Method for eliminating redundant method calls in an object oriented program

[0001] The present invention relates to object oriented programming, and more specifically to efficient performance of processes repeated in related objects.

[0002] Embodiments of the present invention are discussed in the context of JAVA class library performance. This is a very popular form of object-oriented programming (OOP) at the present time because it is applicable to forms of object-oriented programming. Like most object-oriented programming paradigms objects and methods are implemented to be self-contained. Therefore, when a second object is derived from a first object, and a third object is derived from a second object, as in the case of a JAVA string class and its parent classes, a process may be included in the subclasses which duplicates a function in the object in the parent class.

[0003] One example of such an operation is a function to check for a buffer overflow during execution. Normally, if a buffer will not overflow during execution of a subclass, it will not overflow during execution of the parent class (unless the buffer is explicitly modified). However, assuming a method of a derivative object uses a buffer to hold a context of a stream, the object will check buffer capacity before passing execution to the next higher level object. Consequently, excessive, redundant method calls will be inherent in JAVA class libraries. The excessive calls decrease JAVA performance and increase overhead. Data shows that excessive redundant method execution can degrade the performance of certain JAVA™ class library method calls by two times.

[0010] FIG. 1 is a block diagram of a JAVA application 10 through a JAVA application program interface (API)14. A second derivative object (AAA) 16 is derived from a first derivative object AA 18 which in turn is derived from a first object A20. The object AAA 16 and its parent classes will have methods in common. In this particular example, one of the methods of object AAA 16 uses a buffer to hold the contents of a string. In order to make proper use of the buffer, object AAA 16 checks buffer capacity before passing execution to object AA 18. Object AA 18 performs the same function before passing execution to object A 20 within its parent class. Object A 20 being the parent of AA 18, contains the same Ensure Capacity ( ) procedure. Objects AAA 16, AA 18 and A20 comprise sequences of objects derived from a common source library.

[0011] It is desirable to eliminate the redundant method call inherited from a parent class. In this particular example, the redundant process is checking buffer capacity, but the invention is applicable to eliminating other redundant processes called by related objects as well. In the absence of a method in which the buffer is going to be modified, check of buffer capacity for the execution of the method on the related objects need be performed only once.

[0012] In order to inform the system of when the potentially redundant method calls are or are not necessary, information is provided. In one form of this implementation, the object AAA 16 is tagged with a define flag 24 and the object A 20 is tagged with a use flag 28. The object AA 18 may be tagged with a use flag 26. This operation is described with respect to FIG. 2, which is a flow chart. At block 40, the JAVA API 14 examines each successive related object, represented here for example by the objects 16, 18 and 20. At block 42, the API examines whether the object's flag indicates that a buffer check has been performed. If not, at block 44, the buffer check is performed. In this manner, redundant calls are prevented. FIG. 3 is an illustration of a further manner of eliminating redundant “ensure capacity” calls which is transparent to operation. FIG. 3 is a block of JAVA code illustrating a provision of the following constraints.

[0013] For each object, a pair of “root and leaf” flags is defined. The root flag is placed at the JAVA API entry point or in the last object that modifies the buffer. The leaf flag is placed at the leaf function that performs the last redundant check. During the execution of the API 14 to objects 16, 18 and 20 the redundant check is disabled at all objects except the leaf. The check is delayed until as late as possible. If an exception is established at the leaf, the actual signaling will happen at the root.

[0014] In the method as illustrated in FIG. 1, the root flag will be placed in object AAA 16 if object AA 18 does not modify the buffer. The root flag will be placed in object AA 18 if the buffer will be modified. A leaf flag is placed in object A 20. Checks are disabled at object AA 18 and AAA 16 but not object A 20. If an exception is raised during the execution of “ensure capacity” call (in object A 20, the exception will be recorded to have happened in object AAA 16.) The implementation of this technique is illustrated in FIG. 3 which represents code therefore. The program at line 2, determines if an object is a JAVA application program interface. In this case the object modifies shared data at line 3 of the code, the object attribute will be labeled as a root. If the object is not a JAVA API, then the object attribute is labeled as a leaf, as seen at the end of line 4. As seen at line 7, if the object catches an exception to the buffer capacity, the exception caught value is set to one. At lines 9 and 10, if the exception is caught, the objection is attributed to the root.

[0015] FIG. 4 is a flowchart illustrating the using of root/leaf pair inserted in class libraries. Block 60, at block 62, the flag is checked. Block 64 determines whether the flag is a root flag or a leaf flag. In the case of root flag, the performed method is not called and operation proceeds. In the case of a leaf flag, at block 66 the called method is performed and operation proceeds. In this embodiment using the illustration of FIG. 4, the flag 24 is the root flag, and the flag 28 is the leaf flag.

[0016] The present invention also comprises a machine-readable medium as a method. A machine-readable medium includes any mechanism that provides (i.e., stores and/or transmits information in a form readable by a machine (e.g., a computer)). For example, a machine-readable medium includes read only memory (ROM) random access memory (RAM); magnetic disk storage media; optical storage media; flash memory devices; electrical, optical, acoustical or other form of propagated signals (e.g., carrier waves, infrared signals, digital signals, etc.) and the like.

[0017] The invention is also used to construct efficient JAVA class libraries and enable increased performance. The above specification has been written with a view toward enabling those skilled in the art to make many departures from specific examples illustrated herein to produce the method and processor constructed in accordance with the present invention.