Browse Prior Art Database

Extended Iliffe Vectors

IP.com Disclosure Number: IPCOM000114515D
Original Publication Date: 1994-Sep-01
Included in the Prior Art Database: 2005-Mar-28
Document File: 2 page(s) / 44K

Publishing Venue

IBM

Related People

Normington, G: AUTHOR

Abstract

An Iliffe vector consists of an array of address and length pairs. Each pair describes a block of bytes starting at the specified address of the specified length (in bytes).

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 68% of the total text.

Extended Iliffe Vectors

      An Iliffe vector consists of an array of address and length
pairs.  Each pair describes a block of bytes starting at the
specified address of the specified length (in bytes).

      The last entry in the vector is flagged.  In some machine
architectures, it is possible to build the flag into the top bit of
the address.

      A problem arises when it is required to prepend (i.e.,
concatenate to the front) data to an existing Iliffe vector.

      This is often necessary when tagging data to describe its
source.  For example, in a layered software system, each layer might
need to add tag data relative to that layer.   Each time tag data is
added, the corresponding Iliffe vector needs prepending.

      One approach to this problem has involved allocating storage to
contain a larger Iliffe vector, copying the original Iliffe vector
(using a loop in order to detect the end of the vector), and setting
an extra pair to describe the prepended data.

      After the larger vector is finished with, it needs to be
deallocated.

      This process is inefficient.   Also, if the number of pairs in
the original Iliffe vector is unknown, e.g., because its source is an
external piece of software, then the larger Iliffe vector must be
dynamically allocated which is also inefficient.

      The solution is to extend an Iliffe vector to consist of an
array of address and length pairs, as before, followed by an extra
pair. ...