com.sun.jna.VarArgsChecker Maven / Gradle / Ivy
/*
* 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;
import java.lang.reflect.Method;
/**
* Class for checking if a method has vararg parameters.
* Use method {@link VarArgsChecker#create() create()} to create an instance
* of this class. How the returned instance work depends on the capabilities
* of the underlying JVM implementation. On older versions of the VM not supporting
* varargs, the returned VarArgsChecker will always return false
* on calls to {@link VarArgsChecker#isVarArgs(Method) isVarArgs(Method)}.
* @author Max Bureck
*/
abstract class VarArgsChecker {
private VarArgsChecker() {
}
/**
* Implementation actually using Method.isVarArgs()
*/
private static final class RealVarArgsChecker extends VarArgsChecker {
boolean isVarArgs(Method m) {
return m.isVarArgs();
}
int fixedArgs(Method m) {
// In Java, final argument contains all "varargs"
return m.isVarArgs() ? m.getParameterTypes().length - 1 : 0;
}
}
/**
* Implementation always returning false when {@link NoVarArgsChecker#isVarArgs(Method)}
* is called. This implementation will be chosen, if {@link Method#isVarArgs()} is not available
*/
private static final class NoVarArgsChecker extends VarArgsChecker {
boolean isVarArgs(Method m) {
return false;
}
int fixedArgs(Method m) {
return 0;
}
}
/**
* Creates a new instance of a concrete subclass of VarArgsChecker, depending
* if {@link Method#isVarArgs()} exists.
* @return new instance of concrete VarArgsChecker subclass
*/
static VarArgsChecker create() {
try {
// check if Method#isVarArgs() exists
final Method isVarArgsMethod = Method.class.getMethod("isVarArgs", new Class[0]);
if(isVarArgsMethod != null) {
// if it exitsts, return new instance of RealVarArgsChecker
return new RealVarArgsChecker();
} else {
return new NoVarArgsChecker();
}
} catch (NoSuchMethodException e) {
return new NoVarArgsChecker();
} catch (SecurityException e) {
return new NoVarArgsChecker();
}
}
/**
* Checks if the given method was declared to take a variable number of arguments.
* @param m Method to be checked
* @return true if the given method takes a variable number of arguments, false otherwise.
*/
abstract boolean isVarArgs(Method m);
/**
* If variadic, returns the number of fixed arguments to the method.
* @param m Method to be checked
* @return Number of fixed arguments if the given method takes a variable number of arguments, zero otherwise.
*/
abstract int fixedArgs(Method m);
}