jnr.ffi.byref.ByReference 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.Pointer;
import jnr.ffi.Runtime;
/**
* A ByReference subclass is used when a primitive parameter must be passed
* by-reference.
*
* For example, the following C code,
*
* {@code
*
* extern void get_a(int * ap);
*
* int foo(void) {
* int 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 IntByReference ap);
* }
*
* }
*
* and used like this
*
*{@code
*
* IntByReference ap = new IntByReference();
* lib.get_a(ap);
* System.out.printf("a from lib=%d\n", a.getValue());
*
* }
*
* @param
*/
public interface ByReference {
/**
* Gets the size of the native buffer required to store the value
*
* @return the size in bytes of the native type
*/
int nativeSize(Runtime runtime);
/**
* Copies the java value to native memory
*
* @param runtime
* @param memory the native memory buffer.
*/
void toNative(Runtime runtime, Pointer memory, long offset);
/**
* Copies the java value from native memory
*
* @param runtime
* @param memory the native memory buffer.
*/
void fromNative(Runtime runtime, Pointer memory, long offset);
T getValue();
}