Source/JavaScriptCore/API/JSBlockAdaptor.mm - WebKit - Git at Google

 /*
  * Copyright (C) 2013 Apple Inc. All rights reserved.
  *
  * 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
  *    documentation and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */

 #include "config.h"
 #import "JavaScriptCore.h"

 #if JS_OBJC_API_ENABLED

 #import "APICast.h"
 #import "APIShims.h"
 #import "Error.h"
 #import "JSBlockAdaptor.h"
 #import "JSContextInternal.h"
 #import "JSWrapperMap.h"
 #import "JSValue.h"
 #import "JSValueInternal.h"
 #import "ObjcRuntimeExtras.h"
 #import "Operations.h"
 #import "wtf/OwnPtr.h"

 extern "C" {
 id __NSMakeSpecialForwardingCaptureBlock(const char *signature, void (^handler)(NSInvocation *));
 }

 class BlockArgument {
 public:
     virtual ~BlockArgument();
     virtual JSValueRef get(NSInvocation *, NSInteger, JSContext *, JSValueRef*) = 0;

     OwnPtr<BlockArgument> m_next;
 };

 BlockArgument::~BlockArgument()
 {
 }

 class BlockArgumentBoolean : public BlockArgument {
     virtual JSValueRef get(NSInvocation *invocation, NSInteger argumentNumber, JSContext *context, JSValueRef*) override
     {
         bool value;
         [invocation getArgument:&value atIndex:argumentNumber];
         return JSValueMakeBoolean(contextInternalContext(context), value);
     }
 };

 template<typename T>
 class BlockArgumentNumeric : public BlockArgument {
     virtual JSValueRef get(NSInvocation *invocation, NSInteger argumentNumber, JSContext *context, JSValueRef*) override
     {
         T value;
         [invocation getArgument:&value atIndex:argumentNumber];
         return JSValueMakeNumber(contextInternalContext(context), value);
     }
 };

 class BlockArgumentId : public BlockArgument {
     virtual JSValueRef get(NSInvocation *invocation, NSInteger argumentNumber, JSContext *context, JSValueRef*) override
     {
         id value;
         [invocation getArgument:&value atIndex:argumentNumber];
         return objectToValue(context, value);
     }
 };

 class BlockArgumentStruct : public BlockArgument {
 public:
     BlockArgumentStruct(NSInvocation *conversionInvocation, const char* encodedType)
         : m_conversionInvocation(conversionInvocation)
         , m_buffer(encodedType)
     {
     }

 private:
     virtual JSValueRef get(NSInvocation *invocation, NSInteger argumentNumber, JSContext *context, JSValueRef*) override
     {
         [invocation getArgument:m_buffer atIndex:argumentNumber];

         [m_conversionInvocation setArgument:m_buffer atIndex:2];
         [m_conversionInvocation setArgument:&context atIndex:3];
         [m_conversionInvocation invokeWithTarget:[JSValue class]];

         JSValue *value;
         [m_conversionInvocation getReturnValue:&value];
         return valueInternalValue(value);
     }

     RetainPtr<NSInvocation> m_conversionInvocation;
     StructBuffer m_buffer;
 };

 class BlockArgumentTypeDelegate {
 public:
     typedef BlockArgument* ResultType;

     template<typename T>
     static ResultType typeInteger()
     {
         return new BlockArgumentNumeric<T>;
     }

     template<typename T>
     static ResultType typeDouble()
     {
         return new BlockArgumentNumeric<T>;
     }

     static ResultType typeBool()
     {
         return new BlockArgumentBoolean;
     }

     static ResultType typeVoid()
     {
         RELEASE_ASSERT_NOT_REACHED();
         return 0;
     }

     static ResultType typeId()
     {
         return new BlockArgumentId;
     }

     static ResultType typeOfClass(const char*, const char*)
     {
         return new BlockArgumentId;
     }

     static ResultType typeBlock(const char*, const char*)
     {
         return 0;
     }

     static ResultType typeStruct(const char* begin, const char* end)
     {
         StringRange copy(begin, end);
         if (NSInvocation *invocation = valueToTypeInvocationFor(copy))
             return new BlockArgumentStruct(invocation, copy);
         return 0;
     }
 };

