U.S. patent application number 13/274199 was filed with the patent office on 2016-05-05 for unified data type system and method.
This patent application is currently assigned to Microsoft Technology Licensing, LLC. The applicant listed for this patent is George H. Bosworth, Patrick H. Dussud, James S. Miller, Daryl B. Olander. Invention is credited to George H. Bosworth, Patrick H. Dussud, James S. Miller, Daryl B. Olander.
Application Number | 20160124726 13/274199 |
Document ID | / |
Family ID | 27086987 |
Filed Date | 2016-05-05 |
United States Patent
Application |
20160124726 |
Kind Code |
A9 |
Bosworth; George H. ; et
al. |
May 5, 2016 |
UNIFIED DATA TYPE SYSTEM AND METHOD
Abstract
A type system includes a dual representation for basic data
types. One representation is the basic data type representation
common to such basic built-in data types, known as an unboxed value
type or simply as a value type. Each of the basic data types also
has a boxed representation that can be stored in the object
hierarchy of the type system. This dual representation can also be
extended to user-defined types, so that user-defined types may
exist both as an unboxed value type and as an object within the
object hierarchy of the type system. This dual representation
allows the compiler and/or runtime environment to select the most
effective and efficient representation for the data type depending
on the particular need at the moment.
Inventors: |
Bosworth; George H.;
(Woodinville, WA) ; Dussud; Patrick H.; (Bellevue,
WA) ; Miller; James S.; (Bellevue, WA) ;
Olander; Daryl B.; (Boulder, CO) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Bosworth; George H.
Dussud; Patrick H.
Miller; James S.
Olander; Daryl B. |
Woodinville
Bellevue
Bellevue
Boulder |
WA
WA
WA
CO |
US
US
US
US |
|
|
Assignee: |
Microsoft Technology Licensing,
LLC
Redmond
WA
|
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 20120072890 A1 |
March 22, 2012 |
|
|
Family ID: |
27086987 |
Appl. No.: |
13/274199 |
Filed: |
October 14, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10848402 |
May 17, 2004 |
8065668 |
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13274199 |
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09614158 |
Jul 11, 2000 |
6738968 |
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10848402 |
|
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09613289 |
Jul 10, 2000 |
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09614158 |
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Current U.S.
Class: |
717/143 ;
717/141 |
Current CPC
Class: |
G06F 8/437 20130101;
G06F 9/4488 20180201 |
International
Class: |
G06F 9/45 20060101
G06F009/45 |
Claims
1-15. (canceled)
16. A unified type system for use with a computer source language
and associated components which translate source files written in
the computer source language into executable form and execute the
translated source files, wherein at least one source file declares
a variable using a boxed value type yet passes the variable to a
method expecting an unboxed value type representation, the unified
type system comprising: a first value type representation relating
to the boxed value type representation of the variable; and a class
object hierarchy comprising a plurality of object classes, wherein
at least one of the object classes is a second value type
representation relating to the unboxed representation of the
variable, and wherein the second value type is automatically passed
to the method expecting the unboxed value type.
17. A generated output file produced by a front end compiler
system, wherein the front end compiler system is adapted to compile
other common language files, the generated common output file
comprising: a boxed value type representation; metadata
corresponding to the boxed value type representation for converting
the boxed value type representation into an unboxed value type
representation; and output code generated from the front end
compiler system converting between the boxed value type
representation and the unboxed value type representation in
response to a detection of different value types in a runtime
operation.
18. A generated output file as defined in claim 17 wherein the
metadata defines one or more interfaces and wherein the unboxed
value type representation implements the defined one or more
interfaces.
19. A generated output file as defined in claim 18 wherein the
unboxed value type representation inherits one or more
interfaces.
20. A method of performing a method call by a function, wherein the
function expects parameters of a predetermined value type, wherein
the predetermined value type is an unboxed value type, the method
comprising: passing a value type to the function, wherein the
passed value type is a boxed value type; calling the requested
method using the passed value type; looking up the method within a
virtual method table; comparing the passed value type to the
expected value type; if the value type is different from the
expected value type, modifying the value type to match the expected
value type; and executing the method using the value type.
21. A method as defined in claim 20 wherein the boxed value type is
associated with metadata, the metadata defining a list of
interfaces for the unboxed value type, and wherein the method
further comprises: implementing one of the interfaces of the
unboxed value type.
22. A method as defined in claim 21 wherein the metadata is defined
by the user.
23. A method as defined in claim 22 wherein the unboxed value type
inherits one or more interfaces from other unboxed value types.
24. A method as defined in claim 20 wherein the method is performed
at runtime.
25. A method as defined in claim 24 wherein the modified type value
is not stored in a parameter list.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation application and claims
priority to U.S. patent application Ser. No. 10/848,402, filed May
17, 2004, entitled "Unified Data Type System and Method," which
application is incorporated herein by reference in its
entirety.
TECHNICAL FIELD
[0002] The present invention relates to a system and method for
defining and processing data types and more particularly relates to
type systems used by a compiler and/or runtime environment.
BACKGROUND
[0003] Almost from the beginning, computer programming languages
have embodied the notion of data types. Data types include such
basic concepts as a character, string, integer, float, and so
forth. At its lowest level, data stored in a computer is a simple
bit pattern stored in a location of a particular size (e.g., a
32-bit memory location). Data types define the notion of how to
interpret the bit pattern. For example, a particular bit pattern in
a storage location of a particular size might be interpreted one
way if the storage location was deemed to hold a "character" and
another way if the storage location was deemed to hold an
"integer".
[0004] In some computer languages, although the notion of data type
exists, few rules are enforced either by the compiler or any
associated runtime for mixing of different data types in
expressions of a computer program. So no compiler error will be
generated in the C programming language, for example, if an integer
value is multiplied by a floating point number value. In order to
minimize various types of errors, many such languages had built-in
type rules that allowed for the implicit conversion of certain data
types. In other instances, languages included explicit constructs
to "coerce" or convert one data type into another data type.
Needless to say, although such languages provided great
flexibility, certain programming errors could be introduced if care
was not taken when mixing data types in various programming
expressions.
[0005] Strongly typed languages tried to reduce the instances of
programming errors by enforcing strict typing rules. In strongly
typed languages, a compiler error would be generated when data type
mismatches were detected. For example, a compiler error would be
generated in Pascal if a programmer tried to assign a character
value to an integer variable. This had the effect of reducing
certain types of programming errors, but the rules seemed to be too
restrictive.
