Method and apparatus for using a shared library mechanism to facilitate sharing of metadata

• US 6,876,996 B2
• Filed: 03/19/2002
• Issued: 04/05/2005
• Est. Priority Date: 11/14/2001
• Status: Active Grant

• Current Assignee: Oracle America, Inc. (Oracle Corporation)
• Original Assignee: Sun Microsystems Incorporated (Oracle Corporation)
• Inventors: Daynes, Laurent P., Czajkowski, Grzegorz J.
• Primary Examiner(s): Corrielus, Jean M.
• Application Number:
  US10/102,318
• Publication Number:
  US 20030093401A1
• Time in Patent Office: 1,113 Days
• Field of Search: 717/147, 717/136, 717/156, 717/178, 717/144, 717/130, 717/139, 717/148, 717/164, 717/152, 707/1, 707/103, 707/200, 707/2, 707/101, 707/10, 707/104.1, 707/8, 709/229, 711/211, 711/213
• US Class Current: 1/1
• CPC Class Codes: G06F 9/44521 Dynamic linking or loading; Link editing at or after load time, e.g. Java class loading
• CPC Class Codes: G06F 9/45504 Abstract machines for programme code execution, e.g. Java virtual machine [JVM], interpreters, emulators
• CPC Class Codes: Y10S 707/955 Object-oriented
• CPC Class Codes: Y10S 707/99932 Access augmentation or optimizing
• CPC Class Codes: Y10S 707/99942 Manipulating data structure, e.g. compression, compaction, compilation

Abstract

One embodiment of the present invention provides a system that uses a shared library to facilitate sharing objects containing metadata. During operation, the system receives identifiers for a set of objects to be included in the shared library. Next, the system generates a shared library containing the set of objects. In doing so, the system configures a symbol table within the shared library to include an identifier for each object. The system then installs the shared library in a file system, and configures the file system so that the shared library file can be accessed through a set of symbolic names, wherein each object is associated with a different symbolic name. This allows each object in the shared library to be referenced through its own symbolic name. Note that the present invention uses the shared library mechanism in a manner which differs from its typical use (sharing compiled, executable code). In order to avoid generating a shared library for each metadata object, the present invention places many such items together in one shared library. The names of these metadata objects are subsequently used as symbolic names of the file containing the shared library.

Claims

1. A method that uses a shared library mechanism to facilitate sharing objects, comprising:

receiving indentifiers for a set of objects to be included in a shared library, wherein an object in the set objects contains dynamically compiled code to be shared between multiple instances of a language run-time system;

generating the shared library containing the set of objects;

configuring a symbol table within the shared library to include an indentifier for each object in the set of objects;

installing the shared library in a file system; and

configuring the file system so that the shared library can be accessed through a set of symbolic names, wherein file system is configured to load the shared library via different symbolic names in the set of symbolic names so that a first load actually loads the shared library, and subsequent loads return a handled to the previously loaded library, and wherein each object in the shared library is associated with a different symbolic name, so that each object can be referenced through its own symbolic name.

2. The method of claim 1, wherein generating the shared library involves:

placing read-only portions of objects in a read-only region of the shared library; and

placing writeable portions of objects in a writeable region of the shared library.

3. The method of claim 2, further comprising enforcing a copy-on-write policy by ensuring that a write operation to a data item in the writeable region of the shared library is restricted to a local copy of the data item in a local address space of a process that issued the write operation.

4. The method of claim 1, wherein an object in the set of objects defines a class containing methods to be shared between instances of a language run-time system.

5. The method of claim 1, further comprising accessing a target object in the shared library by:

accessing the shared library through a symbolic name associated with the target object; and

looking up the target object in the symbol table of the shared library to determine a location of the target object within the shared library.

6. The method of claim 1, wherein a symbolic names for an object can be inferred from the indentifier for the object.

7. A computer-readable storage medium storing instructions that when executed by a computer cause the computer to perform a method that uses a shared library mechanism to facilitate sharing objects, the method comprising:

receiving indentifiers for a set of objects to be included in the shared library, wherein an object in the set of objects contains dynamically compiled code to be shared between multiple instances of a language run-time system;

generating a shared library containing the set of objects;

configuring a symbol table within the shared library to include an identifier for each object in the set of objects;

installing the shared library in a file system; and

configuring the file system so that the shared library can be accessed through a set of symbolic names, wherein file system is configured to load the shared library via different symbolic names in the set of symbolic names so that a first load actually loads the shared library, and subsequent loads return a handled to the previously loaded library, and wherein each object in the shared library is associated with a different symbolic name, so that each object can be referenced through its own symbolic names.

