Abstract:
A system that provides programming language translation includes a first compiler that compiles a source file in a first programming language into a parsed representation of the first programming language, and a transformation component that receives the parsed representation and generates a token stream from the parsed representation. The token stream comprises second language tokens of a second programming language and at least one compilation phase of the first compiler is skipped. The system further includes a second compiler that compiles the token stream into an object code and skips at least one compilation phase of the second compiler. The transformation component provides the token stream to the second compiler in memory.

Description:
CLAIM OF PRIORITY 
     This application claims priority from the following application, which is hereby incorporated by reference in its entirety: 
     U.S. Provisional Patent Application No. 60/488,648, entitled METHOD AND SYSTEM FOR TRANSLATING PROGRAMMING LANGUAGES, by Kevin Zatloukal, filed Jul. 19, 2003. 
    
    
     FIELD OF THE DISCLOSURE 
     The present invention disclosure relates to the field of compiler design and compiler optimization. 
     BACKGROUND 
     In general, a compiler can translate one computer programming language suitable for processing by humans (the source language) into another computer programming language suitable for processing by machines (the target language). Some computer programming languages may be translated in two phases, by compiling the source code in a first language into the code in a second language, then compiling the source code of the second language to the code in the desired target language. By way of a non-limiting example, Java® Server Page (JSP) files are generally compiled into Java® source files, which are then compiled by a standard Java® compiler into Java® byte codes (i.e., the target language). Usually, such language translation is accomplished with two compilers, which are invoked separately, each reading their input source file from and writing their object code as an output file back to a non-volatile storage, which can be but is not limited to, a hardware disk (referred to as disk). However, translating language source files in two different phases using two different compilers can be inefficient, especially when the output file of the first compiler is output to the disk and has to be input again from the disk by the second compiler. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an illustration of an exemplary prior art compilation process involving a single compiler. 
         FIG. 2  is an illustration of an exemplary prior art JSP translation process using two compilers. 
         FIG. 3  is an illustration of an exemplary in memory language translation process in accordance with one embodiment of the present invention. 
         FIG. 4  is an illustration of an exemplary in memory language translation process in accordance with another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The invention is illustrated by way of example and not by way of limitation in the figures of the accompanying drawings in which like references indicate similar elements. It should be noted that references to “an” or “one” or “some” embodiment(s) in this disclosure are not necessarily to the same embodiment, and such references mean at least one. 
       FIG. 1  is an illustration of an exemplary prior art compilation process involving a single compiler. Although this figure depicts functional steps in a particular order for purposes of illustration, the process is not limited to any particular order or arrangement of steps. One skilled in the art will appreciate that the various steps portrayed in this figure could be omitted, rearranged, combined and/or adapted in various ways. 
     Referring to  FIG. 1 , a single compiler takes a source file as input and produces an object code file as output. The exemplary compilation process can include the following phases:
         The input source file is read by the compiler at step  101 .   Lexical analysis (scanning) at step  102  translates a stream of characters (the source code) into a stream of tokens. By way of a non-limiting example, tokens in the C programming language might include +, −, −&gt;, int, and foo( ). In this example, the first three tokens are operators (two arithmetic and a pointer de-reference), the fourth is a keyword, and the last is an identifier (used to name a function or variable).   Syntactic analysis (parsing) at step  103  determines if the source code (represented by tokens) conforms to the syntax rules of the programming language. By way of a non-limiting example, a syntax rule for a particular language might require that a multiplication operator has a left operand and a right operand. A language grammar may be used to explicitly define the syntax of a programming language. In addition, syntactic analysis can produce a parsed representation of the source file to facilitate further analysis and code generation (e.g., an abstract syntax tree). The parsed representation may contain information about the operators, operands and data types of language expressions and statements in the source files.   Semantic analysis at step  104  examines the parsed representation of the source file, judges whether or not the source code adheres to the semantic rules of the programming language and may augment the parsed representation of the source file with additional information e.g. for subsequent compile phases. A semantic rule, by way of a non-limiting example, might mandate that an integer and an array cannot be multiplied together with the * operator.   Code optimization at step  105  can improve the efficiency of the code by applying specific optimizations to the parsed representation of the source file. By way of a non-limiting example, the optimizer may use techniques such as common sub-expression elimination to identify and eliminate redundant steps expressed in the source code.   Object code generation at step  106  generates the target language for a specific computing platform (e.g., machine code for a specific hardware architecture or byte codes for a specific virtual machine).   An object code file can then be generated (e.g. a class or .exe file) at step  107 .       

