Interface: tos.interfaces.Resource

interface Resource

Please refer to TEP 108 for more information about this interface and its intended use.

The Resource interface can be used to gain access to shared resources. It is always offered as a parameterized interface, and its users gain access to the resource through some predefined arbitration policy.

Author:
Kevin Klues (klueska@cs.wustl.edu)
Version:
$Revision: 1.5 $
Date:
$Date: 2007/04/15 20:05:03 $

Commands
command error_t immediateRequest() Request immediate access to a shared resource.
command bool isOwner() Check if the user of this interface is the current owner of the Resource
command error_t release() Release a shared resource you previously acquired.
command error_t request() Request access to a shared resource.

Events
event void granted() You are now in control of the resource.

Commands - Details

immediateRequest

command error_t immediateRequest()

Request immediate access to a shared resource. You must call release() when you are done with it.

Returns:
SUCCESS When a request has been accepted.
FAIL The request cannot be fulfilled

isOwner

command bool isOwner()

Check if the user of this interface is the current owner of the Resource

Returns:
TRUE It is the owner
FALSE It is not the owner

release

command error_t release()

Release a shared resource you previously acquired.

Returns:
SUCCESS The resource has been released
FAIL You tried to release but you are not the owner of the resource
Note:
This command should never be called between putting in a request and waiting for a granted event. Doing so will result in a potential race condition. There are ways to guarantee that no race will occur, but they are clumsy and overly complicated. Since it doesn't logically make since to be calling release before receiving a granted event, we have opted to keep thing simple and warn you about the potential race.

request

command error_t request()

Request access to a shared resource. You must call release() when you are done with it.

Returns:
SUCCESS When a request has been accepted. The granted() event will be signaled once you have control of the resource.
EBUSY You have already requested this resource and a granted event is pending

Events - Details

granted

event void granted()

You are now in control of the resource.