Token-based linking

• US 6,880,155 B2
• Filed: 02/02/1999
• Issued: 04/12/2005
• Est. Priority Date: 02/02/1999
• Status: Expired due to Term

• Current Assignee: Oracle America, Inc. (Oracle Corporation)
• Original Assignee: Sun Microsystems Incorporated (Oracle Corporation)
• Inventors: Schwabe, Judith E., Susser, Joshua B.
• Primary Examiner(s): CHAVIS, JOHN Q
• Application Number:
  US09/243,108
• Publication Number:
  US 20030028686A1
• Time in Patent Office: 2,261 Days
• Field of Search: 717/162, 717/10, 709/220
• US Class Current: 717/162
• 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

Abstract

A system links architecture neutral code downloaded to a resource constrained computer. The code may be separated into one or more packages having one or more referenceable items. The system maps the one or more referenceable items into corresponding one or more tokens; orders the tokens to correspond to a run-time mode; downloads the packages to the resource constrained computer; and links the packages into an executable code using the ordered tokens.

Claims

1. A method for downloading code to a resource constrained computer, the code being separable into at least one package having at least one referenceable item, comprising:

forming the package;

forming a mapping of the referenceable item to a corresponding token having a token type, tokens belonging to the same token type representing the same kind of referenceable item, each kind of referenceable item in said package having its own independent scope of limited capacity for tokens of the corresponding token type; and

providing the package and the mapping.

6. The method of claim 1, further comprising recording in an image of said package a mapping between said token and said referenceable item.

7. The method of claim 1 wherein said referenceable item comprises a class and said reference comprises a package token and a class token.

8. The method of claim 1 wherein said referenceable item comprises a field and said reference comprises a package token, a class token, and a field token.

9. The method of claim 1 wherein said referenceable item comprises a method and said reference comprises a package token, a class token, and a method token.

14. The method of claim 1 wherein

said package further comprises interfaces and interface method definitions;

and

said method further comprises constructing at least one interface method table for a class.

15. The method of claim 14 wherein said constructing comprises:

obtaining said interfaces;

constructing an ordered table of methods for each interface; and

recording an indication of the implementation of the interface method for each table entry.

16. The method of claim 15 wherein said ordered interface method table entries correspond to token values assigned to interface methods within the scope of said class.

17. The method of claim 16 wherein said indication of said implementation of said interface method comprises an index into a virtual method table.

2. A method for linking code downloaded to a resource constrained computer, the code being separable into at least one package having at least one referenceable item, comprising:

receiving the package;

receiving a mapping of the referenceable item to a corresponding token having a token type, tokens belonging to the same token type representing the same kind of referenceable item, each kind of referenceable item in said package having its own independent scope of limited capacity for tokens of the corresponding token type; and

linking the package using the mapping.

3. A method for linking code downloaded to a computer, the computer comprising a first package that includes a mapping of tokens to externally referenceable items, the method comprising:

receiving a second package comprising at least one reference to an item in said first package, wherein said reference is represented by one or more tokens having a token type, tokens belonging to the same token type representing the same kind of referenceable item, each kind of referenceable item in said package having its own independent scope of limited capacity for tokens of the corresponding token type; and

linking said second package to said first package by resolving said one or more tokens.

10. The method of claim 3, further comprising recording in an image of said package a mapping between said token and said referenceable item.

11. The method of claim 3 wherein said referenceable item comprises a class and said reference comprises a package token and a class token.

12. The method of claim 3 wherein said referenceable item comprises a field and said reference comprises a package token, a class token, and a field token.

13. The method of claim 3 wherein said referenceable item comprises a method and said reference comprises a package token, a class token, and a method token.

18. The method of claim 3, further comprising resolving interface method references during execution using interface method tables, said resolving comprising:

obtaining an associated instance;

obtaining a class description of said instance;

locating an interface table of said interface method in said class description;

locating an interface method entry within an interface table of a referenced method; and

locating the implementation of said interface method based on the table entry content.

