com.sun.jna.ptr.ByReference Maven / Gradle / Ivy
/* Copyright (c) 2007 Timothy Wall, All Rights Reserved
*
* The contents of this file is dual-licensed under 2
* alternative Open Source/Free licenses: LGPL 2.1 or later and
* Apache License 2.0. (starting with JNA version 4.0.0).
*
* You can freely decide which license you want to apply to
* the project.
*
* You may obtain a copy of the LGPL License at:
*
* http://www.gnu.org/licenses/licenses.html
*
* A copy is also included in the downloadable source code package
* containing JNA, in file "LGPL2.1".
*
* You may obtain a copy of the Apache License at:
*
* http://www.apache.org/licenses/
*
* A copy is also included in the downloadable source code package
* containing JNA, in file "AL2.0".
*/
package com.sun.jna.ptr;
import java.lang.reflect.Method;
import com.sun.jna.Memory;
import com.sun.jna.Pointer;
import com.sun.jna.PointerType;
/**
* Provides generic "pointer to type" functionality, often used in C code to
* return values to the caller in addition to a function result.
*
* Derived classes must define setValue(<T>) and
* <T> getValue() methods which write to/read from the
* allocated memory.
*
* This class derives from PointerType instead of Memory in order to restrict
* the API to only getValue/setValue.
*
* NOTE: this class would ideally be replaced by a generic.
*/
public abstract class ByReference extends PointerType {
/**
* Allocates memory at this pointer, to contain the pointed-to value.
*
* @param dataSize
* The number of bytes to allocate. Must match the byte size of
* T in the derived class
* setValue(<T>) and
* <T> getValue() methods.
*/
protected ByReference(int dataSize) {
setPointer(new Memory(dataSize));
}
@Override
public String toString() {
try {
Method getValue = getClass().getMethod("getValue");
Object value = getValue.invoke(this);
if (value == null) {
return String.format("null@0x%x", Pointer.nativeValue(getPointer()));
}
return String.format("%s@0x%x=%s", value.getClass().getSimpleName(), Pointer.nativeValue(getPointer()),
value);
} catch (Exception ex) {
return String.format("ByReference Contract violated - %s#getValue raised exception: %s",
getClass().getName(), ex.getMessage());
}
}
}