[0006] With the advent of object oriented programming languages,
the concept of data types took on new meaning. In object oriented
languages, objects may typically be represented by an object class
hierarchy, where some objects are derived from (or inherit) fields
(also referred to as properties) and methods from other "base
class" objects. Objects in these languages can be a mixture of
fields (typically represented by variables of a particular data
types) and methods or functions which allow manipulation of the
fields or which provide certain functionality. In addition, object
oriented languages also typically include a number of built-in data
types, such as float, integer, character, string and so forth,
which can be used either as basic variables or as fields in an
object. Thus, in Java, for example, a programmer can define a
variable of type integer and define an object with fields, one of
which is of the "integer" data type.
[0007] In object oriented programming languages, there can be
different treatment for objects and basic data types. For example,
an object with a single property of type integer and a variable of
type integer would not be considered to be of the same data type in
many object oriented languages, although at the bottom, both simply
represent an integer. The variable of type integer simply exists as
a bit pattern in a particular storage location with no additional
information, while the object has a storage location of the same
size and additional information (or "metadata") that describes how
to interpret the value in the storage location.
[0008] To provide some sort of equivalency between an object
representation and a basic data type representation, the notion of
"boxing" was conceived. The process of adding metadata to a basic
data type representation to yield an object representation is
termed "being". Similarly, removing the metadata from an object
representation to yield a basic data type representation is termed
"unboxing". However, even with the development of boxing and
unboxing, present compilers and/or runtime systems use a fragmented
notion of data types with strict separation between the notion of
objects and the notion of basic data type representations. Although
this separation has many implications, one area where the
implications are quite apparent is in how these languages treat
user-defined types.
[0009] Even prior to object oriented programming, many, if not
most, programming languages had the notion of user-defined data
types. These programming languages allowed a programmer to build up
new "data types" from the basic built-in types of the language. For
example, a programmer could define a new type "data_point" as
consisting of an x coordinate value of type float and a y
coordinate value of type float. Certain object oriented programming
languages, like Java, however, do not allow extension of the basic
built-in types in this manner. In some such implementations,
user-defined types are only allowed in the form of objects.
Existing solutions have also failed to adequately address the need
for a unified data type system that can be applied during
runtime.
[0010] The present invention addresses, among other things, a
mechanism to avoid the currently fragmented view of data types. The
invention also addresses the inefficiencies associated with using
basic data types where object types would be more efficient and
object types where basic data types would be more efficient.
SUMMARY OF THE INVENTION
[0011] In accordance with the present invention, the above and
other problems are solved by providing a system and method for
efficiently processing user-defined data types. The present
invention provides for a more unified view of the type system of
programming languages, and object oriented programming languages in
particular. In the present invention, the type system includes a
dual representation for basic data types. One representation is the
basic data type representation common to such basic built-in data
types. In this application this representation will be referred to
as a value type representation, or more simply, a value type.
However, unlike other type systems, each of the basic data types
also has a boxed representation that exists in the object hierarchy
of the type system itself. This dual representation can also be
extended to use r defined types, so that user-defined types may
exist both as a value type and as an object within the object
hierarchy of the type system. This allows the compiler and/or
runtime to select the most effective and efficient representation
for the data type depending on the particular need at the
moment.
[0012] In addition to the dual representation of data types,
another aspect of the invention allows for the application of rules
to determine when to use the boxed representation and when to use
the value type (or unboxed) representation of a data type. These
rules can be applied, for example, by a compiler and allow, among
other things, for implicit conversion between the boxed and unboxed
representations of a particular data type.
[0013] In another aspect of the invention, the unified view of the
type system is reflected in the behavior of virtual methods for
objects. One basic feature of objects is that they can inherit
methods from "parent" objects. Such methods may include methods
that take objects as arguments. The dual representation of value
types both as value types and as objects in the hierarchy implies
that value types can have methods and can behave as objects in some
instances and as value types in other instances. Although the
details are discussed more completely below, the practical effect
is that when value types are in their boxed representation, they
can possess type information like other objects. Furthermore, when
value types are in their unboxed representation, they can be valid
arguments to methods that would otherwise expect an object type
(such as a boxed representation). This approach provides entirely
new and powerful programming paradigms to developers. Furthermore,
since both boxed and unboxed representations are available, all
this functionality can be provided without the developer having to
explicitly specify in the source code the value type version (i.e.,
boxed or unboxed) to use or the conversion from one form to
another.
[0014] In one implementation of the present invention, a unified
type system is provided in a runtime environment. A source code
file includes an unboxed value type representation. Metadata is
associated with the unboxed value type representation for
converting the unboxed value type representation into a boxed value
type representation. Output code is generated from the compiler
converting between the unboxed value type representation and the
boxed value type representation in response to a detection of
different types in a runtime operation.
[0015] In another implementation of the present invention, a method
for compiling a source file containing at least one unboxed value
type representation is provided. It is determined that the source
file includes the unboxed value type representation. Metadata is
associated with the unboxed value type representation, responsive
to the determining operation. An operation having operands with
differing types is specified in the source file. One operand is the
unboxed value type representation and another operand is a boxed
value type representation. Output code is emitted from the compiler
for converting one of the operands match the type of the other
operand.
[0016] In other implementations of the present invention, articles
of manufacture are provided as computer program products. One
embodiment of a computer program product provides a computer
program storage medium readable by a computer system and encoding a
computer program for compiling a source file containing at least
one unboxed value type representation. Another embodiment of a
computer program product may be provided in computer data signal
embodied in a carrier wave by a computing system and encoding the
computer program for compiling a source file containing at least
one unboxed value type representation. The computer program product
encodes a computer program for executing on a computer system a
computer process for compiling a source file containing at least
one unboxed value type representation. It is determined that the
source file includes the unboxed value type representation.
Metadata is associated with the unboxed value type representation,
responsive to the determining operation. An operation having
operands with differing types is specified in the source file. One
operand is the unboxed value type representation and another
operand is a boxed value type representation. Output code is
emitted from the compiler for converting one of the operands match
the type of the other operand.
[0017] In a further aspect of the invention, the notion can be
combined with a runtime or execution environment to produce a
unique runtime environment that supports value types, object
classes, and interfaces.
[0018] These and various other features as well as advantages,
which characterize the present invention, will be apparent from a
reading of the following detailed description and a review of the
associated drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 depicts a logical representation of an exemplary
compiler operative to provide a unified view of a type system
according to an embodiment of the present invention.
[0020] FIG. 2 illustrates a computer system that provides the
operating environment for an exemplary embodiment of the present
invention.
[0021] FIG. 3a depicts an exemplary value type list used in an
exemplary embodiment of the present invention to categorize data
types.
