src/jdk.compiler/share/classes/com/sun/tools/sjavac/server/log/LoggingOutputStream.java

/*
 * Copyright (c) 2016, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is 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
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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package com.sun.tools.sjavac.server.log;

import com.sun.tools.sjavac.Log;

import java.io.ByteArrayOutputStream;
import java.io.FilterOutputStream;
import java.io.IOException;
import java.io.OutputStream;

public class LoggingOutputStream extends FilterOutputStream {

    private static final byte[] LINE_SEP = System.lineSeparator().getBytes();

    private final Log.Level level;
    private final String linePrefix;
    private EolTrackingByteArrayOutputStream buf = new EolTrackingByteArrayOutputStream();

    public LoggingOutputStream(OutputStream out, Log.Level level, String linePrefix) {
        super(out);
        this.level = level;
        this.linePrefix = linePrefix;
    }

    @Override
    public void write(int b) throws IOException {
        super.write(b);
        buf.write(b);
        if (buf.isLineComplete()) {
            String line = new String(buf.toByteArray(), 0, buf.size() - LINE_SEP.length);
            Log.log(level, linePrefix + line);
            buf = new EolTrackingByteArrayOutputStream();
        }
    }

    private static class EolTrackingByteArrayOutputStream extends ByteArrayOutputStream {
        private static final byte[] EOL = System.lineSeparator().getBytes();
        private boolean isLineComplete() {
            if (count < EOL.length) {
                return false;
            }
            for (int i = 0; i < EOL.length; i++) {
                if (buf[count - EOL.length + i] != EOL[i]) {
                    return false;
                }
            }
            return true;
        }
    }
}