content: package act.data;
  
  /*-
   * #%L
   * ACT Framework
   * %%
   * Copyright (C) 2014 - 2017 ActFramework
   * %%
   * Licensed 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.
   * #L%
   */
  
  import org.apache.commons.fileupload.FileItemStream;
  import org.apache.commons.fileupload.ProgressListener;
  import org.apache.commons.fileupload.util.Streams;
  
  import java.io.*;
  
  /**
   * <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 := "--" boudary "--"<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 & 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) {
   *            header = chunks.readHeader();
   *            // process headers
   *            // create some output stream
   *            multipartStream.readBodyPart(output);
   *            nextPart = multipartStream.readBoundary();
   *        }
   *    } catch(MultipartStream.MalformedStreamException e) {
   *          // the stream failed to follow required syntax
   *    } catch(IOException) {
   *          // a read or write error occurred
   *    }
   *
   * </pre>
   *
   * @author <a href="mailto:Rafal.Krzewski@e-point.pl">Rafal Krzewski</a>
   * @author <a href="mailto:martinc@apache.org">Martin Cooper</a>
   * @author Sean C. Sullivan
   *
   * @version $Id: MultipartStream.java 174 2007-11-04 21:25:00Z leo $
   */
  public class MultipartStream {
  
      /**
       * Internal class, which is used to invoke the
       * {@link ProgressListener}.
       */
      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;
          }
  
          /** 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
      };
      /**
       * The number of bytes, over and above the boundary size, to use for the
       * keep region.
       */
      private static final int KEEP_REGION_PAD = 3;
      // ----------------------------------------------------------- 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 int keepRegion;
      /**
       * The byte sequence that partitions the stream.
       */
      private byte[] boundary;
      /**
       * 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 characer 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 Use {@link #MultipartStream(InputStream, byte[], ProgressNotifier)},
       * or {@link #MultipartStream(InputStream, byte[], int, ProgressNotifier)}
       */
      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.
       *
       * @see #MultipartStream(InputStream, byte[], ProgressNotifier)
       * @deprecated Use {@link #MultipartStream(InputStream, byte[], int, ProgressNotifier)}.
       */
      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.
       *
       * @see #MultipartStream(InputStream, byte[], ProgressNotifier)
       */
      MultipartStream(InputStream input,
                      byte[] boundary,
                      int bufSize,
                      ProgressNotifier pNotifier) {
          this.input = input;
          this.bufSize = bufSize;
          this.buffer = new byte[bufSize];
          this.notifier = pNotifier;
  
          // We prepend CR/LF to the boundary to chop trailng CR/LF from
          // body-data tokens.
          this.boundary = new byte[boundary.length + BOUNDARY_PREFIX.length];
          this.boundaryLength = boundary.length + BOUNDARY_PREFIX.length;
          this.keepRegion = boundary.length + KEEP_REGION_PAD;
          System.arraycopy(BOUNDARY_PREFIX, 0, this.boundary, 0,
                  BOUNDARY_PREFIX.length);
          System.arraycopy(boundary, 0, this.boundary, BOUNDARY_PREFIX.length,
                  boundary.length);
  
          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 Use {@link #MultipartStream(InputStream, byte[],
       *  ProgressNotifier)}.
       * @see #MultipartStream(InputStream, byte[], int, ProgressNotifier)
       */
      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 MalformedStreamException if the stream ends unexpecetedly or
       *                                  fails to follow required syntax.
       */
      public boolean readBoundary()
              throws 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 (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 can not be changed");
          }
          System.arraycopy(boundary, 0, this.boundary, BOUNDARY_PREFIX.length,
                  boundary.length);
      }
  
      /**
       * <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 MalformedStreamException if the stream ends unexpecetedly.
       */
      public String readHeaders()
              throws MalformedStreamException {
          int i = 0;
          byte[] b = new byte[1];
          // to support multi-byte characters
          ByteArrayOutputStream baos = new ByteArrayOutputStream();
          int sizeMax = HEADER_PART_SIZE_MAX;
          int size = 0;
          while (i < HEADER_SEPARATOR.length) {
              try {
                  b[0] = readByte();
              } catch (IOException e) {
                  throw new MalformedStreamException("Stream ended unexpectedly");
              }
              size++;
              if (b[0] == HEADER_SEPARATOR[i]) {
                  i++;
              } else {
                  i = 0;
              }
              if (size <= sizeMax) {
                  baos.write(b[0]);
              }
          }
  
