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/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 *
 * Copyright (c) 2010-2012 Oracle and/or its affiliates. All rights reserved.
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 * The contents of this file are subject to the terms of either the GNU
 * General Public License Version 2 only ("GPL") or the Common Development
 * and Distribution License("CDDL") (collectively, the "License").  You
 * may not use this file except in compliance with the License.  You can
 * obtain a copy of the License at
 * http://glassfish.java.net/public/CDDL+GPL_1_1.html
 * or packager/legal/LICENSE.txt.  See the License for the specific
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 *
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 * file and include the License file at packager/legal/LICENSE.txt.
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 * GPL Classpath Exception:
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package org.glassfish.jersey.message.internal;

import java.io.IOException;
import java.io.OutputStream;

/**
 * An abstract committing output stream adapter that performs a {@link org.glassfish.jersey.message.internal.OutboundMessageContext.StreamProvider#commit()
 * commit} and then retrieves the {@link org.glassfish.jersey.message.internal.OutboundMessageContext.StreamProvider#getOutputStream() provided output} stream
 * before the first byte is written to the provided stream.
 *
 * Concrete implementations of the class typically override the commit operation
 * to perform any initialization on the adapted output stream.
 *
 * @author Paul Sandoz
 * @author Marek Potociar (marek.potociar at oracle.com)
 */
// TODO make package-private
public final class CommittingOutputStream extends OutputStream {

    /**
     * Adapted output stream.
     */
    private OutputStream adaptedOutput;
    /**
     * Determines whether the stream was already committed or not.
     */
    private boolean isCommitted = false;
    /**
     * Stream provider.
     */
    private OutboundMessageContext.StreamProvider streamProvider;

    /**
     * Construct a new committing output stream using a deferred initialization
     * of the adapted output stream via {@link org.glassfish.jersey.message.internal.OutboundMessageContext.StreamProvider stream provider}.
     */
    public CommittingOutputStream() {
    }

    /**
     * Set the output stream provider.
     *
     * @param streamProvider output stream provider.
     */
    public void setStreamProvider(OutboundMessageContext.StreamProvider streamProvider) {
        this.streamProvider = streamProvider;
    }

    /**
     * Determines whether the stream was already committed or not.
     *
     * @return {@code true} if this stream was already committed, {@code false} otherwise.
     */
    public boolean isCommitted() {
        return isCommitted;
    }

    @Override
    public void write(byte b[]) throws IOException {
        if (b.length > 0) {
            commitWrite();
            adaptedOutput.write(b);
        }
    }

    @Override
    public void write(byte b[], int off, int len) throws IOException {
        if (len > 0) {
            commitWrite();
            adaptedOutput.write(b, off, len);
        }
    }

    @Override
    public void write(int b) throws IOException {
        commitWrite();
        adaptedOutput.write(b);
    }

    @Override
    public void flush() throws IOException {
        commitWrite();
        adaptedOutput.flush();
    }

    @Override
    public void close() throws IOException {
        commitWrite();
        adaptedOutput.close();
    }

    private void commitWrite() throws IOException {
        if (!isCommitted) {
            isCommitted = true;

            streamProvider.commit();

            if (adaptedOutput == null) {
                adaptedOutput = streamProvider.getOutputStream();
            }
        }
    }
}