fastdelegate.h.svn-base

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//						FastDelegate.h 
//	Efficient delegates in C++ that generate only two lines of asm code!
//  Documentation is found at http://www.codeproject.com/cpp/FastDelegate.asp
//
//						- Don Clugston, Mar 2004.
//		Major contributions were made by Jody Hagins.
// History:
// 24-Apr-04 1.0  * Submitted to CodeProject. 
// 28-Apr-04 1.1  * Prevent most unsafe uses of evil static function hack.
//				  * Improved syntax for horrible_cast (thanks Paul Bludov).
//				  * Tested on Metrowerks MWCC and Intel ICL (IA32)
//				  * Compiled, but not run, on Comeau C++ and Intel Itanium ICL.
//	27-Jun-04 1.2 * Now works on Borland C++ Builder 5.5
//				  * Now works on /clr "managed C++" code on VC7, VC7.1
//				  * Comeau C++ now compiles without warnings.
//				  * Prevent the virtual inheritance case from being used on 
//					  VC6 and earlier, which generate incorrect code.
//				  * Improved warning and error messages. Non-standard hacks
//					 now have compile-time checks to make them safer.
//				  * implicit_cast used instead of static_cast in many cases.
//				  * If calling a const member function, a const class pointer can be used.
//				  * MakeDelegate() global helper function added to simplify pass-by-value.
//				  * Added fastdelegate.clear()
// 16-Jul-04 1.2.1* Workaround for gcc bug (const member function pointers in templates)
// 30-Oct-04 1.3  * Support for (non-void) return values.
//				  * No more workarounds in client code!
//					 MSVC and Intel now use a clever hack invented by John Dlugosz:
//				     - The FASTDELEGATEDECLARE workaround is no longer necessary.
//					 - No more warning messages for VC6
//				  * Less use of macros. Error messages should be more comprehensible.
//				  * Added include guards
//				  * Added FastDelegate::empty() to test if invocation is safe (Thanks Neville Franks).
//				  * Now tested on VS 2005 Express Beta, PGI C++
// 24-Dec-04 1.4  * Added DelegateMemento, to allow collections of disparate delegates.
//                * <,>,<=,>= comparison operators to allow storage in ordered containers.
//				  * Substantial reduction of code size, especially the 'Closure' class.
//				  * Standardised all the compiler-specific workarounds.
//                * MFP conversion now works for CodePlay (but not yet supported in the full code).
//                * Now compiles without warnings on _any_ supported compiler, including BCC 5.5.1
//				  * New syntax: FastDelegate< int (char *, double) >. 
// 14-Feb-05 1.4.1* Now treats =0 as equivalent to .clear(), ==0 as equivalent to .empty(). (Thanks elfric).
//				  * Now tested on Intel ICL for AMD64, VS2005 Beta for AMD64 and Itanium.
// 30-Mar-05 1.5  * Safebool idiom: "if (dg)" is now equivalent to "if (!dg.empty())"
//				  * Fully supported by CodePlay VectorC
//                * Bugfix for Metrowerks: empty() was buggy because a valid MFP can be 0 on MWCC!
//                * More optimal assignment,== and != operators for static function pointers.

#ifndef FASTDELEGATE_H
#define FASTDELEGATE_H
#if _MSC_VER > 1000
#pragma once
#endif // _MSC_VER > 1000

#include <memory.h> // to allow <,> comparisons

////////////////////////////////////////////////////////////////////////////////
//						Configuration options
//
////////////////////////////////////////////////////////////////////////////////

// Uncomment the following #define for optimally-sized delegates.
// In this case, the generated asm code is almost identical to the code you'd get
// if the compiler had native support for delegates.
// It will not work on systems where sizeof(dataptr) < sizeof(codeptr). 
// Thus, it will not work for DOS compilers using the medium model.
// It will also probably fail on some DSP systems.
#define FASTDELEGATE_USESTATICFUNCTIONHACK

// Uncomment the next line to allow function declarator syntax.
// It is automatically enabled for those compilers where it is known to work.
//#define FASTDELEGATE_ALLOW_FUNCTION_TYPE_SYNTAX

