** implies *native ownership* for a *Pointer* referenced *native* memory
if the expression is constant. Otherwise the *native* memory has *java ownership*.
See [ReturnedArrayLength Setting](#returnedarraylength-symbol-expression) below.
* Utilizing a *flexible* *elemCount* via **ReturnedArrayLength getValElements()** renders us unable to determine ownership
of pointer referenced *native* memory segment and hence renders ownership *mixed or ambiguous*, [see \[5\]](#signature-const-int32_t--customsize-ambiguous-java-owned). This is due to the fact, that native code may allocate memory and writes its *elemCount* into the designated field *valElements*. In such cases, the user being aware of the underlying API shall utilize `setVal(..)` and `releaseVal()` with care.
* To release native memory with *java ownership*, i.e. a native ByteBuffer, `releaseVal()` can be used.
### GlueGen Struct Settings
#### **Opaque** *Java-primitive-type* *symbol*
See also [Opaque section in manual](manual/index.html#SecOpaque).
* `Opaque long T2_UndefStruct*`
Pointers to `T2_UndefStruct` will be handled opaque,
i.e. as `long` values from the Java side while maintaining their architecture dependent pointer size within native memory.
#### **ImmutableAccess** *symbol*
Immutable access can be set for a whole struct or a single field of a struct.
Immutable access will simply suppress generating setters in the Java code
and hence also reduces the footprint of the generated Java class for such struct.
* `ImmutableAccess TK_Struct`
Immutable access for the whole struct `TK_Struct
Sets pseudo-code flag *ImmutableAccess*, see below.
* `ImmutableAccess TK_Struct.val`
Immutable access for the single field `val` within struct `TK_Struct`
Sets pseudo-code flag *ImmutableAccess*, see below.
#### **MaxOneElement** *symbol*
* `MaxOneElement TK_Struct.val`
Sets field pointer `val`
to point to a array with a maximum of one element and unset initial value (zero elements).
Sets pseudo-code flag *MaxOneElement*, see below.
#### **ReturnedArrayLength** *symbol* *expression*
* `ReturnedArrayLength TK_Struct.val 3`
Sets field pointer `val` to point to a array with three elements.
Sets pseudo-code flag *ConstElemCount*, see below.
Having set *ConstElemCount* also implies *native ownership* for a *Pointer* referenced *native* memory.
* `ReturnedArrayLength TK_Struct.val 1`
Sets field pointer `val` to point to a array with one element.
Sets pseudo-code flags *ConstElemCount* and *MaxOneElement*, see below.
Having set *ConstElemCount* also implies *native ownership* for a *Pointer* referenced *native* memory.
* `ReturnedArrayLength TK_Struct.val getValElements()`
Sets field pointer `val` to point to a array with a variable length as described by the
field `valElements` retrievable via its getter `getValElements()`.
Sets pseudo-code flag *VariaElemCount*, see below.
#### **ReturnsString** *symbol*
A direct C code `char` array or indirect array via pointer can be interpreted as a Java `String`.
* `ReturnsString TK_Struct.name`
Sets field char-array or char-pointer `name` to be additionally interpreted as a Java `String`.
Besides the `byte[]` and `ByteBuffer` getter and setter variants, a `String` variant will be added.
Sets pseudo-code flags *String*, see below.
See [*String Mapping*](#string-mapping) above.
#### **ReturnsStringOnly** *symbol*
* `ReturnsStringOnly TK_Struct.name`
Sets field char-array or char-pointer `name` to be exclusively interpreted as a Java `String`.
Instead of the `byte[]` and `ByteBuffer` getter and setter variants, a `String` variant will be produced.
Sets pseudo-code flags *StringOnly*, see below.
See [*String Mapping*](#string-mapping) above.
### Struct Setter Pseudo-Code
#### Overview
In general we have the following few cases
* Array owned by parent struct itself
* `int32_t val[10]`
* Setter of `val` within range, keeping memory
* `const int32_t val[10]`
* No setter allowed due to const value
* Referenced Memory (array) owned by Java
* `int32_t* val`
* Setter within range, keeping memory, or replacing memory
* `const int32_t* val`
* Setter replacing memory, since memory is non-const but value is const
* Referenced Memory (array) owned by Native Code due to set *ConstElemCount*
* `int32_t* val`
* Setter of `val` within range, keeping memory owned by native code
* `const int32_t* val`
* No setter allowed, since memory is owned by native code and value is const
#### Implemented Pseudo Code
* *ImmutableAccess*: Drops setter, immutable
* *Pointer* & *ConstValue* & *ConstElemCount*: Drops setter, native ownership on const-value
* *Array* & *ConstValue* : Drops setter, const-value array
* *Primitive*
* Single aggregated instance
* Store value within *native* memory
* *Array* | *Pointer*
* *MaxOneElement*
* *Pointer*
* *ConstValue*: Allocate new memory and store value
* *VariaValue*:
* *ConstElemCount*: Reuse *native* memory and store value with matching *elemCount 1*, otherwise Exception
* *VariaElemCount*: Reuse *native* memory and store value with matching *elemCount 1*, otherwise allocates new memory (had *elemCount 0*)
* *Array* & *VariaValue*: Reuse *native* memory and store value (has const *elemCount 1*)
* *else*: *SKIP* setter for const single-primitive array
* *AnyElementCount*
* *String* & *isByteBuffer* & *Pointer*
* *ConstElemCount*: Reuse *native* memory and store UTF-8 bytes with EOS with matching *elemCount*, otherwise Exception
* *StringOnly*: End, no more setter for this field, otherwise continue
* *VariaElemCount*: Allocate new *native* memory and store UTF-8 bytes with EOS
* *StringOnly*: End, no more setter for this field, otherwise continue
* *ConstValue*
* *Pointer*
* *VariaElemCount*: Allocates new *native* memory and store value
* *else*: *SKIP* setter for const primitive array
* *Array* | *ConstElemCount*: Reuse *native* memory and store value with <= *elemCount*, otherwise Exception
* *Pointer* & *VariaElemCount*: Reuse *native* memory and store value with <= *elemCount*, otherwise allocate new *native* memory
* *Struct* ...
### Struct Java Signature Table
Please find below signature table as generated by the *C Declaration* including its *C Modifier*,
e.g. `const` for constant, `[const]` for const and non-const and `empty` for non-const (variable).
Further, the *GlueGen Setting* (see above) impacts the code generation as well.
Below table demonstrates *primitive* types being mapped within a `struct` named `TK_Struct`.