19. The method of claim 18 wherein an indication of said implementation of said interface method comprises an index into a virtual method table.

4. A method for constructing an image of a first package of code on a computer, the code being separable into at least one package having at least one reference to an item in a second package of code, the method comprising:

receiving a mapping of said item to at least one corresponding token having a token type, tokens belonging to the same token type representing the same kind of referenceable item, each kind of referenceable item in said package having its own independent scope of limited capacity for tokens of the corresponding token type;

replacing said at least one reference with said at least one corresponding token; and

forming said package.

5. A method for constructing an image of a first package of code comprising at least one internally referenceable item, the method comprising:

forming a mapping of said at least one internally referenceable item to an optimized numeric value having a type, optimized numeric values belonging to the same type representing the same kind of referenceable item, each kind of referenceable item in said package having its own independent scope of limited capacity for optimized numeric values of the corresponding type;

replacing references to said at least one internally referenceable item with the corresponding numeric value; and

forming the package.

20. The method of claim 5 wherein said package further comprises at least one reference to an internal item.

21. The method of claim 20 wherein said internal item comprises a class and said reference comprises an offset within said package to a class record associated with said class.

22. The method of claim 20 wherein said internal item comprises a static field and said reference comprises an offset within said package to a value for said static field.

23. The method of claim 20 wherein said internal item comprises a static method and said reference comprises an offset within said package to code associated with said static method.

24. The method of claim 20 wherein said internal item comprises an instance field and said reference comprises an offset within said package to a class record of said instance field and a field token.

25. The method of claim 20 wherein said internal item comprises a virtual method and said reference comprises an offset within said package to a class record of said virtual method and a method token.

26. A program storage device readable by a machine, embodying a program of instructions executable by the machine to perform a method for downloading code to a resource-constrained computer, the code being separable into at least one package having at least one referenceable item, the method comprising:

forming the package;

forming a mapping of the referencable item to a corresponding token having a token type, tokens belonging to the same token type representing the same kind of referenceable item, each kind of referenceable item in said package having its own independent scope of limited capacity for tokens of the corresponding token type; and

providing the package and the mapping.

31. The program storage device of claim 26 wherein said method further comprises recording in an image of said package a mapping between said token and said referenceable item.

32. The program storage device of claim 26 wherein said referenceable item comprises a class and said reference comprises a package token and a class token.

33. The program storage device of claim 26 wherein said referenceable item comprises a field and said reference comprises a package token, a class token, and a field token.

34. The program storage device of claim 26 wherein said referenceable item comprises a method and said reference comprises a package token, a class token, and a method token.

39. The program storage device of claim 26 wherein said package further comprises interfaces and interface method definitions;

and said method further comprises constructing at least one interface method table for a class.

40. The program storage device of claim 39 wherein said constructing comprises:

obtaining said interfaces;

constructing an ordered table of methods for each interface; and

recording an indication of the implementation of the interface method for each table entry.

41. The program storage device of claim 40 wherein said ordered interface method table entries correspond to token values assigned to interface methods within the scope of said class.

42. The program storage device of claim 41 wherein said indication of said implementation of said interface method comprises an index into a virtual method table.

27. A program storage device readable by a machine, embodying a program of instructions executable by the machine to perform a method for linking code downloaded to a resource-constrained computer, the code being separable into at least one package having at least one referenceable item, the method comprising:

receiving the package;

receiving a mapping of the referenceable item to a corresponding token having a token type, tokens belonging to the same token type representing the same kind of referenceable item, each kind of referenceable item in said package having its own independent scope of limited capacity for tokens of the corresponding token type; and

linking the package using the mapping.

