com.sun.jna.InvocationMapper Maven / Gradle / Ivy
package com.sun.jna;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
/** Provide a method for overriding how a given function is invoked.
* An instance of this interface may be provided to
* {@link Native#loadLibrary(String, Class, java.util.Map)} as an entry in
* the options map with key {@link Library#OPTION_INVOCATION_MAPPER}.
* This is useful for implementing inlined functions, or functions which
* are actually C preprocessor macros. Given a native library and JNA
* interface method, the mapper may provide a handler which implements the
* desired functionality (which may or may not actually make use of a
* native method).
*
* For example, the GNU C library remaps the stat function
* into a call to _xstat with a slight rearrangement of arguments.
* A mapper for the GNU C library might look like the following:
*
*
* new InvocationMapper() {
* public InvocationHandler getInvocationHandler(NativeLibrary lib, Method m) {
* if (m.getName().equals("stat")) {
* final Function f = lib.getFunction("_xstat");
* return new InvocationHandler() {
* public Object invoke(Object proxy, Method method, Object[] args) {
* Object[] newArgs = new Object[args.length+1];
* System.arraycopy(args, 0, newArgs, 1, args.length);
* newArgs[0] = new Integer(3); // _xstat version
* return f.invoke(newArgs);
* }
* };
* }
* return null;
* }
* }
*
* Another situation is where a header provides a function-like macro or
* inline function definition.
*
*
* // Original C code (macro and inline variations)
* #define allocblock(x) malloc(x * 1024)
* static inline void* allocblock(size_t x) { return malloc(x * 1024); }
*
* // Invocation mapping
* new InvocationMapper() {
* public InvocationHandler getInvocationHandler(NativeLibrary lib, Method m) {
* if (m.getName().equals("allocblock")) {
* final Function f = lib.getFunction("malloc");
* return new InvocationHandler() {
* public Object invoke(Object proxy, Method method, Object[] args) {
* args[0] = ((Integer)args[0]).intValue() * 1024;
* return f.invoke(newArgs);
* }
* };
* }
* return null;
* }
* }
*
* @author twall
*/
public interface InvocationMapper {
/** Return an {@link InvocationHandler} responsible for handling the
* invocation of the given method, or null if the default
* handling should be used. Note that the result of a call to this method
* with a given library and method may be cached.
* @param lib Target library
* @param m Original JNA interface method that was invoked.
*/
InvocationHandler getInvocationHandler(NativeLibrary lib, Method m);
}