Browse Prior Art Database

Symmetrical Command Structure for High Speed Forward and Backward Parsing

IP.com Disclosure Number: IPCOM000122079D
Original Publication Date: 1991-Oct-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 1 page(s) / 57K

Publishing Venue

IBM

Related People

Bolstad, DO: AUTHOR [+3]

Abstract

A structure to allow fast forward and backward parsing of objects in an object data stream is disclosed. Hence, this disclosure will aid in providing high speed object editors and display utilities, and aid in locating a data object's context in the middle of a data stream.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 66% of the total text.

Symmetrical Command Structure for High Speed Forward and Backward
Parsing

      A structure to allow fast forward and backward parsing of
objects in an object data stream is disclosed.  Hence, this
disclosure will aid in providing high speed object editors and
display utilities, and aid in locating a data object's context in the
middle of a data stream.

      Typically, data streams contain variable length structures or
objects within them and are parsed by the receiver from front to
back.  For many applications, this may be suitable, but for many
others, scanning backwards through the data stream may be
advantageous.  But, because most data streams are designed for
forward parsing, backward parsing may be cumbersome or impossible.

      The data stream described has the potential of several variable
length objects within it.  Each of these objects can easily be found
within the data stream, decoded, and have other characteristics
associated with it.  Parsing these objects in the forward direction
from a starting point is not very difficult because object boundaries
are known; however, parsing backwards can be difficult if the object
boundaries cannot be scanned for in the backwards direction. In our
implementation, the start of an object within a data stream is marked
by a byte of 0.  This is then immediately followed by a length byte
and then a command byte for a total of 256 possible object types.
However, within the object itself, more bytes of 0 can...