apache.commons.io.IOUtils;
import org.apache.commons.io.build.AbstractStreamBuilder;
import org.apache.commons.io.function.Erase;
import org.apache.commons.io.function.IOConsumer;
import org.apache.commons.io.function.IOIntConsumer;
/**
* A proxy stream which acts as a {@link FilterInputStream}, by passing all method calls on to the proxied stream, not changing which methods are called.
* <p>
* It is an alternative base class to {@link FilterInputStream} to increase reusability, because {@link FilterInputStream} changes the methods being called,
* such as read(byte[]) to read(byte[], int, int).
* </p>
* <p>
* In addition, this class allows you to:
* </p>
* <ul>
* <li>notify a subclass that <em>n</em> bytes are about to be read through {@link #beforeRead(int)}</li>
* <li>notify a subclass that <em>n</em> bytes were read through {@link #afterRead(int)}</li>
* <li>notify a subclass that an exception was caught through {@link #handleIOException(IOException)}</li>
* <li>{@link #unwrap()} itself</li>
* </ul>
*/
public abstract class ProxyInputStream extends FilterInputStream {
/**
* Abstracts builder properties for subclasses.
*
* @param <T> The InputStream type.
* @param <B> The builder type.
* @since 2.18.0
*/
protected static abstract class AbstractBuilder<T, B extends AbstractStreamBuilder<T, B>> extends AbstractStreamBuilder<T, B> {
private IOIntConsumer afterRead;
/**
* Gets the {@link ProxyInputStream#afterRead(int)} consumer.
*
* @return the {@link ProxyInputStream#afterRead(int)} consumer.
*/
public IOIntConsumer getAfterRead() {
return afterRead;
}
/**
* Sets the {@link ProxyInputStream#afterRead(int)} behavior, null resets to a NOOP.
* <p>
* Setting this value causes the {@link ProxyInputStream#afterRead(int) afterRead} method to delegate to the given consumer.
* </p>
* <p>
* If a subclass overrides {@link ProxyInputStream#afterRead(int) afterRead} and does not call {@code super.afterRead(int)}, then the given consumer is
* not called.
* </p>
* <p>
* This does <em>not</em> override a {@code ProxyInputStream} subclass' implementation of the {@link ProxyInputStream#afterRead(int)} method, it can
* supplement it.
* </p>
*
* @param afterRead the {@link ProxyInputStream#afterRead(int)} behavior.
* @return this instance.
*/
public B setAfterRead(final IOIntConsumer afterRead) {
this.afterRead = afterRead;
return asThis();
}
}
/**
* Tracks whether {@link #close()} has been called or not.
*/
private boolean closed;
/**
* Handles exceptions.
*/
private final IOConsumer<IOException> exceptionHandler;
private final IOIntConsumer afterRead;
/**
* Constructs a new ProxyInputStream.
*
* @param builder How to build an instance.
* @throws IOException if an I/O error occurs.
* @since 2.18.0
*/
@SuppressWarnings("resource")
protected ProxyInputStream(final AbstractBuilder<?, ?> builder) throws IOException {
// the delegate is stored in a protected superclass instance variable named 'in'.
this(builder.getInputStream(), builder);
}
/**
* Constructs a new ProxyInputStream.
*
* @param proxy the InputStream to proxy.
*/
public ProxyInputStream(final InputStream proxy) {
// the delegate is stored in a protected superclass variable named 'in'.
super(proxy);
this.exceptionHandler = Erase::rethrow;
this.afterRead = IOIntConsumer.NOOP;
}
/**
* Constructs a new ProxyInputStream.
*
* @param proxy the InputStream to proxy.
* @param builder How to build an instance.
* @since 2.18.0
*/
protected ProxyInputStream(final InputStream proxy, final AbstractBuilder<?, ?> builder) {
// the delegate is stored in a protected superclass instance variable named 'in'.
super(proxy);
this.exceptionHandler = Erase::rethrow;
this.afterRead = builder.getAfterRead() != null ? builder.getAfterRead() : IOIntConsumer.NOOP;
}
/**
* Called by the {@code read} methods after the proxied call has returned successfully. The argument is the number of bytes returned to the caller or
* {@link IOUtils#EOF EOF} if the end of stream was reached.
* <p>
* The default delegates to the consumer given to {@link AbstractBuilder#setAfterRead(IOIntConsumer)}.
* </p>
* <p>
* Alternatively, a subclasses can override this method to add post-processing functionality without having to override all the read methods.
* </p>
* <p>
* Note this method is <em>not</em> called from {@link #skip(long)} or {@link #reset()}. You need to explicitly override those methods if you want to add
* post-processing steps also to them.
* </p>
*
* @param n number of bytes read, or {@link IOUtils#EOF EOF} if the end of stream was reached.
* @throws IOException Thrown by a subclass or the consumer given to {@link AbstractBuilder#setAfterRead(IOIntConsumer)}.
* @since 2.0
*/
protected void afterRead(final int n) throws IOException {
afterRead.accept(n);
}
/**
* Invokes the delegate's {@link InputStream#available()} method.
*
* @return the number of available bytes, 0 if the stream is closed.
* @throws IOException if an I/O error occurs.
