Class XdrHttpDecodingStream


  • public class XdrHttpDecodingStream
    extends XdrDecodingStream
    The XdrHttpDecodingStream class provides the necessary functionality to XdrDecodingStream to receive XDR data through HTTP tunnels.

    Please note that there is currently no standard about how to tunnel XDR data over HTTP connections. There are a (quite a) few solutions out there, but they are more or less incompatible due to the lack of a RFC.

    This class is responsible solely for receiving ONC/RPC replies. The reply data is base64 encoded and embedded within an ordinary plain ASCII page, as is shown in this example.

         DEADBEEFDEADBEEFDEADBEEF...<CR><LF>
         B0D0EADSDEADBEEFB0D0EADS...<CR><LF>
         ...<CR><LF>
         DEADBE==<CR><LF>
     

    Parsing is minimalistic to make the whole sucker as fast as possible (not looking at Java's performance at all).

    Version:
    $Revision: 1.3 $ $Date: 2005/11/11 21:23:44 $ $State: Exp $ $Locker: $
    Author:
    Harald Albrecht
    • Field Detail

      • httpClient

        private HttpClientConnection httpClient
        Client HTTP tunnel to retrieve embedded XDR records from.
      • buffer

        private byte[] buffer
        The buffer which will be filled from the datagram socket and then be used to supply the information when decoding data.
      • asciiBuffer

        private byte[] asciiBuffer
        The buffer receiving base64 encoded plain ASCII data from a HTTP web server. This buffer is only used for immediate decoding of the binary data, which is then stored in the usual buffer field.
      • asciiBufferSize

        private int asciiBufferSize
        Size of buffer for receiving the base64 encoded plain ASCII data. The encoded data is then immediately decoded after recept into "ordinary" binary data, which is stored in the usual buffer field.
      • bufferIndex

        private int bufferIndex
        The read pointer is an index into the buffer.
      • bufferHighmark

        private int bufferHighmark
        Index of the last four byte word in the buffer, which has been read in from the datagram socket.
    • Constructor Detail

      • XdrHttpDecodingStream

        public XdrHttpDecodingStream​(HttpClientConnection httpClient)
        Constructs a new XdrHttpDecodingStream.
        Parameters:
        httpClient - HTTP client connection from which to read the encoded and embedded ONC/RPC reply message.
    • Method Detail

      • getSenderAddress

        public java.net.InetAddress getSenderAddress()
        Returns the Internet address of the sender of the current XDR data. This method should only be called after beginDecoding(), otherwise it might return stale information.
        Specified by:
        getSenderAddress in class XdrDecodingStream
        Returns:
        InetAddress of the sender of the current XDR data.
      • getSenderPort

        public int getSenderPort()
        Returns the port number of the sender of the current XDR data. This method should only be called after beginDecoding(), otherwise it might return stale information.
        Specified by:
        getSenderPort in class XdrDecodingStream
        Returns:
        Port number of the sender of the current XDR data.
      • beginDecoding

        public void beginDecoding()
                           throws OncRpcException,
                                  java.io.IOException
        Initiates decoding of the next XDR record. For HTTP-based XDR we just read the content delivered with the answer to the POST command.
        Specified by:
        beginDecoding in class XdrDecodingStream
        Throws:
        OncRpcException - if an ONC/RPC error occurs.
        java.io.IOException - if an I/O error occurs.
      • endDecoding

        public void endDecoding()
                         throws OncRpcException,
                                java.io.IOException
        End decoding of the current XDR record. The general contract of endDecoding is that calling it is an indication that the current record is no more interesting to the caller and any allocated data for this record can be freed.

        To help the HTTP connection keeping alive, we swallow all data until we reach the end. If this is not possible, either because the server indicated that it can not keep the connection open, the content length was unknown in advance, or we got an I/O exception, we close the connection.

        Overrides:
        endDecoding in class XdrDecodingStream
        Throws:
        OncRpcException - if an ONC/RPC error occurs.
        java.io.IOException - if an I/O error occurs.
      • close

        public void close()
                   throws OncRpcException,
                          java.io.IOException
        Closes this decoding XDR stream and releases any system resources associated with this stream. A closed XDR stream cannot perform decoding operations and cannot be reopened.

        This implementation frees the allocated buffer but does not close the associated datagram socket. It only throws away the reference to this socket.

        Overrides:
        close in class XdrDecodingStream
        Throws:
        OncRpcException - if an ONC/RPC error occurs.
        java.io.IOException - if an I/O error occurs.
      • fill

        private void fill()
                   throws OncRpcException,
                          java.io.IOException
        Receives more encoded data over the HTTP connection and decodes it into octets, making them available through the buffer field.
        Throws:
        OncRpcException
        java.io.IOException
      • xdrDecodeInt

        public int xdrDecodeInt()
                         throws OncRpcException,
                                java.io.IOException
        Decodes (aka "deserializes") a "XDR int" value received from a XDR stream. A XDR int is 32 bits wide -- the same width Java's "int" data type has.
        Specified by:
        xdrDecodeInt in class XdrDecodingStream
        Returns:
        The decoded int value.
        Throws:
        OncRpcException - if an ONC/RPC error occurs.
        java.io.IOException - if an I/O error occurs.
      • xdrDecodeOpaque

        public byte[] xdrDecodeOpaque​(int length)
                               throws OncRpcException,
                                      java.io.IOException
        Decodes (aka "deserializes") an opaque value, which is nothing more than a series of octets (or 8 bits wide bytes). Because the length of the opaque value is given, we don't need to retrieve it from the XDR stream. This is different from xdrDecodeOpaque(byte[], int, int) where first the length of the opaque value is retrieved from the XDR stream.
        Specified by:
        xdrDecodeOpaque in class XdrDecodingStream
        Parameters:
        length - Length of opaque data to decode.
        Returns:
        Opaque data as a byte vector.
        Throws:
        OncRpcException - if an ONC/RPC error occurs.
        java.io.IOException - if an I/O error occurs.
      • xdrDecodeOpaque

        public void xdrDecodeOpaque​(byte[] opaque,
                                    int offset,
                                    int length)
                             throws OncRpcException,
                                    java.io.IOException
        Decodes (aka "deserializes") a XDR opaque value, which is represented by a vector of byte values, and starts at offset with a length of length. Only the opaque value is decoded, so the caller has to know how long the opaque value will be. The decoded data is always padded to be a multiple of four (because that's what the sender does).
        Specified by:
        xdrDecodeOpaque in class XdrDecodingStream
        Parameters:
        opaque - Byte vector which will receive the decoded opaque value.
        offset - Start offset in the byte vector.
        length - the number of bytes to decode.
        Throws:
        OncRpcException - if an ONC/RPC error occurs.
        java.io.IOException - if an I/O error occurs.