 class BlockResult {
 public:
     virtual ~BlockResult()
     {
     }

     virtual void set(NSInvocation *, JSContext *, JSValueRef, JSValueRef*) = 0;
 };

 class BlockResultVoid : public BlockResult {
     virtual void set(NSInvocation *, JSContext *, JSValueRef, JSValueRef*) override
     {
     }
 };

 template<typename T>
 class BlockResultInteger : public BlockResult {
     virtual void set(NSInvocation *invocation, JSContext *context, JSValueRef result, JSValueRef* exception) override
     {
         T value = (T)JSC::toInt32(JSValueToNumber(contextInternalContext(context), result, exception));
         [invocation setReturnValue:&value];
     }
 };

 template<typename T>
 class BlockResultDouble : public BlockResult {
     virtual void set(NSInvocation *invocation, JSContext *context, JSValueRef result, JSValueRef* exception) override
     {
         T value = (T)JSValueToNumber(contextInternalContext(context), result, exception);
         [invocation setReturnValue:&value];
     }
 };

 class BlockResultBoolean : public BlockResult {
     virtual void set(NSInvocation *invocation, JSContext *context, JSValueRef result, JSValueRef*) override
     {
         bool value = JSValueToBoolean(contextInternalContext(context), result);
         [invocation setReturnValue:&value];
     }
 };

 class BlockResultStruct : public BlockResult {
 public:
     BlockResultStruct(NSInvocation *conversionInvocation, const char* encodedType)
         : m_conversionInvocation(conversionInvocation)
         , m_buffer(encodedType)
     {
     }

 private:
     virtual void set(NSInvocation *invocation, JSContext *context, JSValueRef result, JSValueRef*) override
     {
         JSValue *value = [JSValue valueWithValue:result inContext:context];
         [m_conversionInvocation invokeWithTarget:value];
         [m_conversionInvocation getReturnValue:m_buffer];
         [invocation setReturnValue:&value];
     }

     RetainPtr<NSInvocation> m_conversionInvocation;
     StructBuffer m_buffer;
 };

 @implementation JSBlockAdaptor {
     RetainPtr<NSString> m_signatureWithOffsets;
     RetainPtr<NSString> m_signatureWithoutOffsets;
     OwnPtr<BlockResult> m_result;
     OwnPtr<BlockArgument> m_arguments;
     size_t m_argumentCount;
 }

 // Helper function to add offset information back into a block signature.
 static NSString *buildBlockSignature(NSString *prefix, const char* begin, const char* end, unsigned long long& offset, NSString *postfix)
 {
     StringRange copy(begin, end);
     NSString *result = [NSString stringWithFormat:@"%@%s%@%@", prefix, copy.get(), @(offset), postfix];
     NSUInteger size;
     NSGetSizeAndAlignment(copy, &size, 0);
     if (size < 4)
         size = 4;
     offset += size;
     return result;
 }

 - (id)initWithBlockSignatureFromProtocol:(const char*)encodedType
 {
     self = [super init];
     if (!self)
         return nil;

     m_signatureWithoutOffsets = [NSString stringWithUTF8String:encodedType];
     m_argumentCount = 0;

     // Currently only adapting JavaScript functions to blocks returning void.
     const char* resultTypeBegin = encodedType;
     if (*encodedType++ != 'v')
         return self;
     OwnPtr<BlockResult> result = adoptPtr(new BlockResultVoid);
     const char* resultTypeEnd = encodedType;

     if (encodedType[0] != '@' || encodedType[1] != '?')
         return self;
     encodedType += 2;

     // The first argument to a block is the block itself.
     NSString *signature = @"@?0";
     unsigned long long offset = sizeof(void*);

     OwnPtr<BlockArgument> arguments;
     OwnPtr<BlockArgument>* nextArgument = &arguments;
     while (*encodedType) {
         const char* begin = encodedType;
         OwnPtr<BlockArgument> argument = adoptPtr(parseObjCType<BlockArgumentTypeDelegate>(encodedType));
         if (!argument)
             return self;
         const char* end = encodedType;

         // Append the type & stack offset of this argument to the signature string.
         signature = buildBlockSignature(signature, begin, end, offset, @"");

