/*
 * 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.tomcat.util.http.fileupload;

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

import org.apache.tomcat.util.http.fileupload.impl.FileUploadIOException;
import org.apache.tomcat.util.http.fileupload.util.Closeable;
import org.apache.tomcat.util.http.fileupload.util.Streams;


 Low level API for processing file uploads.
 This class can be used to process data streams conforming to MIME
'multipart' format as defined in
RFC 1867. Arbitrarily
large amounts of data in the stream can be processed under constant
memory usage.
 The format of the stream is defined in the following way:


  multipart-body := preamble 1*encapsulation close-delimiter epilogue

  encapsulation := delimiter body CRLF

  delimiter := "--" boundary CRLF

  close-delimiter := "--" boundary "--"

  preamble := <ignore>

  epilogue := <ignore>

  body := header-part CRLF body-part

  header-part := 1*header CRLF

  header := header-name ":" header-value

  header-name := <printable ascii characters except ":">

  header-value := <any ascii characters except CR & LF>

  body-data := <arbitrary data>


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 required to have a boundary token of the same length as the parent stream (see setBoundary(byte[])). 
Here is an example of usage of this class.

  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
  }

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

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

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

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

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

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

        
Called to indicate that bytes have been read.
Params:
pBytes – Number of bytes, which have been read./**
         * 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.
/**
         * Called to indicate, that a new file item has been detected.
         */
        public void noteItem() {
            ++items;
            notifyListener();
        }

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

    }

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

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

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

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

    
The maximum length of header-part that will be processed (10 kilobytes = 10240 bytes.). /**
     * The maximum length of {@code header-part} 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.
/**
     * 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 header-part (CRLFCRLF). /**
     * A byte sequence that marks the end of {@code header-part}
     * ({@code CRLFCRLF}).
     */
    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 (CRLF). /**
     * A byte sequence that that follows a delimiter that will be
     * followed by an encapsulation ({@code CRLF}).
     */
    protected static final byte[] FIELD_SEPARATOR = {CR, LF};

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

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

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

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

    
The length of the boundary token plus the leading CRLF--. /**
     * The length of the boundary token plus the leading {@code CRLF--}.
     */
    private int boundaryLength;

    
The amount of data, in bytes, that must be kept in the buffer in order
to detect delimiters reliably.
/**
     * 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.
/**
     * The byte sequence that partitions the stream.
     */
    private final byte[] boundary;

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

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

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

    
The index of first valid character in the buffer.


0 <= head < bufSize
/**
     * 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.


0 <= tail <= bufSize
/**
     * 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.
/**
     * The content encoding to use when reading headers.
     */
    private String headerEncoding;

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

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

    
 Constructs a MultipartStream with a custom size buffer. 
 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.
Params:
input –  The InputStream to serve as a data source.
boundary – The token used for dividing the stream into encapsulations.
bufSize –  The size of the buffer to be used, in bytes.
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/**
     * <p> Constructs a {@code MultipartStream} 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} to serve as a data source.
     * @param boundary The token used for dividing the stream into
     *                 {@code encapsulations}.
     * @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;
    }

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

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

    
Retrieves the character encoding used when reading the headers of an individual part. When not specified, or null, the platform default encoding is used. 
Returns:
The encoding used to read part headers./**
     * Retrieves the character encoding used when reading the headers of an
     * individual part. When not specified, or {@code null}, 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 null, the platform default encoding is used. 
Params:
encoding – The encoding used to read part headers./**
     * Specifies the character encoding to be used when reading the headers of
     * individual parts. When not specified, or {@code null}, 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 buffer, and refills it as necessary. 
Throws:
IOException – if there is no more data available.
Returns:
The next byte from the input stream./**
     * Reads a byte from the {@code buffer}, 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 boundary token, and checks whether more encapsulations are contained in the stream. 
Throws:
FileUploadIOException – if the bytes read from the stream exceeded the size limits
MalformedStreamException – if the stream ends unexpectedly or
                                 fails to follow required syntax.
Returns:
true if there are more encapsulations in this stream; false otherwise./**
     * Skips a {@code boundary} token, and checks whether more
     * {@code encapsulations} are contained in the stream.
     *
     * @return {@code true} if there are more encapsulations in
     *         this stream; {@code false} 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;
    }

    
Changes the boundary token used for partitioning the stream.
This method allows single pass processing of nested multipart
streams.
The boundary token of the nested stream is required to be of the same length as the boundary token in parent stream. 
Restoring the parent stream boundary token after processing of a
nested stream is left to the application.
Params:
boundary – The boundary to be used for parsing of the nested
                stream.
Throws:
IllegalBoundaryException – if the boundary has a different length than the one being currently parsed./**
     * <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}
     * 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}
     *                                  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.
/**
     * 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++;
            }
        }
    }

    
Reads the header-part of the current encapsulation. 
Headers are returned verbatim to the input stream, including the trailing CRLF marker. Parsing is left to the application. 
TODO allow limiting maximum header size to
protect against abuse.
Throws:
FileUploadIOException – if the bytes read from the stream exceeded the size limits.
MalformedStreamException – if the stream ends unexpectedly.
Returns:
The header-part of the current encapsulation./**
     * <p>Reads the {@code header-part} of the current
     * {@code encapsulation}.
     *
     * <p>Headers are returned verbatim to the input stream, including the
     * trailing {@code CRLF} 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} 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(String.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;
    }