////////////////////////////////////////////////////////////////////////////////
//						Compiler identification for workarounds
//
////////////////////////////////////////////////////////////////////////////////

// Compiler identification. It's not easy to identify Visual C++ because
// many vendors fraudulently define Microsoft's identifiers.
#if defined(_MSC_VER) && !defined(__MWERKS__) && !defined(__VECTOR_C) && !defined(__ICL) && !defined(__BORLANDC__)
#define FASTDLGT_ISMSVC

#if (_MSC_VER <1300) // Many workarounds are required for VC6.
#define FASTDLGT_VC6
#pragma warning(disable:4786) // disable this ridiculous warning
#endif

#endif

// Does the compiler uses Microsoft's member function pointer structure?
// If so, it needs special treatment.
// Metrowerks CodeWarrior, Intel, and CodePlay fraudulently define Microsoft's 
// identifier, _MSC_VER. We need to filter Metrowerks out.
#if defined(_MSC_VER) && !defined(__MWERKS__)
#define FASTDLGT_MICROSOFT_MFP

#if !defined(__VECTOR_C)
// CodePlay doesn't have the __single/multi/virtual_inheritance keywords
#define FASTDLGT_HASINHERITANCE_KEYWORDS
#endif
#endif

// Does it allow function declarator syntax? The following compilers are known to work:
#if defined(FASTDLGT_ISMSVC) && (_MSC_VER >=1310) // VC 7.1
#define FASTDELEGATE_ALLOW_FUNCTION_TYPE_SYNTAX
#endif

// Gcc(2.95+), and versions of Digital Mars, Intel and Comeau in common use.
#if defined (__DMC__) || defined(__GNUC__) || defined(__ICL) || defined(__COMO__)
#define FASTDELEGATE_ALLOW_FUNCTION_TYPE_SYNTAX
#endif

// It works on Metrowerks MWCC 3.2.2. From boost.Config it should work on earlier ones too.
#if defined (__MWERKS__)
#define FASTDELEGATE_ALLOW_FUNCTION_TYPE_SYNTAX
#endif

#ifdef __GNUC__ // Workaround GCC bug #8271 
	// At present, GCC doesn't recognize constness of MFPs in templates
#define FASTDELEGATE_GCC_BUG_8271
#endif



////////////////////////////////////////////////////////////////////////////////
//						General tricks used in this code
//
// (a) Error messages are generated by typdefing an array of negative size to
//     generate compile-time errors.
// (b) Warning messages on MSVC are generated by declaring unused variables, and
//	    enabling the "variable XXX is never used" warning.
// (c) Unions are used in a few compiler-specific cases to perform illegal casts.
// (d) For Microsoft and Intel, when adjusting the 'this' pointer, it's cast to
//     (char *) first to ensure that the correct number of *bytes* are added.
//
////////////////////////////////////////////////////////////////////////////////
//						Helper templates
//
////////////////////////////////////////////////////////////////////////////////


namespace fastdelegate {
namespace detail {	// we'll hide the implementation details in a nested namespace.

//		implicit_cast< >
// I believe this was originally going to be in the C++ standard but 
// was left out by accident. It's even milder than static_cast.
// I use it instead of static_cast<> to emphasize that I'm not doing
// anything nasty. 
// Usage is identical to static_cast<>
template <class OutputClass, class InputClass>
inline OutputClass implicit_cast(InputClass input){
	return input;
}

//		horrible_cast< >
// This is truly evil. It completely subverts C++'s type system, allowing you 
// to cast from any class to any other class. Technically, using a union 
// to perform the cast is undefined behaviour (even in C). But we can see if
// it is OK by checking that the union is the same size as each of its members.
// horrible_cast<> should only be used for compiler-specific workarounds. 
// Usage is identical to reinterpret_cast<>.

