Streams.java

/*
 * 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 com.blade.mvc.multipart;

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

/**
 * Utility class for working with streams.
 */
public final class Streams {

    /**
     * Private constructor, to prevent instantiation. This class has only static methods.
     */
    private Streams() {
        // does nothing
    }

    /**
     * Default buffer size for use in {@link #copy(InputStream, OutputStream, boolean)}.
     */
    private static final int DEFAULT_BUFFER_SIZE = 8192;

    /**
     * Copies the contents of the given {@link InputStream} to the given {@link OutputStream}. Shortcut for
     * <p>
     * <pre>copy(pInputStream, pOutputStream, new byte[8192]);</pre>
     *
     * @param pInputStream  The input stream, which is being read. It is guaranteed, that {@link InputStream#close()} is
     *                      called on the stream.
     * @param pOutputStream The output stream, to which data should be written. May be null, in which case the input
     *                      streams contents are simply discarded.
     * @param pClose        True guarantees, that {@link OutputStream#close()} is called on the stream. False indicates, that
     *                      only {@link OutputStream#flush()} should be called finally.
     * @return Number of bytes, which have been copied.
     * @throws IOException An I/O error occurred.
     */
    public static long copy(InputStream pInputStream, OutputStream pOutputStream, boolean pClose) throws IOException {
        return copy(pInputStream, pOutputStream, pClose, new byte[DEFAULT_BUFFER_SIZE]);
    }

    /**
     * Copies the contents of the given {@link InputStream} to the given {@link OutputStream}.
     *
     * @param pIn     The input stream, which is being read. It is guaranteed, that {@link InputStream#close()} is called on
     *                the stream.
     * @param pOut    The output stream, to which data should be written. May be null, in which case the input streams
     *                contents are simply discarded.
     * @param pClose  True guarantees, that {@link OutputStream#close()} is called on the stream. False indicates, that
     *                only {@link OutputStream#flush()} should be called finally.
     * @param pBuffer Temporary buffer, which is to be used for copying data.
     * @return Number of bytes, which have been copied.
     * @throws IOException An I/O error occurred.
     */
    public static long copy(InputStream pIn, OutputStream pOut, boolean pClose, byte[] pBuffer) throws IOException {
        OutputStream out = pOut;
        InputStream in = pIn;
        try {
            long total = 0;
            for (; ; ) {
                int res = in.read(pBuffer);
                if (res == -1) {
                    break;
                }
                if (res > 0) {
                    total += res;
                    if (out != null) {
                        out.write(pBuffer, 0, res);
                    }
                }
            }
            if (out != null) {
                if (pClose) {
                    out.close();
                } else {
                    out.flush();
                }
                out = null;
            }
            in.close();
            in = null;
            return total;
        } finally {
            if (in != null) {
                try {
                    in.close();
                } catch (Throwable t) {
                    /* Ignore me */
                }
            }
            if (pClose && out != null) {
                try {
                    out.close();
                } catch (Throwable t) {
                    /* ignore me */
                }
            }
        }
    }

    /**
     * This convenience method allows to read a <code>org.apache.commons.fileupload.FileItemStream</code>'s content into a
     * string. The platform's default character encoding is used for converting bytes into characters.
     *
     * @param pStream The input stream to read.
     * @return The streams contents, as a string.
     * @throws IOException An I/O error occurred.
     * @see #asString(InputStream, String)
     */
    public static String asString(InputStream pStream) throws IOException {
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        copy(pStream, baos, true);
        return baos.toString();
    }

    /**
     * This convenience method allows to read a <code>org.apache.commons.fileupload.FileItemStream</code>'s content into a
     * string, using the given character encoding.
     *
     * @param pStream   The input stream to read.
     * @param pEncoding The character encoding, typically "UTF-8".
     * @return The streams contents, as a string.
     * @throws IOException An I/O error occurred.
     * @see #asString(InputStream)
     */
    public static String asString(InputStream pStream, String pEncoding) throws IOException {
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        copy(pStream, baos, true);
        return baos.toString(pEncoding);
    }

}