*/
@Override
public int available() throws IOException {
if (in != null && !isClosed()) {
try {
return in.available();
} catch (final IOException e) {
handleIOException(e);
}
}
return 0;
}
/**
* Invoked by the {@code read} methods before the call is proxied. The number
* of bytes that the caller wanted to read (1 for the {@link #read()}
* method, buffer length for {@link #read(byte[])}, etc.) is given as
* an argument.
* <p>
* Subclasses can override this method to add common pre-processing
* functionality without having to override all the read methods.
* The default implementation does nothing.
* </p>
* <p>
* Note this method is <em>not</em> called from {@link #skip(long)} or
* {@link #reset()}. You need to explicitly override those methods if
* you want to add pre-processing steps also to them.
* </p>
*
* @since 2.0
* @param n number of bytes that the caller asked to be read.
* @throws IOException if the pre-processing fails in a subclass.
*/
@SuppressWarnings("unused") // Possibly thrown from subclasses.
protected void beforeRead(final int n) throws IOException {
// no-op default
}
/**
* Checks if this instance is closed and throws an IOException if so.
*
* @throws IOException if this instance is closed.
*/
void checkOpen() throws IOException {
Input.checkOpen(!isClosed());
}
/**
* Invokes the delegate's {@link InputStream#close()} method.
*
* @throws IOException if an I/O error occurs.
*/
@Override
public void close() throws IOException {
IOUtils.close(in, this::handleIOException);
closed = true;
}
/**
* Handles any IOExceptions thrown; by default, throws the given exception.
* <p>
* This method provides a point to implement custom exception
* handling. The default behavior is to re-throw the exception.
* </p>
*
* @param e The IOException thrown.
* @throws IOException if an I/O error occurs.
* @since 2.0
*/
protected void handleIOException(final IOException e) throws IOException {
exceptionHandler.accept(e);
}
/**
* Tests whether this instance is closed.
*
* @return whether this instance is closed.
*/
boolean isClosed() {
return closed;
}
/**
* Invokes the delegate's {@link InputStream#mark(int)} method.
*
* @param readLimit read ahead limit.
*/
@Override
public synchronized void mark(final int readLimit) {
if (in != null) {
in.mark(readLimit);
}
}
/**
* Invokes the delegate's {@link InputStream#markSupported()} method.
*
* @return {@code true} if this stream instance supports the mark and reset methods; {@code false} otherwise.
* @see #mark(int)
* @see #reset()
*/
@Override
public boolean markSupported() {
return in != null && in.markSupported();
}
/**
* Invokes the delegate's {@link InputStream#read()} method unless the stream is closed.
*
* @return the byte read or {@link IOUtils#EOF EOF} if we reached the end of stream.
* @throws IOException if an I/O error occurs.
*/
@Override
public int read() throws IOException {
try {
beforeRead(1);
final int b = in.read();
afterRead(b != EOF ? 1 : EOF);
return b;
} catch (final IOException e) {
handleIOException(e);
return EOF;
}
}
/**
* Invokes the delegate's {@link InputStream#read(byte[])} method.
*
* @param b the buffer to read the bytes into.
* @return the number of bytes read or {@link IOUtils#EOF EOF} if we reached the end of stream.
* @throws IOException
* <ul>
* <li>If the first byte cannot be read for any reason other than the end of the file,
* <li>if the input stream has been closed, or</li>
* <li>if some other I/O error occurs.</li>
* </ul>
*/
@Override
public int read(final byte[] b) throws IOException {
try {
beforeRead(IOUtils.length(b));
final int n = in.read(b);
afterRead(n);
return n;
} catch (final IOException e) {
handleIOException(e);
return EOF;
}
}
/**
* Invokes the delegate's {@link InputStream#read(byte[], int, int)} method.
*
* @param b the buffer to read the bytes into.
* @param off The start offset.
* @param len The number of bytes to read.
* @return the number of bytes read or {@link IOUtils#EOF EOF} if we reached the end of stream.
* @throws IOException
* <ul>
* <li>If the first byte cannot be read for any reason other than the end of the file,
* <li>if the input stream has been closed, or</li>
* <li>if some other I/O error occurs.</li>
* </ul>
*/
@Override
public int read(final byte[] b, final int off, final int len) throws IOException {
try {
beforeRead(len);
final int n = in.read(b, off, len);
afterRead(n);
return n;
} catch (final IOException e) {
handleIOException(e);
return EOF;
}
}
/**
* Invokes the delegate's {@link InputStream#reset()} method.
*
* @throws IOException if this stream has not been marked or if the mark has been invalidated.
*/
@Override
public synchronized void reset() throws IOException {
try {
in.reset();
} catch (final IOException e) {
handleIOException(e);
}
}
/**
* Package-private for testing.
*
* @param in The input stream to set in {@link java.io.FilterInputStream#in}.
*/
void setIn(final InputStream in) {
this.in = in;
}
/**
* Invokes the delegate's {@link InputStream#skip(long)} method.
*
* @param n the number of bytes to skip.
* @return the actual number of bytes skipped.
* @throws IOException if the stream does not support seek, or if some other I/O error occurs.
*/
@Override
public long skip(final long n) throws IOException {
try {
return in.skip(n);
} catch (final IOException e) {
handleIOException(e);
return 0;
}
}
/**
* Unwraps this instance by returning the underlying {@link InputStream}.
* <p>
* Use with caution; useful to query the underlying {@link InputStream}.
* </p>
*
* @return the underlying {@link InputStream}.
* @since 2.16.0
*/
public InputStream unwrap() {
return in;
}
}