src/jdk.jcmd/share/classes/sun/tools/common/PrintStreamPrinter.java

/*
 * Copyright (c) 2019, 2021, 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 sun.tools.common;

import java.io.BufferedInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintStream;
import java.util.Arrays;

import static java.nio.charset.StandardCharsets.UTF_8;

/**
 * A helper class which prints the content of input streams to print streams.
 */
public class PrintStreamPrinter {

    /**
     * Reads characters in UTF-8 format from the input stream and prints them
     * with the given print stream. Closes the input stream before it returns.
     *
     * @return The number of printed characters.
     */
    public static long drainUTF8(InputStream is, PrintStream ps) throws IOException {
        long result = 0;

        try (BufferedInputStream bis = new BufferedInputStream(is);
             InputStreamReader isr = new InputStreamReader(bis, UTF_8)) {
            char c[] = new char[256];
            int n;

            do {
                n = isr.read(c);

                if (n > 0) {
                    result += n;
                    ps.print(n == c.length ? c : Arrays.copyOf(c, n));
                }
            } while (n > 0);
        }

        return result;
    }
}