          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, 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 {
          final InputStream istream = newInputStream();
          return (int) Streams.copy(istream, output, false);
      }
  
      /**
       * 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;
          try {
              // Discard all data up to the delimiter.
              discardBodyData();
  
              // Read boundary - if succeded, 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;
          }
      }
  
      /**
       * 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 first;
          int match = 0;
          int maxpos = tail - boundaryLength;
          for (first = head;
               (first <= maxpos) && (match != boundaryLength);
               first++) {
              first = findByte(boundary[0], first);
              if (first == -1 || (first > maxpos)) {
                  return -1;
              }
              for (match = 1; match < boundaryLength; match++) {
                  if (buffer[first + match] != boundary[match]) {
                      break;
                  }
              }
          }
          if (match == boundaryLength) {
              return first - 1;
          }
          return -1;
      }
  
      /**
       * Thrown to indicate that the input stream fails to follow the
       * required syntax.
       */
      public static class MalformedStreamException
              extends IOException {
  
          /**
           * 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 {
  
          /**
           * 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 org.apache.commons.fileupload.util.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.
           */
          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.
           */
          public int read() throws IOException {
              if (closed) {
                  throw new FileItemStream.ItemSkippedException();
              }
              if (available() == 0) {
                  if (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.
           */
          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.
           */
          public void close() throws IOException {
              if (closed) {
                  return;
              }
              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.
           */
          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;
              int bytesRead = input.read(buffer, pad, bufSize - pad);
              if (bytesRead == -1) {
                  // The last pad amount is left in the buffer.
                  // Boundary can't be in there so signal an error
                  // condition.
                  throw new MalformedStreamException(
                          "Stream ended unexpectedly");
              }
              // notifier.noteBytesRead(bytesRead);
              tail = pad + bytesRead;
              findSeparator();
              return available();
          }
  
          /**
           * Returns, whether the stream is closed.
           * @return True, if the stream is closed, otherwise false.
           */
          public boolean isClosed() {
              return closed;
          }
      }
  
      // ------------------------------------------------------ Debugging methods
      // These are the methods that were used to debug this stuff.
      /*
      // Dump data.
      protected void dump()
      {
      System.out.println("01234567890");
      byte[] temp = new byte[buffer.length];
      for(int i=0; i<buffer.length; i++)
      {
      if (buffer[i] == 0x0D || buffer[i] == 0x0A)
      {
      temp[i] = 0x21;
      }
      else
      {
      temp[i] = buffer[i];
      }
      }
      System.out.println(new String(temp));
      int i;
      for (i=0; i<head; i++)
      System.out.print(" ");
      System.out.println("h");
      for (i=0; i<tail; i++)
      System.out.print(" ");
      System.out.println("t");
      System.out.flush();
      }
      // Main routine, for testing purposes only.
      //
      // @param args A String[] with the command line arguments.
      // @throws Exception, a generic exception.
      public static void main( String[] args )
      throws Exception
      {
      File boundaryFile = new File("boundary.dat");
      int boundarySize = (int)boundaryFile.length();
      byte[] boundary = new byte[boundarySize];
      FileInputStream input = new FileInputStream(boundaryFile);
      input.read(boundary,0,boundarySize);
      input = new FileInputStream("multipart.dat");
      MultipartStream chunks = new MultipartStream(input, boundary);
      int i = 0;
      String header;
      OutputStream output;
      boolean nextChunk = chunks.skipPreamble();
      while (nextChunk)
      {
      header = chunks.readHeaders();
      System.out.println("!"+header+"!");
      System.out.println("wrote part"+i+".dat");
      output = new FileOutputStream("part"+(i++)+".dat");
      chunks.readBodyData(output);
      nextChunk = chunks.readBoundary();
      }
      }
       */
  }
  