WebNSObjectExtras.mm   [plain text]

/*
* Copyright (C) 2008, 2009 Apple Inc. All rights reserved.
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* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
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* its contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
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* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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#import "WebNSObjectExtras.h"

#import <wtf/Assertions.h>

@interface WebMainThreadInvoker : NSProxy
{
id target;
id exception;
}
@end

static bool returnTypeIsObject(NSInvocation *invocation)
{
// Could use either _C_ID or NSObjCObjectType, but it seems that neither is
// both available and non-deprecated on all versions of Mac OS X we support.
return strchr([[invocation methodSignature] methodReturnType], '@');
}

@implementation WebMainThreadInvoker

- (id)initWithTarget:(id)passedTarget
{
target = passedTarget;
return self;
}

- (void)forwardInvocation:(NSInvocation *)invocation
{
[invocation setTarget:target];
[invocation performSelectorOnMainThread:@selector(_webkit_invokeAndHandleException:) withObject:self waitUntilDone:YES];
if (exception) {
id exceptionToThrow = [exception autorelease];
exception = nil;
@throw exceptionToThrow;
} else if (returnTypeIsObject(invocation)) {
// _webkit_invokeAndHandleException retained the return value on the main thread.
// Now autorelease it on the calling thread.
id returnValue;
[invocation getReturnValue:&returnValue];
[returnValue autorelease];
}
}

- (NSMethodSignature *)methodSignatureForSelector:(SEL)selector
{
return [target methodSignatureForSelector:selector];
}

- (void)handleException:(id)passedException
{
ASSERT(!exception);
exception = [passedException retain];
}

@end

@implementation NSInvocation (WebMainThreadInvoker)

- (void)_webkit_invokeAndHandleException:(WebMainThreadInvoker *)exceptionHandler
{
@try {
[self invoke];
} @catch (id exception) {
[exceptionHandler handleException:exception];
return;
}
if (returnTypeIsObject(self)) {
// Retain the return value on the main thread.
// -[WebMainThreadInvoker forwardInvocation:] will autorelease it on the calling thread.
id value;
[self getReturnValue:&value];
[value retain];
}
}

@end

@implementation NSObject (WebNSObjectExtras)

+ (id)_webkit_invokeOnMainThread
{
return [[[WebMainThreadInvoker alloc] initWithTarget:self] autorelease];
}

- (id)_webkit_invokeOnMainThread
{
return [[[WebMainThreadInvoker alloc] initWithTarget:self] autorelease];
}

@end