/*
    * 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 & 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>
   *
   * @version $Id: MultipartStream.java 1456933 2013-03-15 12:36:11Z markt $
   */
  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 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 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[],
      * org.apache.commons.fileupload.MultipartStream.ProgressNotifier)},
      * or {@link #MultipartStream(InputStream, byte[], int,
      * org.apache.commons.fileupload.MultipartStream.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.
      *
      * @see #MultipartStream(InputStream, byte[],
      *   MultipartStream.ProgressNotifier)
      * @deprecated 1.2.1 Use {@link #MultipartStream(InputStream, byte[], int,
      *  org.apache.commons.fileupload.MultipartStream.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.
      *
      * @see #MultipartStream(InputStream, byte[],
      *     MultipartStream.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 trailing CR/LF from
         // body-data tokens.
         this.boundary = new byte[boundary.length + BOUNDARY_PREFIX.length];
         this.boundaryLength = boundary.length + BOUNDARY_PREFIX.length;
         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);
 
         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,
      *     MultipartStream.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[],
      *  MultipartStream.ProgressNotifier)}.
      * @see #MultipartStream(InputStream, byte[], int,
      *  MultipartStream.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 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 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)",
                                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 {
         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 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;
         }
     }
 
     /**
      * 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 {
 
         /**
          * 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.
          */
         public boolean isClosed() {
             return closed;
         }
 
     }
 
 }