A similar mapping is produced for `struct` types, i.e. *compounds*.
| C Mod | C Declaration | Java Setter | Java Getter | GlueGen Setting | Ownership | Remarks |
|:--------|:--------------|:-----------------------------------------------------------------|:--------------------------------------|:-----------------------------------------------|:----------|:----------|
| | | | static boolean usesNativeCode() | | | Java, static,
*true* if using native code |
| | | | static int size() | | | Java, static,
native size in bytes |
| | | | static TK_Struct create() | | | Java, static ctor |
| | | | static TK_Struct create(ByteBuffer) | | | Java, static ctor
w/ existing ByteBuffer |
| | | | static TK_Struct derefPointer(long addr) | | | Java, static ctor
dereferencing ByteBuffer
at native address of size() |
| | | | ByteBuffer getBuffer() | | | Java,
underlying ByteBuffer |
| | | | long getDirectBufferAddress() | | | Java, native address
of underlying getBuffer() |
| | int32_t val | setVal(int v) | int getVal() | | Parent | |
| const | int32_t val | *none* | int getVal() | | Parent | Read only |
| | int32_t val | *none* | int getVal() | **ImmutableAccess** | Parent | Read only |
| [const] | int32_t* val | setVal(int v) \[[1](#signature-int32_t--maxoneelement-java-owned)\]\[[2](#signature-const-int32_t--maxoneelement-java-owned)\]
releaseVal() | int getVal()
boolean isValNull()
int getValElemCount() | **MaxOneElement** | Java | Starts w/ null elements,
max 1 element |
| const | int32_t* val | *none* | int getVal()
boolean isValNull()
static int getValElemCount() | **ReturnedArrayLength 1** | Native | Const element count 1 |
| | int32_t* val | setVal(int v) | int getVal()
boolean isValNull()
static int getValElemCount() | **ReturnedArrayLength 1** | Native | Const element count 1 | |
| | int32_t val[3]| setVal(int[] src, int srcPos, int destPos, int len) \[[3](#signature-int32_t3-constelemcount-3-parent-owned)\] | IntBuffer getVal()
int[] getVal(int srcPos, int[] dest, int destPos, int len) | | Parent | Reuses parent memory,
fixed size. |
| const | int32_t val[3]| *none* | IntBuffer getVal()
int[] getVal(int srcPos, int[] dest, int destPos, int len) | | Parent | Read only |
| const | int32_t* val | *none* | IntBuffer getVal()
int[] getVal(int srcPos, int[] dest, int destPos, int len)
boolean isValNull()
static int getValElemCount() | **ReturnedArrayLength 3** | Native | Read only
Const element count 3 |
| | int32_t* val | setVal(int[] src, int srcPos, int destPos, int len) \[[4](#signature-int32_t--constelemcount-3-natively-owned)\] | IntBuffer getVal()
int[] getVal(int srcPos, int[] dest, int destPos, int len)
boolean isValNull()
static int getValElemCount() | **ReturnedArrayLength 3** | Native | Const element count 3.
Reuses native memory,
fixed size. |
| | int32_t* val | setVal(boolean subset, int[] src, int srcPos, int destPos, int len) \[[5](#signature-int32_t--freesize-java-owned)\]
releaseVal() | IntBuffer getVal()
int[] getVal(int srcPos, int[] dest, int destPos, int len)
boolean isValNull()
int getValElemCount() | | Java | Starts w/ null elements.
Reuses or replaces Java memory,
variable size. |
| const | int32_t* val | setVal(int[] src, int srcPos, int len) \[[6](#signature-const-int32_t--freesize-java-owned)\]
releaseVal() | IntBuffer getVal()
int[] getVal(int srcPos, int[] dest, int destPos, int len)
boolean isValNull()
int getValElemCount() | | Java | Starts w/ null elements.
Replaces Java memory,
variable size. |
| | int32_t* val | setVal(boolean subset, int[] src, int srcPos, int destPos, int len) \[[7](#signature-int32_t--customsize-ambiguous-ownership)\]
releaseVal() | IntBuffer getVal()
int[] getVal(int srcPos, int[] dest, int destPos, int len)
boolean isValNull() | **ReturnedArrayLength getValCount()** | **Ambiguous** | Variable element count
using field *valCount*,
which has getter and setter |
| const | int32_t* val | setVal(int[] src, int srcPos, int len) \[[8](#signature-const-int32_t--customsize-ambiguous-ownership)\]
releaseVal() | IntBuffer getVal()
int[] getVal(int srcPos, int[] dest, int destPos, int len)
boolean isValNull() | **ReturnedArrayLength getValCount()** | **Ambiguous** | Variable element count
using field *valCount*,
which has getter and setter |
| [const] | char* name | setName(String srcVal)
releaseVal() | String getName()
boolean isNameNull()
int getNameElemCount() | **ReturnsStringOnly** | Java | String only, w/ EOS |
| [const] | char* name | setName(String srcVal)
setName(byte[] src, int srcPos, int destPos, int len)
releaseVal() | String getNameAsString()
ByteBuffer getName()
boolean isNameNull()
int getNameElemCount() | **ReturnsString** | Java | String and byte access, w/ EOS|
### Struct Java Signature Examples
#### Signature `int32_t *` MaxOneElement, Java owned
* `void com.jogamp.gluegen.test.junit.generation.TK_Field.setVariaInt32PointerMaxOneElemElemCount(int src)`
Setter for native field variaInt32PointerMaxOneElem, referencing a Java owned array with variable element count of 0 initial elements.
Maximum element count is 1.
Native Signature:
* field-type (PointerType) 'int32_t *' -> (int32_t) * , size [fixed false, lnx64 8], const[false], pointer*1
* referenced (IntType) typedef 'int32_t', size [fixed true, lnx64 4], const[false], int
Will reuse memory if existing, otherwise allocating memory.
#### Signature `const int32_t *` MaxOneElement, Java owned
* `TK_Field com.jogamp.gluegen.test.junit.generation.TK_Field.setConstInt32PointerMaxOneElem(int src)`
Setter for native field variaInt32PointerMaxOneElem, referencing a Java owned array with variable element count of 0 initial elements.
Maximum element count is 1.
Native Signature:
* field-type (PointerType) 'int32_t *' -> (const int32_t) * , size [fixed false, lnx64 8], const[false], pointer*1
* referenced (IntType) typedef 'int32_t', size [fixed true, lnx64 4], const[native, true], int
Always replaces memory due to `const` value modifier.
#### Signature `int32_t[3]` ConstElemCount 3, Parent owned
* `TK_Field com.jogamp.gluegen.test.junit.generation.TK_Field.setVariaInt32ArrayConstLen(int[] src, int srcPos, int destPos, int length)`
Setter for native field variaInt32ArrayConstLen, being an array with fixed element count of 3 elements.
Native Field Signature (ArrayType) 'int32_t *', size [fixed false, lnx64 12], const[false], array*1
Copies the given source elements into the respective field's existing memory.
Parameters:
* src the source array of elements
* srcPos starting element position within the source array with 'srcPos >= 0` && `srcPos + length <= src.length`, otherwise an IndexOutOfBoundsException is thrown
* destPos starting element position within the destination with 'destPos >= 0` && `destPos + length <= elemCount`, otherwise an exception is thrown
* length the element count to be copied with 'length >= 0` && `srcPos + length <= src.length` && `destPos + length <= elemCount`, otherwise an IndexOutOfBoundsException is thrown
Returns:
* this instance of chaining
#### Signature `int32_t *` ConstElemCount 3, Natively owned
* `TK_Field com.jogamp.gluegen.test.junit.generation.TK_Field.setVariaInt32PointerConstLen(int[] src, int srcPos, int destPos, int length)`
Setter for native field variaInt32PointerConstLen, referencing a natively owned array with fixed element count of 3 elements.