    
Reads body-data from the current encapsulation and writes its contents into the output Stream. 
Arbitrary large amounts of data can be processed by this method using a constant size buffer. (see constructor). 
Params:
output – The Stream to write data into. May be null, in which case this method is equivalent to discardBodyData().
Throws:
MalformedStreamException – if the stream ends unexpectedly.
IOException –              if an i/o error occurs.
Returns:
the amount of data written./**
     * <p>Reads {@code body-data} from the current
     * {@code encapsulation} and writes its contents into the
     * output {@code Stream}.
     *
     * <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} 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 ItemInputStream. 
Returns:
A new instance of ItemInputStream./**
     * Creates a new {@link ItemInputStream}.
     * @return A new instance of {@link ItemInputStream}.
     */
    public ItemInputStream newInputStream() {
        return new ItemInputStream();
    }

    
 Reads body-data from the current encapsulation and discards it. 
Use this method to skip encapsulations you don't need or don't
understand.
Throws:
MalformedStreamException – if the stream ends unexpectedly.
IOException –              if an i/o error occurs.
Returns:
The amount of data discarded./**
     * <p> Reads {@code body-data} from the current
     * {@code encapsulation} 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 encapsulation. 
Throws:
IOException – if an i/o error occurs.
Returns:
true if an encapsulation was found in the stream./**
     * Finds the beginning of the first {@code encapsulation}.
     *
     * @return {@code true} if an {@code encapsulation} was found in
     *         the stream.
     *
     * @throws IOException if an i/o error occurs.
     */
    public boolean skipPreamble() throws IOException {
        // First delimiter may be not preceded 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 count first bytes in the arrays a and b. 
Params:
a –     The first array to compare.
b –     The second array to compare.
count – How many bytes should be compared.
Returns:
true if count first bytes in arrays a and b are equal./**
     * Compares {@code count} first bytes in the arrays
     * {@code a} and {@code b}.
     *
     * @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} if {@code count} first bytes in arrays
     *         {@code a} and {@code b} 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 buffer, starting at the specified position. 
Params:
value – The value to find.
pos –   The starting position for searching.
Returns:
The position of byte found, counting from beginning of the buffer, or -1 if not found./**
     * Searches for a byte of specified value in the {@code buffer},
     * starting at the specified {@code position}.
     *
     * @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}, or {@code -1} 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 boundary in the buffer region delimited by head and tail. 
Returns:
The position of the boundary found, counting from the beginning of the buffer, or -1 if not found./**
     * Searches for the {@code boundary} in the {@code buffer}
     * region delimited by {@code head} and {@code tail}.
     *
     * @return The position of the boundary found, counting from the
     *         beginning of the {@code buffer}, or {@code -1} 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.
/**
     * 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.
/**
         * The UID to use when serializing this instance.
         */
        private static final long serialVersionUID = 6466926458059796677L;

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

        
Constructs an MalformedStreamException with the specified detail message. 
Params:
message – The detail message./**
         * Constructs an {@code MalformedStreamException} 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.
/**
     * Thrown upon attempt of setting an invalid boundary token.
     */
    public static class IllegalBoundaryException extends IOException {

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

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

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

    }

    
An InputStream for reading an items contents. /**
     * 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.
/**
         * 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.
/**
         * 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.
/**
         * The current offset in the buffer.
         */
        private int pos;

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

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

        
Called for finding the separator.
/**
         * 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.
Returns:
Number of bytes, which have been read so far./**
         * 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.
Returns:
Number of bytes in the buffer./**
         * 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.
/**
         * Offset when converting negative bytes to integers.
         */
        private static final int BYTE_POSITIVE_OFFSET = 256;

        
Returns the next byte in the stream.
Throws:
IOException – An I/O error occurred.
Returns:
The next byte in the stream, as a non-negative
  integer, or -1 for EOF./**
         * 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.
Params:
b – The destination buffer, where to write to.
off – Offset of the first byte in the buffer.
len – Maximum number of bytes to read.
Throws:
IOException – An I/O error occurred.
Returns:
Number of bytes, which have been actually read,
  or -1 for EOF./**
         * 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./**
         * Closes the input stream.
         *
         * @throws IOException An I/O error occurred.
         */
        @Override
        public void close() throws IOException {
            close(false);
        }

        
Closes the input stream.
Params:
pCloseUnderlying – Whether to close the underlying stream
  (hard close)
Throws:
IOException – An I/O error occurred./**
         * 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.
Params:
bytes – Number of bytes to skip.
Throws:
IOException – An I/O error occurred.
Returns:
The number of bytes, which have actually been
  skipped./**
         * 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.
Throws:
IOException – An I/O error occurred.
Returns:
Number of available bytes/**
         * 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.
Returns:
True, if the stream is closed, otherwise false./**
         * Returns, whether the stream is closed.
         *
         * @return True, if the stream is closed, otherwise false.
         */
        @Override
        public boolean isClosed() {
            return closed;
        }

    }

}