# MultipartStream.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;

    import static java.lang.String.format;

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

    import org.apache.commons.fileupload.FileUploadBase.FileUploadIOException;
    import org.apache.commons.fileupload.util.Closeable;
    import org.apache.commons.fileupload.util.Streams;

    /**
     * <p> Low level API for processing file uploads.
     *
     * <p> This class can be used to process data streams conforming to MIME
     * 'multipart' format as defined in
     * <a href="http://www.ietf.org/rfc/rfc1867.txt">RFC 1867</a>. Arbitrarily
     * large amounts of data in the stream can be processed under constant
     * memory usage.
     *
     * <p> The format of the stream is defined in the following way:<br>
     *
     * <code>
     *   multipart-body := preamble 1*encapsulation close-delimiter epilogue<br>
     *   encapsulation := delimiter body CRLF<br>
     *   delimiter := "--" boundary CRLF<br>
     *   close-delimiter := "--" boundary "--"<br>
     *   preamble := &lt;ignore&gt;<br>
     *   epilogue := &lt;ignore&gt;<br>
     *   body := header-part CRLF body-part<br>
     *   header-part := 1*header CRLF<br>
     *   header := header-name ":" header-value<br>
     *   header-name := &lt;printable ascii characters except ":"&gt;<br>
     *   header-value := &lt;any ascii characters except CR &amp; LF&gt;<br>
     *   body-data := &lt;arbitrary data&gt;<br>
     * </code>
     *
     * <p>Note that body-data can contain another mulipart entity.  There
     * is limited support for single pass processing of such nested
     * streams.  The nested stream is <strong>required</strong> to have a
     * boundary token of the same length as the parent stream (see {@link
     * #setBoundary(byte[])}).
     *
     * <p>Here is an example of usage of this class.<br>
     *
     * <pre>
     *   try {
     *     MultipartStream multipartStream = new MultipartStream(input, boundary);
     *     boolean nextPart = multipartStream.skipPreamble();
     *     OutputStream output;
     *     while(nextPart) {
     *       String header = multipartStream.readHeaders();
     *       // process headers
     *       // create some output stream
     *       multipartStream.readBodyData(output);
     *       nextPart = multipartStream.readBoundary();
     *     }
     *   } catch(MultipartStream.MalformedStreamException e) {
     *     // the stream failed to follow required syntax
     *   } catch(IOException e) {
     *     // a read or write error occurred
     *   }
     * </pre>
     */
    public class MultipartStream {

        /**
         * Internal class, which is used to invoke the
         * {@link ProgressListener}.
         */
        public static class ProgressNotifier {

            /**
             * The listener to invoke.
             */
            private final ProgressListener listener;

            /**
             * Number of expected bytes, if known, or -1.
             */
            private final long contentLength;

            /**
             * Number of bytes, which have been read so far.
             */
            private long bytesRead;

            /**
             * Number of items, which have been read so far.
             */
            private int items;

            /**
             * Creates a new instance with the given listener
             * and content length.
             *
             * @param pListener The listener to invoke.
             * @param pContentLength The expected content length.
             */
            ProgressNotifier(ProgressListener pListener, long pContentLength) {
                listener = pListener;
                contentLength = pContentLength;
            }

            /**
             * Called to indicate that bytes have been read.
             *
             * @param pBytes Number of bytes, which have been read.
             */
            void noteBytesRead(int pBytes) {
                /* Indicates, that the given number of bytes have been read from
                 * the input stream.
                 */
                bytesRead += pBytes;
                notifyListener();
            }

            /**
             * Called to indicate, that a new file item has been detected.
             */
            void noteItem() {
                ++items;
                notifyListener();
            }

            /**
             * Called for notifying the listener.
             */
            private void notifyListener() {
                if (listener != null) {
                    listener.update(bytesRead, contentLength, items);
                }
            }

        }

        // ----------------------------------------------------- Manifest constants

        /**
         * The Carriage Return ASCII character value.
         */
        public static final byte CR = 0x0D;

        /**
         * The Line Feed ASCII character value.
         */
        public static final byte LF = 0x0A;