Native Signature:
* field-type (PointerType) 'int32_t *' -> (int32_t) * , size [fixed false, lnx64 8], const[false], pointer*1
* referenced (IntType) typedef 'int32_t', size [fixed true, lnx64 4], const[false], int
Copies the given source elements into the respective field's existing memory.
Parameters:
* src the source array of elements
* srcPos starting element position within the source array with 'srcPos >= 0` && `srcPos + length <= src.length`, otherwise an IndexOutOfBoundsException is thrown
* destPos starting element position within the destination with 'destPos >= 0` && `destPos + length <= elemCount`, otherwise an exception is thrown
* length the element count to be copied with 'length >= 0` && `srcPos + length <= src.length` && `destPos + length <= elemCount`, otherwise an IndexOutOfBoundsException is thrown
Returns:
* this instance of chaining
#### Signature `int32_t *` FreeSize, Java owned
* `TK_Field com.jogamp.gluegen.test.junit.generation.TK_Field.setVariaInt32PointerVariaLen(boolean subset, int[] src, int srcPos, int destPos, int length)`
Setter for native field variaInt32PointerVariaLen, referencing a Java owned array with variable element count of 0 initial elements.
Native Signature:
* field-type (PointerType) 'int32_t *' -> (int32_t) * , size [fixed false, lnx64 8], const[false], pointer*1
* referenced (IntType) typedef 'int32_t', size [fixed true, lnx64 4], const[false], int
Copies the given source elements into the respective field, either writing into the existing memory or creating a new memory and referencing it.
Parameters:
* subset if `true` keeps the underlying memory and only allows to set up to `elemCount` elements. Otherwise may replace the underlying memory if `destPos + length != elemCount`.
* src the source array of elements
* srcPos starting element position within the source array with 'srcPos >= 0` && `srcPos + length <= src.length`, otherwise an IndexOutOfBoundsException is thrown
* destPos starting element position within the destination with 'destPos >= 0`. If `subset == true`, `destPos + length <= elemCount` also must be be `true`. Otherwise an exception is thrown
* length the element count to be copied with 'length >= 0` && `srcPos + length <= src.length`, otherwise an IndexOutOfBoundsException is thrown
Returns:
* this instance of chaining
#### Signature `const int32_t *` FreeSize, Java owned
* `TK_Field com.jogamp.gluegen.test.junit.generation.TK_Field.setConstInt32PointerVariaLen(int[] src, int srcPos, int length)`
Setter for native field constInt32PointerVariaLen, referencing a Java owned array with variable element count of 0 initial elements.
Native Signature:
* field-type (PointerType) 'int32_t *' -> (const int32_t) * , size [fixed false, lnx64 8], const[false], pointer*1
* referenced (IntType) typedef 'int32_t', size [fixed true, lnx64 4], const[native, true], int
Replaces the respective field's memory with a new memory segment containing given source elements and referencing it.
Parameters:
* src the source array of elements
* srcPos starting element position within the source array with 'srcPos >= 0` && `srcPos + length <= src.length`, otherwise an IndexOutOfBoundsException is thrown
* length the element count to be copied with 'length >= 0` && `srcPos + length <= src.length`, otherwise an IndexOutOfBoundsException is thrown
Returns:
* this instance of chaining
#### Signature `int32_t *` CustomSize, Ambiguous ownership
* `TK_Field com.jogamp.gluegen.test.junit.generation.TK_Field.setVariaInt32PointerCustomLen(boolean subset, int[] src, int srcPos, int destPos, int length)`
Setter for native field variaInt32PointerCustomLen, referencing a mixed and ambigously owned (warning) array with variable element count of getVariaInt32PointerCustomLenElemCount() elements.
Native Signature:
* field-type (PointerType) 'int32_t *' -> (int32_t) * , size [fixed false, lnx64 8], const[false], pointer*1
* referenced (IntType) typedef 'int32_t', size [fixed true, lnx64 4], const[false], int
Copies the given source elements into the respective field, either writing into the existing memory or creating a new memory and referencing it.
Parameters:
* subset if `true` keeps the underlying memory and only allows to set up to `elemCount` elements. Otherwise may replace the underlying memory if `destPos + length != elemCount`.
* src the source array of elements
* srcPos starting element position within the source array with 'srcPos >= 0` && `srcPos + length <= src.length`, otherwise an IndexOutOfBoundsException is thrown
* destPos starting element position within the destination with 'destPos >= 0`. If `subset == true`, `destPos + length <= elemCount` also must be be `true`. Otherwise an exception is thrown
* length the element count to be copied with 'length >= 0` && `srcPos + length <= src.length`, otherwise an IndexOutOfBoundsException is thrown
Returns:
* this instance of chaining
#### Signature `const int32_t *` CustomSize, Ambiguous ownership
* `TK_Field com.jogamp.gluegen.test.junit.generation.TK_Field.setConstInt32PointerCustomLen(int[] src, int srcPos, int length)`
Setter for native field constIntxxPointerCustomLen, referencing a mixed and ambigously owned (**warning**) array with variable element count of getConstIntxxPointerCustomLenElemCount() elements.
Native Signature:
* field-type (PointerType) 'int32_t *' -> (const int32_t) * , size [fixed false, lnx64 8], const[false], pointer*1
* referenced (IntType) typedef 'int32_t', size [fixed true, lnx64 4], const[native, true], int
Replaces the respective field's memory with a new memory segment containing given source elements and referencing it.
Parameters:
* src the source array of elements
* srcPos starting element position within the source array with 'srcPos >= 0` && `srcPos + length <= src.length`, otherwise an IndexOutOfBoundsException is thrown
* length the element count to be copied with 'length >= 0` && `srcPos + length <= src.length`, otherwise an IndexOutOfBoundsException is thrown
Returns:
* this instance of chaining
### Struct Pointer-Pointer Support
See primitive [*Pointer Mapping*](#pointer-mapping) above.
*Pointer* are exposed in the following examples
```
typedef struct {
int32_t* int32PtrArray[10];
int32_t** int32PtrPtr;
...
} T2_PointerStorage;
```
or via and undefined forward-declared struct
```
typedef struct T2_UndefStruct* T2_UndefStructPtr;
typedef struct {
...
T2_UndefStructPtr undefStructPtr;
T2_UndefStructPtr undefStructPtrArray[10];
T2_UndefStructPtr* undefStructPtrPtr;
const T2_UndefStructPtr* constUndefStructPtrPtr;
} T2_PointerStorage;
```
and the following GlueGen configuration
```
Opaque long T2_UndefStruct*
Ignore T2_UndefStruct
```
*TODO: Enhance documentation*
### Struct Function-Pointer Support
GlueGen supports function pointers as struct fields,
generating function calls as methods as well function-pointer opaque getter and setter as `long` types.
The latter only in case if mutable, i.e. non-const.
#### Example
Assume the following C Header file example:
```
typedef struct {
int32_t balance;
} T2_UserData;
typedef int32_t ( * T2_CustomFuncA)(void* aptr);
typedef int32_t ( * T2_CustomFuncB)(T2_UserData* pUserData);
typedef struct {
...