[0022] FIG. 3b depicts an exemplary object class hierarchy used in
an exemplary embodiment of the present invention to organize
objects.
[0023] FIG. 4 depicts a set of boxed and unboxed data types.
[0024] FIG. 5 depicts a more detailed logical representation of the
exemplary compiler system of FIG. 1.
[0025] FIG. 6 illustrates a method for boxing and unboxing a value
type in an exemplary embodiment of the present invention.
[0026] FIG. 7 illustrates a method for implementing the boxing and
unboxing of a value type at runtime in an embodiment of the present
invention.
[0027] FIG. 8 illustrates an alternative method for implementing
the boxing and unboxing of a value type at runtime in an embodiment
of the present invention.
DETAILED DESCRIPTION
[0028] Exemplary embodiments of the present invention provide for a
more unified view of the type system of programming languages, and
object oriented programming languages in particular. An exemplary
type system includes a dual representation for basic data types.
One representation is the basic data type representation referred
to as an unboxed value type or simply as a value type. An unboxed
value type is generally not accompanied by type information in the
output code emitted from a compiler. In an embodiment of the
present invention, however, each of the basic data types also has a
boxed representation that exists in the object hierarchy of the
type system and is accompanied by type information (e.g., specified
by metadata) in the output code emitted from the compiler. This
dual representation can also be extended b user-defined types, so
that user-defined types may exist both as an unboxed value type and
as an object (i.e., boxed value type) within the object hierarchy
of the type system. This allows the compiler and/or runtime to
select the most effective and efficient representation for the data
type depending on the particular need at the moment.
[0029] FIG. 1 depicts a logical representation of a compiler
operating to provide a unified view of a type system in an
embodiment of the present invention. A source file 100 represents
source program code that is prepared in compliance with a given
programming language specification, including without limitation
specifications relating to C Language, C++, or any other high level
source programming language or intermediate language. The source
file 100 may include instructions and data for performing one or
more operations in a runtime environment 102. In the illustrated
embodiment, the source file 100 is received by a compiler 104,
which translates the source code into output code 108 (e.g., object
code or executable code). In an alternative embodiment of the
present invention, it should be understood that the compiler 104
may be incorporated into the runtime environment 102 (e.g., as a
Just-In-Time (JIT) compiler) as shown in FIG. 5.
[0030] In an alterative embodiment of the present invention, the
source code of the source file 100 may first be translated into an
intermediate language before being received by the compiler 104, as
represented by an intermediate language code file 106. It should be
understood that the following discussion addresses an embodiment in
which source file 100 is input to the compiler 104, although it is
contemplated that either source code or intermediate code may be
input to the compiler 104 in an embodiment of the present
invention. Likewise, both source code and intermediate code may
have compatible structures and syntaxes for defining data and
associated data types within the scope of the present
invention.
[0031] Generally, a compiler is a program that translates source
code (or intermediate language code) into object code or executable
code. The compiler derives its name from the way it works, looking
at an entire piece of source code and collecting and reorganizing
the instructions and data therein. In some implementations, a
second stage includes a linker that links the compiled object code
with other object code to produce an executable program. In other
implementations, this linking process is performed just prior to or
during runtime and is referred to as "late binding" or "runtime
binding".
[0032] As discussed, programming languages typically have a notion
of data types. Data within the source file 100 generally consists
of two data types: (1) value types 110 and (2) objects 112. For
clarity, classes and object names and discussed herein are
represented by capitalized names and value types and value type
variable names are labeled with lower case names. Data may be
defined in a source file as a "value type" using a variable name
and an associated type indicator. For example, data representing an
index may be defined as "int index;", where "int" is the data type
indicator and "index" is the variable name. Alternatively, data may
be defined in a source file as an "object" using an object name, a
class indicator, and a class definition. For example, the exemplary
source code set forth below defines a class called Rect, comprising
four Cartesian coordinates defining the four corners of a
rectangle.
TABLE-US-00001 Class Rect { Cartesian UpperLeft; Cartesian
UpperRight; Cartesian LowerLeft; Cartesian LowerRight; float area;
} Rect RectObject;
[0033] The statement "Rect RectObject" defines an object
"RectObject" (the object name) of class "Rect" (the class
indicator). Note that the RectObject may also include other objects
and value types, such as objects "UpperLeft", "UpperRight",
"LowerLeft", and "LowerRight", of class Cartesian (the class
definition of which is not shown) and a value type "area" of data
type "float". It should also be understood that the discussion
above merely represents an exemplary definition of data in a source
file, and that alternative data structures and syntaxes of data
definition are contemplated within the scope of the present
invention.
[0034] The compiler 104 may include or have access to one or more
of a variety of built-in data types, including built-in value types
114 and a basic object class hierarchy 116, and type rules 118 for
converting between and defining the relationship between various
data types. Generally, built-in value types represent value types
that are believed to be fundamental to the programming language and
commonly used by programmers, such as "int" for an integer, "char"
for a character, and "float" for a floating point number.
[0035] Likewise, the basic object class hierarchy 116 includes
fundamental and commonly used classes in an inheritance hierarchy.
For example, a root class in the hierarchy may define a
"BasicObject", which includes fundamental characteristics (e.g.,
data and functions) of a basic object in the programming language.
Children of the root class may be defined to "inherit" or "extend"
the BasicObject class for more specific uses. For example, a
"Shape" class and a "Point" class may inherit from the BasicObject
class, and a "Rect" class and a "Circle" class may inherit from the
"Shape" class. The combination of basic classes comprises an object
class hierarchy. Another example object class hierarchy is
illustrated in FIG. 3b and is discussed below.
[0036] In many programming languages, both built-in value types and
basic classes may be extended or customized. For example, in C
language, a developer may define a new value type using the keyword
"typedef". For example, a value type "coordinate" may be defined as
a structure containing two floating point numbers representing X-Y
coordinates on a Cartesian plane, as set forth below.
TABLE-US-00002 typedef struct { float x; float y; } coordinate;
[0037] Likewise, source code may extend the basic object class
hierarchy by inheriting or extending one or more of the basic
classes For example, a user-defined object may extend the basic
Shape class to define a "CustomShape" class. Referring again to
FIG. 1, both built-in value types and user-defined value types may
be represented in source code by value types 110, and both basic
and user-defined objects may be represented in source code by
objects 112.
[0038] In an embodiment of the present invention, the compiler 104
may include type rules 118 that provide the compiler with
instructions for properly converting between different value types.
