org.eclipse.swt.internal.Callback Maven / Gradle / Ivy
Show all versions of org.eclipse.swt.win32.win32.x86 Show documentation
/*******************************************************************************
* Copyright (c) 2000, 2012 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.eclipse.swt.internal;
/**
* 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;
int /*long*/ address, errorResult;
boolean isStatic, isArrayBased;
static final String PTR_SIGNATURE = C.PTR_SIZEOF == 4 ? "I" : "J"; //$NON-NLS-1$ //$NON-NLS-2$
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; //$NON-NLS-1$ //$NON-NLS-2$
/**
* 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, int /*long*/ 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 int /*long*/ bind (Callback callback, Object object, String method, String signature, int argCount, boolean isStatic, boolean isArrayBased, int /*long*/ 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 int /*long*/ 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 ();
/**
* This might be called directly from native code in environments
* which can generate spurious events. Check before removing it.
*
* @deprecated
*
* @param ignore true if callbacks should not be invoked
*/
static final void ignoreCallbacks (boolean ignore) {
setEnabled (!ignore);
}
/**
* 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);
}