T2_CustomFuncA customFuncAVariantsArray[10];
T2_CustomFuncA* customFuncAVariantsArrayPtr;
T2_CustomFuncB customFuncBVariantsArray[10];
T2_CustomFuncB* customFuncBVariantsArrayPtr;
} T2_PointerStorage;
typedef struct {
...
const T2_CustomFuncA CustomFuncA1;
T2_CustomFuncB CustomFuncB1;
} T2_InitializeOptions;
```
and the following GlueGen configuration
```
Opaque long void*
EmitStruct T2_UserData
StructPackage T2_UserData com.jogamp.gluegen.test.junit.generation
EmitStruct T2_InitializeOptions
StructPackage T2_InitializeOptions com.jogamp.gluegen.test.junit.generation
```
This will lead to the following result for `const T2_CustomFuncA customFuncA1`
```
/**
* Getter for native field CustomFuncA1, being a struct owned function pointer.
*
* Native Field Signature (PointerType) typedef 'T2_CustomFuncA' -> int32_t (*)(void * aptr), size [fixed false, lnx64 8], const[false], pointer*1, funcPointer
*
*/
public final long getCustomFuncA1() { .. }
/** Interface to C language function:
int32_t CustomFuncA1(void * aptr)
*/
public final int CustomFuncA1(long aptr) { ... }
```
and similar to `T2_CustomFuncB customFuncB1`
```
/**
* Setter for native field CustomFuncB1, being a struct owned function pointer.
*
* Native Field Signature (PointerType) typedef 'T2_CustomFuncB' -> int32_t (*)(T2_UserData * pUserData), size [fixed false, lnx64 8], const[false], pointer*1, funcPointer
*
*/
public final T2_InitializeOptions setCustomFuncB1(long src) { .. }
/**
* Getter for native field CustomFuncB1, being a struct owned function pointer.
*
* Native Field Signature (PointerType) typedef 'T2_CustomFuncB' -> int32_t (*)(T2_UserData * pUserData), size [fixed false, lnx64 8], const[false], pointer*1, funcPointer
*
*/
public final long getCustomFuncB1() { .. }
/** Interface to C language function:
int32_t CustomFuncB1(T2_UserData * pUserData)
*/
public final int CustomFuncB1(T2_UserData pUserData) { .. }
```
## Java Callback
GlueGen supports registering Java callback methods
to receive asynchronous and off-thread native toolkit events,
where a generated native callback function dispatches the events to Java.
### Implementation Details
Implementation generates a static Java callback dispatcher for each defined `SetCallbackFunction`, which gets invoked by the generated native static counterpart with all arguments required.
The *static callback* utilizes its own synchronization for thread-safety and fetches the required data set stored at `SetCallbackFunction` to dispatch the call to the users' `CallbackFunction`.
In case the callback has been removed already, the *static callback* simply bails out quietly.
The native code does not create, release or manage heap memory and therefore is considered safe.
### *JavaCallback* *UserParam* Mapping
Usually the same `UserParam` type is used in both items (or hooks), `SetCallbackFunctionName` and `CallbackFunctionType`,
which we call a homogeneous `UserParam` mapping.
Even in a homogeneous `UserParam` mapping, handling of the `UserParam` value might differ in the native binding code.
To specify a non homogeneous `UserParam` mapping, i.e. heterogeneous `UserParam` mapping,
the `UserParam` index of the `SetCallbackFunction` must be [set in the configuration](#javacallback-configuration).
The following mappings are supported.
#### Pure Java Object User Type (default)
A pure Java *Object type* is used for both, `SetCallbackFunctionName` and `CallbackFunctionType`.
It's a homogeneous `UserParam` mapping, where the native side receives a simple unique ID and shall not dereference the *pointer*.
The static Java callback dispatcher fetches the Java `UserParam` *Object* from the key-mapped data value.
Instead of using the default plain Java `Object` type, a [custom *UserParamClass*](#custom-callback-userparamclass) can be specified [in the configuration](#javacallback-configuration), which is recommended for more clarity in the resulting API.
#### Struct Type User Param (Homogeneous)
A [GlueGen generated *Struct type*](#struct-mapping) is used for both, `SetCallbackFunctionName` and `CallbackFunctionType`.
It's a homogeneous `UserParam` mapping, where the native side receives the actual native struct address.
The static Java callback dispatcher dereferences the received native struct address (*long*), i.e. rebuilding the *struct Object* to be passed to the users' `CallbackFunction`.
#### Struct Type User Param (Heterogeneous)
An anonymous pointer (*long*) for `SetCallbackFunctionName` and a [GlueGen generated *struct type*](#struct-mapping) for `CallbackFunctionType` is being used.
It's a heterogeneous `UserParam` mapping, where the toolkit is expected to place the given anonymous pointer inside the defined *struct type* passed to the `CallbackFunction`.
The `SetCallback-UserParamIndex` for the different parameter-type is [set in the configuration](#javacallback-configuration).
The static Java callback dispatcher dereferences the received native struct address (*long*), i.e. rebuilding the *struct Object* to be passed to the users' `CallbackFunction`.
### *JavaCallback* Configuration
Configuration directives are as follows:
JavaCallbackDef [ []]
JavaCallbackKey * *
`JavaCallbackDef` and `JavaCallbackKey` use the name of the `SetCallbackFunction` as its first attribute,
as it is core to the semantic mapping of all resources. They also have to use the same `CallbackFunctionType`.
`JavaCallbackDef` attributes:
- `SetCallbackFunction`: `SetCallbackFunction` name of the native toolkit API responsible to set the callback
- `SetCallback-UserParamIndex`: `UserParam` parameter-index of the `SetCallbackFunction`
- `CallbackFunctionType`: The native toolkit API typedef-name of the function-pointer-type, aka the callback type name
- `CallbackFunction-UserParamIndex`: The `userParam` parameter-index of the `CallbackFunctionType`, which allows to [indicate a heterogeneous `UserParam`](#struct-type-user-param-heterogeneous)
- `Callback-UserParamClass`: Optional [custom *UserParamClass*](#custom-callback-userparamclass) overriding the default `Object` for non-compound `UserParam` types.
- `Callback-KeyClass`: Optional [custom *KeyClass*](#custom-callback-keyclass), providing the hash-map-key.
The `SetCallbackFunction` is utilized to set the `CallbackFunction` as well as to remove it passing `null` for the `CallbackFunction`.
If mapping the `CallbackFunction` to keys, the user must specify the same key arguments when setting and removing the `CallbackFunction`.
#### *JavaCallback* Key Definition
If no keys are defined via `JavaCallbackKey` or not manually injected using a custom `Callback-KeyClass`, see below,
the `CallbackFunction` has global scope.
In case keys are defined via `JavaCallbackKey` and no manually injected custom `Callback-KeyClass` used,
a public `Callback-KeyClass` is being generated covering the defined keys.
Keys allow to limit the scope, i.e. map multiple `CallbackFunction` to the different keys.
To remove a previously set `CallbackFunction` via `SetCallbackFunction`, the key arguments must match.
`JavaCallbackKey` attributes
- `SetCallbackFunction`: `SetCallbackFunction` name of the native toolkit API responsible to set the callback
- `SetCallback-ParamIndex`: List of parameter indices of the `SetCallbackFunction`, denoting the key(s) limiting the callback scope, i.e. the callback and all resources will be mapped to this key. The optional `Callback-KeyClass` may override this semantic.