        /**
         * The dash (-) ASCII character value.
         */
        public static final byte DASH = 0x2D;

        /**
         * The maximum length of <code>header-part</code> that will be
         * processed (10 kilobytes = 10240 bytes.).
         */
        public static final int HEADER_PART_SIZE_MAX = 10240;

        /**
         * The default length of the buffer used for processing a request.
         */
        protected static final int DEFAULT_BUFSIZE = 4096;

        /**
         * A byte sequence that marks the end of <code>header-part</code>
         * (<code>CRLFCRLF</code>).
         */
        protected static final byte[] HEADER_SEPARATOR = {CR, LF, CR, LF};

        /**
         * A byte sequence that that follows a delimiter that will be
         * followed by an encapsulation (<code>CRLF</code>).
         */
        protected static final byte[] FIELD_SEPARATOR = {CR, LF};

        /**
         * A byte sequence that that follows a delimiter of the last
         * encapsulation in the stream (<code>--</code>).
         */
        protected static final byte[] STREAM_TERMINATOR = {DASH, DASH};

        /**
         * A byte sequence that precedes a boundary (<code>CRLF--</code>).
         */
        protected static final byte[] BOUNDARY_PREFIX = {CR, LF, DASH, DASH};

        // ----------------------------------------------------------- Data members

        /**
         * The input stream from which data is read.
         */
        private final InputStream input;

        /**
         * The length of the boundary token plus the leading <code>CRLF--</code>.
         */
        private int boundaryLength;

        /**
         * The amount of data, in bytes, that must be kept in the buffer in order
         * to detect delimiters reliably.
         */
        private final int keepRegion;

        /**
         * The byte sequence that partitions the stream.
         */
        private final byte[] boundary;

        /**
         * The table for Knuth-Morris-Pratt search algorithm.
         */
        private final int[] boundaryTable;

        /**
         * The length of the buffer used for processing the request.
         */
        private final int bufSize;

        /**
         * The buffer used for processing the request.
         */
        private final byte[] buffer;

        /**
         * The index of first valid character in the buffer.
         * <br>
         * 0 <= head < bufSize
         */
        private int head;

        /**
         * The index of last valid character in the buffer + 1.
         * <br>
         * 0 <= tail <= bufSize
         */
        private int tail;

        /**
         * The content encoding to use when reading headers.
         */
        private String headerEncoding;

        /**
         * The progress notifier, if any, or null.
         */
        private final ProgressNotifier notifier;

        // ----------------------------------------------------------- Constructors

        /**
         * Creates a new instance.
         *
         * @deprecated 1.2.1 Use {@link #MultipartStream(InputStream, byte[], int,
         * ProgressNotifier)}
         */
        @Deprecated
        public MultipartStream() {
            this(null, null, null);
        }

        /**
         * <p> Constructs a <code>MultipartStream</code> with a custom size buffer
         * and no progress notifier.
         *
         * <p> Note that the buffer must be at least big enough to contain the
         * boundary string, plus 4 characters for CR/LF and double dash, plus at
         * least one byte of data.  Too small a buffer size setting will degrade
         * performance.
         *
         * @param input    The <code>InputStream</code> to serve as a data source.
         * @param boundary The token used for dividing the stream into
         *                 <code>encapsulations</code>.
         * @param bufSize  The size of the buffer to be used, in bytes.
         *
         * @deprecated 1.2.1 Use {@link #MultipartStream(InputStream, byte[], int,
         * ProgressNotifier)}.
         */
        @Deprecated
        public MultipartStream(InputStream input, byte[] boundary, int bufSize) {
            this(input, boundary, bufSize, null);
        }

