Date: Fri, 3 Mar 95 17:39:00 PST
From: wmb@FirmWorks.COM (Mitch Bradley)
Subject: Item #248: Extension to Core - size method

P1275 Open Firmware Working Group Proposal -- Proposal #248 Ver 0

Title:		Extension to Core - "size" method

Author:		Mitch Bradley

Date:		March 3, 1995

Ed/Tech:	Technical

Synopsis:	Add "size" method to various device classes

Doc & Version:	None

Problem:

For packages that refer to a mass-storage device or to a portion
(e.g. a partition or a file) of that device, some clients (e.g. an ARC
veneer) need to know the size of the entity.

Proposal:	

In a future standard describing extension to the core standard, define a
new standard method named "size", which can apply to any package for which
size information is relevant.  The "size" method would be required for
future packages of the device classes "block" and "byte", for the related
support package "disk-label", and for future support packages that
interpose on those packages to provide file services.  In general, a "size"
method is likely to be appropriate for any package that has a "seek" method.
(The converse is not necessarily true; for example a sequential-access
device might have a well-defined size, but not allow seeking.)

Also define a new standard method "#blocks" for "block" and "byte" device
classes.

The "disk-label" standard support package and packages of device type "block"
and "byte" shall implement the following method:

size		( -- d )						M

    Return the size of the device in bytes.

    Return, as a double number "d", the number of bytes of storage
    associated with the device or instance.  If the size cannot be
    determined, return the double number -1.


Packages of device type "block" and "byte" shall implement the following
method:

#blocks		( -- u )						M

    Return the size of the device in blocks.

    Return, as an unsigned number "u", the number of blocks of storage
    associated with the device or instance, where a "block" is a unit
    of storage consisting of the number of bytes returned by the package's
    "block-size" method.  If the size cannot be determined, or if the
    number of blocks exceeds the range of an unsigned number, return
    the maximum unsigned integer (which, because of Open Firmware's
    assumption of two's complement arithmetic) is equivalent to the
    signed number -1).

[ P1275 Item #248 -- Received: Fri Mar  3 17:42:13 PST 1995 ]