jnr.ffi.byref.AddressByReference Maven / Gradle / Ivy
/*
* Copyright (C) 2008-2010 Wayne Meissner
*
* This file is part of the JNR project.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package jnr.ffi.byref;
import jnr.ffi.Address;
import jnr.ffi.Pointer;
import jnr.ffi.Runtime;
/**
* AddressByReference is used when the address of a primitive pointer value must be passed
* as a parameter to a function.
*
* For example, the following C code,
*
* {@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
*
* {@code
* interface Lib {
* void get_a(@Out AddressByReference ap);
* }
* }
*
* and used like this
*
*
* AddressByReference ap = new AddressByReference();
* lib.get_a(ap);
* System.out.println("a from lib=" + a.getValue());
*
*/
public final class AddressByReference extends AbstractReference {
/**
* Creates a new reference to an integer value
*/
public AddressByReference() {
super(Address.valueOf(0));
}
/**
* Creates a new reference to an address value
*
* @param value the initial native value
*/
public AddressByReference(Address value) {
super(checkNull(value));
}
/**
* Copies the address value to native memory
*
* @param memory the native memory buffer
*/
public void marshal(Pointer memory, long offset) {
memory.putAddress(offset, value.nativeAddress());
}
/**
* Copies the address value from native memory
*
* @param memory the native memory buffer.
*/
public void unmarshal(Pointer memory, long offset) {
value = Address.valueOf(memory.getAddress(offset));
}
/**
* Gets the native size of type of reference
*
* @return The size of the native type this reference points to
*/
public int nativeSize(Runtime runtime) {
return runtime.addressSize();
}
}