         *nextArgument = argument.release();
         nextArgument = &(*nextArgument)->m_next;
         ++m_argumentCount;
     }

     // Prefix the signature with the return type & total stackframe size.
     // (this call will also add the return type size to the offset,
     // which is a nonsense, but harmless since this is the last use).
     signature = buildBlockSignature(@"", resultTypeBegin, resultTypeEnd, offset, signature);

     m_signatureWithOffsets = signature;
     m_result = result.release();
     m_arguments = arguments.release();

     return self;
 }

 // The JSBlockAdaptor stores the type string taken from the protocol. This string
 // does not contain invocation layout information. The signature from the block
 // does contain the stackframe offsets. Skip these when comparing strings.
 - (bool)blockMatchesSignature:(id)block
 {
     if (!_Block_has_signature(block))
         return false;

     const char* withoutOffsets = [m_signatureWithoutOffsets UTF8String];
     const char* signature = _Block_signature(block);

     while (true) {
         while (isdigit(*withoutOffsets))
             ++withoutOffsets;
         while (isdigit(*signature))
             ++signature;

         if (*withoutOffsets != *signature)
             return false;
         if (!*withoutOffsets)
             return true;
         ++withoutOffsets;
         ++signature;
     }
 }

 - (id)blockFromValue:(JSValueRef)argument inContext:(JSContext *)context withException:(JSValueRef*)exception
 {
     JSGlobalContextRef contextRef = contextInternalContext(context);

     // Check for null/undefined.
     if (JSValueIsUndefined(contextRef, argument) || JSValueIsNull(contextRef, argument))
         return nil;

     JSObjectRef function = 0;
     if (id object = tryUnwrapObjcObject(contextRef, argument)) {
         // Check if the argument is an Objective-C block.
         if ([object isKindOfClass:getNSBlockClass()]) {
             if ([self blockMatchesSignature:object])
                 return object;
         }
     } else if (m_signatureWithOffsets && JSValueIsObject(contextRef, argument)) {
         // Check if the argument is a JavaScript function
         // (and that were able to create a forwarding block for this signature).
         JSObjectRef object = JSValueToObject(contextRef, argument, exception);
         if (JSObjectIsFunction(contextRef, object))
             function = object;
     }

     if (!function) {
         JSC::APIEntryShim entryShim(toJS(contextRef));
         *exception = toRef(JSC::createTypeError(toJS(contextRef), "Invalid argument supplied for Objective-C block"));
         return nil;
     }

     // Captured variables.
     JSBlockAdaptor *adaptor = self;
     JSValue *value = [JSValue valueWithValue:function inContext:context];

     // FIXME: https://bugs.webkit.org/show_bug.cgi?id=105895
     // Currently only supporting void functions.
     return __NSMakeSpecialForwardingCaptureBlock([m_signatureWithOffsets UTF8String], ^(NSInvocation *invocation){
         // FIXME: https://bugs.webkit.org/show_bug.cgi?id=105894
         // Rather than requiring that the context be retained, it would probably be more
         // appropriate to use a new JSContext instance (creating one if necessary).
         // It would be nice if we could throw a JS exception here, but without a context we have
         // nothing to work with.
         JSContext *context = value.context;
         if (!context)
             return;
         JSGlobalContextRef contextRef = contextInternalContext(context);

         JSValueRef argumentArray[adaptor->m_argumentCount];

         size_t argumentNumber = 0;
         BlockArgument* arguments = adaptor->m_arguments.get();
         for (BlockArgument* argument = arguments; argument; argument = argument->m_next.get()) {
             JSValueRef exception = 0;
             argumentArray[argumentNumber] = argument->get(invocation, argumentNumber + 1, context, &exception);
             if (exception) {
                 [context notifyException:exception];
                 return;
             }

             ++argumentNumber;
         }
         size_t argumentCount = argumentNumber;

         JSValueRef exception = 0;
         JSObjectCallAsFunction(contextRef, JSValueToObject(contextRef, valueInternalValue(value), 0), 0, argumentCount, argumentArray, &exception);
         if (exception) {
             [context notifyException:exception];
             return;
         }
     });
 }

 @end

 #endif
	/*
	* Copyright (C) 2013 Apple Inc. All rights reserved.
	*
	* 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
	* documentation and/or other materials provided with the distribution.
	*
	* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
	* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
	* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
	* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
	* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
	* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
	* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
	* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
	* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	*/

	#include "config.h"
	#import "JavaScriptCore.h"

	#if JS_OBJC_API_ENABLED

	#import "APICast.h"
	#import "APIShims.h"
	#import "Error.h"
	#import "JSBlockAdaptor.h"
	#import "JSContextInternal.h"
	#import "JSWrapperMap.h"
	#import "JSValue.h"
	#import "JSValueInternal.h"
	#import "ObjcRuntimeExtras.h"
	#import "Operations.h"
	#import "wtf/OwnPtr.h"

	extern "C" {
	id __NSMakeSpecialForwardingCaptureBlock(const char signature, void (^handler)(NSInvocation ));
	}

	class BlockArgument {
	public:
	virtual ~BlockArgument();
	virtual JSValueRef get(NSInvocation , NSInteger, JSContext , JSValueRef*) = 0;

	OwnPtr<BlockArgument> m_next;
	};

	BlockArgument::~BlockArgument()
	{
	}

	class BlockArgumentBoolean : public BlockArgument {
	virtual JSValueRef get(NSInvocation invocation, NSInteger argumentNumber, JSContext context, JSValueRef*) override
	{
	bool value;
	[invocation getArgument:&value atIndex:argumentNumber];
	return JSValueMakeBoolean(contextInternalContext(context), value);
	}
	};

	template<typename T>
	class BlockArgumentNumeric : public BlockArgument {
	virtual JSValueRef get(NSInvocation invocation, NSInteger argumentNumber, JSContext context, JSValueRef*) override
	{
	T value;
	[invocation getArgument:&value atIndex:argumentNumber];
	return JSValueMakeNumber(contextInternalContext(context), value);
	}
	};

	class BlockArgumentId : public BlockArgument {
	virtual JSValueRef get(NSInvocation invocation, NSInteger argumentNumber, JSContext context, JSValueRef*) override
	{
	id value;
	[invocation getArgument:&value atIndex:argumentNumber];
	return objectToValue(context, value);
	}
	};

	class BlockArgumentStruct : public BlockArgument {
	public:
	BlockArgumentStruct(NSInvocation conversionInvocation, const char encodedType)
	: m_conversionInvocation(conversionInvocation)
	, m_buffer(encodedType)
	{
	}

	private:
	virtual JSValueRef get(NSInvocation invocation, NSInteger argumentNumber, JSContext context, JSValueRef*) override
	{
	[invocation getArgument:m_buffer atIndex:argumentNumber];

	[m_conversionInvocation setArgument:m_buffer atIndex:2];
	[m_conversionInvocation setArgument:&context atIndex:3];
	[m_conversionInvocation invokeWithTarget:[JSValue class]];

	JSValue *value;
	[m_conversionInvocation getReturnValue:&value];
	return valueInternalValue(value);
	}

	RetainPtr<NSInvocation> m_conversionInvocation;
	StructBuffer m_buffer;
	};

	class BlockArgumentTypeDelegate {
	public:
	typedef BlockArgument* ResultType;

	template<typename T>
	static ResultType typeInteger()
	{
	return new BlockArgumentNumeric<T>;
	}

	template<typename T>
	static ResultType typeDouble()
	{
	return new BlockArgumentNumeric<T>;
	}

	static ResultType typeBool()
	{
	return new BlockArgumentBoolean;
	}

	static ResultType typeVoid()
	{
	RELEASE_ASSERT_NOT_REACHED();
	return 0;
	}

	static ResultType typeId()
	{
	return new BlockArgumentId;
	}

	static ResultType typeOfClass(const char, const char)
	{
	return new BlockArgumentId;
	}

	static ResultType typeBlock(const char, const char)
	{
	return 0;
	}

	static ResultType typeStruct(const char* begin, const char* end)
	{
	StringRange copy(begin, end);
	if (NSInvocation *invocation = valueToTypeInvocationFor(copy))
	return new BlockArgumentStruct(invocation, copy);
	return 0;
	}
	};

	class BlockResult {
	public:
	virtual ~BlockResult()
	{
	}

	virtual void set(NSInvocation , JSContext , JSValueRef, JSValueRef*) = 0;
	};

	class BlockResultVoid : public BlockResult {
	virtual void set(NSInvocation , JSContext , JSValueRef, JSValueRef*) override
	{
	}
	};

	template<typename T>
	class BlockResultInteger : public BlockResult {
	virtual void set(NSInvocation invocation, JSContext context, JSValueRef result, JSValueRef* exception) override
	{
	T value = (T)JSC::toInt32(JSValueToNumber(contextInternalContext(context), result, exception));
	[invocation setReturnValue:&value];
	}
	};

	template<typename T>
	class BlockResultDouble : public BlockResult {
	virtual void set(NSInvocation invocation, JSContext context, JSValueRef result, JSValueRef* exception) override
	{
	T value = (T)JSValueToNumber(contextInternalContext(context), result, exception);
	[invocation setReturnValue:&value];
	}
	};

	class BlockResultBoolean : public BlockResult {
	virtual void set(NSInvocation invocation, JSContext context, JSValueRef result, JSValueRef*) override
	{
	bool value = JSValueToBoolean(contextInternalContext(context), result);
	[invocation setReturnValue:&value];
	}
	};

	class BlockResultStruct : public BlockResult {
	public:
	BlockResultStruct(NSInvocation conversionInvocation, const char encodedType)
	: m_conversionInvocation(conversionInvocation)
	, m_buffer(encodedType)
	{
	}

	private:
	virtual void set(NSInvocation invocation, JSContext context, JSValueRef result, JSValueRef*) override
	{
	JSValue *value = [JSValue valueWithValue:result inContext:context];
	[m_conversionInvocation invokeWithTarget:value];
	[m_conversionInvocation getReturnValue:m_buffer];
	[invocation setReturnValue:&value];
	}

	RetainPtr<NSInvocation> m_conversionInvocation;
	StructBuffer m_buffer;
	};

	@implementation JSBlockAdaptor {
	RetainPtr<NSString> m_signatureWithOffsets;
	RetainPtr<NSString> m_signatureWithoutOffsets;
	OwnPtr<BlockResult> m_result;
	OwnPtr<BlockArgument> m_arguments;
	size_t m_argumentCount;
	}

	// Helper function to add offset information back into a block signature.
	static NSString buildBlockSignature(NSString prefix, const char* begin, const char* end, unsigned long long& offset, NSString *postfix)
	{
	StringRange copy(begin, end);
	NSString *result = [NSString stringWithFormat:@"%@%s%@%@", prefix, copy.get(), @(offset), postfix];
	NSUInteger size;
	NSGetSizeAndAlignment(copy, &size, 0);
	if (size < 4)
	size = 4;
	offset += size;
	return result;
	}

	- (id)initWithBlockSignatureFromProtocol:(const char*)encodedType
	{
	self = [super init];
	if (!self)
	return nil;

	m_signatureWithoutOffsets = [NSString stringWithUTF8String:encodedType];
	m_argumentCount = 0;

	// Currently only adapting JavaScript functions to blocks returning void.
	const char* resultTypeBegin = encodedType;
	if (*encodedType++ != 'v')
	return self;
	OwnPtr<BlockResult> result = adoptPtr(new BlockResultVoid);
	const char* resultTypeEnd = encodedType;

	if (encodedType[0] != '@' \|\| encodedType[1] != '?')
	return self;
	encodedType += 2;

	// The first argument to a block is the block itself.
	NSString *signature = @"@?0";
	unsigned long long offset = sizeof(void*);

	OwnPtr<BlockArgument> arguments;
	OwnPtr<BlockArgument>* nextArgument = &arguments;
	while (*encodedType) {
	const char* begin = encodedType;
	OwnPtr<BlockArgument> argument = adoptPtr(parseObjCType<BlockArgumentTypeDelegate>(encodedType));
	if (!argument)
	return self;
	const char* end = encodedType;

	// Append the type & stack offset of this argument to the signature string.
	signature = buildBlockSignature(signature, begin, end, offset, @"");

	*nextArgument = argument.release();
	nextArgument = &(*nextArgument)->m_next;
	++m_argumentCount;
	}

	// Prefix the signature with the return type & total stackframe size.
	// (this call will also add the return type size to the offset,
	// which is a nonsense, but harmless since this is the last use).
	signature = buildBlockSignature(@"", resultTypeBegin, resultTypeEnd, offset, signature);

	m_signatureWithOffsets = signature;
	m_result = result.release();
	m_arguments = arguments.release();

	return self;
	}

	// The JSBlockAdaptor stores the type string taken from the protocol. This string
	// does not contain invocation layout information. The signature from the block
	// does contain the stackframe offsets. Skip these when comparing strings.
	- (bool)blockMatchesSignature:(id)block
	{
	if (!_Block_has_signature(block))
	return false;

	const char* withoutOffsets = [m_signatureWithoutOffsets UTF8String];
	const char* signature = _Block_signature(block);

	while (true) {
	while (isdigit(*withoutOffsets))
	++withoutOffsets;
	while (isdigit(*signature))
	++signature;

	if (withoutOffsets != signature)
	return false;
	if (!*withoutOffsets)
	return true;
	++withoutOffsets;
	++signature;
	}
	}

	- (id)blockFromValue:(JSValueRef)argument inContext:(JSContext )context withException:(JSValueRef)exception
	{
	JSGlobalContextRef contextRef = contextInternalContext(context);

	// Check for null/undefined.
	if (JSValueIsUndefined(contextRef, argument) \|\| JSValueIsNull(contextRef, argument))
	return nil;

	JSObjectRef function = 0;
	if (id object = tryUnwrapObjcObject(contextRef, argument)) {
	// Check if the argument is an Objective-C block.
	if ([object isKindOfClass:getNSBlockClass()]) {
	if ([self blockMatchesSignature:object])
	return object;
	}
	} else if (m_signatureWithOffsets && JSValueIsObject(contextRef, argument)) {
	// Check if the argument is a JavaScript function
	// (and that were able to create a forwarding block for this signature).
	JSObjectRef object = JSValueToObject(contextRef, argument, exception);
	if (JSObjectIsFunction(contextRef, object))
	function = object;
	}

	if (!function) {
	JSC::APIEntryShim entryShim(toJS(contextRef));
	*exception = toRef(JSC::createTypeError(toJS(contextRef), "Invalid argument supplied for Objective-C block"));
	return nil;
	}

	// Captured variables.
	JSBlockAdaptor *adaptor = self;
	JSValue *value = [JSValue valueWithValue:function inContext:context];

	// FIXME: https://bugs.webkit.org/show_bug.cgi?id=105895
	// Currently only supporting void functions.
	return __NSMakeSpecialForwardingCaptureBlock([m_signatureWithOffsets UTF8String], ^(NSInvocation *invocation){
	// FIXME: https://bugs.webkit.org/show_bug.cgi?id=105894
	// Rather than requiring that the context be retained, it would probably be more
	// appropriate to use a new JSContext instance (creating one if necessary).
	// It would be nice if we could throw a JS exception here, but without a context we have
	// nothing to work with.
	JSContext *context = value.context;
	if (!context)
	return;
	JSGlobalContextRef contextRef = contextInternalContext(context);

	JSValueRef argumentArray[adaptor->m_argumentCount];

	size_t argumentNumber = 0;
	BlockArgument* arguments = adaptor->m_arguments.get();
	for (BlockArgument* argument = arguments; argument; argument = argument->m_next.get()) {
	JSValueRef exception = 0;
	argumentArray[argumentNumber] = argument->get(invocation, argumentNumber + 1, context, &exception);
	if (exception) {
	[context notifyException:exception];
	return;
	}

	++argumentNumber;
	}
	size_t argumentCount = argumentNumber;

	JSValueRef exception = 0;
	JSObjectCallAsFunction(contextRef, JSValueToObject(contextRef, valueInternalValue(value), 0), 0, argumentCount, argumentArray, &exception);
	if (exception) {
	[context notifyException:exception];
	return;
	}
	});
	}

	@end

	#endif