# 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 org.apache.commons.fileupload.util;

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

    import org.apache.commons.fileupload.InvalidFileNameException;
    import org.apache.commons.io.IOUtils;
    import org.apache.commons.io.output.NullOutputStream;

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

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

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

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

        /**
         * Checks, whether the given file name is valid in the sense,
         * that it doesn't contain any NUL characters. If the file name
         * is valid, it will be returned without any modifications. Otherwise,
         * an {@link InvalidFileNameException} is raised.
         *
         * @param fileName The file name to check
         * @return Unmodified file name, if valid.
         * @throws InvalidFileNameException The file name was found to be invalid.
         */
        public static String checkFileName(final String fileName) {
            if (fileName != null  &&  fileName.indexOf('\u0000') != -1) {
                // fileName.replace("\u0000", "\\0")
                final StringBuilder sb = new StringBuilder();
                for (int i = 0;  i < fileName.length();  i++) {
                    final char c = fileName.charAt(i);
                    switch (c) {
                        case 0:
                            sb.append("\\0");
                            break;
                        default:
                            sb.append(c);
                            break;
                    }
                }
                throw new InvalidFileNameException(fileName,
                        "Invalid file name: " + sb);
            }
            return fileName;
        }

        /**
         * Copies the contents of the given {@link InputStream}
         * to the given {@link OutputStream}. Shortcut for
         * <pre>
         *   copy(pInputStream, outputStream, new byte[8192]);
         * </pre>
         *
         * @param inputStream The input stream, which is being read.
         * It is guaranteed, that {@link InputStream#close()} is called
         * on the stream.
         * @param outputStream The output stream, to which data should
         * be written. May be null, in which case the input streams
         * contents are simply discarded.
         * @param closeOutputStream 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(final InputStream inputStream, final OutputStream outputStream,
                                final boolean closeOutputStream)
                throws IOException {
            return copy(inputStream, outputStream, closeOutputStream, new byte[DEFAULT_BUFFER_SIZE]);
        }

        /**
         * Copies the contents of the given {@link InputStream}
         * to the given {@link OutputStream}.
         *
         * @param inputStream The input stream, which is being read.
         *   It is guaranteed, that {@link InputStream#close()} is called
         *   on the stream.
         * @param outputStream The output stream, to which data should
         *   be written. May be null, in which case the input streams
         *   contents are simply discarded.
         * @param closeOutputStream True guarantees, that {@link OutputStream#close()}
         *   is called on the stream. False indicates, that only
         *   {@link OutputStream#flush()} should be called finally.
         * @param buffer 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(final InputStream inputStream, final OutputStream outputStream, final boolean closeOutputStream, final byte[] buffer)
                throws IOException {
            try {
                return IOUtils.copyLarge(inputStream, outputStream != null ? outputStream : NullOutputStream.INSTANCE, buffer);
            } finally {
                IOUtils.closeQuietly(inputStream);
                if (closeOutputStream) {
                    IOUtils.closeQuietly(outputStream);
                }
            }
        }

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

    }