multipartstream.java

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     * 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) constructor}).
     *
     * @param output The <code>Stream</code> to write data into.
     *
     * @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 {
        boolean done = false;
        int pad;
        int pos;
        int bytesRead;
        int total = 0;
        while (!done) {
            // Is boundary token present somewere in the buffer?
            pos = findSeparator();
            if (pos != -1) {
                // Write the rest of the data before the boundary.
                output.write(buffer, head, pos - head);
                total += pos - head;
                head = pos;
                done = true;
            } else {
                // Determine how much data should be kept in the
                // buffer.
                if (tail - head > keepRegion) {
                    pad = keepRegion;
                } else {
                    pad = tail - head;
                }
                // Write out the data belonging to the body-data.
                output.write(buffer, head, tail - head - pad);

                // 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;
                bytesRead = input.read(buffer, pad, bufSize - pad);

                // [pprrrrrrr]
                if (bytesRead != -1) {
                    tail = pad + bytesRead;
                } else {
                    // The last pad amount is left in the buffer.
                    // Boundary can't be in there so write out the
                    // data you have and signal an error condition.
                    output.write(buffer, 0, pad);
                    output.flush();
                    total += pad;
                    throw new MalformedStreamException(
                            "Stream ended unexpectedly");
                }
            }
        }
        output.flush();
        return total;
    }


    /**
     * <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 {
        boolean done = false;
        int pad;
        int pos;
        int bytesRead;
        int total = 0;
        while (!done) {
            // Is boundary token present somewere in the buffer?
            pos = findSeparator();
            if (pos != -1) {
                // Write the rest of the data before the boundary.
                total += pos - head;
                head = pos;
                done = true;
            } else {
                // Determine how much data should be kept in the
                // buffer.
                if (tail - head > keepRegion) {
                    pad = keepRegion;
                } else {
                    pad = tail - head;
                }
                total += tail - head - pad;

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

                // Refill buffer with new data.
                head = 0;
                bytesRead = input.read(buffer, pad, bufSize - pad);

                // [pprrrrrrr]
                if (bytesRead != -1) {
                    tail = pad + bytesRead;
                } else {
                    // The last pad amount is left in the buffer.
                    // Boundary can't be in there so signal an error
                    // condition.
                    total += pad;
                    throw new MalformedStreamException(
                            "Stream ended unexpectedly");
                }
            }
        }
        return total;
    }


    /**
     * 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;
    }

    /**
     * Returns a string representation of this object.
     *
     * @return The string representation of this object.
     */
    public String toString() {
        StringBuffer sbTemp = new StringBuffer();
        sbTemp.append("boundary='");
        sbTemp.append(String.valueOf(boundary));
        sbTemp.append("'\nbufSize=");
        sbTemp.append(bufSize);
        return sbTemp.toString();
    }

    /**
     * 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);
        }
    }


    // ------------------------------------------------------ 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();
        }
    }

    */
}