NoCloseOutputStream.java

/*
 * Copyright (c) 2024, Stein Eldar Johnsen
 *
 * 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 net.morimekta.io;

import java.io.IOException;
import java.io.OutputStream;
import java.util.Objects;
import java.util.concurrent.atomic.AtomicBoolean;

/**
 * Output stream that protects its wrapped stream from being closed. The
 * wrapper itself is closable, but closing it only prevents further writes
 * without closing the underlying stream.
 */
public class NoCloseOutputStream extends OutputStream {
    private final OutputStream  out;
    private final AtomicBoolean closed = new AtomicBoolean(false);

    /**
     * Create a no-close output stream.
     *
     * @param out The output stream to not close.
     */
    public NoCloseOutputStream(OutputStream out) {
        Objects.requireNonNull(out, "out == null");
        this.out = out;
    }

    @Override
    public void write(int b) throws IOException {
        if (closed.get()) {
            throw new IOException("Stream is closed");
        }
        out.write(b);
    }

    @Override
    public void write(byte[] b, int off, int len) throws IOException {
        if (closed.get()) {
            throw new IOException("Stream is closed");
        }
        out.write(b, off, len);
    }

    @Override
    public void write(byte[] b) throws IOException {
        if (closed.get()) {
            throw new IOException("Stream is closed");
        }
        out.write(b);
    }

    @Override
    public void flush() throws IOException {
        if (!closed.get()) {
            out.flush();
        }
    }

    @Override
    public void close() throws IOException {
        closed.set(true);
    }
}