- `CallbackFunctionType`: The native toolkit API typedef-name of the function-pointer-type, the same callback type name as defined in `JavaCallbackDef`
- `CallbackFunction-ParamIndex`: List of parameter indices of the `CallbackFunctionType`, matching the semantic parameter of `SetCallback-ParamIndex`.
#### Custom `Callback-UserParamClass`
Instead of using the default plain Java `Object` for non-compound `UserParam` types, a custom `Callback-UserParamClass` can be specified [in the configuration](#javacallback-configuration), which produces more clarity in the resulting API.
#### Custom `Callback-KeyClass`
The `Callback-KeyClass` is the optional user-written hash-map-key definition
and shall handle all key parameter of the `SetCallbackFunction` as defined via `JavaCallbackKey`, see above.
`Callback-KeyClass` may be used to add external key-components, e.g. current-thread or a toolkit dependent context.
The `Callback-KeyClass` shall implement the following hash-map-key standard methods
- `boolean equals(Object)`
- `int hashCode()`
- `Callback-KeyClassName(...)` constructor receiving all key parameter of `SetCallbackFunction` as defined via `JavaCallbackKey`, see above.
#### Required *LibraryOnLoad*
Note that [`LibraryOnLoad `](#libraryonload-librarybasename-for-jni_onload-) must be specified in exactly one native code-unit within one native library.
It provides code to allow the generated native callback-function to attach the current thread to the `JavaVM*`, retrieving a valid `JNIEnv*`, see [`LibraryOnLoad `](#libraryonload-librarybasename-for-jni_onload-) for details.
### *JavaCallback* Generated Interfaces, Classes and Methods
The public `CallbackFunction` interface is generated.
The default public `Callback-KeyClass` is generated if keys are used and no custom class is specified, see above.
The public toolkit API `SetCallbackFunction` method is being generated.
Additional public *maintenance* methods are generated. In case keys are being used, they expect `Callback-KeyClass` as an argument, otherwise they expect no argument for global scope.
In case a `Callback-KeyClass` is used, the additional *maintenance* methods are:
- *Set<`Callback-KeyClass`> get`SetCallbackFunctionName`Keys()*
- *boolean is`SetCallbackFunctionName`Mapped(`Callback-KeyClass`)* queries whether `SetCallbackFunctionName` is mapped to key.
- *`CallbackFunction` get`SetCallbackFunctionName`(`Callback-KeyClass`)* returns the mapped `CallbackFunction`, null if not mapped
- *`Callback-UserParamClass` get`SetCallbackFunctionName`UserParam(`Callback-KeyClass`)* returns the mapped `userParam` object, null if not mapped
- *void release`SetCallbackFunctionName`(`Callback-KeyClass`)* releases the mapped `CallbackFunction` data set associated via `SetCallbackFunctionName`.
- *int releaseAll`SetCallbackFunctionName`()* releases complete mapped `CallbackFunction` data set associated via `SetCallbackFunctionName`.
If no `Callback-KeyClass` is used, the additional *maintenance* methods are:
- *boolean is`SetCallbackFunctionName`Mapped()* queries whether `SetCallbackFunctionName` is mapped.
- *`CallbackFunction` get`SetCallbackFunctionName`()* returns the mapped `CallbackFunction`, null if not mapped
- *`Callback-UserParamClass` get`SetCallbackFunctionName`UserParam()* returns the mapped `userParam` object, null if not mapped
- *void release`SetCallbackFunctionName`()* releases the mapped `CallbackFunction` data set associated via `SetCallbackFunctionName`.
Note that the *release`SetCallbackFunctionName`(\*)* and *releaseAll`SetCallbackFunctionName`()* methods are not the *proper toolkit API way* to remove the callback,
try to use original `SetCallbackFunctionName` API method instead using a `null` `CallbackFunction` reference.
### *JavaCallback* Notes
Please consider the following *currently enabled* constraints using JavaCallback
- Only one interface callback-method binding is allowed for a native callback function, e.g. `T2_CallbackFunc01` (see above)
- Implying that the native single function-pointer typedef must be mapped to a single Java method within its interface
- Hence it must be avoided that multiple method variation are produced, e.g. due to `char*` to `byte[]` and `String` mapping etc.
- The native callback function can only return no-value, i.e. `void`, or a primitive type. Usually `void` is being used in toolkit APIs.
- The native callback function argument types must be convertible to JNI Java types as (previously) supported for function return values,
using the same conversion function `CMethodBindingEmitter.emitBodyMapCToJNIType(..)`.
- To remove a JavaCallback the `SetCallbackFunction` must be called with `null` for the `CallbackFunction` argument
but with the same [*key arguments* (see `JavaCallbackKey`)](#javacallback-key-definition) as previously called to set the callback.
- Exactly one native code-unit within the library must specify [`LibraryOnLoad libraryBasename`](#libraryonload-librarybasename-for-jni_onload-)
- `SetCallbackFunction`, all *maintenance* methods and the native callback dispatcher **are thread-safe**
- ...
### JavaCallback Example 1
This example demonstrates a [homogeneous *Java Object* `UserParam` mapping](#pure-java-object-user-type-default) with a [globally scoped](#javacallback-key-definition) `CallbackFunction` and `UserParam`.
The callback `T2_CallbackFunc01` has global scope, i.e. is not mapped to any key and can be only set globally.
C-API header snippet:
```
typedef void ( * T2_CallbackFunc01)(size_t id, const char* msg, void* usrParam);
/** Sets the given `cbFunc` and associated `usrParam` as the callback. Passing NULL for `func` _and_ same `usrParam` removes the callback and its associated resources. */
void MessageCallback01(T2_CallbackFunc01 cbFunc, void* usrParam);
void InjectMessageCallback01(size_t id, const char* msg);
```
and the following GlueGen configuration
```
# JavaCallback requires `JNI_OnLoad*(..)` and `JVMUtil_GetJNIEnv(..)`
LibraryOnLoad Bindingtest2
ArgumentIsString T2_CallbackFunc01 1
ArgumentIsString InjectMessageCallback01 1
# Define a JavaCallback.
# Set JavaCallback via function `MessageCallback01` if `T2_CallbackFunc01` argument is non-null, otherwise removes the mapped callback and associated resources.
#
# It uses the function-pointer argument `T2_CallbackFunc01` as the callback function type
# and marks `T2_CallbackFunc01`s 3rd argument (index 2) as the mandatory user-param.
#
# This callback has no keys defines, rendering it of global scope!
#
# Explicit maintenance methods are generated, passing the keys as paramters
# - `boolean isMessageCallback01Mapped()` queries whether `MessageCallback0` is mapped globally
# - `T2_CallbackFunc01 getMessageCallback01()` returns the global T2_CallbackFunc01, null if not mapped
# - `Object getMessageCallback01UserParam()` returns the global `usrParam` object, null if not mapped
# - `void releaseMessageCallback01()` releases callback data skipping toolkit API. Favor passing `null` callback ref to `MessageCallback01(..)`
JavaCallbackDef MessageCallback01 1 T2_CallbackFunc01 2
```
Note that [`LibraryOnLoad Bindingtest2`](#libraryonload-librarybasename-for-jni_onload-) must be specified in exactly one native code-unit within the library.
