common-utils/src/main/java/org/warp/commonutils/stream/SafeOutputStream.java

package org.warp.commonutils.stream;

import java.io.Closeable;
import java.io.Flushable;
import java.io.OutputStream;
import java.util.Objects;
import org.jetbrains.annotations.NotNull;

/**
 * This abstract class is the superclass of all classes representing
 * an output stream of bytes. An output stream accepts output bytes
 * and sends them to some sink.
 * <p>
 * Applications that need to define a subclass of
 * {@code OutputStream} must always provide at least a method
 * that writes one byte of output.
 *
 * @author  Arthur van Hoff
 * @see     java.io.BufferedOutputStream
 * @see     java.io.ByteArrayOutputStream
 * @see     java.io.DataOutputStream
 * @see     java.io.FilterOutputStream
 * @see     java.io.InputStream
 * @see     java.io.OutputStream#write(int)
 * @since   1.0
 */
public abstract class SafeOutputStream extends OutputStream implements Closeable, Flushable {
	/**
	 * Constructor for subclasses to call.
	 */
	public SafeOutputStream() {}

	/**
	 * Returns a new {@code OutputStream} which discards all bytes.  The
	 * returned stream is initially open.  The stream is closed by calling
	 * the {@code close()} method.  Subsequent calls to {@code close()} have
	 * no effect.
	 *
	 * <p> While the stream is open, the {@code write(int)}, {@code
	 * write(byte[])}, and {@code write(byte[], int, int)} methods do nothing.
	 * After the stream has been closed, these methods all throw {@code
	 * IOException}.
	 *
	 * <p> The {@code flush()} method does nothing.
	 *
	 * @return an {@code OutputStream} which discards all bytes
	 *
	 * @since 11
	 */
	public static java.io.OutputStream nullOutputStream() {
		return new java.io.OutputStream() {
			private volatile boolean closed;

			private void ensureOpen() {
				if (closed) {
					throw new IllegalStateException("Stream closed");
				}
			}

			@Override
			public void write(int b) {
				ensureOpen();
			}

			@Override
			public void write(byte @NotNull [] b, int off, int len) {
				Objects.checkFromIndexSize(off, len, b.length);
				ensureOpen();
			}

			@Override
			public void close() {
				closed = true;
			}
		};
	}

	/**
	 * Writes the specified byte to this output stream. The general
	 * contract for {@code write} is that one byte is written
	 * to the output stream. The byte to be written is the eight
	 * low-order bits of the argument {@code b}. The 24
	 * high-order bits of {@code b} are ignored.
	 * <p>
	 * Subclasses of {@code OutputStream} must provide an
	 * implementation for this method.
	 *
	 * @param      b   the {@code byte}.
	 */
	public abstract void write(int b);

	/**
	 * Writes {@code b.length} bytes from the specified byte array
	 * to this output stream. The general contract for {@code write(b)}
	 * is that it should have exactly the same effect as the call
	 * {@code write(b, 0, b.length)}.
	 *
	 * @param      b   the data.
	 * @see        java.io.OutputStream#write(byte[], int, int)
	 */
	public void write(byte @NotNull [] b) {
		write(b, 0, b.length);
	}

	/**
	 * Writes {@code len} bytes from the specified byte array
	 * starting at offset {@code off} to this output stream.
	 * The general contract for {@code write(b, off, len)} is that
	 * some of the bytes in the array {@code b} are written to the
	 * output stream in order; element {@code b[off]} is the first
	 * byte written and {@code b[off+len-1]} is the last byte written
	 * by this operation.
	 * <p>
	 * The {@code write} method of {@code OutputStream} calls
	 * the write method of one argument on each of the bytes to be
	 * written out. Subclasses are encouraged to override this method and
	 * provide a more efficient implementation.
	 * <p>
	 * If {@code b} is {@code null}, a
	 * {@code NullPointerException} is thrown.
	 * <p>
	 * If {@code off} is negative, or {@code len} is negative, or
	 * {@code off+len} is greater than the length of the array
	 * {@code b}, then an {@code IndexOutOfBoundsException} is thrown.
	 *
	 * @param      b     the data.
	 * @param      off   the start offset in the data.
	 * @param      len   the number of bytes to write.
	 */
	public void write(byte[] b, int off, int len) {
		Objects.checkFromIndexSize(off, len, b.length);
		// len == 0 condition implicitly handled by loop bounds
		for (int i = 0 ; i < len ; i++) {
			write(b[off + i]);
		}
	}

	/**
	 * Flushes this output stream and forces any buffered output bytes
	 * to be written out. The general contract of {@code flush} is
	 * that calling it is an indication that, if any bytes previously
	 * written have been buffered by the implementation of the output
	 * stream, such bytes should immediately be written to their
	 * intended destination.
	 * <p>
	 * If the intended destination of this stream is an abstraction provided by
	 * the underlying operating system, for example a file, then flushing the
	 * stream guarantees only that bytes previously written to the stream are
	 * passed to the operating system for writing; it does not guarantee that
	 * they are actually written to a physical device such as a disk drive.
	 * <p>
	 * The {@code flush} method of {@code OutputStream} does nothing.
	 *
	 */
	public void flush() {
	}

	/**
	 * Closes this output stream and releases any system resources
	 * associated with this stream. The general contract of {@code close}
	 * is that it closes the output stream. A closed stream cannot perform
	 * output operations and cannot be reopened.
	 * <p>
	 * The {@code close} method of {@code OutputStream} does nothing.
	 *
	 */
	public void close() {
	}
}