For example, in C Language, a source code instruction may assign an
integer value to a floating point variable (e.g., "float
amount=total;", where "total" is a data value of type integer and
"amount" is a floating point number variable). The C compiler can
apply the type rules 118 to automatically convert the integer
"total" into a floating point number value before generating
instructions for assigning the value to variable "amount".
Alternatively, the compiler 104 may not provide the appropriate
type rule for a given value type combination and operation (e.g.,
assigning an "integer" value to a "coordinate" variable). In such
situations, the compiler may issue a compiler error or throw a
runtime exception to signal the error.
[0039] In an embodiment of the present invention, source code
instructions for performing operations between value types and
objects by boxing and/or unboxing one or both of the operands may
be compiled and executed transparently to the developer. In a first
example, a source code instruction indicates that a value with a
value type is to be assigned to an object (e.g., a value with an
"integer" value type is assigned to an object of the "Integer"
class). To perform such an assignment without boxing would
typically cause a compiler error because the types of the operands
are not equivalent (i.e., the assignment does not satisfy a type
rule). Without boxing/unboxing, a compiler does not perform the
assignment because the "integer" value type is not associated with
metadata required to populate the Integer object's metadata portion
(see FIG. 4).
[0040] Instead, the compiler 104 detects the discrepancy between
types and generates metadata and compiler code to "box" the
"integer" value, thereby converting the value type into an object,
so that the boxed value type can be assigned to the Integer object.
If the types include a built-in value type, the compiler may be
pre-configured with the metadata required to box the value type. If
the types include a user-defined value type, the user can provide
the required metadata for the compiler to use in the boxing
operation. The metadata defining a user-defined type may describe a
sequence of bits (i.e., the value) and includes the type name,
field names for all fields in the type, field types for all fields,
and operations that can be performed in association with the type
(e.g., methods). The metadata defining a user-defined type can also
include a list of interfaces that the type will implement in its
boxed form. Finally, the metadata can include an indication as to
where a boxed version of the value type will fit within the object
class hierarchy 116, described below in connection with FIG. 3b.
Thereafter, the compiler 104 generates the object code for
assigning the "boxed value type" (or object) to the Integer
object.
[0041] Rather than generate code to box and unbox value types at
the compiler, other embodiments may implement the concept of dual
representation in different ways. For example, if the runtime
environment that is the target of the code (such as runtime
environment 102) can box and unbox value types, then the compiler
need only output a box or unbox command as appropriate and the
runtime can perform the actual work. In other implementations,
boxed and unboxed representations can exist simultaneously with no
need for either the compiler or the runtime environment to generate
code that boxes or unboxes value types. In other implementations,
only the boxed representations may be generated with a mechanism to
bypass or ignore the metadata portion when unboxed version is
desired.
[0042] The output code 108 produced by the compiler 104 logically
includes the compiled objects 120 and both boxed and unboxed
representations (122 and 124) of the value types defined in the
source file 100. In one embodiment, all value types are compiled to
logically produce both boxed and unboxed representations. The dual
representations of the value type itself may occupy effectively the
same storage location or, in an alternative embodiment, in
individual and distinct storage locations. In another embodiment,
only those value types interacting with objects are to be boxed,
thereby reducing the size of the output code 108 (i.e., unnecessary
metadata is omitted). Furthermore, another embodiment of the
present invention may retain a single version of the value type
(i.e., boxed or unboxed) at a time, converting dynamically between
the two versions, as needed. As such, only one version of the value
type need be maintained at any one time, the value type version
being dynamically converted by code generated by the compiler in
accordance with a given operation (e.g., an assignment, a function
call with object parameters, etc.).
[0043] In addition, the output code 108 may include metadata in
associated with a value type. Alternatively, the output 108 may
include a machine or executable code representation of the object
created by the boxing operation. In yet another alternative, the
machine or executable code representation may be generated at
runtime, as discussed below.
[0044] Another example of source code instructions performing
operations between value types and objects by boxing and/or
unboxing is provided in the case in which a boxed value type is to
be assigned to a value with a unboxed value type (e.g., an object
of the Integer class is assigned to a value with an integer value
type). To perform such an assignment without unboxing would
typically cause a compiler error because the types of the operands
are not equivalent. In an embodiment of the present invention,
however; the compiler 104 detects the discrepancy between types and
generates code to converts the object to an unboxed value type by
deleting or ignoring the metadata associated with the boxed value
type, so that the unboxed value type can be assigned to the
"integer" value type.
[0045] FIG. 2 and the following discussion are intended to provide
a brief, general description of a suitable computing environment in
which the invention may be implemented. While the invention will be
described in the general context of an application program that
runs on an operating system in conjunction with a personal
computer, those skilled in the art will recognize that the
invention also may be implemented in combination with other program
modules. Generally, program modules include routines, programs,
components, data structures, etc. that perform particular tasks or
implement particular abstract data types. Moreover, those skilled
in the art will appreciate that the invention may be practiced with
other computer system configurations, including hand-held devices,
multiprocessor systems, microprocessor-based or programmable
consumer electronics, minicomputers, mainframe computers, and the
like. The invention may also be practiced in distributed computing
environments where tasks are performed by remote processing devices
that are linked through a communications network. In a distributed
computing environment, program modules may be located in both local
and remote memory storage devices.
[0046] With reference to FIG. 2, an exemplary system for
implementing the invention includes a conventional personal
computer 20, including a processing unit 21, a system memory 22,
and a system bus 23 that couples the system memory to the
processing unit 21. The system memory 22 includes read only memory
(ROM) 24 and random access memory (RAM) 25. A basic input/output
system 26 (BIOS), containing the basic routines that help to
transfer information between elements within the personal computer
20, such as during start-up, is stored in ROM 24. The personal
computer 20 further includes a hard disk drive 27, a magnetic disk
drive 28, e.g., to read from or write to a removable disk 29, and
an optical disk drive 30, e.g., for reading a CD-ROM disk 31 or to
read from or write to other optical media. The hard disk drive 27,
magnetic disk drive 28, and optical disk drive 30 are connected to
the system bus 23 by a hard disk drive interface 32, a magnetic
disk drive interface 33, and an optical drive interface 34,
respectively. The drives and their associated computer-readable
media provide nonvolatile storage for the personal computer 20.
Although the description of computer-readable media above refers to
a hard disk, a removable magnetic disk and a CD-ROM disk, it should
be appreciated by those skilled in the art that other types of
media which are readable by a computer, such as magnetic cassettes,
flash memory cards, digital video disks, Bernoulli cartridges, and
the like, may also be used in the exemplary operating
environment.
[0047] A number of program modules may be stored in the drives and
RAM 25, including an operating system 35, a source file 100, a
Runtime System 102, and a compiler 104. A user may enter commands
and information into the personal computer 20 through a keyboard 40
and pointing device, such as a mouse 42. Other input devices (not
shown) may include a microphone, joystick, game pad, satellite
dish, scanner, or the like. These and other input devices are often
connected to the processing unit 21 through a serial port interface
46 that is coupled to the system bus, but may be connected by other
interfaces, such as a game port or a universal serial bus (USB). A
monitor 47 or other type of display device is also connected to the
system bus 23 via an interface, such as a video adapter 48. In
addition to the monitor, personal computers typically include other
peripheral output devices (not shown), such as speakers or
printers.
[0048] The personal computer 20 may operate in a networked
environment using logical connections to one or more remote
computers, such as a remote computer 49. The remote computer 49 may
be a server, a router, a peer device or other common network node,
and typically includes many or all of the elements described
relative to the personal computer 20, although only a memory
storage device 50 has been illustrated in FIG. 2. The logical
connections depicted in FIG. 2 include a local area network (LAN)
51 and a wide area network (WAN) 52. Such networking environments
are commonplace in offices, enterprise-wide computer networks,
intranets and the Internet.
[0049] When used in a LAN networking environment, the personal
computer 20 is connected to the LAN 51 through a network interface
53. When used in a WAN networking environment, the personal
computer 20 typically includes a modem 54 or other means for
establishing communications over the WAN 52, such as the Internet.
The modem 54, which may be internal or external, is connected to
the system bus 23 via the serial port interface 46. In a networked
environment, program modules depicted relative to the personal
computer 20, or portions thereof, may be stored in the remote
memory storage device. It will be appreciated that the network
connections shown are exemplary and other means of establishing a
communications link between the computers may be used.
[0050] Computing device, such as personal computer 20, typically
includes at least some form of computer readable media. Computer
readable media can be any available media that can be accessed by
personal computer 20. By way of example, and not limitation,
computer readable media may comprise computer storage media and
communication media. Computer storage media includes volatile and
nonvolatile, removable and non-removable media implemented in any
method or technology for storage of information such as computer
readable instructions, data structures, program modules or other
data. Computer storage media includes, but is not limited to, RAM,
ROM, EEPROM, flash memory or other memory technology, CD-ROM,
digital versatile disks (DVD) or other optical storage, magnetic
cassettes, magnetic tape, magnetic disk storage or other magnetic
storage devices, or any other medium which can be used to store the
desired information and which can be accessed by personal computer
20. Communication media typically embodies computer readable
instructions, data structures, program modules or other data in a
modulated data signal such as a carrier wave or other transport
mechanism and includes any information delivery media. The term
"modulated data signal" means a signal that has one or more of its
characteristics set or changed in such a manner as to encode
information in the signal. By way of example, and not limitation,
communication media includes wired media such as a wired network or
direct-wired connection, and wireless media such as acoustic, RF,
infrared and other wireless media. Combinations of any of the above
should also be included within the scope of computer readable
media. Computer readable media may also be referred to as computer
program product.
[0051] As described above, in connection with FIG. 1, a compiler
104 receives and compiles a source file 100 written for a runtime
environment 102 or any other execution environment. FIG. 3a depicts
an exemplary value type classification system 300 for the computer
language in which the source file 100 is written. The source file
100 may utilize both built-in value types 302 and user-defined
value types 304. Generally, value types define the notion of how to
interpret the bit patterns of data stored in a computer. For
example, a value may be a simple bit pattern representing an
integer or a floating point number. Each value has a type that
describes both the size of the storage that the value occupies as
well as the meaning of the bits in the value's representation. For
example, a value of "2" may be of type "int16." Type "int16"
indicates that the bits of the value's representation mean that the
value is an integer. Type "int16" further indicates that the value
occupies the storage necessary to store a signed 16-bit integer.
The type also describes for the compiler the operations that can be
performed on the value's representation. Generally, for unboxed
value types, the type information is not emitted into the output
code. Type "int16" is an example of a built-in value type in an
embodiment of the present invention. The previous discussion
relating to value types can apply to both user-defined value types
and built-in types so that they can be efficiently processed at
runtime. If the compiler does not already have access to the
metadata for a given value type, particularly for user-defined
value types, the user can provide the metadata in a source code
file or configuration file.
[0052] An exemplary list of data types is depicted in FIG. 3a. The
list includes a group of built-in value types 302 and a group of
user-defined value types 304. User-defined value types 304 can
include virtually any kind of data structure. In most source
languages, a user can create a user-defined value type by utilizing
combinations of built-in types, such as by defining a type name, a
field name for each field in the type, and a field type for each
field. In this one illustrative example, the point data type 306 is
a two-value data type that defines the Cartesian coordinates of a
point in a two-dimensional space. The circle data type 308 is a
two-value data type that includes a value of point data type
defining a circle's center point and a second value of integer data
type defining the magnitude of the radius of the circle. The
rectangle data type is a four-value data type that includes a value
of point data type for each of a rectangle's corners. Notably, the
circle data type 308 and the rectangle data type 310 may utilize
the point data type 306. Thus, it can be said that the circle data
type 308 and the rectangle data types 310 "inherits" from the point
data type 306. In some implementations, this may be a true
inheritance; in others, this may simply imply that one value type
is used to build other value types.
[0053] A user can create metadata to describe a boxed form of a
value type. For example, the process of creating a user-defined
value type may include a step of specifying the metadata for that
type needed for boxing a value type. Typically, the metadata
defining a user-defined type 304 describes a sequence of bits
(i.e., the value) and includes the type name, field names for all
fields in the type, field types for all fields, and operations that
can be performed in association with the type (e.g., methods). The
metadata defining a user-defined type can also include a list of
interfaces that the type will implement in its boxed form. Finally,
the metadata can include an indication as to where a boxed version
of the type will fit within the object class hierarchy 116,
described below in connection with FIG. 3b. This metadata may be
used by the compiler, the loader, and/or the runtime environment to
verify type safety and manage boxed versions of the value type.
[0054] FIG. 3b depicts an exemplary object class hierarchy 350.
Generally, objects of the class hierarchy 350 are more complex data
types than value types 300. Each object is self-typing, in that
each object's type is explicitly stored in its representation in
the output code. An object has an identity (e.g., object name,
class name) that distinguishes it from all other objects. Each
object has fields (or data members) that can be used to store other
data, including values (with associated value types) and methods
associated with the object. Of course, the fields in an object can
themselves be objects. An object can also include location
information (e.g., a pointer) and interface information. The
objects of a class hierarchy, such as class hierarchy 350,
typically derive from a base root object. In FIG. 3b, such a base
root object is illustrated by BaseObject 320. Thus, other objects
are shown below BaseObject 320 in the object class hierarchy 350
and, therefore, inherit from the BaseObject 320.
[0055] The object class hierarchy of FIG. 3b illustrates the dual
representation of value types in one aspect of the invention. FIG.
3b shows a representative class hierarchy that includes the boxed
representations of the value types illustrated in FIG. 3a. In the
object class hierarchy 350, built-in value types 352 (e.g., integer
325, floats 326, and Boolean 328) and user-defined value types 354
(e.g., point 330, rectangle 332, and circle 334) are stored as any
other object 356 within the object class hierarchy. The built-in
value types 352 and user-defined value types 354 depicted in FIG.
3b are boxed value types. Thus, the built-in value types 352 and
user-defined value types 354 may be processed at runtime on the
same basis as any other object in the hierarchy. As stated above, a
boxed value type is created from an unboxed value type by
associating the unboxed value type with metadata providing the
boxed value type with object-like attributes. Metadata will be
described in more detail in connection with FIG. 4.
[0056] Notably, a "child" object, such as Object y, inherits the
attributes of a "parent" object, such as Object x. If a method is
associated with Object x, for example, then the method is also
associated with Object y, by inheritance. One aspect illustrated in
FIG. 3b is that the boxed representations of value types may
include parent-child relationships, even though there is no notion
of parent-child relationship in value types. For example, in FIG.
3b both circle and rectangle derive from point. Similarly, child
boxed value types (e.g., circle value type 334) inherit methods and
other attributes from parent boxed value types (e.g., point value
type 330). Such inherited methods are referred to as virtual
methods. Because of the dual representation of value and object
types in the present invention, developers need not worry which
form is passed to methods. Thus, an unboxed value type may be
passed into an object method where a boxed representation is
expected or vice versa. The compiler and/or runtime can select the
appropriate representation either at compile or run time as
appropriate for the particular implementation.
[0057] The dual representation of value types both as unboxed value
types and as boxed value types in the object class hierarchy
implies that value types can have methods and can behave as objects
in some instances and as unboxed value types in other instances.
The practical effect is that when value types are in their boxed
representation, they can have methods like other objects. When
value types are in their unboxed representation, they can be valid
arguments to methods that would otherwise expect an object type
(such as a boxed representation). Because both the boxed and
unboxed value type representations can be made available, this
functionality can be provided without the developer having to
explicitly specify either what version to use or the conversion
from one form to another.
[0058] A data type fully describes a value if it completely defines
the value's representation and the operations that can be performed
on the value. For a data type, defining the value's representation
entails describing the sequence of bits that make up the value's
representation. Defining the set of operations that can be
performed on a data type entails specifying named methods for each
operation. A named method describes an operation that can be
performed in association with a data type.
[0059] For an object, defining the object's representation entails
describing the object's location and the sequence of bits that make
up the object's representation. Thus an object includes a
definition of the object's contents and the operations that may be
performed on that object. When an object contains a value, this
definition includes the value's representation and the operations
that can be legally performed in association with the value (e.g.,
methods). Defining an object entails describing the sequence of
bits that make up the value's representation (self describing
data), the location of the object (pointer data), and at least one
named method for the object (interface data).
[0060] Thus, an object differs from an unboxed data type, in that
an object includes not just raw data (i.e., a value
representation), but also other data including the location of the
object. This other data is stored in the object as metadata.
Advantageously, metadata can be stored in a way that is independent
of any particular programming language. Thus, metadata provides a
common interchange mechanism for use between tools that manipulate
objects (e.g., compilers, debuggers).
[0061] Turning now to FIG. 4, an unboxed value type 400 is depicted
as containing only raw value data 401 (i.e., a value
representation). A boxed value type 402 is depicted as containing
raw value data 401, as well as metadata 404. For every value type
(built-in or user-defined), a corresponding boxed value type can be
created. Boxed data types have the characteristics of objects, as
described above, because the metadata provides a means for
associating the boxed data type with value-describing data,
location data, and method data. Thus, the association of metadata
with the boxed value type permits the storage of the boxed value
type within the object class hierarchy 320 of FIG. 3b. In an
exemplary embodiment of the present invention, the boxed and
unboxed value types depicted in FIG. 4 can be stored in the output
code 108 (FIG. 1). It should be understood that FIG. 4 illustrates
a logical representation of a boxed value type, indicating that
metadata is associated with the storage location of the value
type.
[0062] Functional software components of another system 500 that
incorporates aspects of the present invention are shown in FIG. 5.
The system 500 incorporates at least one front end compiler, such
as compilers 502, 504 and 506, which are not intended to show
requirements of the present invention but merely to illustrate
concepts of the present invention applied to multiple or combined
front end systems. The front end compilers 502, 504 and 506 are
capable of parsing and analyzing different types of source language
files, such as source files 508, 510 and 512, respectively. These
source files 508, 510 and 512 can include built-in value types,
user-defined value types, and objects. In this embodiment, the
front end compilers 502, 504 and 506 each produce a common language
output file 514, 516 and 518. Generally, compilers 502, 504 and 506
are functionally similar to compiler 104, described in connection
with FIG. 1.
[0063] In an exemplary embodiment of the present invention, the
common language output files 514, 516 and 518 have executable
instructions in a "common" (in the sense of universal) intermediate
language suitable for representing the concepts of a plurality of
different types of source languages, e.g., procedural, functional
and object oriented languages, so that only one type of
intermediate language need be used regardless of the specific
source language used. The executable instructions within the common
language output files 514, 516 and 518 can be either instructions
that can be directly executed by a processor (e.g., object or
native machine code) or an "intermediate" type instruction (e.g.
Java bytecodes, p-code, or other intermediate language) that is
executed within some type of execution environment.
[0064] The front end compilers 502, 504 and 506, in addition to
being able to read and analyze their respective source files 508,
510 and 512, are capable of reading and analyzing files represented
in the common language. Moreover, a library declarations file 520
of functions represented in the common language is available for
use by the front end compilers 502, 504 and 506.
[0065] The common language files 514, 516 and 518, once compiled,
may be transmitted to an execution environment or runtime
environment 522. In this application, execution environment and
runtime environment are used interchangeably. The execution
environment may be either a direct execution environment, a managed
runtime environment or an unmanaged runtime environment.
Advantageously, any necessary conversions of unboxed value types to
boxed value types (or vice versa) may be performed either at the
compiler stage, thereby permitting the use of such converted value
types without regard to the managed or unmanaged status of the
runtime environment, or by the runtime environment. Indeed, the
environment may be any other type of environment capable of reading
and executing the compiled files 514, 516 and 518. The runtime
environment 522 shown in FIG. 5 represents a managed environment
having a plurality of features, functions and services, as
discussed below.
[0066] Prior to being supplied to the runtime environment 522, each
output file 514, 516 and 518 may undergo optional processing prior
to as illustrated by the separate optional processing section 524
or the integral optional processing section 526. Generally,
optional processing may involve verification, type checking, and or
any translation of the common language file into a form suitable
for use by the runtime environment 522. Hence, optional processing
may be used to translate, interpret or otherwise convert the
received common output files 514, 516 and 518, into output code
that can be executed in the execution environment 522.
[0067] In the case where the execution environment 522 is a managed
runtime environment as shown in FIG. 5, then runtime environment
itself has a loader 530 which loads the files for execution. The
loader 530 receives the executable file and resolves necessary
references and loads the code. The environment may provide a stack
walker 532, i.e., the piece of code that manages the method calls
and provides for the identification of the sequence of method calls
on a stack at a given point in time. A layout engine 534 may also
be provided, which establishes the layout, in memory, of the
various objects and other elements as part of the application to be
executed. The execution environment may further provide a security
module 536 to prevent unauthorized use of resources by determining
whether certain code has permission to access certain system
resources (or even execute at all). The runtime environment may
further provide memory management services, such as a garbage
collector 538, and other developer services 540, such as debuggers
and profiling. Other types of services that can be provided by a
managed execution environment include verification of code before
it is executed, among others.
[0068] The execution environment 522 may further utilize a common
library program file 528, which has the actual implementation
information to carry out the functionality of the common library
declarations 520.
[0069] During runtime, the output files 514, 516 and 518 are loaded
into the runtime environment 522. Importantly, the information that
is provided to the runtime environment, such as the boxed or
unboxed value types shown in FIG. 4, is used by the runtime
environment to shape objects prior to runtime. The layout engine
generally uses the information to create data structures for each
of the types of classes including the appropriate method and field
information.
[0070] FIG. 6 depicts an operation flow for boxing and unboxing an
individual value type in an exemplary embodiment of the present
invention. Because the boxing and unboxing can be done
automatically, both versions of a particular data type can be made
to be always available at runtime. Accordingly, the most efficient
form of the value type can be selectively used, depending on the
situation (e.g., assigning an unboxed value type to an object). Of
course, the conversion can also be avoided in instances where the
compiler 104 determines that the converted form of the value type
is not needed.
[0071] The logical operations in FIG. 6 are implemented (1) as a
sequence of computer implemented steps or a program module running
on a computing system and/or (2) as interconnected logic circuits
or machine logic modules within the computing system. The
implementation is a matter of choice dependent on the performance
requirements of the computing system implementing the invention.
Accordingly, the logical operations making up the embodiments of
the present invention described herein are referred to variously as
operations, steps or modules. It will be recognized by one skilled
in the art that these operations, steps and modules may be
implemented in software, in firmware, in special purpose digital
logic, and any combination thereof without deviating from the
spirit and scope of the present invention as recited within the
claims attached hereto.
[0072] In one embodiment of the present invention, the operations
of FIG. 6 start at step 600 and proceed to unboxed test operation
602. Test operation 602 detects whether the source file includes a
trigger requiring an unboxed to boxed conversion. An unboxed to
boxed conversion trigger can be any entity in the source file that
indicates that an unboxed to boxed conversion is needed. Examples
of unboxed to boxed conversion triggers include situations where an
unboxed value type is assigned to a boxed value type and where an
unboxed value type is passed to an object expecting a boxed value
type or another object. In both of these example cases, an unboxed
to boxed conversion would be required. If test operation 602
detects that the source file includes a trigger requiring an
unboxed to boxed conversion, then the operation flow branches YES
to unboxed value type emit operation 604. The unboxed value type
emit operation 604 emits code from the compiler to perform the
unboxed to boxed conversion, the unboxed value type, and the
metadata associated with the unboxed value type to the runtime
environment via the output code. The operation flow then proceeds
to conversion operation 608, which at runtime converts or builds a
boxed value type from the emitted code, the unboxed value type, and
the metadata associated with the unboxed value type. Operation flow
proceeds to operation 619 and ends for the converted value
type.
[0073] The boxed value type can include the definition of the type
name, the field names, field types, and operations that can be
performed in association with the boxed value type (e.g., methods).
Creation of the boxed value type can also include the creation of
metadata representing the appropriate position of the boxed value
type in an object class hierarchy and any relationships with other
boxed value types.
[0074] Notably, boxed test operation 610 is also reached if a
determination is made at unboxed test operation 602 that the source
file does not include a trigger requiring an unboxed to boxed
conversion. Boxed test operation 610 detects whether the source
file includes a conversion trigger requiring a boxed to unboxed
conversion. If the source file does not include a conversion
trigger requiring an unboxed to boxed conversion, then the
operation flow branches NO to step 612 and ends for the converted
value type.
[0075] On the other hand, if boxed test operation 610 detects that
the source file includes a conversion trigger requiring an unboxed
to boxed conversion, then the operation flow branches YES to boxed
value type emit operation 614. The boxed value type emit operation
614 emits code to perform the boxed to unboxed conversion, the
boxed value type, and the metadata associated with the boxed value
type to the runtime environment via the output code. The operation
flow then proceeds to conversion operation 616 and converts or
builds an unboxed value type from the code to perform the boxed to
unboxed conversion, the boxed value type, and the metadata
associated with the boxed value type in the output code.
[0076] A boxed to unboxed conversion trigger can be any entity in
the source file that indicates that the conversion is needed.
Examples of conversion triggers include situations where a boxed
value type is assigned to an unboxed value type and where a boxed
value type is passed to an object expecting an unboxed value type.
In both of these example cases, a boxed to unboxed conversion would
be required. The operation flow proceeds to step 618 and ends with
regard to the converted value type.
[0077] It will be appreciated that the operation of FIG. 6 may be
modified so that a conversion is not necessarily performed for each
value type detected in a source file. A preliminary determination
may also be made as to whether a conversion is appropriate. For
example, a compiler may recognize that a boxed, built-in value type
is never implemented in its unboxed format by the source file. In
such a case, a conversion may be avoided as unnecessary.
[0078] As discussed, the process described with regard to FIG. 6
relates to the logical processing of an individual value type.
Typically, however, multiple value types are included in a source
code file and may require boxing and unboxing as appropriate. In
one embodiment of the present invention, the detecting operations
602 and 610 and the emitting operations 604 and 614 are generally
performed for multiple value types during a compilation stage
before proceeding to the converting operations 608 and 616 during
runtime. In this manner, most (or all) required converting code is
emitted into the output code for execution during runtime.
[0079] In an alternative embodiment of the present invention,
however, the detecting operations 602 and 610 and the emitting
operations 604 and 614 may also be performed during runtime. The
"emitting" operations are embodied by a call to boxing or unboxing
code during runtime. Such an embodiment is disclosed with regard to
FIGS. 7 and 8, for example.
[0080] During execution of the object code 106 (FIG. 1), the
runtime environment, such as runtime environment 522 (FIG. 5), may
determine whether to use the boxed or unboxed version of a
particular data type as in the implementation of a virtual method.
In an embodiment, the flow 700 illustrates a particular situation
wherein the runtime environment performs the selection operation,
as compared to the compiler. Initially, the flow generally begins
with defining operation 702, which defines a particular value type
that is to be used in a function call. Defining the value type
generally relates to providing some information as to whether the
value type is boxed or unboxed. In an embodiment, a bit may be
associated with the value type and the bit is either set or cleared
depending on whether the value type is boxed or unboxed.
[0081] Once the value type has been defined, pass operation 704
passes the defined the value type to a particular function. In
essence during compile time, the compiler emitted code to provide
for the passing of the value type to the function during runtime.
Passing a parameter of this sort to a function is straightforward
and effectively provides the necessary value type information to
the function for operation.
[0082] The particular function that receives the defined value type
expects either a boxed or unboxed value type. Therefore, following
the passing operation 704, determination act 706 determines whether
the passed value type is the same as the expected value type. The
determination may be a simple testing of a bit associated with the
value type or some other operation that evaluates the type of data
passed to the function.
[0083] If determination operation 706 determines that the passed
value type is not the same as the expected value type, flow
branches NO to modify operation 708. Modify operation either boxes
or unboxes the passed value type, and passes the new value type to
the function. In an embodiment where the function expected a boxed
value type but received an unboxed value type, step 708 boxes the
value type. On the other hand, had the function expected an unboxed
value type but received a boxed value type, then operation 708
would unbox the value type. The result of the box operation 708 is
a pointer to an object describing the unboxed value type. Following
the modification operation 708, flow continues with call operation
710, which is described below.
[0084] If the determination step 706 determined that the passed
value type was the same as the expected value type, then flow
branches YES to call operation 710. Essentially, had the function
received a value type that was expected, no modification, such as
modification operation 708, would be necessary. Thus, flow
continues with call operation 710.
[0085] Call operation 710 calls a member method associated with the
defined function. The method may be a virtual method, e.g., wherein
the compiler could not determine one certain method to call at
compile time and therefore implemented multiple versions, such as
in the case with superclasses or in the case wherein the function
may receive both boxed and unboxed versions of value types. The
member method is related to a user defined method for operating on
the passed value type. At compile time, the compiler emits the code
for performing the various methods within the function. However,
since the function may receive different types, the compiler does
not insert the specific code within the function for each type.
Instead, the compiler creates a virtual method table. The virtual
method table comprises the necessary information to perform the
method for each of the specific value types that the function may
receive.
[0086] Therefore, once the method has been called at 710, the
runtime environment executes the method call using the reference to
the appropriate method in the virtual method table. More
specifically, lookup operation 712 looks up the particular method
related to the passed value type. Once the particular method for
that type is found, execute operation 714 executes the method for
that value type.
[0087] As stated, the above-described flow of operations is able to
handle either boxed or unboxed parameters. A key feature relates to
the use of a virtual table to provide methods for the different
value types that may be passed to a particular function. Since the
function may receive different types and since the compiler is
unaware of which type the function will receive, the runtime
environment performs the necessary analysis and resolves any
discrepancies between value types.
[0088] A flow 800 of operations in an alternative embodiment to
that shown in FIG. 7 is shown in FIG. 8. The first two acts of flow
800, define operation 802 and pass operation 804 are similar to
acts 702 and 704 described above in conjunction with FIG. 7. That
is, define operation 802 defines the value type as boxed or unboxed
and then pass operation 804 passes the value to the function.
[0089] Once passed, call operation 806 then calls the member
function. This act is similar to call operation 710 described above
wherein the actual method is called. Following the call operation
806, lookup operation 808 looks up the called method for the passed
value type in the virtual method table. Lookup operation 808 is
similar to operation 712 described above.
[0090] Following call operation 806 and lookup operation 808,
determination act 810 determines whether the passed value type is
the same as the expected value type. Determination act 810 is
similar to the determination act 706 described above in that the
passed value type is analyzed against the expected form of the
value type. One difference, however, is that the code for
performing the determination act may actually reside in the front
portion of the called method code, as described below.
[0091] If the determination act 810 determines that the passed
value type is different from the expected form, then flow branches
NO to modify operation 812. Modify operation 812 is similar to
modify operation 708 described above in conjunction with FIG. 7.
Essentially, if the modification is necessary, modification act 812
performs the necessary acts required to box or unbox the value type
as needed, (e.g., calls appropriate boxing or unboxing code). Once
modified, execute operation 814 executes the method using the
modified value type.
[0092] If, on the other hand, determination act 810 determines that
the passed value type is the same as the expected value type, then
execute operation 814 performs the method using the passed value
type. Since the passed value type was the same as the expected
value type, then no modification act, such as act 812, is needed
prior to execution.
[0093] The embodiment shown in FIG. 8 allows the caller object to
simply call a method and pass a value type to that function that
performs the method. The caller does not have to make a
determination as to whether the value type is correct. Such a
caller object may then be streamlined such that it performs fewer
operations. The tradeoff, however, is that the method or some other
module must perform the determination operation. In essence, the
plumbing may reside as a small portion of code that is performed
prior to the execution of the method. When the number of callers
outweighs the number of called methods, such a streamlining of the
caller objects may be helpful.
[0094] Thus, the present invention is presently embodied as a
method, apparatus, or article of manufacture, such as computer
readable media or program product containing a computer program,
for processing objects of various programming languages and for
boxing and unboxing a user-defined data type. While the invention
has been particularly shown and described with reference to
preferred embodiments thereof, it will be understood by those
skilled in the art that various other changes in the form and
details may be made therein without departing form the spirit and
scope of the invention.
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