        /**
         * <p> Constructs a <code>MultipartStream</code> with a custom size buffer.
         *
         * <p> Note that the buffer must be at least big enough to contain the
         * boundary string, plus 4 characters for CR/LF and double dash, plus at
         * least one byte of data.  Too small a buffer size setting will degrade
         * performance.
         *
         * @param input    The <code>InputStream</code> to serve as a data source.
         * @param boundary The token used for dividing the stream into
         *                 <code>encapsulations</code>.
         * @param bufSize  The size of the buffer to be used, in bytes.
         * @param pNotifier The notifier, which is used for calling the
         *                  progress listener, if any.
         *
         * @throws IllegalArgumentException If the buffer size is too small
         *
         * @since 1.3.1
         */
        public MultipartStream(InputStream input,
                byte[] boundary,
                int bufSize,
                ProgressNotifier pNotifier) {

            if (boundary == null) {
                throw new IllegalArgumentException("boundary may not be null");
            }
            // We prepend CR/LF to the boundary to chop trailing CR/LF from
            // body-data tokens.
            this.boundaryLength = boundary.length + BOUNDARY_PREFIX.length;
            if (bufSize < this.boundaryLength + 1) {
                throw new IllegalArgumentException(
                        "The buffer size specified for the MultipartStream is too small");
            }

            this.input = input;
            this.bufSize = Math.max(bufSize, boundaryLength * 2);
            this.buffer = new byte[this.bufSize];
            this.notifier = pNotifier;

            this.boundary = new byte[this.boundaryLength];
            this.boundaryTable = new int[this.boundaryLength + 1];
            this.keepRegion = this.boundary.length;

            System.arraycopy(BOUNDARY_PREFIX, 0, this.boundary, 0,
                    BOUNDARY_PREFIX.length);
            System.arraycopy(boundary, 0, this.boundary, BOUNDARY_PREFIX.length,
                    boundary.length);
            computeBoundaryTable();

            head = 0;
            tail = 0;
        }

        /**
         * <p> Constructs a <code>MultipartStream</code> with a default size buffer.
         *
         * @param input    The <code>InputStream</code> to serve as a data source.
         * @param boundary The token used for dividing the stream into
         *                 <code>encapsulations</code>.
         * @param pNotifier An object for calling the progress listener, if any.
         *
         *
         * @see #MultipartStream(InputStream, byte[], int, ProgressNotifier)
         */
        MultipartStream(InputStream input,
                byte[] boundary,
                ProgressNotifier pNotifier) {
            this(input, boundary, DEFAULT_BUFSIZE, pNotifier);
        }

        /**
         * <p> Constructs a <code>MultipartStream</code> with a default size buffer.
         *
         * @param input    The <code>InputStream</code> to serve as a data source.
         * @param boundary The token used for dividing the stream into
         *                 <code>encapsulations</code>.
         *
         * @deprecated 1.2.1 Use {@link #MultipartStream(InputStream, byte[], int,
         *  ProgressNotifier)}.
         */
        @Deprecated
        public MultipartStream(InputStream input,
                byte[] boundary) {
            this(input, boundary, DEFAULT_BUFSIZE, null);
        }

        // --------------------------------------------------------- Public methods

        /**
         * Retrieves the character encoding used when reading the headers of an
         * individual part. When not specified, or <code>null</code>, the platform
         * default encoding is used.
         *
         * @return The encoding used to read part headers.
         */
        public String getHeaderEncoding() {
            return headerEncoding;
        }

        /**
         * Specifies the character encoding to be used when reading the headers of
         * individual parts. When not specified, or <code>null</code>, the platform
         * default encoding is used.
         *
         * @param encoding The encoding used to read part headers.
         */
        public void setHeaderEncoding(String encoding) {
            headerEncoding = encoding;
        }

        /**
         * Reads a byte from the <code>buffer</code>, and refills it as
         * necessary.
         *
         * @return The next byte from the input stream.
         *
         * @throws IOException if there is no more data available.
         */
        public byte readByte() throws IOException {
            // Buffer depleted ?
            if (head == tail) {
                head = 0;
                // Refill.
                tail = input.read(buffer, head, bufSize);
                if (tail == -1) {
                    // No more data available.
                    throw new IOException("No more data is available");
                }
                if (notifier != null) {
                    notifier.noteBytesRead(tail);
                }
            }
            return buffer[head++];
        }