It provides code to allow the generated native callback-function to attach the current thread to the `JavaVM*` generating a new `JNIEnv*`in daemon mode -
or just to retrieve the thread's `JNIEnv*`, if already attached to the `JavaVM*`.
This will lead to the following interface
```
public interface Bindingtest2 {
/** JavaCallback interface: T2_CallbackFunc01 -> void (*T2_CallbackFunc01)(size_t id, const char * msg, void * usrParam) */
public static interface T2_CallbackFunc01 {
/** Interface to C language function:
void callback(size_t id, const char * msg, void * usrParam)
Alias for: T2_CallbackFunc01 */
public void callback(long id, String msg, Object usrParam);
}
...
/** Entry point (through function pointer) to C language function:
void MessageCallback01(T2_CallbackFunc01 cbFunc, void * usrParam)
*/
public void MessageCallback01(T2_CallbackFunc01 cbFunc, Object usrParam);
/** Returns if callback is mapped for
public void MessageCallback01(T2_CallbackFunc01 cbFunc, Object usrParam) **/
public boolean isMessageCallback01Mapped();
/** Returns T2_CallbackFunc01 callback for
public void MessageCallback01(T2_CallbackFunc01 cbFunc, Object usrParam) **/
public T2_CallbackFunc01 getMessageCallback01();
/** Returns user-param for
public void MessageCallback01(T2_CallbackFunc01 cbFunc, Object usrParam) **/
public Object getMessageCallback01UserParam();
/** Releases callback data skipping toolkit API. Favor passing `null` callback ref to
public void MessageCallback01(T2_CallbackFunc01 cbFunc, Object usrParam) **/
public void releaseMessageCallback01();
/** Entry point (through function pointer) to C language function:
void InjectMessageCallback01(size_t id, const char * msg)
*/
public void InjectMessageCallback01(long id, String msg);
```
### JavaCallback Example 2a (Default *KeyClass*)
This example demonstrates a [homogeneous *Java Object* `UserParam` mapping](#pure-java-object-user-type-default) with a [key-mapped](#javacallback-key-definition) `CallbackFunction` and `UserParam`.
Additionally a [custom *UserParamClass*](#custom-callback-userparamclass) `ALCcontext` is being used for more clarity in the resulting API.
This example is derived from OpenAL's `AL_SOFT_callback_buffer` extension.
The callback `ALBUFFERCALLBACKTYPESOFT` is mapped to `buffer` name, i.e. one callback can be set for each buffer.
C-API Header snipped
```
typedef void ( * ALBUFFERCALLBACKTYPESOFT)(int buffer /* key */, void *userptr, int sampledata, int numbytes);
void alBufferCallback0(int buffer /* key */, int format, int freq, ALBUFFERCALLBACKTYPESOFT callback, void *userptr);
void alBufferCallback0Inject(int buffer, int sampledata, int numbytes);
```
and the following GlueGen configuration
```
# Define a JavaCallback.
# Set JavaCallback via function `alBufferCallback0` if `ALBUFFERCALLBACKTYPESOFT` argument is non-null, otherwise removes the mapped callback and associated resources.
#
# It uses the function-pointer argument `ALBUFFERCALLBACKTYPESOFT` as the callback function type
# and marks `ALBUFFERCALLBACKTYPESOFT`s 2nd argument (index 1) as the mandatory user-param.
#
# This callback defines one key, `buffer`, index 0 of alBufferCallback0(..) parameter list, limiting it to buffer-name scope!
# The `buffer` key allows setting one callback per buffer-name, compatible with the `AL_SOFT_callback_buffer` spec.
#
# Explicit queries are generated, passing the keys as paramters
# - `Set getAlBufferCallback0Keys()` returns set of Key { int buffer }
# - `boolean isAlBufferCallback0Mapped(AlBufferCallback0Key)` queries whether `alBufferCallback0` is mapped to `buffer`.
# - `ALBUFFERCALLBACKTYPESOFT getAlBufferCallback0(AlBufferCallback0Key)` returns the `buffer` mapped ALEVENTPROCSOFT, null if not mapped
# - `ALCcontext getAlBufferCallback0UserParam(AlBufferCallback0Key)` returns the `buffer` mapped `userptr` object, null if not mapped
# - `void releaseAllAlBufferCallback0()` releases all callback data mapped via Key { int buffer } skipping toolkit API. Favor passing `null` callback ref to `alBufferCallback0(..)`
# - `void releaseAlBufferCallback0(AlBufferCallback0Key)` releases callback data mapped to Key { int buffer } skipping toolkit API. Favor passing `null` callback ref to `alBufferCallback0(..)`
JavaCallbackDef alBufferCallback0 4 ALBUFFERCALLBACKTYPESOFT 1 ALCcontext
JavaCallbackKey alBufferCallback0 0 ALBUFFERCALLBACKTYPESOFT 0
```
leading to the following interface
```
/** JavaCallback interface: ALBUFFERCALLBACKTYPESOFT -> void (*ALBUFFERCALLBACKTYPESOFT)(int buffer, void * userptr, int sampledata, int numbytes) */
public static interface ALBUFFERCALLBACKTYPESOFT {
/** Interface to C language function:
void callback(int buffer, void * userptr, int sampledata, int numbytes)
Alias for: ALBUFFERCALLBACKTYPESOFT */
public void callback(int buffer, ALCcontext userptr, int sampledata, int numbytes);
}
...
/** Key { int buffer } for
public void alBufferCallback0(int buffer, int format, int freq, ALBUFFERCALLBACKTYPESOFT callback, Object userptr) **/
public static class AlBufferCallback0Key {
public final int buffer;
public AlBufferCallback0Key(int buffer) {
this.buffer = buffer;
}
@Override
public boolean equals(final Object o) {
if( this == o ) {
return true;
}
if( !(o instanceof AlBufferCallback0Key) ) {
return false;
}
final AlBufferCallback0Key o2 = (AlBufferCallback0Key)o;
return buffer == o2.buffer;
}
@Override
public int hashCode() {
// 31 * x == (x << 5) - x
int hash = buffer;
return hash;
}
}
...
