/*
* Copyright (C) 2012 The Android Open Source Project
*
* Licensed 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 com.android.io;
import com.android.annotations.NonNull;
import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;
/**
* Wraps an {@link InputStream} to change its closing behavior:
* this makes it possible to ignore close operations or have them perform a
* {@link InputStream#reset()} instead (if supported by the underlying stream)
* or plain ignored.
* <p/>
* This is useful to pass a stream to an XML parser or validator that automatically
* closes its input stream -- which makes it impossible to validate a stream and then
* parse it without reacquiring the stream.
* <p/>
* Example of usage:
* <pre>
* // Get a stream that supports mark/reset in case the original does not
* InputStream buffered = new BufferedInputStream(source);
* // Mark the beginning of the stream and indicate how much buffering is acceptable
* buffered.mark(500000);
* // Wrap the stream so that closing it actually just resets it to the mark
* NonClosingInputStream stream = new NonClosingInputStream(buffered);
* stream.setCloseBehavior(CloseBehavior.RESET)
* // pass it to a schema validator (pseudo code, real code is way more verbose.)
* SAXParserFactory...newSAXParser().parse(stream) ...
* // the validator parser closes the stream, which resets it to the beginning
* // so passing it another parser will actually parse the whole stream
* SAXParser...parse(stream) ...
* </pre>
*/
public class NonClosingInputStream extends FilterInputStream {
private final InputStream mInputStream;
private CloseBehavior mCloseBehavior = CloseBehavior.CLOSE;
public enum CloseBehavior {
/**
* The behavior of {@link NonClosingInputStream#close()} is to close the
* underlying input stream. This is the default.
*/
CLOSE,
/**
* The behavior of {@link NonClosingInputStream#close()} is to ignore the
* close request and do nothing.
*/
IGNORE,
/**
* The behavior of {@link NonClosingInputStream#close()} is to call
* {@link InputStream#reset()} on the underlying stream. This will
* only succeed if the underlying stream supports it, e.g. it must
* have {@link InputStream#markSupported()} return true <em>and</em>
* the caller should have called {@link InputStream#mark(int)} at some
* point before.
*/
RESET
}
/**
* Wraps an existing stream into this filtering stream.
* @param in A non-null input stream.
*/
public NonClosingInputStream(@NonNull InputStream in) {
super(in);
mInputStream = in;
}
/**
* Returns the current {@link CloseBehavior}.
* @return the current {@link CloseBehavior}. Never null.
*/
@NonNull
public CloseBehavior getCloseBehavior() {
return mCloseBehavior;
}
/**
* Changes the current {@link CloseBehavior}.
*
* @param closeBehavior A new non-null {@link CloseBehavior}.
* @return Self for chaining.
*/
public NonClosingInputStream setCloseBehavior(@NonNull CloseBehavior closeBehavior) {
mCloseBehavior = closeBehavior;
return this;
}
/**
* Performs the requested {@code close()} operation, depending on the current
* {@link CloseBehavior}.
*/
@Override
public void close() throws IOException {
switch (mCloseBehavior) {
case IGNORE:
break;
case RESET:
mInputStream.reset();
break;
case CLOSE:
mInputStream.close();
break;
}
}
}