8. The computer-readable storage medium of claim 7, wherein generating the shared library involves:

placing read-only portions of objects in a read-only region of the shared library; and

placing writeable portions of objects in a writeable region of the shared library.

9. The computer-readable storage medium of claim 8, wherein the method further comprises enforcing a copy-on-write policy by ensuring that a write operation to a data item in the writeable region of the shared library is restricted to a local copy of the data item in a local address space of a process that issued the write operation.

10. The computer-readable storage medium of claim 7, wherein an object in the set of objects defines a class containing methods to be shared between instances of a language run-time system.

11. The computer-readable storage medium of claim 7, wherein the method further comprises accessing a target object in the shared library by:

accessing the shared library through a symbolic name associated with the target object; and

looking up the target object in the symbol table of the shared library to determine a location of the target object within that shared library.

12. The computer-readable storage medium of claim 7, wherein a symbolic name for an object can be inferred from the identifier for the object.

13. An apparatus that uses a shared library mechanism to facilitate sharing objects, comprising

a library generation mechanism that is configured to generate a shared library, wherein the shared library contains a set of objects, wherein an object in the set of objects contains dynamically compiled code to be shared between instances of a language run-time system;

wherein the library generation mechanism is configured to populate a symbol table within the shared library to include an identifier for each object in the set of objects; and

a library installation mechanism that is configured to install the shared library in a file system;

wherein library installation mechanism is configure to load the shared library via different symbolic names in the set of symbolic names so that a first load actually loads the shared library, and subsequent loads return a handled to the previously loaded library;

wherein the library installation mechanism is configured to update the file system so that the shared library can be accessed through a set of symbolic names; and

wherein each object in the shared library is associated with a different symbolic name, so that each object can be referenced through its own symbolic name.

14. The apparatus of claim 13, wherein the library generation mechanism is configured to:

place read-only portions of objects in a read-only region of the shared library; and

to

place writeable portions of objects in a writeable region of the shared library.

15. The apparatus of claim 14, further comprising a copy-on-write mechanism, which ensures that a write operation to a data item in the writeable region of the shared library is restricted to a local copy of the data item in a local address space of a process that issued the write operation.

16. The apparatus of claim 13, wherein an object in the set of objects defines a class containing methods to be shared between instances of a language run-time system.

17. The apparatus of claim 13, further comprising a library access mechanism that is configured to:

accessing a target object in the shared library through a symbolic name associated with the target object; and

to

look up the target object in the symbol table of the shared library to determine a location of the target object within the shared library.

18. The apparatus of claim 13, wherein a symbolic name for an object can be inferred from the identifier for the object.

19. A computer system that uses a shared library to facilitate sharing objects, comprising:

a file system;

the shared library with the file system that contains a set of objects, wherein an object in the set of objects contains dynamically compiled code to be shared between multiple instances of a language run-time system; and

a symbol table within the shared library that includes an identifier for each object in the set of objects;

wherein the file system is configured so that the shared library can be accessed through a set of symbolic names;

wherein file system is configured to load the shared library via different symbolic names in the set of symbolic names so that a first load actually loads the shared library, and subsequent loads return a handled to the previously loaded library; and

wherein each object in the shared library is associated with a different symbolic name, so that each object can be referenced through its own symbolic name.

20. The computer system of claim 19, wherein shared library includes

a read only section containing read-only portions of objects;

and

a writeable section containing writeable portions of objects.

21. The computer system of claim 20, wherein the shared library includes a copy-on-write mechanism, which ensures that a write operation to a data item in the writeable section of the shared library is restricted to a local copy of the data item in a local address space of a process that issued the write operation.

22. The computer system of claim 19, wherein an object in the set of objects defines a class containing methods to be shared between instances of a language run-time system.

23. The computer system of claim 19, wherein a symbolic name for an object can be inferred from the identifier for the object.