Browse Prior Art Database

Handling Structure Alignment in a Message-Passing System

IP.com Disclosure Number: IPCOM000114596D
Original Publication Date: 1995-Jan-01
Included in the Prior Art Database: 2005-Mar-29
Document File: 4 page(s) / 142K

Publishing Venue

IBM

Related People

Tureman, PG: AUTHOR

Abstract

Disclosed is a method for aligning message structure between sending and receiving processors of a distributed heterogeneous messaging system.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 40% of the total text.

Handling Structure Alignment in a Message-Passing System

      Disclosed is a method for aligning message structure between
sending and receiving processors of a distributed heterogeneous
messaging system.

      In a message-passing network composed of processors of
differing architectures, different processors may have conflicting
requirements for the alignment of fields within the message.
Resolving this conflict imposes an extra burden on the designer of
the application, and an unwise initial choice of alignment rule can
make it difficult to port the application to a new processor
architecture.  Furthermore, the requirement to add padding bytes
between the fields of a message to align them correctly can impose
additional costs when the message is sent over transaction processing
lines.

      Provided is a solution to this problem, in which messages may
be sent across network from a sending program in any one of a variety
of alignment rules, and then the messages are presented to the
receiving program in the alignment rule of that program's choice.
Communication facilities within the network take responsibility for
converting the messages between the alignment rules of the sending
and receiving programs.

      Optionally, the network's communication facilities may change
the alignment rule of a message before transmitting it over
transaction processing link, to minimise the number of bytes
transmitted.  There is no need to change the rule again at the
receiving end of the link, but only when it is delivered to the
receiving program,and then only if requested.

      In a message-queuing system, in which application programs
communicate asynchronously by the sending program placing a message
on a queue for the receiving program to take from the queue when the
receiving program is ready, a queue may hold messages in a variety of
alignment rules.  The alignment rule is preferably only changed to
that
required by the receiving program when it is obtained from the queue.

IMPLEMENTATION

      Sending - When a message is sent the sending program attaches
to it an indication of the alignment rule used.  In a preferred
implementation of the invention, the network's communications
facilities will also handle the conversion of the message data
between different representations, and the indication of the
alignment rule used will be passed by the application in a similar
manner to information such as the integer representation (e.g., big-
or little-endian) of the message data.  For example, the indication
of alignment rule may be via a parameter on the "put message"
operation.  Any scheme that supports conversion of the message data
must also convey an indication of the order and types of the fields
making up the message, including the sizes of each field.  This
information is also needed by this invention.

      The most convenient alignment rule to use will depend on the
processor architecture, the programming...