       FIG. 2  is an illustration of an exemplary prior art JSP translation process using two compilers instead of one. Although this figure depicts functional steps in a particular order for purposes of illustration, the process is not limited to any particular order or arrangement of steps. One skilled in the art will appreciate that the various steps portrayed in this figure could be omitted, rearranged, combined and/or adapted in various ways. 
     Referring to  FIG. 2 , the JSP translation process can be divided into two compiling phases executed by two different compilers. In the first phase, a JSP compiler reads the JSP source file at step  201 , performs lexical analysis at step  202 , syntactic analysis at step  203 , semantic analysis at step  204 , optimization at step  205  and code generation at step  206  before writing the resulting Java® source file from memory to storage at step  207 . In the second phase, a Java® compiler reads the Java® source file from disk back into memory at step  208  and again performs lexical analysis at step  209 , syntactic analysis at step  210 , semantic analysis at step  211 , optimization at step  212  and code generation at step  213  before writing the final Java® class file to disk at step  214 . 
     As is evident from the descriptions above, the process of compiling language source files using two different compilers (e.g., JSP and Java®) includes inherent inefficiencies. Most notably, since the first compiler (i.e., the JSP compiler) has a fully parsed representation of the Java® source file, it is inefficient to write the Java® source file to disk just so that the second compiler (i.e., the Java® compiler) has to read it from disk again and reproduce a parsed representation. In addition, it is inefficient to load and execute two separate compilation processes. 
     Embodiments of the present invention enable the language translation process involving more than one compilers to be completed entirely in memory, making it faster and more efficient. Two approaches can be adopted: in one embodiment, a transformation component is employed, which is capable of generating a token stream from the parsed representation of a source file produced by the first compiler and providing it to the parser of the second compiler, skipping the “Optimization”, “Code Generation”, and “Write Output File” phases of the first compiler and the “Read Input File” and “Lexical Analysis” phases of the second compiler; in another embodiment, the bit stream produced by the code generator of the first compiler is passed directly to the lexical analyzer of the second compiler instead of writing the bit stream to disk, then reading it back from the disk, eliminating the “Write Output File” phase of the first compiler and the “Read Input File” phase of the second compiler. It will be apparent to those skill in the art that both approaches are not limited to any particular source language or target language. 
       FIG. 3  is an illustration of an exemplary in memory language translation process in accordance with one embodiment of the invention. Although this figure depicts functional steps in a particular order for purposes of illustration, the process is not limited to any particular order or arrangement of steps. One skilled in the art will appreciate that the various steps portrayed in this figure could be omitted, rearranged, combined and/or adapted in various ways. 
     Referring to  FIG. 3 , the black boxes represent processes traditionally carried out by a first compiler and the white boxes represent processes traditionally carried out by a second compiler. The compilation stages potentially eliminated by the exemplary process are highlighted in gray. The compilers and their components can communicate in a number of ways, including but not limited to: memory, database(s), file(s), network communication, and/or other suitable means. 
     Referring again to  FIG. 3 , after reading the source file at step  301 , the first compiler performs one or more of lexical analysis at step  302 , syntax analysis at step  303 , semantic analysis at step  304  before generating a parsed representation (e.g., a parse tree) of the source file. Then, the parsed representation can be converted into a stream of tokens suitable for providing to the second compiler by a transformation component capable of generating tokens from parse tree at step  315 . The parser of the second compiler may accept the token stream at step  310 , perform one or more of syntactic analysis at step  311 , semantic analysis at step  312 , optimization at step  313  and then generate code at step  314 . 
     In some embodiments, the “Optimization” (step  305 ), “Code Generation” (step  306 ), and “Write Output File” (step  307 ) phases of a first compiler and the “Read Input File” (step  308 ) and “Lexical Analysis” (step  309 ) phases of a second compiler may be omitted if the parsed representation of the first language produced by the first compiler is converted into a token stream and provided to the parser of the second compiler. 
     In some embodiments, the generation of tokens from a parse tree by the transformation component can be performed in memory. Such in-memory operation may avoid the inefficiency in computing resource utilization caused by writing the output file to a disk by the first compiler and reading the same file again from the disk by the second compiler. 