/** Returns set of Key { int buffer } for
void alBufferCallback0(int buffer, int format, int freq, ALBUFFERCALLBACKTYPESOFT callback, ALCcontext userptr) */
public Set getAlBufferCallback0Keys();
/** Returns whether callback Key { int buffer } is mapped for
void alBufferCallback0(int buffer, int format, int freq, ALBUFFERCALLBACKTYPESOFT callback, ALCcontext userptr) */
public boolean isAlBufferCallback0Mapped(AlBufferCallback0Key key);
/** Returns ALBUFFERCALLBACKTYPESOFT callback mapped to Key { int buffer } for
void alBufferCallback0(int buffer, int format, int freq, ALBUFFERCALLBACKTYPESOFT callback, ALCcontext userptr) */
public ALBUFFERCALLBACKTYPESOFT getAlBufferCallback0(AlBufferCallback0Key key);
/** Returns user-param mapped to Key { int buffer } for
void alBufferCallback0(int buffer, int format, int freq, ALBUFFERCALLBACKTYPESOFT callback, ALCcontext userptr) */
public ALCcontext getAlBufferCallback0UserParam(AlBufferCallback0Key key);
/** Releases all callback data mapped via Key { int buffer } skipping toolkit API. Favor passing `null` callback ref to
void alBufferCallback0(int buffer, int format, int freq, ALBUFFERCALLBACKTYPESOFT callback, ALCcontext userptr) */
public int releaseAllAlBufferCallback0();
/** Releases callback data mapped to Key { int buffer } skipping toolkit API. Favor passing `null` callback ref to
void alBufferCallback0(int buffer, int format, int freq, ALBUFFERCALLBACKTYPESOFT callback, ALCcontext userptr) */
public void releaseAlBufferCallback0(AlBufferCallback0Key key);
/** Entry point (through function pointer) to C language function:
void alBufferCallback0(int buffer, int format, int freq, ALBUFFERCALLBACKTYPESOFT callback, void * userptr)
*/
public void alBufferCallback0(int buffer, int format, int freq, ALBUFFERCALLBACKTYPESOFT callback, ALCcontext userptr);
/** Entry point (through function pointer) to C language function:
void alBufferCallback0Inject(int buffer, int sampledata, int numbytes)
*/
public void alBufferCallback0Inject(int buffer, int sampledata, int numbytes);
```
### JavaCallback Example 2b (Custom *KeyClass*, different key-parameter order)
Similar example as example 2a, but using a [custom *KeyClass*](#custom-callback-keyclass) to map `CallbackFunction` and `UserParam` and also accommodating a different key-parameter order between `SetCallbackFunction` and `CallbackFunction`.
C-API Header snipped
```
typedef void ( * ALBUFFERCALLBACKTYPESOFT)(int buffer /* key */, void *userptr, int sampledata, int numbytes);
void alBufferCallback1(void *user_ptr, int buffer_key /* key */, int format, int freq, ALBUFFERCALLBACKTYPESOFT callback);
void alBufferCallback1Inject(int buffer, int sampledata, int numbytes);
```
GlueGen configuration snippet with the added option attribute for the `Callback-KeyClass` in directive `JavaCallbackDef`.
```
JavaCallbackDef alBufferCallback1 0 ALBUFFERCALLBACKTYPESOFT 1 ALCcontext com.jogamp.gluegen.test.junit.generation.Test4JavaCallback.CustomAlBufferCallback1Key
JavaCallbackKey alBufferCallback1 1 ALBUFFERCALLBACKTYPESOFT 0
```
Implementation utilizes a custom `Callback-KeyClass` implementation for `void alBufferCallback1(int buffer, int format, int freq, ALBUFFERCALLBACKTYPESOFT callback, ALCcontext userptr)`,
which uses one key, i.e. `buffer`.
```
public static class CustomAlBufferCallback1Key {
private final int buffer;
public CustomAlBufferCallback1Key(final int buffer) {
this.buffer = buffer;
}
@Override
public boolean equals(final Object o) {
if( this == o ) {
return true;
}
if( !(o instanceof CustomAlBufferCallback1Key) ) {
return false;
}
final CustomAlBufferCallback1Key o2 = (CustomAlBufferCallback1Key)o;
return buffer == o2.buffer;
}
@Override
public int hashCode() {
return buffer;
}
@Override
public String toString() {
return "CustomALKey[this "+toHexString(System.identityHashCode(this))+", buffer "+buffer+"]";
}
}
```
### JavaCallback Example 5b (UserParam part of 2 component-key)
Similar example as example 2a, but having the `UserParam` as part of the 2 component-key
*and* defining `Callback-UserParamClass` class as `ALCcontext`.
C-API Header snipped
```
typedef void ( * ALEVENTPROCSOFT)(int eventType, int object, int param, int length, const char *message, void *userParam /* key */);
void alEventCallback1(int object /* key */, ALEVENTPROCSOFT callback, void *userParam /* key */);
```
GlueGen configuration snippet with the added option attribute for the `Callback-UserParamClass` in directive `JavaCallbackDef`.
```
ArgumentIsPascalString ALEVENTPROCSOFT 3 4
JavaCallbackDef alEventCallback1 2 ALEVENTPROCSOFT 5 ALCcontext
JavaCallbackKey alEventCallback1 0 2 ALEVENTPROCSOFT 1 5
```
Resulting to the default `KeyClass`
```
/** Key { int object, ALCcontext userParam } for
void alEventCallback1(int object, ALEVENTPROCSOFT callback, ALCcontext userParam) */
public static class AlEventCallback1Key {
public final int object;
public final ALCcontext userParam;
public AlEventCallback1Key(int object, ALCcontext userParam) {
this.object = object;
this.userParam = userParam;
}
@Override
public boolean equals(final Object o) {
if( this == o ) {
return true;
}
if( !(o instanceof AlEventCallback1Key) ) {
return false;
}
final AlEventCallback1Key o2 = (AlEventCallback1Key)o;
return object == o2.object &&
userParam == o2.userParam;
}
@Override
public int hashCode() {
// 31 * x == (x << 5) - x
int hash = object;
hash = ((hash << 5) - hash) + System.identityHashCode( userParam );
return hash;
}
}
```
### JavaCallback Example 11a (*Homogeneous Struct Type*)
This example demonstrates a [homogeneous *Struct* `UserParam` mapping](#struct-type-user-param-homogeneous) with a [key-mapped](#javacallback-key-definition) `CallbackFunction` and `UserParam`.
The callback `T2_CallbackFunc11` is passed by the toolkit to the `CallbackFunction` and by the user to the registration method `MessageCallback11b(..)`.
C-API Header snipped
```
typedef struct {
int32_t ApiVersion;
void* Data;
long i;
long r;
size_t id;
} T2_Callback11UserType;
typedef void ( * T2_CallbackFunc11)(size_t id, const T2_Callback11UserType* usrParam, long val);
void MessageCallback11a(size_t id /* key */, T2_CallbackFunc11 cbFunc, const T2_Callback11UserType* usrParam);
void MessageCallback11aInject(size_t id, long val);
```
and the following GlueGen configuration
```
JavaCallbackDef MessageCallback11a 2 T2_CallbackFunc11 1
JavaCallbackKey MessageCallback11a 0 T2_CallbackFunc11 0
```
leading to the following interface
```
/** JavaCallback interface: T2_CallbackFunc11 -> void (*T2_CallbackFunc11)(size_t id, const T2_Callback11UserType * usrParam, long val) */
public static interface T2_CallbackFunc11 {
/** Interface to C language function:
void callback(size_t id, const T2_Callback11UserType * usrParam, long val)
Alias for: T2_CallbackFunc11 */
public void callback(long id, T2_Callback11UserType usrParam, long val);
}
...
public static class MessageCallback11aKey { ... }
...