28. A program storage device readable by a machine, embodying a program of instructions executable by the machine to perform a method for linking code downloaded to a computer, the computer comprising a first package that includes a mapping of tokens to externally referenceable items, the method comprising:

receiving a second package comprising at least one reference to an item in said first package, wherein said reference is represented by one or more tokens having a token type, tokens belonging to the same token type representing the same kind of referenceable item, each kind of referenceable item in said package having its own independent scope of limited capacity for tokens of the corresponding token type; and

linking said second package to said first package by resolving said one or more tokens.

35. The program storage device of claim 28 wherein said method further comprises recording in an image of said package a mapping between said token and said referenceable item.

36. The program storage device of claim 28 wherein said referenceable item comprises a class and said reference comprises a package token and a class token.

37. The program storage device of claim 28 wherein said referenceable item comprises a field and said reference comprises a package token, a class token, and a field token.

38. The program storage device of claim 28 wherein said referenceable item comprises a method and said reference comprises a package token, a class token, and a method token.

43. The program storage device of claim 28 wherein said method further comprises resolving interface method references during execution using interface method tables, said resolving comprising:

obtaining an associated instance;

obtaining a class description of said instance;

locating an interface table of said interface method in said class description;

locating an interface method entry within an interface table of a referenced method; and

locating the implementation of said interface method based on the table entry content.

44. The program storage device of claim 43 wherein an indication of said implementation of said interface method comprises an index into a virtual method table.

29. A program storage device readable by a machine, embodying a program of instructions executable by the machine to perform a method for constructing an image of a first package of code on a computer, the code being separable into at least one package having at least one reference to an item in a second package of code, the method comprising:

receiving a mapping of said item to at least one corresponding token having a token type, tokens belonging to the same token type representing the same kind of referenceable item, each kind of referenceable item in said package having its own independent scope of limited capacity for tokens of the corresponding token type;

replacing said at least one reference with said at least one corresponding token; and

forming said package.

30. A program storage device for constructing an image of a first package of code comprising at least one internally referenceable item, the method comprising:

forming a mapping of said at least one internally referenceable item to an optimized numeric value having a type, optimized numeric values belonging to the same type representing the same kind of referenceable item, each kind of referenceable item in said package having its own independent scope of limited capacity for optimized numeric values of the corresponding type;

replacing references to said at least one internally referenceable item with the corresponding numeric value; and

forming the package.

45. The program storage device of claim 30 wherein said package further comprises at least one reference to an internal item.

46. The program storage device of claim 45 wherein said internal item comprises a class and said reference comprises an offset within said package to a class record associated with said class.

47. The program storage device of claim 45 wherein said internal item comprises a static field and said reference comprises an offset within said package to a value for said static field.

48. The program storage device of claim 45 wherein said internal item comprises a static method and said reference comprises an offset within said package to code associated with said static method.

49. The program storage device of claim 45 wherein said internal item comprises an instance field and said reference comprises an offset within said package to a class record of said instance field and a field token.

50. The program storage device of claim 45 wherein said internal item comprises a virtual method and said reference comprises an offset within said package to a class record of said virtual method and a method token.

51. An apparatus for downloading code to a resource-constrained computer, the code being separable into at least one package having at least one referenceable item, the apparatus comprising:

means for forming the package;

means for forming a mapping of the referencable item to a corresponding token having a token type, tokens belonging to the same token type representing the same kind of referenceable item, each kind of referenceable item in said package having its own independent scope of limited capacity for tokens of the corresponding token type; and

means for providing the package and the mapping.

56. The apparatus of claim 51, further means for comprising recording in an image of said package a mapping between said token and said referenceable item.

57. The apparatus of claim 51, wherein said referenceable item comprises a class and said reference comprises a package token and a class token.

58. The apparatus of claim 51, wherein said referenceable item comprises a field and said reference comprises a package token, a class token, and a field token.

59. The apparatus of claim 51, wherein said referenceable item comprises a method and said reference comprises a package token, a class token, and a method token.

64. The apparatus of claim 51 wherein

said package further comprises interfaces and interface method definitions;

and

said apparatus further comprises means for constructing at least one interface method table for a class.

