org.fusesource.hawtjni.runtime.Callback Maven / Gradle / Ivy
/*******************************************************************************
* Copyright (c) 2000, 2007 IBM Corporation and others.
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Contributors:
* IBM Corporation - initial API and implementation
*******************************************************************************/
package org.fusesource.hawtjni.runtime;
/**
* Instances of this class represent entry points into Java which can be invoked
* from operating system level callback routines.
*
* IMPORTANT: A callback is only valid when invoked on the thread which created
* it. The results are undefined (and typically bad) when a callback is passed
* out to the operating system (or other code) in such a way that the callback
* is called from a different thread.
*/
public class Callback {
Object object;
String method, signature;
int argCount;
long /* int */ address, errorResult;
boolean isStatic, isArrayBased;
static final String PTR_SIGNATURE = "J"; /* C.PTR_SIZEOF == 4 ? "I" : "J"; */
static final String SIGNATURE_0 = getSignature(0);
static final String SIGNATURE_1 = getSignature(1);
static final String SIGNATURE_2 = getSignature(2);
static final String SIGNATURE_3 = getSignature(3);
static final String SIGNATURE_4 = getSignature(4);
static final String SIGNATURE_N = "([" + PTR_SIGNATURE + ")" + PTR_SIGNATURE;
/**
* Constructs a new instance of this class given an object to send the
* message to, a string naming the method to invoke and an argument count.
* Note that, if the object is an instance of Class it is
* assumed that the method is a static method on that class.
*
* @param object
* the object to send the message to
* @param method
* the name of the method to invoke
* @param argCount
* the number of arguments that the method takes
*/
public Callback(Object object, String method, int argCount) {
this(object, method, argCount, false);
}
/**
* Constructs a new instance of this class given an object to send the
* message to, a string naming the method to invoke, an argument count and a
* flag indicating whether or not the arguments will be passed in an array.
* Note that, if the object is an instance of Class it is
* assumed that the method is a static method on that class.
*
* @param object
* the object to send the message to
* @param method
* the name of the method to invoke
* @param argCount
* the number of arguments that the method takes
* @param isArrayBased
* true if the arguments should be passed in an
* array and false otherwise
*/
public Callback(Object object, String method, int argCount, boolean isArrayBased) {
this(object, method, argCount, isArrayBased, 0);
}
/**
* Constructs a new instance of this class given an object to send the
* message to, a string naming the method to invoke, an argument count, a
* flag indicating whether or not the arguments will be passed in an array
* and a value to return when an exception happens. Note that, if the object
* is an instance of Class it is assumed that the method is a
* static method on that class.
*
* @param object
* the object to send the message to
* @param method
* the name of the method to invoke
* @param argCount
* the number of arguments that the method takes
* @param isArrayBased
* true if the arguments should be passed in an
* array and false otherwise
* @param errorResult
* the return value if the java code throws an exception
*/
public Callback(Object object, String method, int argCount, boolean isArrayBased, long /* int */errorResult) {
/* Set the callback fields */
this.object = object;
this.method = method;
this.argCount = argCount;
this.isStatic = object instanceof Class;
this.isArrayBased = isArrayBased;
this.errorResult = errorResult;
/* Inline the common cases */
if (isArrayBased) {
signature = SIGNATURE_N;
} else {
switch (argCount) {
case 0:
signature = SIGNATURE_0;
break; //$NON-NLS-1$
case 1:
signature = SIGNATURE_1;
break; //$NON-NLS-1$
case 2:
signature = SIGNATURE_2;
break; //$NON-NLS-1$
case 3:
signature = SIGNATURE_3;
break; //$NON-NLS-1$
case 4:
signature = SIGNATURE_4;
break; //$NON-NLS-1$
default:
signature = getSignature(argCount);
}
}
/* Bind the address */
address = bind(this, object, method, signature, argCount, isStatic, isArrayBased, errorResult);
}
/**
* Allocates the native level resources associated with the callback. This
* method is only invoked from within the constructor for the argument.
*
* @param callback
* the callback to bind
* @param object
* the callback's object
* @param method
* the callback's method
* @param signature
* the callback's method signature
* @param argCount
* the callback's method argument count
* @param isStatic
* whether the callback's method is static
* @param isArrayBased
* whether the callback's method is array based
* @param errorResult
* the callback's error result
*/
static native synchronized long /* int */ bind(Callback callback, Object object, String method, String signature, int argCount, boolean isStatic, boolean isArrayBased,
long /* int */errorResult);
/**
* Releases the native level resources associated with the callback, and
* removes all references between the callback and other objects. This helps
* to prevent (bad) application code from accidentally holding onto
* extraneous garbage.
*/
public void dispose() {
if (object == null)
return;
unbind(this);
object = method = signature = null;
address = 0;
}
/**
* Returns the address of a block of machine code which will invoke the
* callback represented by the receiver.
*
* @return the callback address
*/
public long /* int */getAddress() {
return address;
}
/**
* Returns the SWT platform name.
*
* @return the platform name of the currently running SWT
*/
public static native String getPlatform();
/**
* Returns the number of times the system has been recursively entered
* through a callback.
*
* Note: This should not be called by application code.
*
*
* @return the entry count
*
* @since 2.1
*/
public static native int getEntryCount();
static String getSignature(int argCount) {
String signature = "("; //$NON-NLS-1$
for (int i = 0; i < argCount; i++)
signature += PTR_SIGNATURE;
signature += ")" + PTR_SIGNATURE; //$NON-NLS-1$
return signature;
}
/**
* Indicates whether or not callbacks which are triggered at the native
* level should cause the messages described by the matching
* Callback objects to be invoked. This method is used to
* safely shut down SWT when it is run within environments which can
* generate spurious events.
*
* Note: This should not be called by application code.
*
*
* @param enable
* true if callbacks should be invoked
*/
public static final native synchronized void setEnabled(boolean enable);
/**
* Returns whether or not callbacks which are triggered at the native level
* should cause the messages described by the matching Callback
* objects to be invoked. This method is used to safely shut down SWT when
* it is run within environments which can generate spurious events.
*
* Note: This should not be called by application code.
*
*
* @return true if callbacks should not be invoked
*/
public static final native synchronized boolean getEnabled();
/**
* Immediately wipes out all native level state associated with all
* callbacks.
*
* WARNING: This operation is extremely dangerous, and
* should never be performed by application code.
*
*/
public static final native synchronized void reset();
/**
* Releases the native level resources associated with the callback.
*
* @see #dispose
*/
static final native synchronized void unbind(Callback callback);
}