/** Returns set of Key { long id } for
void MessageCallback11a(long id, T2_CallbackFunc11 cbFunc, T2_Callback11UserType usrParam) */
public Set getMessageCallback11aKeys();
/** Returns whether callback Key { long id } is mapped for
void MessageCallback11a(long id, T2_CallbackFunc11 cbFunc, T2_Callback11UserType usrParam) */
public boolean isMessageCallback11aMapped(MessageCallback11aKey key);
/** Returns T2_CallbackFunc11 callback mapped to Key { long id } for
void MessageCallback11a(long id, T2_CallbackFunc11 cbFunc, T2_Callback11UserType usrParam) */
public T2_CallbackFunc11 getMessageCallback11a(MessageCallback11aKey key);
/** Returns user-param mapped to Key { long id } for
void MessageCallback11a(long id, T2_CallbackFunc11 cbFunc, T2_Callback11UserType usrParam) */
public T2_Callback11UserType getMessageCallback11aUserParam(MessageCallback11aKey key);
/** Releases all callback data mapped via Key { long id } skipping toolkit API. Favor passing `null` callback ref to
void MessageCallback11a(long id, T2_CallbackFunc11 cbFunc, T2_Callback11UserType usrParam) */
public int releaseAllMessageCallback11a();
/** Releases callback data mapped to Key { long id } skipping toolkit API. Favor passing `null` callback ref to
void MessageCallback11a(long id, T2_CallbackFunc11 cbFunc, T2_Callback11UserType usrParam) */
public void releaseMessageCallback11a(MessageCallback11aKey key);
/** Entry point (through function pointer) to C language function:
void MessageCallback11a(size_t id, T2_CallbackFunc11 cbFunc, const T2_Callback11UserType * usrParam)
*/
public void MessageCallback11a(long id, T2_CallbackFunc11 cbFunc, T2_Callback11UserType usrParam);
/** Entry point (through function pointer) to C language function:
void MessageCallback11aInject(size_t id, long val)
*/
public void MessageCallback11aInject(long id, long val);
```
### JavaCallback Example 11b (*Heterogeneous Pointer/Struct Type*)
This example demonstrates a [heterogeneous *Struct* `UserParam` mapping](#struct-type-user-param-heterogeneous) with a [key-mapped](#javacallback-key-definition) `CallbackFunction` and `UserParam`.
The callback `T2_CallbackFunc11` is managed by the toolkit and passed to the callback function, while user passes a `void*` as a `long` value to the registration method `MessageCallback11b(..)`. The toolkit associates the users' `void*` pointer with the `T2_CallbackFunc11`.
C-API Header snipped
```
typedef struct {
int32_t ApiVersion;
void* Data;
long i;
long r;
size_t id;
} T2_Callback11UserType;
typedef void ( * T2_CallbackFunc11)(size_t id, const T2_Callback11UserType* usrParam, long val);
void MessageCallback11b(size_t id /* key */, T2_CallbackFunc11 cbFunc, void* Data);
void MessageCallback11bInject(size_t id, long val);
```
and the following GlueGen configuration
```
JavaCallbackDef MessageCallback11b 2 T2_CallbackFunc11 1
JavaCallbackKey MessageCallback11b 0 T2_CallbackFunc11 0
```
leading to the following interface
```
/** JavaCallback interface: T2_CallbackFunc11 -> void (*T2_CallbackFunc11)(size_t id, const T2_Callback11UserType * usrParam, long val) */
public static interface T2_CallbackFunc11 {
/** Interface to C language function:
void callback(size_t id, const T2_Callback11UserType * usrParam, long val)
Alias for: T2_CallbackFunc11 */
public void callback(long id, T2_Callback11UserType usrParam, long val);
}
...
public static class MessageCallback11bKey { ... }
...
/** Returns set of Key { long id } for
void MessageCallback11b(long id, T2_CallbackFunc11 cbFunc, long Data) */
public Set getMessageCallback11bKeys();
/** Returns whether callback Key { long id } is mapped for
void MessageCallback11b(long id, T2_CallbackFunc11 cbFunc, long Data) */
public boolean isMessageCallback11bMapped(MessageCallback11bKey key);
/** Returns T2_CallbackFunc11 callback mapped to Key { long id } for
void MessageCallback11b(long id, T2_CallbackFunc11 cbFunc, long Data) */
public T2_CallbackFunc11 getMessageCallback11b(MessageCallback11bKey key);
/** Returns user-param mapped to Key { long id } for
void MessageCallback11b(long id, T2_CallbackFunc11 cbFunc, long Data) */
public Object getMessageCallback11bUserParam(MessageCallback11bKey key);
/** Releases all callback data mapped via Key { long id } skipping toolkit API. Favor passing `null` callback ref to
void MessageCallback11b(long id, T2_CallbackFunc11 cbFunc, long Data) */
public int releaseAllMessageCallback11b();
/** Releases callback data mapped to Key { long id } skipping toolkit API. Favor passing `null` callback ref to
void MessageCallback11b(long id, T2_CallbackFunc11 cbFunc, long Data) */
public void releaseMessageCallback11b(MessageCallback11bKey key);
/** Entry point (through function pointer) to C language function:
void MessageCallback11b(size_t id, T2_CallbackFunc11 cbFunc, void * Data)
*/
public void MessageCallback11b(long id, T2_CallbackFunc11 cbFunc, long Data);
/** Entry point (through function pointer) to C language function:
void MessageCallback11bInject(size_t id, long val)
*/
public void MessageCallback11bInject(long id, long val);
```
*TODO: Enhance documentation*
## Misc Configurations
### `LibraryOnLoad ` for `JNI_OnLoad*(..)` ...
`LibraryOnLoad ` *can* be specified in one native code-unit within one native library maximum, otherwise multiple function definitions would occur.
In case [Java™ callback methods are used](#java-callback), it is required to have `LibraryOnLoad ` specified in exactly one native code-unit within one native library.
`LibraryOnLoad ` generates native JNI code to handle the `JavaVM*` instance
- `JavaVM* JVMUtil_GetJavaVM()` returning the static `JavaVM*` instance for `LibraryBasename` set by `JNI_OnLoad*()`
- `JNI_OnLoad(..)` setting the static `JavaVM*` instance for `LibraryBasename`, used for dynamic libraries,
- `JNI_OnLoad_(..)` setting the static `JavaVM*` instance for `LibraryBasename`, used for static libraries,
Further the following functions are produced to attach and detach the current thread to and from the JVM, getting and releasing the `JNIEnv*`
- `JNIEnv* JVMUtil_GetJNIEnv(int asDaemon, int* jvmAttached)` returns the `JNIEnv*` with current thread being newly attached to the `JavaVM*` **if** result `*jvmAttached == true`, otherwise the current thread was already attached to the `JavaVM*`
- `void JVMUtil_ReleaseJNIEnv(JNIEnv* env, int detachJVM)` releases the `JNIEnv*`, i.e. detaching the current thread from the `JavaVM*` **if** `detachJVM == true`, otherwise funtion does nothing.
## Platform Header Files
GlueGen provides convenient platform headers,
which can be included in your C header files for native compilation and GlueGen code generation.
Example:
```
#include
#include
uint64_t test64;
size_t size1;
ptrdiff_t ptr1;
```
To compile this file you have to include the following folder to your compilers system includes, ie `-I`:
```
gluegen/make/stub_includes/platform
```
To generate code for this file you have to include the following folder to your GlueGen `includeRefid` element:
```
gluegen/make/stub_includes/gluegen
```
## Pre-Defined Macros
To identity a GlueGen code generation run, GlueGen defines the following macros:
```
#define __GLUEGEN__ 2
```