StderrStream.java

/* ========================================================================
 * PlantUML : a free UML diagram generator
 * ========================================================================
 *
 * (C) Copyright 2009-2025, Arnaud Roques
 *
 * Project Info:  https://plantuml.com
 *
 * If you like this project or if you find it useful, you can support us at:
 *
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 *
 * This file is part of PlantUML.
 *
 * PlantUML is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * PlantUML distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
 * License for more details.
 *
 * You should have received a copy of the GNU General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301,
 * USA.
 *
 *
 * Original Author:  Arnaud Roques
 *
 */
package net.sourceforge.plantuml.teavm.c;

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

/**
 * The standard error of the C build, for the diagnostics of {@code -pipe} (line
 * number and message of a syntax error, read by tools such as Kroki): the bytes
 * are written as they are, in binary mode, straight to the file descriptor 2.
 * <p>
 * It does not depend on the {@code System.err} of the classlib of the TeaVM C
 * backend, which is a text stream (see {@link StdoutStream}).
 * <p>
 * Only create it when {@code TeaVM.isC()}: elsewhere the native method fails.
 */
public final class StderrStream extends OutputStream {
	// ::remove file when JAVA8

	// The native method reads the start of its array: go through a block
	private final byte[] block = new byte[8192];

	public StderrStream() {
	}

	@Override
	public void write(int b) throws IOException {
		block[0] = (byte) b;
		send(1);
	}

	@Override
	public void write(byte[] buffer, int offset, int length) throws IOException {
		while (length > 0) {
			final int count = Math.min(length, block.length);
			System.arraycopy(buffer, offset, block, 0, count);
			send(count);
			offset += count;
			length -= count;
		}
	}

	private void send(int count) throws IOException {
		if (NativeStdin.writeError(block, count) != 0)
			throw new IOException("Cannot write to the standard error");
	}

}