        /**
         * Skips a <code>boundary</code> token, and checks whether more
         * <code>encapsulations</code> are contained in the stream.
         *
         * @return <code>true</code> if there are more encapsulations in
         *         this stream; <code>false</code> otherwise.
         *
         * @throws FileUploadIOException if the bytes read from the stream exceeded the size limits
         * @throws MalformedStreamException if the stream ends unexpectedly or
         *                                  fails to follow required syntax.
         */
        public boolean readBoundary()
                throws FileUploadIOException, MalformedStreamException {
            byte[] marker = new byte[2];
            boolean nextChunk = false;

            head += boundaryLength;
            try {
                marker[0] = readByte();
                if (marker[0] == LF) {
                    // Work around IE5 Mac bug with input type=image.
                    // Because the boundary delimiter, not including the trailing
                    // CRLF, must not appear within any file (RFC 2046, section
                    // 5.1.1), we know the missing CR is due to a buggy browser
                    // rather than a file containing something similar to a
                    // boundary.
                    return true;
                }

                marker[1] = readByte();
                if (arrayequals(marker, STREAM_TERMINATOR, 2)) {
                    nextChunk = false;
                } else if (arrayequals(marker, FIELD_SEPARATOR, 2)) {
                    nextChunk = true;
                } else {
                    throw new MalformedStreamException(
                    "Unexpected characters follow a boundary");
                }
            } catch (FileUploadIOException e) {
                // wraps a SizeException, re-throw as it will be unwrapped later
                throw e;
            } catch (IOException e) {
                throw new MalformedStreamException("Stream ended unexpectedly");
            }
            return nextChunk;
        }

        /**
         * <p>Changes the boundary token used for partitioning the stream.
         *
         * <p>This method allows single pass processing of nested multipart
         * streams.
         *
         * <p>The boundary token of the nested stream is <code>required</code>
         * to be of the same length as the boundary token in parent stream.
         *
         * <p>Restoring the parent stream boundary token after processing of a
         * nested stream is left to the application.
         *
         * @param boundary The boundary to be used for parsing of the nested
         *                 stream.
         *
         * @throws IllegalBoundaryException if the <code>boundary</code>
         *                                  has a different length than the one
         *                                  being currently parsed.
         */
        public void setBoundary(byte[] boundary)
                throws IllegalBoundaryException {
            if (boundary.length != boundaryLength - BOUNDARY_PREFIX.length) {
                throw new IllegalBoundaryException(
                "The length of a boundary token cannot be changed");
            }
            System.arraycopy(boundary, 0, this.boundary, BOUNDARY_PREFIX.length,
                    boundary.length);
            computeBoundaryTable();
        }

        /**
         * Compute the table used for Knuth-Morris-Pratt search algorithm.
         */
        private void computeBoundaryTable() {
            int position = 2;
            int candidate = 0;

            boundaryTable[0] = -1;
            boundaryTable[1] = 0;

            while (position <= boundaryLength) {
                if (boundary[position - 1] == boundary[candidate]) {
                    boundaryTable[position] = candidate + 1;
                    candidate++;
                    position++;
                } else if (candidate > 0) {
                    candidate = boundaryTable[candidate];
                } else {
                    boundaryTable[position] = 0;
                    position++;
                }
            }
        }

        /**
         * <p>Reads the <code>header-part</code> of the current
         * <code>encapsulation</code>.
         *
         * <p>Headers are returned verbatim to the input stream, including the
         * trailing <code>CRLF</code> marker. Parsing is left to the
         * application.
         *
         * <p><strong>TODO</strong> allow limiting maximum header size to
         * protect against abuse.
         *
         * @return The <code>header-part</code> of the current encapsulation.
         *
         * @throws FileUploadIOException if the bytes read from the stream exceeded the size limits.
         * @throws MalformedStreamException if the stream ends unexpectedly.
         */
        public String readHeaders() throws FileUploadIOException, MalformedStreamException {
            int i = 0;
            byte b;
            // to support multi-byte characters
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            int size = 0;
            while (i < HEADER_SEPARATOR.length) {
                try {
                    b = readByte();
                } catch (FileUploadIOException e) {
                    // wraps a SizeException, re-throw as it will be unwrapped later
                    throw e;
                } catch (IOException e) {
                    throw new MalformedStreamException("Stream ended unexpectedly");
                }
                if (++size > HEADER_PART_SIZE_MAX) {
                    throw new MalformedStreamException(
                            format("Header section has more than %s bytes (maybe it is not properly terminated)",
                                   Integer.valueOf(HEADER_PART_SIZE_MAX)));
                }
                if (b == HEADER_SEPARATOR[i]) {
                    i++;
                } else {
                    i = 0;
                }
                baos.write(b);
            }

