Package jnr.ffi.byref

Class PointerByReference

java.lang.Object

jnr.ffi.byref.AbstractReference<Pointer>

jnr.ffi.byref.PointerByReference

All Implemented Interfaces:

ByReference<Pointer>

public final class PointerByReference
extends AbstractReference<Pointer>

AddressByReference is used when the address of a pointer must be passed as a parameter to a function.

For example, the following C code,

 
 extern void get_a(void** ap);

 void* foo(void) {
     void* a;
     // pass a reference to 'a' so get_a() can fill it out
     get_a(&a);

     return a;
 }
 
 

Would be declared in java as

 
 interface Lib {
     void get_a(@Out PointerByReference ap);
 }
 
 

and used like this

 
 PointerByReference ap = new PointerByReference();
 lib.get_a(ap);
 Pointer ptr = ap.getValue();
 System.out.println("ptr from lib=" + a.getValue());
 System.out.println("ptr contents=" + ptr.getInt(0));
 
 

Constructor Summary

Constructors

Constructor	Description
PointerByReference()	Creates a new reference to a pointer value with a null default value.
PointerByReference(Pointer value)	Creates a new reference to a pointer value

Method Summary

Modifier and Type	Method	Description
void	fromNative(Runtime runtime, Pointer memory, long offset)	Copies the java value from native memory
int	nativeSize(Runtime runtime)	Gets the size of the native buffer required to store the value
void	toNative(Runtime runtime, Pointer memory, long offset)	Copies the java value to native memory

Methods inherited from class jnr.ffi.byref.AbstractReference

checkNull, getValue

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

PointerByReference

public PointerByReference()

Creates a new reference to a pointer value with a null default value.

PointerByReference

public PointerByReference(Pointer value)

Creates a new reference to a pointer value

Parameters:

value - the initial pointer value

Method Detail

toNative

public final void toNative(Runtime runtime,
                           Pointer memory,
                           long offset)

Description copied from interface: ByReference

Copies the java value to native memory

Parameters:

runtime - The current runtime.

memory - The native memory buffer.

offset - The offset of the field.

fromNative

public final void fromNative(Runtime runtime,
                             Pointer memory,
                             long offset)

Description copied from interface: ByReference

Copies the java value from native memory

Parameters:

runtime - The current runtime.

memory - the native memory buffer.

offset - The offset of the field.

nativeSize

public final int nativeSize(Runtime runtime)

Description copied from interface: ByReference

Gets the size of the native buffer required to store the value

Parameters:

runtime - The current runtime.

Returns:

the size in bytes of the native type