Method and system for allowing a single-user application executing in a multi-user environment to create objects having both user-global and system global visibility

• US 6,023,721 A
• Filed: 05/14/1997
• Issued: 02/08/2000
• Est. Priority Date: 05/14/1997
• Status: Expired due to Term

• Current Assignee: Citrix Systems, Inc. (Cloud Software Group)
• Original Assignee: Citrix Systems, Inc. (Cloud Software Group)
• Inventors: Cummings, Christopher R.
• Primary Examiner(s): Maung, Zarni
• Assistant Examiner(s): Barot, Bharat
• Application Number:
  US08/855,901
• Time in Patent Office: 1,000 Days
• Field of Search: 395/200.3-200.33, 395/200.57-200.59, 395/674, 395/676-677, 395/680, 395/682-684, 709/200-203, 709/227-229, 709/100-108, 709/302-304, 707/8-10
• US Class Current: 709/201
• CPC Class Codes: G06F 9/4843 by program, e.g. task dispatcher, supervisor, operating system
• CPC Class Codes: H04L 67/00 Network arrangements or protocols for supporting network services or applications user-to-user messaging H04L51/00; network arrangements, protocols or services for supporting real-time applications in data packet communications networks H04L65/00
• CPC Class Codes: H04L 69/329 in the application layer [OSI layer 7]
• CPC Class Codes: H04L 9/40 Network security protocols
• CPC Class Codes: Y10S 707/99938 Concurrency, e.g. lock management in shared database

Abstract

A method and system for allowing a single-user application executing in a multi-user environment to create objects having both user-global and system-global visibility begins by intercepting an API function call to create or modify a named object. A set of rules is consulted which may explicitly or implicitly define the visibility to be associated with the named object. If a rule is found for the named object it is used to define the visibility level for that object. If, however, a rule is not encountered in the rule set, then the visibility of a named object is set according to a default procedure.

Claims

1. A method for allowing an unmodified single-user application program to operate in a multi-user operating system environment and to create both user-global objects and system-global objects, the method comprising the steps of:

(a) intercepting a request from the unmodified single-user application program directed at a default function of the operating system to instantiate an object, the interception being effected by directing the request to an alternate function, the alternate function replacing the default function and having the same name and being called in the same way as the default function;

(b) determining a visibility level for the object;

(c) instantiating the object; and

(d) assigning the determined visibility level to the instantiated object.

2. The method of claim 1 wherein step (b) further comprises:

(b-a) accessing a data table including a mapping between objects and visibility levels;

(b-b) locating an entry corresponding to the object; and

(b-c) determining from the located entry a visibility level for the object.

3. The method of claim 2 wherein step (b-a) comprises accessing a registry data structure including a mapping between objects and visibility levels.

4. The method of claim 1 wherein step (d) further comprises assigning the determined visibility level to the instantiated object by setting an attribute bit associated with the instantiated object.

5. The method of claim 1 wherein step (d) further comprises assigning the determined visibility level to the instantiated object by assigning a level to the instantiated object indicative of the determined visibility level.

6. The method of claim 1, wherein the alternate fuinction accepts only a subset of parameters normally accepted by the default function of the operating system.

7. The method of claim 1, wherein the alternate function of step (a) is formed by replacing a portion of the default function of the operating system by inserting additional code into the default function.

8. A method for allowing an unmodified single-user application program to operate in a multi-user operating system environment and to create both user-global objects and system-global objects, the method comprising the steps of:

(a) intercepting a request from the unmodified single-user application program directed at a default function of the operating system to instantiate an object, the interception being effected by directing the request to an alternate function, the alternate function replacing the default function and having the same name and being called in the same way as the default function;

(b) triggering an interrupt in response to the intercepted request that executes instructions in a hardware device coupled to the unmodified single-user application program,

(c) determining a visibility level for the object;

(d) instantiating the object in response to the instructions executed by the hardware device coupled to the unmodified single-user application program; and

(e) assigning the determined visibility level to the instantiated object.

9. A method for overriding a default operation of a multi-user operating system when executing a single-user application program under control of the multi-user operating system, comprising the steps of:

a) intercepting an application program interface call directed to a default function of the multi-user operating system for instantiating a named object associated with the execution of the single-user application program prior to instantiating the named object by the multi-user operating system, the interception being effected by directing the application program interface call to an alternate function, wherein the alternate function replaces the default function and has the same name and is called in the same way as the default function of the multi-user operating system;

b) accessing, via the alternate function of the multi-user operating system, a set of rules associated with the single-user application program to determine a visibility level for the named object; and

c) instantiating the named object in accordance with the set of rules, wherein steps a)-c) are performed without modifying the single-user application program.

10. The method of claim 9 further comprising the step of forming the alternate function by replacing a portion of the code in the default function.

11. An article of manufacture having computer-readable program means for allowing an unmodified single-user application program to operate in a multi-user operating system environment and to create both user-global objects and system-global objects embodied thereon, comprising:

(a) computer-readable program means for intercepting a request directed at a default function of the operating system to instantiate an object from the unmodified single-user application program the interception being effected by directing the request to an alternate function, the alternate function replacing the default function and having the same name and being called in the same way as the default function;

(b) computer-readable program means for determining a visibility level for the object;

(c) computer-readable program means for instantiating the object; and

(d) computer-readable program means for assigning the determined visibility level to the instantiated object.

12. The article of claim 11 further comprising:

(b-a) computer-readable program means for accessing a data table including a mapping between objects and visibility levels;

(b-b) computer-readable program means for locating an entry corresponding to the object; and

(b-c) computer-readable program means for determining from the located entry a visibility level for the object.

13. The article of claim 11 further comprising computer-readable program means for accessing a registry data structure including a mapping between objects and visibility levels.

14. The article of claim 11 further comprising computer-readable program means for assigning the determined visibility level to the instantiated object by setting an attribute bit associated with the instantiated object.

15. The article of claim 11 further comprising computer-readable program means for assigning the determined visibility level to the instantiated object by assigning a level to the instantiated object indicative of the determined visibility level.