65. The apparatus of claim 64 wherein said constructing comprises:

means for obtaining said interfaces;

means for constructing an ordered table of methods for each interface; and

means for recording an indication of the implementation of the interface method for each table entry.

66. The apparatus of claim 65 wherein said ordered interface method table entries correspond to token values assigned to interface methods within the scope of said class.

67. The apparatus of claim 66 wherein said indication of said implementation of said interface method comprises an index into a virtual method table.

52. An apparatus for linking code downloaded to a resource-constrained computer, the code being separable into at least one package having at least one referenceable item, the apparatus comprising:

means for receiving the package;

means for receiving a mapping of the referenceable item to a corresponding token having a token type, tokens belonging to the same token type representing the same kind of referenceable item, each kind of referenceable item in said package having its own independent scope of limited capacity for tokens of the corresponding token type; and

means for linking the package using the mapping.

53. An apparatus for linking code downloaded to a computer, the computer comprising a first package that includes a mapping of tokens to externally referenceable items, the apparatus comprising:

means for receiving a second package comprising at least one reference to an item in said first package, wherein said reference is represented by one or more tokens having a token type, tokens belonging to the same token type representing the same kind of referenceable item, each kind of referenceable item in said package having its own independent scope of limited capacity for tokens of the corresponding token type; and

means for linking said second package to said first package by resolving said one or more tokens.

60. The apparatus of claim 53, further comprising means for recording in an image of said package a mapping between said token and said referenceable item.

61. The apparatus of claim 53, wherein said referenceable item comprises a class and said reference comprises a package token and a class token.

62. The apparatus of claim 53 wherein said referenceable item comprises a field and said reference comprises a package token, a class token, and a field token.

63. The apparatus of claim 53 wherein said referenceable item comprises a method and said reference comprises a package token, a class token, and a method token.

68. The apparatus of claim 53, further comprises means for resolving interface method references during execution using interface method tables, said means for resolving comprising:

means for obtaining an associated instance;

means for obtaining a class description of said instance;

means for locating an interface table of said interface method in said class description;

means for locating an interface method entry within an interface table of a referenced method; and

means for locating the implementation of said interface method based on the table entry content.

69. The apparatus of claim 68 wherein an indication of said implementation of said interface method comprises an index into a virtual method table.

54. An apparatus for constructing an image of a first package of code on a computer, the code being separable into at least one package having at least one reference to an item in a second package of code, the apparatus comprising:

means for receiving a mapping of said item to at least one corresponding token having a token type, tokens belonging to the same token type representing the same kind of referenceable item, each kind of referenceable item in said package having its own independent scope of limited capacity for tokens of the corresponding token type;

means for replacing said at least one reference with said at least one corresponding token; and

means for forming said package.

55. An apparatus for constructing an image of a first package of code comprising at least one internally referenceable item, the apparatus comprising;

means for forming a mapping of said at least one internally referenceable item to an optimized numeric value having a type, optimized numeric values belonging to the same type representing the same kind of referenceable item, each kind of referenceable item in said package having its own independent scope of limited capacity for optimized numeric values of the corresponding type;

means for replacing references to said at least one internally referenceable item with the corresponding numeric value; and

means for forming the package.

70. The apparatus of claim 55 wherein said package further comprises at least one reference to an internal item.

71. The apparatus of claim 70 wherein said internal item comprises a class and said reference comprises an offset within said package to a class record associated with said class.

72. The apparatus of claim 70 wherein said internal item comprises a static field and said reference comprises an offset within said package to a value for said static field.

73. The apparatus of claim 70 wherein said internal item comprises a static method and said reference comprises an offset within said package to code associated with said static method.

74. The apparatus of claim 70 wherein said internal item comprises an instance field and said reference comprises an offset within said package to a class record of said instance field and a field token.

75. The apparatus of claim 70 wherein said internal item comprises a virtual method and said reference comprises an offset within said package to a class record of said virtual method and a method token.