            String headers = null;
            if (headerEncoding != null) {
                try {
                    headers = baos.toString(headerEncoding);
                } catch (UnsupportedEncodingException e) {
                    // Fall back to platform default if specified encoding is not
                    // supported.
                    headers = baos.toString();
                }
            } else {
                headers = baos.toString();
            }

            return headers;
        }

        /**
         * <p>Reads <code>body-data</code> from the current
         * <code>encapsulation</code> and writes its contents into the
         * output <code>Stream</code>.
         *
         * <p>Arbitrary large amounts of data can be processed by this
         * method using a constant size buffer. (see {@link
         * #MultipartStream(InputStream,byte[],int,
         *   MultipartStream.ProgressNotifier) constructor}).
         *
         * @param output The <code>Stream</code> to write data into. May
         *               be null, in which case this method is equivalent
         *               to {@link #discardBodyData()}.
         *
         * @return the amount of data written.
         *
         * @throws MalformedStreamException if the stream ends unexpectedly.
         * @throws IOException              if an i/o error occurs.
         */
        public int readBodyData(OutputStream output)
                throws MalformedStreamException, IOException {
            return (int) Streams.copy(newInputStream(), output, false); // N.B. Streams.copy closes the input stream
        }

        /**
         * Creates a new {@link ItemInputStream}.
         * @return A new instance of {@link ItemInputStream}.
         */
        ItemInputStream newInputStream() {
            return new ItemInputStream();
        }

        /**
         * <p> Reads <code>body-data</code> from the current
         * <code>encapsulation</code> and discards it.
         *
         * <p>Use this method to skip encapsulations you don't need or don't
         * understand.
         *
         * @return The amount of data discarded.
         *
         * @throws MalformedStreamException if the stream ends unexpectedly.
         * @throws IOException              if an i/o error occurs.
         */
        public int discardBodyData() throws MalformedStreamException, IOException {
            return readBodyData(null);
        }

        /**
         * Finds the beginning of the first <code>encapsulation</code>.
         *
         * @return <code>true</code> if an <code>encapsulation</code> was found in
         *         the stream.
         *
         * @throws IOException if an i/o error occurs.
         */
        public boolean skipPreamble() throws IOException {
            // First delimiter may be not preceeded with a CRLF.
            System.arraycopy(boundary, 2, boundary, 0, boundary.length - 2);
            boundaryLength = boundary.length - 2;
            computeBoundaryTable();
            try {
                // Discard all data up to the delimiter.
                discardBodyData();

                // Read boundary - if succeeded, the stream contains an
                // encapsulation.
                return readBoundary();
            } catch (MalformedStreamException e) {
                return false;
            } finally {
                // Restore delimiter.
                System.arraycopy(boundary, 0, boundary, 2, boundary.length - 2);
                boundaryLength = boundary.length;
                boundary[0] = CR;
                boundary[1] = LF;
                computeBoundaryTable();
            }
        }

        /**
         * Compares <code>count</code> first bytes in the arrays
         * <code>a</code> and <code>b</code>.
         *
         * @param a     The first array to compare.
         * @param b     The second array to compare.
         * @param count How many bytes should be compared.
         *
         * @return <code>true</code> if <code>count</code> first bytes in arrays
         *         <code>a</code> and <code>b</code> are equal.
         */
        public static boolean arrayequals(byte[] a,
                byte[] b,
                int count) {
            for (int i = 0; i < count; i++) {
                if (a[i] != b[i]) {
                    return false;
                }
            }
            return true;
        }

