1 *******************************

     2 * Ideas on Data Serialization *

     3 *******************************

     4 

     5 1. Overview of XDR

     6 (1) What are the features of XDR

     7     a. Used in SunRPC

     8     b. Symmetric conversion

     9     c. No tags

    10     d. Primitive data types:

    11        integers, floating point numbers, enumerations and booleans

    12     e. Constructed data types:

    13        strings, arrays, opaque data, unions, pointers

    14 

    15 (2) How to use XDR for data serialization

    16     a. Don't have to use RPCGEN 

    17     b. Use XDR library routines plus programmer-supplied conversion routines

    18     c. XDR streams: memory streams, I/O streams, record streams

    19     d. Example of memory streams:

    20        xdrmem_create (xdrs, buf, BUFSIZE, XDR_ENCODE);

    21        xdr_int (xdrs, &i);

    22        xdr_destroy (xdrs);

    23     e. Construct conversion routines for more complicated data types 

    24 

    25 2. Overview of NDR

    26 (1) What are the features of NDR

    27     a. Used in DCE RPC

    28     b. Asymmetric conversion

    29     c. Architecture tag to specify:

    30        big endian or little endian for integer representation

    31        ASCII or EBCDIC for character representation

    32        IEEE or IBM or CRAY or VAX for floating-point representation

    33     d. Primitive data types:

    34        booleans, integers and enumerated types, floating-point numbers, uninterpreted octets 

    35     e. Constructed data types:

    36        arrays, strings, structures, unions, pipes, pointers 

    37 

    38 (2) How to use NDR for data serialization

    39     a. Use IDL encoding services stubs which are generated by IDL compiler

    40        with Interface Definition File and Attribute Configuration File

    41     b. Similar to XDR libray routines, but can't be provided by programmer

    42 

    43 3. Comparison of XDR and NDR

    44 (1) Symetric v. Asymetric conversion

    45     a. Asymetric conversion allows more flexibility

    46     b. Symmetric conversion doesn't require the architecture tag

    47 

    48 (2) NDR supports more data types

    49     a. Conformanent arrays, varying arrays, conformanent-varying arrays

    50     b. Array of strings, structures containing arrays

    51     c. Pipes

    52 

    53 (3) Availability

    54     a. XDR library is widely available

    55     b. DCE IDL compiler for NDR is not