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The Apache Log4j Implementation
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/*
 * 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 org.apache.logging.log4j.core.util;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.Reader;
import java.io.Writer;

/**
 * Copied from Apache Commons IO revision 1686747.
 */
public class IOUtils {

    /**
     * The default buffer size ({@value}) to use for
     * {@link #copyLarge(InputStream, OutputStream)}
     * and
     * {@link #copyLarge(Reader, Writer)}
     */
    private static final int DEFAULT_BUFFER_SIZE = 1024 * 4;

    /**
     * Represents the end-of-file (or stream).
     */
    public static final int EOF = -1;

    /**
     * Copies chars from a Reader to a Writer.
     * 
     * This method buffers the input internally, so there is no need to use a
     * BufferedReader.
     * 

     * Large streams (over 2GB) will return a chars copied value of
     * -1 after the copy has completed since the correct
     * number of chars cannot be returned as an int. For large streams
     * use the copyLarge(Reader, Writer) method.
     *
     * @param input the Reader to read from
     * @param output the Writer to write to
     * @return the number of characters copied, or -1 if > Integer.MAX_VALUE
     * @throws NullPointerException if the input or output is null
     * @throws IOException          if an I/O error occurs
     * @since 1.1
     */
    public static int copy(final Reader input, final Writer output) throws IOException {
        final long count = copyLarge(input, output);
        if (count > Integer.MAX_VALUE) {
            return -1;
        }
        return (int) count;
    }

    /**
     * Copies chars from a large (over 2GB) Reader to a Writer.
     * 

     * This method buffers the input internally, so there is no need to use a
     * BufferedReader.
     * 

     * The buffer size is given by {@link #DEFAULT_BUFFER_SIZE}.
     *
     * @param input the Reader to read from
     * @param output the Writer to write to
     * @return the number of characters copied
     * @throws NullPointerException if the input or output is null
     * @throws IOException          if an I/O error occurs
     * @since 1.3
     */
    public static long copyLarge(final Reader input, final Writer output) throws IOException {
        return copyLarge(input, output, new char[DEFAULT_BUFFER_SIZE]);
    }

    /**
     * Copies chars from a large (over 2GB) Reader to a Writer.
     * 

     * This method uses the provided buffer, so there is no need to use a
     * BufferedReader.
     * 

     *
     * @param input the Reader to read from
     * @param output the Writer to write to
     * @param buffer the buffer to be used for the copy
     * @return the number of characters copied
     * @throws NullPointerException if the input or output is null
     * @throws IOException          if an I/O error occurs
     * @since 2.2
     */
    public static long copyLarge(final Reader input, final Writer output, final char[] buffer) throws IOException {
        long count = 0;
        int n;
        while (EOF != (n = input.read(buffer))) {
            output.write(buffer, 0, n);
            count += n;
        }
        return count;
    }

    /**
     * Gets the contents of a Reader as a String.
     * 
     * This method buffers the input internally, so there is no need to use a
     * BufferedReader.
     *
     * @param input the Reader to read from
     * @return the requested String
     * @throws NullPointerException if the input is null
     * @throws IOException          if an I/O error occurs
     */
    public static String toString(final Reader input) throws IOException {
        final StringBuilderWriter sw = new StringBuilderWriter();
        copy(input, sw);
        return sw.toString();
    }

}