        /**
         * Searches for a byte of specified value in the <code>buffer</code>,
         * starting at the specified <code>position</code>.
         *
         * @param value The value to find.
         * @param pos   The starting position for searching.
         *
         * @return The position of byte found, counting from beginning of the
         *         <code>buffer</code>, or <code>-1</code> if not found.
         */
        protected int findByte(byte value,
                int pos) {
            for (int i = pos; i < tail; i++) {
                if (buffer[i] == value) {
                    return i;
                }
            }

            return -1;
        }

        /**
         * Searches for the <code>boundary</code> in the <code>buffer</code>
         * region delimited by <code>head</code> and <code>tail</code>.
         *
         * @return The position of the boundary found, counting from the
         *         beginning of the <code>buffer</code>, or <code>-1</code> if
         *         not found.
         */
        protected int findSeparator() {

            int bufferPos = this.head;
            int tablePos = 0;

            while (bufferPos < this.tail) {
                while (tablePos >= 0 && buffer[bufferPos] != boundary[tablePos]) {
                    tablePos = boundaryTable[tablePos];
                }
                bufferPos++;
                tablePos++;
                if (tablePos == boundaryLength) {
                    return bufferPos - boundaryLength;
                }
            }
            return -1;
        }

        /**
         * Thrown to indicate that the input stream fails to follow the
         * required syntax.
         */
        public static class MalformedStreamException extends IOException {

            /**
             * The UID to use when serializing this instance.
             */
            private static final long serialVersionUID = 6466926458059796677L;

            /**
             * Constructs a <code>MalformedStreamException</code> with no
             * detail message.
             */
            public MalformedStreamException() {
                super();
            }

            /**
             * Constructs an <code>MalformedStreamException</code> with
             * the specified detail message.
             *
             * @param message The detail message.
             */
            public MalformedStreamException(String message) {
                super(message);
            }

        }

        /**
         * Thrown upon attempt of setting an invalid boundary token.
         */
        public static class IllegalBoundaryException extends IOException {

            /**
             * The UID to use when serializing this instance.
             */
            private static final long serialVersionUID = -161533165102632918L;

            /**
             * Constructs an <code>IllegalBoundaryException</code> with no
             * detail message.
             */
            public IllegalBoundaryException() {
                super();
            }

            /**
             * Constructs an <code>IllegalBoundaryException</code> with
             * the specified detail message.
             *
             * @param message The detail message.
             */
            public IllegalBoundaryException(String message) {
                super(message);
            }

        }

        /**
         * An {@link InputStream} for reading an items contents.
         */
        public class ItemInputStream extends InputStream implements Closeable {

            /**
             * The number of bytes, which have been read so far.
             */
            private long total;

            /**
             * The number of bytes, which must be hold, because
             * they might be a part of the boundary.
             */
            private int pad;

            /**
             * The current offset in the buffer.
             */
            private int pos;

            /**
             * Whether the stream is already closed.
             */
            private boolean closed;

            /**
             * Creates a new instance.
             */
            ItemInputStream() {
                findSeparator();
            }

            /**
             * Called for finding the separator.
             */
            private void findSeparator() {
                pos = MultipartStream.this.findSeparator();
                if (pos == -1) {
                    if (tail - head > keepRegion) {
                        pad = keepRegion;
                    } else {
                        pad = tail - head;
                    }
                }
            }

            /**
             * Returns the number of bytes, which have been read
             * by the stream.
             *
             * @return Number of bytes, which have been read so far.
             */
            public long getBytesRead() {
                return total;
            }

            /**
             * Returns the number of bytes, which are currently
             * available, without blocking.
             *
             * @throws IOException An I/O error occurs.
             * @return Number of bytes in the buffer.
             */
            @Override
            public int available() throws IOException {
                if (pos == -1) {
                    return tail - head - pad;
                }
                return pos - head;
            }