     In some embodiments, the transformation component may perform a traversal of the parse tree, in which zero or more tokens suitable for processing by the second compiler are emitted for each node in the parse tree generated by the first compiler. Such traversal may be implemented as an in-order tree traversal, a technique well known in the art. 
     In some embodiments, the parse tree generated by the first compiler may be adjusted before it is traversed in order to change the order in which nodes in the tree are processed. Such adjustment may be performed in order to account for, as non-limiting examples, differences in the ordering, precedence, semantics of operations and other suitable situations in the first and second languages. 
     In some embodiments, the creation of the transformation component may be facilitated by starting with the existing code generator of the first compiler and modifying it to generate tokens suitable for processing by the parser of the second compiler. Such an approach avoids the generation of a character stream suitable for processing by the lexical analyzer of the second compiler. 
     In some embodiments, the creation of the transformation component may be facilitated by starting with the existing lexical analyzer of the second compiler and modifying it to read its input directly from the parse tree of the first compiler instead of reading its input from a character stream, e.g. from disk. 
       FIG. 4  is an illustration of an exemplary in memory language translation process in accordance with another embodiment of the invention. Although this figure depicts functional steps in a particular order for purposes of illustration, the process is not limited to any particular order or arrangement of steps. One skilled in the art will appreciate that the various steps portrayed in this figure could be omitted, rearranged, combined and/or adapted in various ways. 
     Referring to  FIG. 4 , the black boxes represent processes traditionally carried out by a first compiler and the white boxes represent processes traditionally carried out by a second compiler similar to  FIG. 3 . The compilation stages potentially eliminated by the exemplary process are highlighted in gray. The compilers and their components can communicate in a number of ways, including but not limited to: memory, database(s), file(s), network communication, and/or other suitable means. 
     Referring again to  FIG. 4 , steps  401 - 414  perform similar operations as steps  301 - 314  with the exception that the bit stream produced by the code generator of the first compiler at step  406  is passed directly to the lexical analyzer of the second compiler at step  409  instead of writing the bit stream to disk, then reading it back from the disk. Such adjustment may eliminate the “Write Output File” (step  407 ) phase of the first compiler and the “Read Input File” (step  408 ) phase of the second compiler and enable the entire language compilation process to be performed entirely in memory, making it faster and more efficient. 
     One embodiment may be implemented using a conventional general purpose or a specialized digital computer or microprocessor(s) programmed according to the teachings of the present disclosure, as will be apparent to those skilled in the computer art. Appropriate software coding can readily be prepared by skilled programmers based on the teachings of the present disclosure, as will be apparent to those skilled in the software art. The invention may also be implemented by the preparation of integrated circuits or by interconnecting an appropriate network of conventional component circuits, as will be readily apparent to those skilled in the art. 
     One embodiment includes a computer program product which is a storage medium (media) having instructions stored thereon/in which can be used to program a computer to perform any of the features presented herein. The storage medium can include, but is not limited to, any type of disk including floppy disks, optical discs, DVD, CD-ROMs, microdrive, and magneto-optical disks, ROMs, RAMs, EPROMs, EEPROMs, DRAMs, VRAMs, flash memory devices, magnetic or optical cards, nanosystems (including molecular memory ICs), or any type of media or device suitable for storing instructions and/or data. 
     Stored on any one of the computer readable medium (media), the present invention includes software for controlling both the hardware of the general purpose/specialized computer or microprocessor, and for enabling the computer or microprocessor to interact with a human user or other mechanism utilizing the results of the present invention. Such software may include, but is not limited to, device drivers, operating systems, execution environments/containers, and applications. 
     The foregoing description of the preferred embodiments of the present invention has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations will be apparent to the practitioner skilled in the art. Particularly, while the concept “translation” or “translating” is used in the embodiments of the systems and methods described above, it will be evident that such concept can be interchangeably used with equivalent concepts such as, compilation or compiling, and other suitable concepts; while the concept “in memory” is used in the embodiments of the systems and methods described above, it will be evident that such concept can be interchangeably used with equivalent concepts such as, without accessing a disk, and other suitable concepts; while the concept “object code or file” is used in the embodiments of the systems and methods described above, it will be evident that such concept can be interchangeably used with equivalent concepts such as, executable code or file, and other suitable concepts. Embodiments were chosen and described in order to best describe the principles of the invention and its practical application, thereby enabling others skilled in the art to understand the invention, the various embodiments and with various modifications that are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalents.