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diff --git a/doc/manual/index.html b/doc/manual/index.html new file mode 100755 index 0000000..6c29000 --- /dev/null +++ b/doc/manual/index.html @@ -0,0 +1,1454 @@ +<H1>GlueGen Manual</H1> + +<H2> Table of Contents </H2> + +Chapter 1 - Introduction +<UL> +<LI> <a href = "#SecIntroduction">Introduction</a> +<LI> <a href = "#SecStructure">Structure of the Generated Glue Code</a> +<LI> <a href = "#SecUnique">Unique Features</a> +<LI> <a href = "#SecBackground">Background and Design Principles</a> +</UL> + +Chapter 2 - Using GlueGen +<UL> +<LI> <a href = "#SecBasic">Basic Operation</a> +<LI> <a href = "#SecPCPP">PCPP</a> +<LI> <a href = "#SecError">Error Reporting</a> +<LI> <a href = "#SecStub">Stub Headers</a> +<LI> <a href = "#Sec32">32- and 64-bit Considerations</a> +<LI> <a href = "#SecOpaque">Opaque Directives</a> +<LI> <a href = "#SecConfiguration">Configuration File Directives</a> + <UL> + <LI> <a href = "#SecJavaEmitter">JavaEmitter Configuration</a> + <LI> <a href = "#SecProcAddressEmitter">ProcAddressEmitter Configuration</a> + </UL> +</UL> + +Chapter 3 - Configuration File Examples<BR> +TO DO: +<UL> +<LI> Example with XVisualInfo* return type +<LI> Example with GLXFBConfig* (e.g. glXChooseFBConfig) +<LI> More... +</UL> + +<H2> Chapter 1 - Introduction </H2> + +<H3> <a name="SecIntroduction">Introduction</a> </H3> + +<P> + +GlueGen is a tool which automatically generates the Java and JNI code +necessary to call C libraries. It reads as input ANSI C header files +and separate configuration files which provide control over many +aspects of the glue code generation. GlueGen uses a complete ANSI C +parser and an internal representation (IR) capable of representing all +C types to represent the APIs for which it generates interfaces. It +has the ability to perform significant transformations on the IR +before glue code emission. GlueGen is currently powerful enough to +bind even low-level APIs such as the Java Native Interface (JNI) and +the AWT Native Interface (JAWT) back up to the Java programming +language. This allows libraries needing to access such low-level APIs +to be written in Java instead of a combination of handwritten JNI and +C code as well as Java code. + +</P> +<P> + +GlueGen is currently used to generate the JOGL interface to the OpenGL +3D graphics API and the JOAL interface to the OpenAL audio library. In +the case of JOGL, GlueGen is used not only to bind OpenGL to Java, but +also the low-level windowing system APIs on the Windows, X11 and Mac +OS X platforms. The implementation of the JOGL library is thereby +written in the Java programming language rather than in C, which has +offered considerable advantages during the development of the library. + +</P> +<P> + +GlueGen is designed in modular form and can be extended to alter the +glue code emission style or to generate interface code for other +languages than Java. + +</P> +<P> + +This manual describes how to use GlueGen to bind new C libraries to +the Java programming language. + +<H3> <a name="SecStructure">Structure of the Generated Glue Code</a> </H3> + +<P> + +GlueGen supports two basic styles of glue code generation: everything +in one class, or a separate interface and implementing class. The +first mode, "AllStatic", exposes the underlying C functions as a set +of static Java methods in a concrete class. This is a straightforward +binding mechanism, but has the disadvantage of tying users to a +concrete class (which may or may not be a problem) and makes it more +difficult to support certain kinds of call-through-function-pointer +semantics required by certain C APIs. The second mode, +"InterfaceAndImpl", exposes the C functions as methods in an interface +and emits the implementation of that interface into a separate class +and package. The implementing class is not intended to be in the +public API; this more strongly separates the user from the +implementation of the API. Additionally, because it is necessary to +hold an instance of the implementing class in order to access the +underlying C routines, it is easier to support situations where +call-through-function-pointer semantics must be followed, in +particular where those function pointers might change from instance to +instance. + +</P> +<P> + +The generated glue code follows some basic rules in binding C APIs to +Java: + +<UL> + +<LI> C primitive types are exposed as the corresponding Java primitive + type. + +<LI> Pointers to typed C primitives (<code>int*</code>, + <code>float*</code>) are bound to java.nio Buffer subclasses + (<code>IntBuffer</code>, <code>FloatBuffer</code>) and optionally + to Java arrays (<code>int[]</code>, <code>float[]</code>). + + <UL> + + <LI> If a C function takes such a pointer as an outgoing argument, + two method overloadings will generally be produced; one which + accepts a Buffer, and one which accepts a primitive array plus + an integer offset argument. The variant taking a Buffer may + accept either a "direct" NIO Buffer or a non-direct one + (wrapping a Java array). The exception is when such a routine + is specified by the <a href="#NioDirectOnly">NioDirectOnly</a> + directive to keep a persistent pointer to the passed storage, + in which case only the Buffer variant will be generated, and + will only accept a direct Buffer as argument. + + <LI> If a C function returns such a pointer as its result, it will + be exposed as the corresponding Buffer type. In this case it is + also typically necessary to specify to GlueGen via the <a + href="#ReturnValueCapacity">ReturnValueCapacity</a> directive + the number of addressable elements in the resulting array. + + </UL> + +<LI> Pointers to <code>void*</code> are bound to java.nio.Buffer. + + <UL> + + <LI> By default any C function accepting a <code>void*</code> + argument will allow either a direct or non-direct java.nio + Buffer to be passed as argument. If the <a + href="#NioDirectOnly">NioDirectOnly</a> directive is specified, + however, only a direct Buffer will be accepted. + + <LI> Similar rules for <code>void*</code> return values apply to + those for pointers to typed primitives. + + </UL> + +<LI> To avoid an explosion in the number of generated methods, if a + particular API accepts more than one typed primitive pointer + argument, only two overloadings continue to be produced: one + accepting all arrays as arguments and one accepting all Buffers + as arguments. When calling the variant accepting Buffers, all of + the Buffers passed in a particular call must be either direct or + non-direct. Mixing of direct and non-direct Buffers in a given + function call is not supported. + +<LI> When a java.nio Buffer is passed from Java to C, the position of + the Buffer is taken into account. The resulting pointer passed to + C is equal to the base address of the Buffer plus the position + scaled appropriately for the size of the primitive elements in + the Buffer. This feature is called "auto-slicing", as it mimics + the behavior of calling Buffer.slice() without the overhead of + explicit object creation. + +<LI> Pointers to constant <code>char*</code> may be bound to + java.lang.String using the <a + href="#ArgumentIsString">ArgumentIsString</a> or <a + href="#ReturnsString">ReturnsString</a> directives. + +<LI> <code>#define</code> statements in header files mapping names to + constant values are exposed as public static final constant + values in either the generated interface or AllStatic class. + +<LI> C structs encountered during the glue code generation process and + referenced by the C functions are exposed as Java classes of the + same name (typically the name to which the struct is typedefed). + Each primitive field in the struct is exposed as two methods; a + getter, which accepts no arguments, and a setter, which accepts + as argument a primitive value of the type of the field. Static + factory methods are exposed allowing allocation of these structs + from Java code. The backing storage for these Java classes is a + direct java.nio Buffer. GlueGen fully supports returning of + pointers to C structs up to Java. + +</UL> + +<H3><a name="SecUnique">Unique Features</a></H3> + +GlueGen contains several unique features making it both a powerful and +easy-to-use tool. + +<UL> + +<LI> C structs are exposed as Java classes. The generated code for + these classes supports both 32-bit and 64-bit platforms. + +<LI> C structs containing function pointers are exposed as Java + classes with methods. This makes it easy to interact with + low-level C APIs such as the AWT Native Interface (JAWT) from the + Java programming language level. + + <UL> + + <LI> In this context, GlueGen automatically detects which argument + to the various function pointers indicates the "this" pointer, + hiding it at the Java level and passing it automatically. + + <LI> GlueGen offers automatic handling of JNI-specific data types + such as <code>JNIEnv*</code> and <code>jobject</code>. The tool + understands that the <code>JNIEnv*</code> argument is implicit + and that <code>jobject</code> maps to java.lang.Object at the + Java programming language level. While this is most useful when + binding JDK-internal APIs such as the JAWT to Java, there may + be other JNI libraries which expose C functions taking these + data types, and GlueGen can very easily bind to them. + + </UL> + +</UL> + +<H3><a name="SecBackground">Background and Design Principles</a></H3> + +<P> + +This section provides motivation for the design of the GlueGen tool +and is not necessary to understand how to use the tool. + +</P> +<P> + +There are many tools available for assisting in the autogeneration of +foreign function interfaces for various high-level languages. Only a +few examples include <a +href="http://alumni.media.mit.edu/~kbrussel/Header2Scheme/">Header2Scheme</a>, +an early tool allowing binding of a limited subset of C++ to the +Scheme programming language; <a href="http://www.swig.org/">SWIG</a>, +a tool released at roughly the same time as Header2Scheme which by now +supports binding C and C++ libraries to a variety of scripting +languages; and <a href="http://www.jniwrapper.com/">JNIWrapper</a>, a +commercial tool automating the binding of C APIs to Java. Other +language-specific tools such as Perl's XS, Boost.Python and many +others exist. + +</P> +<P> + +GlueGen was designed with a few key principles in mind. The most +fundamental was to support binding of the lowest-level APIs on a given +platform up to the Java programming language. The intended goal, in +the context of the JOGL project, was to allow subsets of the Win32 and +X11 APIs to be exposed to Java, and to use those APIs to write the +behind-the-scenes OpenGL context creation and management code in Java +instead of C. This informed several other design goals: + +<UL> + +<LI> Avoid touching the C headers as much as possible. This makes it + easier to upgrade to a more recent version of the C API just by + copying in a new set of headers. + +<LI> Avoid touching the generated glue code completely. + +<LI> Avoid having to hand-write a lot of generated glue code. Instead, + handle many complex constructs automatically and provide + sufficient control over the glue code generation to avoid having + to handwrite certain native methods where one or two lines of + tweaking would suffice. + +<LI> Support all C constructs in the parser and intermediate + representation. The rationale is that it is acceptable to cut + corners in the number of constructs supported in the Java + binding, but not whether the tool can internally represent it in + its C type system. This design goal implies starting with + complete a ANSI C parser coupled with a complete C type system. + +<LI> As the tool is targetting the Java programming language, build + the tool in the Java programming language. + +</UL> + +In order to make the problem more tractable, support for binding C++ +to the Java programming language was not considered. C++ adds many +constructs over ANSI C which make it much more difficult to reason +about and to find a useful subset to support binding to Java. +Additionally, it seems that there are relatively few C++-specific +libraries in general use which could be usefully bound to Java, +although this may be a matter of opinion. + +</P> +<P> + +GlueGen was designed with the Java programming language in mind, but +is not necessarily restricted to generating glue code for the Java +language. The tool is divided into separate parse and code generation +phases, and the internal representation is fairly easy to iterate +over. The core driver of GlueGen may therefore be useful in producing +other tools which autogenerate foreign function interfaces to C +libraries for other languages. + +</P> + +<H3><a name="SecBasic">Basic Operation</a></H3> + +<P> + +GlueGen accepts four kinds of command-line arguments: + +<UL> +<LI> -I<em>dir</em> (optional) adds <em>dir</em> to the include path. + Similarly to a C compiler or preprocessor, GlueGen scans a set of + directories to locate header files it encounters in + <code>#include</code> directives. Unlike most C preprocessors, + however, GlueGen has no default include path, so it is typically + necessary to supply at least one <code>-I</code> option on the + command line in order to handle any <code>#include</code> + directives in the file being parsed. + +<LI> -E<em>emitterClassName</em> (optional) uses + <em>emitterClassName</em> as the fully-qualified name of the + emitter class which will be used by GlueGen to generate the glue + code. The emitter class must implement the + <code>com.sun.gluegen.GlueEmitter</code> interface. If this + option is not specified, a + <code>com.sun.gluegen.JavaEmitter</code> will be used by default. + +<LI> -C<em>cfgFile</em> adds <em>cfgFile</em> to the list of + configuration files used to set up the chosen emitter. This is + the means by which a large number of options are passed in to the + GlueGen tool and to the emitter in particular. Configuration + files are discussed more in the following section. + +<LI> [ filename | - ] selects the file or standard input from which + GlueGen should read the C header file for which glue code should + be generated. This must be the last command-line argument, and + only one filename argument is supported. To cause multiple header + files to be parsed, write a small .c file #including the multiple + headers and point GlueGen at the .c file. +</UL> + +<H3><a name="SecPCPP">PCPP</a></H3> + +<P> + +GlueGen contains and uses a minimal C preprocessor called the "Pseudo +C Pre-Processor", or PCPP. A slightly specialized C preprocessor is +required for correct glue code generation with most libraries. +Constant values intended for use by end users are defined in many C +libraries' headers using <code>#define</code>s rather than constant +int declarations, and if the header is processed by a full C +preprocessor then the #define statements will be stripped become +unavailable for processing by the glue code generator. + +</P> +<P> + +PCPP is largely an invisible part of the glue code generation process; +however, it has certain limitations which make it difficult to parse +certain header files. First, it does not support macro evaluation in +any form, so if a header relies on macro evaluation in order to +generate code, PCPP will fail. It is possible that PCPP may fail +silently in this situation, causing GlueGen to simply not produce code +for the associated constructs. If GlueGen's output is not as expected +and there is heavy use of the C preprocessor in the header, run PCPP +against the header directly (PCPP takes simply the -I and filename +arguments accepted by GlueGen) and examine the output. + +</P> +<P> + +Second, PCPP contains only limited support for <code>#if</code> +clauses. Generally speaking, its handling of <code>#if defined(foo) || +defined(bar)</code> constructs is limited to approximately what is +required to handle the OpenGL header files. If the header being parsed +relies on moderately complicated expressions being evaluated by the C +preprocessor, check the output from PCPP and ensure it is as expected. + +</P> +<P> + +Contributions to PCPP would be especially welcome. It would be very +desirable to turn it into a full-blown C preprocessor with simply the +option of passing through #define statements unchanged. + +</P> + +<H3><a name="SecError">Error Reporting</a></H3> + +<P> + +Error reporting by GlueGen's parser is currently less than ideal. +Because PCPP makes <code>#include</code> directives disappear +completely with respect to the C parser (it appears that the +<code>#line</code> directives it emits are not being consumed properly +-- an area which needs more investigation), the line numbers reported +in parse failures are incorrect in all but the simplest cases. This +makes it difficult to determine in exactly what header file and on +exactly what construct the C parser failed. + +</P> +<P> + +Fortunately, there is a relatively simple workaround. PCPP can be run +with all of the same -I arguments passed to GlueGen and the result +piped to a new .c file. GlueGen can then be invoked on that .c file +(now containing no <code>#include</code> directives) and the line +numbers on any parse failures will be correct. + +</P> + +<H3><a name="SecStub">Stub Headers</a></H3> + +<P> + +As much as is possible, GlueGen is intended to operate on unmodified C +header files, so that it is easy to upgrade the given C API being +bound to Java simply by dropping in a new set of header files. +However, most C headers contain references to standard headers like +<code>stdio.h</code>, and if this header is parsed by GlueGen, the +tool will automatically attempt to generate Java entry points for such +routines as <code>fread</code> and <code>fwrite</code>, among others. +It is impractical to exclude these APIs on a case by case basis. +Therefore, the suggested technique to avoid polluting the binding with +these APIs is to "stub out" the headers. + +</P> +<P> + +GlueGen searches the include path for headers in the order the include +directories were specified to the tool. Placing another directory in +front of the one in which the bulk of the headers are found allows, +for example, an alternative <code>stdio.h</code> to be inserted which +contains few or no declarations but which satisfies the need of the +dependent header to find such a file. + +</P> +<P> + +GlueGen uses a complete ANSI and GNU C parser written by John Mitchell +and Monty Zukowski from the set of grammars available for the ANTLR +tool by Terrence Parr. As a complete C parser, this grammar requires +all data types encountered during the parse to be fully defined. Often +a particular header will be included by another one in order to pick +up data type declarations rather than API declarations. Stubbing out +the header with a smaller one providing a "fake" type declaration is a +useful technique for avoiding the binding of unnecessary APIs during +the glue code process. + +</P> +<P> + +Here's an example from the JOGL glue code generation process. The +<code>glext.h</code> header defining OpenGL extensions references +<code>stddef.h</code> in order to pick up the <code>ptrdiff_t</code> +data type. We choose to not include the real stddef.h but instead to +swap in a stub header. The contents of this header are therefore as +follows: + +<pre> + #if defined(_WIN64) + typedef __int64 ptrdiff_t; + #elif defined(__ia64__) || defined(__x86_64__) + typedef long int ptrdiff_t; + #else + typedef int ptrdiff_t; + #endif +</pre> + +This causes the ptrdiff_t data type to be defined appropriately for +the current architecture. It will be referenced during the glue code +generation and cause a Java value of the appropriate type (int or +long) to be used to represent it. + +</P> +<P> + +This is not the best example because it involves a data type which +changes size between 32- and 64-bit platforms, and there are otner +considerations to take into account in these situations (see the +section <a href="#Sec32">32- and 64-bit considerations</a>). Here's +another example, again from the JOGL source tree. JOGL binds the AWT +Native Interface, or JAWT, up to the Java programming language so that +the low-level code which binds OpenGL contexts to Windows device +contexts may be written in Java. The JDK's <code>jawt_md.h</code> on +the Windows platform includes <code>windows.h</code> to pick up the +definitions of data types such as <code>HWND</code> (window handle) +and <code>HDC</code> (handle to device context). However, it is +undesirable to try to parse the real <code>windows.h</code> just to +pick up these typedefs; not only does this header contain thousands of +unneeded APIs, but it also uses certain macro constructs not supported +by GlueGen's <a href="#SecPCPP">minimal C preprocessor</a>. To avoid +these problems, a "stub" <code>windows.h</code> header is placed in +GlueGen's include path containing only the necessary typedefs: + +<pre> + typedef struct _handle* HANDLE; + typedef HANDLE HDC; + typedef HANDLE HWND; +</pre> + +Note that it is essential that the type being specified to GlueGen is +compatible at least in semantics with the real definition of the +HANDLE typedef in the real <code>windows.h</code>, so that during +compilation of GlueGen's autogenerated C code, when the real +<code>windows.h</code> is referenced by the C compiler, the +autogenerated code will compile correctly. + +</P> +<P> + +This example is not really complete as it also requires <a +href="#Sec32">consideration of the size of data types on 32- and +64-bit platforms</a> as well as a discussion of how certain <a +href="#SecOpaque">opaque data types</a> are described to GlueGen and +exposed in its autogenerated APIs. Nonetheless, it illustrates at a +basic level why using a stub header is necessary and useful in certain +situations. + +</P> + +<H3><a name="Sec32">32- and 64-bit Considerations</a></H3> + +<P> + +When binding C functions to the Java programming language, it is +important that the resulting Java code support execution on a 64-bit +platform if the associated native methods are compiled appropriately. +In other words, the public Java API should not change if the +underlying C data types change to another data model such as LP64 (in +which longs and pointers become 64-bit). + +</P> +<P> + +GlueGen internally maintains two descriptions of the underlying C data +model: one for 32-bit architectures and one for 64-bit architectures. +These machine descriptions are used when deciding the mapping between +integral C types such as int and long and the corresponding Java +types, as well as when laying out C structs for access by the Java +language. For each autogenerated C struct accessor, both a 32-bit and +64-bit variant are generated behind the scenes, ensuring that the +resulting Java code will run correctly on both 32-bit and 64-bit +architectures. + +</P> +<P> + +When generating the main class containing the bulk of the method +bindings, GlueGen uses the 64-bit machine description to map C data +types to Java data types. This ensures that the resulting code will +run properly on 64-bit platforms. Note that it also generally means +that C <code>long</code>s will be mapped to Java <code>long</code>s, +since an LP64 data model is assumed. + +</P> +<P> + +If <a href="#SecOpaque">Opaque directives</a> are used to cause a +given C integer or pointer data type to be mapped directly to a Java +primitive type, care should be taken to make sure that the Java +primitive type is wide enough to hold all of the data even on 64-bit +platforms. Even if the data type is defined in the header file as +being only a 32-bit C integer, if there is a chance that on a 64-bit +platform the same header may define the data type as a 64-bit C +integer or long, the Opaque directive should map the C type to a Java +long. + +</P> + +<H3><a name="SecOpaque">Opaque Directives</a></H3> + +<P> + +Complex header files may contain declarations for certain data types +that are either too complex for GlueGen to handle or unnecessarily +complex from the standpoint of glue code generation. In these +situations a stub header may be used to declare a suitably compatible +typedef for the data type. An <a href="#Opaque">Opaque</a> directive +can be used to map the resulting typedef to a Java primitive type if +it is undesirable to expose it as a full-blown Java wrapper class. + +</P> +<P> + +GlueGen hashes all typedefs internally down to their underlying +primitive type. (This is probably not really correct according to the +C type system, but is correct enough from a glue code generation +standpoint, where if the types are compatible they are considered +equivalent.) This means that if the parser encounters + +<pre> + typedef void* LPVOID; +</pre> + +then an Opaque directive stating + +<pre> + Opaque long LPVOID +</pre> + +will cause all <code>void*</code> or <code>LPVOID</code> arguments in +the API to be mapped to Java longs, which is almost never desirable. +Unfortunately, it is not currently possible to distinguish between the +LPVOID typedef and the underlying <code>void*</code> data type in this +situation. + +</P> +<P> + +A similar problem occurs for other data types for which Opaque +directives may be desired. For example, a Windows HANDLE equates to a +typedef to <code>void*</code>, but performing this typedef in a stub +header and then adding the Opaque directive + +<pre> + Opaque long HANDLE +</pre> + +will cause all void* arguments to be exposed as Java longs instead of +Buffers, which is again undesirable. Attempting to work around the +problem by typedef'ing HANDLE to an integral type, as in: + +<pre> + typedef long HANDLE; +</pre> + +may itself have problems, because GlueGen will assume the two integral +types are compatible and not perform any intermediate casts between +HANDLE and jlong in the autogenerated C code. (When casting between a +pointer type and a JNI integral type such as jlong in C code, GlueGen +automatically inserts casts to convert the pointer first to an +"intptr_t" and then to the appropriate JNI type, in order to silence +compiler warnings and/or errors.) + +</P> +<P> + +What is desired is to produce a new type name distinct from all others +but still compatible with the pointer semantics of the original type. +Then an Opaque directive can be used to map the new type name to, for +example, a Java long. + +</P> +<P> + +To implement this in the context of the HANDLE example, the following +typedef may be inserted into the stub header: + +<pre> + typedef struct _handle* HANDLE; +</pre> + +This uses a pointer to an anonymous struct name to produce a new +pointer type. This is legal ANSI C and is supported by GlueGen's +parser without having seen a declaration for "struct _handle". +Subsequently, an Opaque directive can be used to map the HANDLE data +type to a Java long: + +<pre> + Opaque long HANDLE +</pre> + +Now HANDLEs are exposed to Java as longs as desired. A similar +technique is used to expose XIDs on the X11 platform as Java longs. + + +<H3><a name="SecConfiguration">Configuration File Directives</a></H3> + +<P> + +In addition to the C headers, GlueGen requires a certain amount of +metadata in the form of configuration files in order to produce its +glue code. There are three basic reasons for this: first, GlueGen must +be informed into which Java classes the C methods are to be bound; +second, there are many configuration options for the generated glue +code, and passing them all on the command line is infeasible; and +third, there are ambiguities in many constructs in the C programming +language which must be resolved before a Java binding can be produced. + +</P> +<P> + +The contents of the configuration file are dependent on the class of +emitter specified to GlueGen. Currently there are three built-in +emitter classes: JavaEmitter, which produces a basic, static Java +binding of C functions; ProcAddressEmitter, which extends JavaEmitter +by calling the underlying C functions through function pointers, +resulting in more dynamic behavior and supporting C APIs with optional +functionality; and GLEmitter, which specializes ProcAddressEmitter to +support some OpenGL-specific constructs. The GLEmitter will be ignored +in this manual as it is specialized for JOGL and provides very little +additional functionality beyond the ProcAddressEmitter. The +JavaEmitter and ProcAddressEmitter support many options in their +configuration files. As the ProcAddressEmitter is a subclass of +JavaEmitter, all of the constructs in the JavaEmitter's configuration +files are also legal in the ProcAddressEmitter's configuration files. + +</P> +<P> + +The configuration files have a very simple line-by-line structure, and +are parsed by a very rudimentary, hand-written parser. Each +non-whitespace and non-comment line (note: comment lines begin with +'#') contains a directive like <code>Package</code>, +<code>Style</code> or <code>JavaClass</code> followed by arguments to +that directive. There are a certain set of directives that are +required for any code generation; others are optional and their +omission results in some default behavior. Directives are +case-insensitive. + +</P> +<P> + +The following is an exhaustive list of the options currently supported +by each of these emitters' configuration files. It is difficult to see +exactly how to use the tool based simply on these descriptions, so the +examples (FIXME) may be more helpful in seeing exactly how to +structure a configuration file for proper glue code generation. + +</P> + + +<H4><a name="SecJavaEmitter">JavaEmitter Configuration</a></H4> + +<P> + +Note that only a very few of the following directives are specified as +being "required" rather than "optional"; these indicate the minimal +directives needed for a valid configuration file to begin to get glue +code to be produced. In general, these are <a +href="#Package">Package</a>, <a href="#ImplPackage">ImplPackage</a>, +<a href="#JavaClass">JavaClass</a>, <a +href="#ImplJavaClass">ImplJavaClass</a>, and <a +href="#Style">Style</a>. Other directives such as <a +href="#NioDirectOnly">NioDirectOnly</a> are required in some +circumstances for the glue code to be correct, and some such as <a +href="#ReturnedArrayLength">ReturnedArrayLength</a>, <a +href="#ReturnValueCapacity">ReturnValueCapacity</a>, and <a +href="#ReturnValueLength">ReturnValueLength</a> should be specified in +some situations in order for certain return values to be useful at the +Java level. + +</P> +<P> + +The following directives are specified in alphabetical order, although +this is not necessarily the best semantic order. + +</P> + +<dl> + + +<dt><strong><a name="AccessControl">AccessControl</a></strong> +<dd> Syntax: <code>AccessControl [method name] [ PUBLIC | PROTECTED | +PRIVATE | PACKAGE_PRIVATE ]</code> <br> + +(optional) Controls the access control of a certain Java method +corresponding to a C function. The access control of all APIs defaults +to public. This is useful when using the C binding of a particular +function only as one implementation strategy of the real public API +and using <a href="#CustomJavaCode">CustomJavaCode</a> to write the +exposed API. In this case is most useful in conjunction with <a +href="#RenameJavaMethod">RenameJavaMethod</a>. + + +<dt><strong><a name="ArgumentIsString">ArgumentIsString</a></strong> +<dd> Syntax: <code>ArgumentIsString [function name] +[indices...]</code> where the first argument index is 0 <br> + +(optional) For a C function with one or more outgoing +<code>char*</code> (or compatible data type) arguments, indicates that +those arguments are semantically null-terminated C strings rather than +arbitrary arrays of bytes. The generated glue code will be modified to +emit those arguments as java.lang.String objects rather than +<code>byte[]</code> or <code>ByteBuffer</code>. + + +<dt><strong><a name="ClassJavadoc">ClassJavadoc</a></strong> +<dd> Syntax: <code>ClassJavadoc [class name] [code...]</code> <br> + +(optional) Causes the specified line of code to be emitted in the +appropriate place in the generated code to become the per-class +Javadoc for the specified class. By default GlueGen produces no +Javadoc for its generated classes, so this is the mechanism by which a +user can emit Javadoc for these classes. The specified Javadoc +undergoes no transformation by GlueGen, so the initial +<code>/**</code> and trailing <code>*/</code> must be included in the +correct place. Each line of Javadoc is emitted in the order +encountered during parsing of the configuration files. + + +<dt><strong><a name="CustomCCode">CustomCCode</a></strong> +<dd>Syntax: <code>CustomCCode [code...]</code> <br> + +(optional) Causes the specified line of C code to be emitted into the +generated native code for the implementing class. Currently there is +no way (and no real need) to be able to emit custom C code into any +other generated .c file, so the class name in the <a +href="#CustomJavaCode">CustomJavaCode</a> directive is omitted. + + +<dt><strong><a name="CustomJavaCode">CustomJavaCode</a></strong> +<dd>Syntax: <code>CustomJavaCode [class name] [code...]</code> <br> + +(optional) Causes the specified line of Java code to be emitted into +the specified generated Java class. Can be used to emit code into any +generated class: the public interface, the implementing class, the +sole concrete class (in the case of the AllStatic <a +href="#Style">Style</a>), or any of the Java classes corresponding to +referenced C structs in the parsed headers. This usage is somewhat +verbose, and the <a href="#IncludeAs">IncludeAs</a> directive provides +a more concise way of including large bodies of Java code into the +generated code. + + +<dt><strong><a name="EmitStruct">EmitStruct</a></strong> +<dd>Syntax: <code>EmitStruct [C struct type name]</code> <br> + +(optional) Forces a Java class to be emitted for the specified C +struct. Normally only those structs referenced directly by the parsed +C APIs have corresponding Java classes emitted. + + +<dt><strong><a name="Extends">Extends</a></strong> +<dd>Syntax: <code>Extends [Java interface name] [interface name to +extend] </code> <br> + +(optional) Causes the specified autogenerated Java interface to +declare that it extends another one. This directive may only be +applied to autogenerated interfaces, not concrete classes. For +concrete classes, use the <a href="#Implements">Implements</a> +directive. + + +<dt><strong><a name="HierarchicalNativeOutput">HierarchicalNativeOutput</a></strong> +<dd>Syntax: <code>HierarchicalNativeOutput true</code> <br> + +(optional) If "true", makes subdirectories for the generated native +code matching the package names of the associated classes. This is +typically not needed (or desired, as it complicates the compilation +process for this native code) and defaults to false. + + +<dt><strong><a name="Ignore">Ignore</a></strong> +<dd> Syntax: <code>Ignore [regexp]</code> <br> + +(optional) Ignores one or more functions or data types matching the +regexp argument which are encountered during parsing of the C +headers. By default GlueGen will emit all encountered C functions as +well as Java classes corresponding to all C structs referenced by +those functions. Related directives are <a +href="#IgnoreNot">IgnoreNot</a>, <a href="#Unignore">Unignore</a> and +<a href="#EmitStruct">EmitStruct</a>. + + +<dt><strong><a name="IgnoreField">IgnoreField</a></strong> +<dd> Syntax: <code>IgnoreField [struct type name] [field name]</code> +<br> + +(optional) Causes the specified field of the specified struct type +to be ignored during code generation, typically because it is too +complex for GlueGen to handle. + + +<dt><strong><a name="IgnoreNot">IgnoreNot</a></strong> +<dd> Syntax: see <a href="#Ignore">Ignore</a>. + +(optional) Similar to the <a href="#Ignore">Ignore</a> directive, but +evaluates the negation of the passed regexp when deciding whether to +ignore the given function or data type. NOTE: there is currently no +mechanism for using <a href="#Unignore">Unignore</a> with +IgnoreNot. This is a bug. The IgnoreNot mechanism may ultimately turn +out to be superfluous. + + +<dt><strong><a name="Implements">Implements</a></strong> +<dd> Syntax: <code>Implements [Java class name] [interface name to +implement]</code> <br> + +(optional) Causes the specified autogenerated Java concrete class to +declare that it implements the specified interface. This directive may +only be applied to autogenerated concrete classes, not interfaces. For +interfaces, use the <a href="#Extends">Extends</a> directive. + + +<dt><strong><a name="ImplJavaClass">ImplJavaClass</a></strong> +<dd> Syntax: <code>ImplJavaClass [class name]</code> <br> + +(optional) Specifies the name of the typically non-public, +implementation Java class which contains the concrete Java and native +methods for the glue code. If the emission style is AllStatic, there +is no distinction between the public and implementation class and +ImplJavaClass should not be specified. Otherwise, if the ImplJavaClass +is unspecified, it defaults to the JavaClass name plus "Impl". (If +both are unspecified in this configuration, an error is reported.) See +also <a href="#JavaClass">JavaClass</a>. + + +<dt><strong><a name="ImplPackage">ImplPackage</a></strong> +<dd> Syntax: <code>ImplPackage [package name]</code> <br> + +(optional) Specifies the package name into which the implementing +class containing the concrete Java and native methods will be emitted, +assuming an emission style of InterfaceAndImpl or ImplOnly. If +AllStatic, there is no separate implementing class from the public +interface. If the emission style is not AllStatic and the ImplPackage +is not specified, it defaults to the Package plus ".impl". See also <a +href="#Package">Package</a>. + + +<dt><strong><a name="Import">Import</a></strong> +<dd>Syntax: <code>Import [package name]</code> (no trailing semicolon) +<br> + +(optional) Adds an import statement at the top of each generated Java +source file. + + +<dt><strong><a name="Include">Include</a></strong> +<dd> Syntax: <code>Include [filename]</code> <br> + +(optional) Causes another configuration file to be read at the current +point in parsing the current configuration file. The filename argument +may be either absolute or relative; in the latter case it is specified +relative to the location of the current configuration file. + + +<dt><strong><a name="IncludeAs">IncludeAs</a></strong> +<dd>Syntax: <code>IncludeAs [prefix tokens] [filename]</code> <br> + +(optional) Similar to the <a href="#Include">Include</a> directive, +but prepends the specified prefix tokens on to every line of the file +to be read. The last token parsed is the name of the file to be +read. This allows, for example, <a +href="#CustomJavaCode">CustomJavaCode</a> to be stored as Java source +rather than in the configuration file; in this example the +configuration file might contain <code>IncludeAs CustomJavaCode +MyClass MyClass-CustomJavaCode.java</code>. + + +<dt><strong><a name="JavaClass">JavaClass</a></strong> +<dd> Syntax: <code>JavaClass [class name]</code> <br> + +(optional / required) Specifies the name of the public, +non-implementation Java class or interface into which the glue code +will be generated. If the emission style is not ImplOnly, the +JavaClass directive is required. See also <a +href="#ImplJavaClass">ImplJavaClass</a>. + + +<dt><strong><a name="JavaEpilogue">JavaEpilogue</a></strong> +<dd>Syntax: <code>JavaEpilogue [C function name] [code...]</code> <br> + +(optional) Adds the specified code as an epilogue in the Java method +for the specified C function; this code is run after the underlying C +function has been called via the native method but before any result +is returned. No transformations are currently performed on this code, +unlike in the <a href="#ReturnedArrayLength">ReturnedArrayLength</a> +and other directives. See also <a +href="#JavaPrologue">JavaPrologue</a>. + + +<dt><strong><a name="JavaOutputDir">JavaOutputDir</a></strong> +<dd> Syntax: <code>JavaOutputDir [directory name]</code> <br> + +(optional) Specifies the root directory into which the emitted +Java code will be produced. Subdirectories for the packages of the +associated Java classes will be automatically created. If unspecified, +defaults to the current working directory. + + +<dt><strong><a name="JavaPrologue">JavaPrologue</a></strong> +<dd> Syntax: <code>JavaPrologue [C function name] [code...]</code> +<br> + +(optional) Adds the specified code as a prologue in the Java method +for the specified C function; this code is run before the underlying C +function is called via the native method. No transformations are +currently performed on this code, unlike in the <a +href="#ReturnedArrayLength">ReturnedArrayLength</a> and other +directives. See also <a href="#JavaEpilogue">JavaEpilogue</a>. + + +<dt><strong><a name="ManuallyImplement">ManuallyImplement</a></strong> +<dd> Syntax: <code>ManuallyImplement [function name]</code> <br> + +(optional) Indicates to GlueGen to not produce a method into the +implementing class for the specified C function; the user must provide +one via the <a href="#CustomJavaCode">CustomJavaCode</a> directive. If +the emission style is InterfaceAndImpl or InterfaceOnly, a public +method will still be generated for the specified function. + + +<dt><strong><a name="NativeOutputDir">NativeOutputDir</a></strong> +<dd> Syntax: <code>NativeOutputDir [directory name]</code> <br> + +(optional) Specifies the root directory into which the emitted JNI +code will be produced. If unspecified, defaults to the current working +directory. See also <a +href="#HierarchicalNativeOutput">HierarchicalNativeOutput</a>. + + +<dt><strong><a name="NioDirectOnly">NioDirectOnly</a></strong> +<dd> Syntax: <code>NioDirectOnly [function name]</code> <br> + +(required when necessary) When passing a pointer down to a C API, it +is semantically undefined whether the underlying C code expects to +treat that pointer as a persistent pointer, living past the point of +return of the function call, or whether the pointer is used only +during the duration of the function call. For APIs taking C primitive +pointers such as <code>void*</code>, <code>float*</code>, etc., +GlueGen will typically generate up to two overloaded Java methods, one +taking a <code>Buffer</code> or <code>Buffer</code> subclass such as +<code>FloatBuffer</code>, and one taking a primitive array such as +<code>float[]</code>. (In the case of <code>void*</code> outgoing +arguments, GlueGen produces only one variant taking a Buffer.) +Normally the generated glue code accepts either a "direct" or +non-"direct" buffer (according to the New I/O APIs) as argument. +However, if the semantics of the C function are that it either expects +to hold on to this pointer past the point of the function call, or if +it can block while holding on to the pointer, the +<code>NioDirectOnly</code> directive <strong>must</strong> be +specified for this C function in order for the generated glue code to +be correct. Failing to observe this requirement may cause JVM hangs or +crashes. + + +<dt><strong><a name="Opaque">Opaque</a></strong> +<dd> Syntax: <code>Opaque [Java primitive data type] [C data +type]</code> <br> + +(optional) Causes a particular C data type to be exposed in opaque +form as a Java primitive type. This is most useful for certain pointer +types for which it is not desired to generate full Java classes but +instead expose them to Java as e.g. <code>long</code>s. It is also +useful for forcing certain integral C data types to be exposed as e.g. +<code>long</code> to Java to ensure 64-bit cleanliness of the +generated glue code. See the (FIXME) examples. The C data type may +be a multiple-level pointer type; for example <code>Opaque long +void**</code>. Note that it is not currently supported to make a given +data type opaque for just a few functions; the Opaque directive +currently applies to all C functions in the headers being parsed. +This means that sweeping Opaque declarations like <code>Opaque long +void*</code> will likely have unforseen and undesirable consequences. + + +<dt><strong><a name="Package">Package</a></strong> +<dd> Syntax: <code>Package [package name]</code> (no trailing +semicolon) <br> + +(optional / required) Specifies the package into which the public +interface or class for the autogenerated glue code will be +generated. Required whenever the emission style is not ImplOnly. See +also <a href="#ImplPackage">ImplPackage</a>. + + +<dt><strong><a name="RangeCheck">RangeCheck</a></strong> +<dd> Syntax: <code>RangeCheck [C function name] [argument number] +[expression]</code> <br> + +(optional) Causes a range check to be performed on the specified array +or Buffer argument of the specified autogenerated Java method. This +range check ensures, for example, that a certain number of elements +are remaining in the passed Buffer, knowing that the underlying C API +will access no more than that number of elements. For range checks +that should be expressed in terms of a number of bytes rather than a +number of elements, see the <a +href="#RangeCheckBytes">RangeCheckBytes</a> directive. As in the <a +href="#ReturnedArrayLength">ReturnedArrayLength</a> and other +directives, MessageFormat expressions such as "{0}" are replaced with +the corresponding incoming argument name, where the first incoming +argument is index 0. + + +<dt><strong><a name="RangeCheckBytes">RangeCheckBytes</a></strong> +<dd> Syntax: <code>RangeCheckBytes [C function name] [argument number] +[expression]</code> <br> + +(optional) Same as the <a href="#RangeCheck">RangeCheck</a> directive, +but the specified expression is treated as a minimum number of bytes +remaining rather than a minimum number of elements remaining. + + +<dt><strong><a name="RenameJavaMethod">RenameJavaMethod</a></strong> +<dd> Syntax: <code>RenameJavaMethod [from name] [to name]</code> <br> + +(optional) Causes the specified C function to be emitted under a +different name in the Java binding. This is most useful in conjunction +with the <a href="#AccessControl">AccessControl</a> directive when the +C function being bound to Java is only one potential implementation of +the public API, or when a considerable amount of Java-side custom code +is desired to wrap the underlying C native method entry point. + + +<dt><strong><a name="RenameJavaType">RenameJavaType</a></strong> +<dd> Syntax: <code>RenameJavaType [from name] [to name]</code> <br> + +(optional) Causes the specified C struct to be exposed as a Java class +under a different name. This only applies to autogenerated classes +corresponding to C structs encountered during glue code generation; +full control is provided over the name of the top-level classes +associated with the set of C functions via the <a +href="#JavaClass">JavaClass</a> and <a +href="#ImplJavaClass">ImplJavaClass</a> directives. + + +<dt><strong><a name="ReturnedArrayLength">ReturnedArrayLength</a></strong> +<dd> Syntax: <code>ReturnedArrayLength [C function name] +[expression]</code> where <code>expression</code> is a legal Java +expression with MessageFormat specifiers such as "{0}". These +specifiers will be replaced in the generated glue code with the +incoming argument names where the first argument to the method is +numbered 0. <br> + +(optional) For a function returning a compound C pointer type such as +an <code>XVisualInfo*</code>, indicates that the returned pointer is +to be treated as an array and specifies the length of the returned +array as a function of the arguments passed to the function. Note that +this directive differs subtly from <a +href="#ReturnValueCapacity">ReturnValueCapacity</a> and +ReturnValueLength. It is also sometimes most useful in conjunction +with the <a +href="#TemporaryCVariableDeclaration">TemporaryCVariableDeclaration</a> +and TemporaryCVariableAssignment directives. + + +<dt><strong><a name="ReturnsString">ReturnsString</a></strong> +<dd> Syntax: <code>ReturnsString [function name]</code> <br> + +(optional) Indicates that the specified C function which returns a +<code>char*</code> or compatible type actually returns a +null-terminated C string which should be exposed as a +java.lang.String. + + +<dt><strong><a name="ReturnValueCapacity">ReturnValueCapacity</a></strong> +<dd> Syntax: <code>ReturnValueCapacity [C function name] +[expression]</code> <br> + +(optional) Specifies the capacity of a java.nio <code>Buffer</code> or +subclass wrapping a C primitive pointer such as <code>char*</code> or +<code>float*</code> being returned from a C function. Typically +necessary in order to properly use such pointer return results from +Java. As in the <a href="#ReturnedArrayLength">ReturnedArrayLength</a> +directive, argument name substitution is performed on MessageFormat +expressions such as "{0}" where the first argument is index 0. + + +<dt><strong><a name="ReturnValueLength">ReturnValueLength</a></strong> +<dd> Syntax: <code>ReturnValueLength [C function name] +[expression]</code> <br> + +(optional) Specifies the length of a returned array of pointers, +typically to C structs, from a C function. This differs from the <a +href="#ReturnedArrayLength">ReturnedArrayLength</a> directive in the +pointer indirection to the array elements. The <a +href="#ReturnedArrayLength">ReturnedArrayLength</a> directive handles +slicing up of a linear array of structs, while the ReturnValueLength +directive handles boxing of individual elements of the array (which +are pointers) in to the Java class which wraps that C struct type. See +the (FIXME) examples for a concrete example of usage. As in the <a +href="#ReturnedArrayLength">ReturnedArrayLength</a> directive, +argument name substitution is performed on MessageFormat expressions +such as "{0}" where the first argument is index 0. + + +<dt><strong><a name="RuntimeExceptionType">RuntimeExceptionType</a></strong> +<dd> Syntax: <code>RuntimeExceptionType [class name]</code> <br> + +(optional) Specifies the class name of the exception type which should +be thrown when run-time related exceptions occur in the generated glue +code, for example if a non-direct Buffer is passed to a method for +which <a href="#NioDirectOnly">NioDirectOnly</a> was +specified. Defaults to <code>RuntimeException</code>. + + +<dt><strong><a name="StructPackage">StructPackage</a></strong> +<dd> Syntax: <code>StructPackage [C struct type name] [package +name]</code>. Package name contains no trailing semicolon. <br> + +(optional) Indicates that the specified Java class corresponding to +the specified C struct should be placed in the specified package. By +default, these autogenerated Java classes corresponding to C structs +are placed in the main package (that defined by <a +href="#PackageName">PackageName</a>). + + +<dt><strong><a name="Style">Style</a></strong> +<dd> Syntax: <code> Style [ AllStatic | InterfaceAndImpl | +InterfaceOnly | ImplOnly ] </code> <br> + +(optional) Defines how the Java API for the parsed C headers is +structured. If AllStatic, one concrete Java class will be generated +containing static methods corresponding to the C entry points. If +InterfaceAndImpl, a public Java interface will be generated into the +<a href="#Package">Package</a> with non-static methods corresponding +to the C functions, and an "implementation" concrete Java class +implementing this interface will be generated into the <a +href="#ImplPackage">ImplPackage</a>. If InterfaceOnly, the +InterfaceAndImpl code generation style will be followed, but only the +interface will be generated. If ImplOnly, the InterfaceAndImpl code +generation style will be followed, but only the concrete implementing +class will be generated. The latter two options are useful when +generating a public API in which certain operations are unimplemented +on certain platforms; platform-specific implementation classes can be +generated which implement or leave unimplemented various parts of the +API. + + +<dt><strong><a name="TemporaryCVariableAssignment">TemporaryCVariableAssignment</a></strong> +<dd> Syntax: <code>TemporaryCVariableAssignment [C function name] +[code...]</code> <br> + +(optional) Inserts a C variable assignment declared using the <a +href="#TemporaryCVariableDeclaration">TemporaryCVariableDeclaration</a> +directive in to the body of a particular autogenerated native +method. The assignment is performed immediately after the call to the +underlying C function completes. This is typically used in +conjunction with the <a +href="#ReturnValueCapacity">ReturnValueCapacity</a> or <a +href="#ReturnValueLength">ReturnValueLength</a> directives to capture +the size of a returned C buffer or array of pointers. See the (FIXME) +examples for a concrete example of usage of this directive. Note that +unlike, for example, the <a +href="#ReturnedArrayLength">ReturnedArrayLength</a> directive, no +substitution is performed on the supplied code, so the user must +typically have previously looked at the generated code and seen what +work needed to be done and variables needed to be examined at exactly +that line. + + +<dt><strong><a name="TemporaryCVariableDeclaration">TemporaryCVariableDeclaration</a></strong> +<dd> Syntax: <code>TemporaryCVariableDeclaration [C function name] +[code...]</code> <br> + +(optional) Inserts a C variable declaration in to the body of a +particular autogenerated native method. This is typically used in +conjunction with the <a +href="#TemporaryCVariableAssignment">TemporaryCVariableAssignment</a> +and <a href="#ReturnValueCapacity">ReturnValueCapacity</a> or <a +href="#ReturnValueLength">ReturnValueLength</a> directives to capture +the size of a returned C buffer or array of pointers. See the (FIXME) +examples for a concrete example of usage of this directive. + + +<dt><strong><a name="Unignore">Unignore</a></strong> +<dd> Syntax: <code>Unignore [regexp]</code> <br> + +(optional) Removes a previously-defined <a href="#Ignore">Ignore</a> +directive. This is useful when one configuration file includes +another and wishes to disable some of the Ignores previously +specified. + + +<dt><strong><a name="Unimplemented">Unimplemented</a></strong> +<dd> Syntax: <code>Unimplemented [regexp]</code> <br> + +(optional) Causes the binding for the functions matching the passed +regexp to have bodies generated which throw the stated <a +href="#RuntimeExceptionType">RuntimeExceptionType</a> indicating that +this function is unimplemented. This is most useful when an API +contains certain functions that are not supported on all platforms and +there are multiple implementing classes being generated, one per +platform. + + +</dl> + +<H4><a name="SecProcAddressEmitter">ProcAddressEmitter Configuration</a></H4> + +<P> + +The ProcAddressEmitter is a subclass of the core JavaEmitter which +knows how to call C functions through function pointers. In +particular, the ProcAddressEmitter detects certain constructs in C +header files which imply that the APIs are intended to be called +through function pointers, and generates the glue code appropriately +to support that. + +</P> +<P> + +The ProcAddressEmitter detects pairs of functions and function pointer +typedefs in a set of header files. If it finds a matching pair, it +converts the glue code emission style for that API to look for the +function to call in an autogenerated table called a ProcAddressTable +rather than linking the autogenerated JNI code directly to the +function. It then changes the calling convention of the underlying +native method to pass the function pointer from Java down to C, where +the call-through-function-pointer is performed. + +</P> +<P> + +The ProcAddressEmitter discovers the function and function pointer +pairs by being informed of the mapping between their names by the +user. In the OpenGL and OpenAL libraries, there are fairly simple +mappings between the functions and function pointers. For example, in +the OpenGL <code>glext.h</code> header file, one may find the +following pair: + +<pre> + GLAPI void APIENTRY glFogCoordf (GLfloat); +... + typedef void (APIENTRYP PFNGLFOGCOORDFPROC) (GLfloat coord); +</pre> + +Therefore the mapping rule between the function name and the function +pointer typedef for the OpenGL extension header file is "PFN + +Uppercase(funcname) + PROC". Similarly, in the OpenAL 1.1 header +files, one may find the following pair: + +<pre> + AL_API void AL_APIENTRY alEnable( ALenum capability ); +... + typedef void (AL_APIENTRY *LPALENABLE)( ALenum capability ); +</pre> + +Therefore the mapping rule between the function name and the function +pointer typedef for the OpenAL header files is "LP + +Uppercase(funcname)". + +</P> +<P> + +These are the two principal function pointer-based APIs toward which +the GlueGen tool has currently been applied. It may turn out to be +that this simple mapping heuristic is insufficient, in which case it +will need to be extended in a future version of the GlueGen tool. + +</P> +<P> + +Note that it is currently the case that in order for the +ProcAddressEmitter to notice that a given function should be called +through a function pointer, it must see both the function prototype as +well as the function pointer typedef. Some headers, in particular the +OpenAL headers, have their <code>#ifdefs</code> structured in such a +way that either the declaration or the typedef is visible, but not +both simultaneously. Because the <a href="#SecPCPP">PCPP</a> C +preprocessor GlueGen uses obeys <code>#ifdefs</code>, it is in a +situation like this that the headers would have to be modified to +allow GlueGen to see both declarations. + +</P> +<P> + +The following directives are specified in alphabetical order, although +this is not necessarily the best semantic order. The +ProcAddressEmitter also accepts all of the directives supported by the +JavaEmitter. The required directives are <a +href="#GetProcAddressTableExpr">GetProcAddressTableExpr</a> and <a +href="#ProcAddressNameExpr">ProcAddressNameExpr</a>. + +</P> + +<dl> + +<dt><strong><a name="EmitProcAddressTable">EmitProcAddressTable</a></strong> +<dd> Syntax: <code>EmitProcAddressTable [true | false]</code> <br> + +(optional) Indicates whether to emit the ProcAddressTable during glue +code generation. Defaults to false. + + +<dt><strong><a name="ForceProcAddressGen">ForceProcAddressGen</a></strong> +<dd> Syntax: <code>ForceProcAddressGen [function name]</code> <br> + +(optional) Indicates that a ProcAddressTable entry should be produced +for the specified function even though it does not have an associated +function pointer typedef in the header. This directive does not +currently cause the autogenerated Java and C code to change to +call-through-function-pointer style, which should probably be +considered a bug. (FIXME) + + +<dt><strong><a name="GetProcAddressTableExpr">GetProcAddressTableExpr</a></strong> +<dd> Syntax: <code>GetProcAddressTableExpr [expression]</code> <br> + +(required) Defines the Java code snippet used by the generated glue +code to fetch the ProcAddressTable containing the function pointers +for the current API. It is up to the user to decide where to store the +ProcAddressTable. Common places for it include in an instance field of +the implementing class, in an associated object with which there is a +one-to-one mapping, or in a static field of another class accessed by +a static method. In the JOGL project, for example, each GLImpl +instance has an associated GLContext in an instance field called +"_context", so the associated directive is +<code>GetProcAddressTableExpr _context.getGLProcAddressTable()</code>. +In the JOAL project, the ProcAddressTables are currently held in a +separate class accessed via static methods, so one of the associated +directives is <code>GetProcAddressTableExpr +ALProcAddressLookup.getALCProcAddressTable()</code>. + + +<dt><strong><a name="ProcAddressNameExpr">ProcAddressNameExpr</a></strong> +<dd> Syntax: <code>ProcAddressNameExpr [expression]</code> <br> + +(required) Defines the mapping from function name to function pointer +typedef to be able to properly identify this function as needing +call-through-function-pointer semantics. The supplied expression uses +a set of simple commands to describe certain operations on the +function name: + +<UL> +<LI> <code>$UpperCase(arg)</code> converts the argument to + uppercase. "UpperCase" is case-insensitive. +<LI> <code>$LowerCase(arg)</code> converts the argument to + lowercase. "LowerCase" is case-insensitive. +<LI> <code>{0}</code> represents the name of the function. +<LI> Any other string represents a constant string. +<LI> Concatenation is implicit. +</UL> + +The corresponding ProcAddressNameExpr for the OpenGL extension +functions as described at the start of this section is <code>PFN +$UPPERCASE({0}) PROC</code>. The ProcAddressNameExpr for the OpenAL +functions as described at the start of this section is <code>LP +$UPPERCASE({0})</code>. + + +<dt><strong><a name="ProcAddressTableClassName">ProcAddressTableClassName</a></strong> +<dd> Syntax: <code>ProcAddressTableClassName [class name]</code> <br> + +(optional) Specifies the class name into which the table containing +the function pointers will be emitted. Defaults to "ProcAddressTable". + + +<dt><strong><a name="ProcAddressTablePackage">ProcAddressTablePackage</a></strong> +<dd> Syntax: <code>ProcAddressTablePackage [package name] (no +trailing semicolon)</code> <br> + +(optional) Specifies the package into which to produce the +ProcAddressTable for the current set of APIs. Defaults to the +implementation package specified by the <a +href="#ImplPackage">ImplPackage</a> directive. + + +<dt><strong><a name="SkipProcAddressGen">SkipProcAddressGen</a></strong> +<dd> Syntax: <code>SkipProcAddressGen [function name]</code> <br> + +(optional) Indicates that the default behavior of +call-through-function-pointer should be skipped for this function +despite the fact that it has an associated function pointer typedef in +the header. + +</dl> |