            /**
             * Offset when converting negative bytes to integers.
             */
            private static final int BYTE_POSITIVE_OFFSET = 256;

            /**
             * Returns the next byte in the stream.
             *
             * @return The next byte in the stream, as a non-negative
             *   integer, or -1 for EOF.
             * @throws IOException An I/O error occurred.
             */
            @Override
            public int read() throws IOException {
                if (closed) {
                    throw new FileItemStream.ItemSkippedException();
                }
                if (available() == 0 && makeAvailable() == 0) {
                    return -1;
                }
                ++total;
                int b = buffer[head++];
                if (b >= 0) {
                    return b;
                }
                return b + BYTE_POSITIVE_OFFSET;
            }

            /**
             * Reads bytes into the given buffer.
             *
             * @param b The destination buffer, where to write to.
             * @param off Offset of the first byte in the buffer.
             * @param len Maximum number of bytes to read.
             * @return Number of bytes, which have been actually read,
             *   or -1 for EOF.
             * @throws IOException An I/O error occurred.
             */
            @Override
            public int read(byte[] b, int off, int len) throws IOException {
                if (closed) {
                    throw new FileItemStream.ItemSkippedException();
                }
                if (len == 0) {
                    return 0;
                }
                int res = available();
                if (res == 0) {
                    res = makeAvailable();
                    if (res == 0) {
                        return -1;
                    }
                }
                res = Math.min(res, len);
                System.arraycopy(buffer, head, b, off, res);
                head += res;
                total += res;
                return res;
            }

            /**
             * Closes the input stream.
             *
             * @throws IOException An I/O error occurred.
             */
            @Override
            public void close() throws IOException {
                close(false);
            }

            /**
             * Closes the input stream.
             *
             * @param pCloseUnderlying Whether to close the underlying stream
             *   (hard close)
             * @throws IOException An I/O error occurred.
             */
            public void close(boolean pCloseUnderlying) throws IOException {
                if (closed) {
                    return;
                }
                if (pCloseUnderlying) {
                    closed = true;
                    input.close();
                } else {
                    for (;;) {
                        int av = available();
                        if (av == 0) {
                            av = makeAvailable();
                            if (av == 0) {
                                break;
                            }
                        }
                        skip(av);
                    }
                }
                closed = true;
            }

            /**
             * Skips the given number of bytes.
             *
             * @param bytes Number of bytes to skip.
             * @return The number of bytes, which have actually been
             *   skipped.
             * @throws IOException An I/O error occurred.
             */
            @Override
            public long skip(long bytes) throws IOException {
                if (closed) {
                    throw new FileItemStream.ItemSkippedException();
                }
                int av = available();
                if (av == 0) {
                    av = makeAvailable();
                    if (av == 0) {
                        return 0;
                    }
                }
                long res = Math.min(av, bytes);
                head += res;
                return res;
            }

            /**
             * Attempts to read more data.
             *
             * @return Number of available bytes
             * @throws IOException An I/O error occurred.
             */
            private int makeAvailable() throws IOException {
                if (pos != -1) {
                    return 0;
                }

                // Move the data to the beginning of the buffer.
                total += tail - head - pad;
                System.arraycopy(buffer, tail - pad, buffer, 0, pad);

                // Refill buffer with new data.
                head = 0;
                tail = pad;

                for (;;) {
                    int bytesRead = input.read(buffer, tail, bufSize - tail);
                    if (bytesRead == -1) {
                        // The last pad amount is left in the buffer.
                        // Boundary can't be in there so signal an error
                        // condition.
                        final String msg = "Stream ended unexpectedly";
                        throw new MalformedStreamException(msg);
                    }
                    if (notifier != null) {
                        notifier.noteBytesRead(bytesRead);
                    }
                    tail += bytesRead;

                    findSeparator();
                    int av = available();

                    if (av > 0 || pos != -1) {
                        return av;
                    }
                }
            }

            /**
             * Returns, whether the stream is closed.
             *
             * @return True, if the stream is closed, otherwise false.
             */
            @Override
            public boolean isClosed() {
                return closed;
            }

        }

    }