// This union is declared outside the horrible_cast because BCC 5.5.1
// can't inline a function with a nested class, and gives a warning.
template <class OutputClass, class InputClass>
union horrible_union{
	OutputClass out;
	InputClass in;
};

template <class OutputClass, class InputClass>
inline OutputClass horrible_cast(const InputClass input){
	horrible_union<OutputClass, InputClass> u;
	// Cause a compile-time error if in, out and u are not the same size.
	// If the compile fails here, it means the compiler has peculiar
	// unions which would prevent the cast from working.
	typedef int ERROR_CantUseHorrible_cast[sizeof(InputClass)==sizeof(u) 
		&& sizeof(InputClass)==sizeof(OutputClass) ? 1 : -1];
	u.in = input;
	return u.out;
}

////////////////////////////////////////////////////////////////////////////////
//						Workarounds
//
////////////////////////////////////////////////////////////////////////////////

// Backwards compatibility: This macro used to be necessary in the virtual inheritance
// case for Intel and Microsoft. Now it just forward-declares the class.
#define FASTDELEGATEDECLARE(CLASSNAME)	class CLASSNAME;

// Prevent use of the static function hack with the DOS medium model.
#ifdef __MEDIUM__
#undef FASTDELEGATE_USESTATICFUNCTIONHACK
#endif

//			DefaultVoid - a workaround for 'void' templates in VC6.
//
//  (1) VC6 and earlier do not allow 'void' as a default template argument.
//  (2) They also doesn't allow you to return 'void' from a function.
//
// Workaround for (1): Declare a dummy type 'DefaultVoid' which we use
//   when we'd like to use 'void'. We convert it into 'void' and back
//   using the templates DefaultVoidToVoid<> and VoidToDefaultVoid<>.
// Workaround for (2): On VC6, the code for calling a void function is
//   identical to the code for calling a non-void function in which the
//   return value is never used, provided the return value is returned
//   in the EAX register, rather than on the stack. 
//   This is true for most fundamental types such as int, enum, void *.
//   Const void * is the safest option since it doesn't participate 
//   in any automatic conversions. But on a 16-bit compiler it might
//   cause extra code to be generated, so we disable it for all compilers
//   except for VC6 (and VC5).
#ifdef FASTDLGT_VC6
// VC6 workaround
typedef const void * DefaultVoid;
#else
// On any other compiler, just use a normal void.
typedef void DefaultVoid;
#endif

// Translate from 'DefaultVoid' to 'void'.
// Everything else is unchanged
template <class T>
struct DefaultVoidToVoid { typedef T type; };

template <>
struct DefaultVoidToVoid<DefaultVoid> {	typedef void type; };

// Translate from 'void' into 'DefaultVoid'
// Everything else is unchanged
template <class T>
struct VoidToDefaultVoid { typedef T type; };

template <>
struct VoidToDefaultVoid<void> { typedef DefaultVoid type; };



////////////////////////////////////////////////////////////////////////////////
//						Fast Delegates, part 1:
//
//		Conversion of member function pointer to a standard form
//
////////////////////////////////////////////////////////////////////////////////

// GenericClass is a fake class, ONLY used to provide a type.
// It is vitally important that it is never defined, so that the compiler doesn't
// think it can optimize the invocation. For example, Borland generates simpler
// code if it knows the class only uses single inheritance.

// Compilers using Microsoft's structure need to be treated as a special case.
#ifdef  FASTDLGT_MICROSOFT_MFP

#ifdef FASTDLGT_HASINHERITANCE_KEYWORDS
	// For Microsoft and Intel, we want to ensure that it's the most efficient type of MFP 
	// (4 bytes), even when the /vmg option is used. Declaring an empty class 
	// would give 16 byte pointers in this case....
	class __single_inheritance GenericClass;
#endif
	// ...but for Codeplay, an empty class *always* gives 4 byte pointers.
	// If compiled with the /clr option ("managed C++"), the JIT compiler thinks
	// it needs to load GenericClass before it can call any of its functions,
	// (compiles OK but crashes at runtime!), so we need to declare an 
	// empty class to make it happy.
	// Codeplay and VC4 can't cope with the unknown_inheritance case either.
	class GenericClass {};
#else
	class GenericClass;
#endif

// The size of a single inheritance member function pointer.
const int SINGLE_MEMFUNCPTR_SIZE = sizeof(void (GenericClass::*)());

//						SimplifyMemFunc< >::Convert()
//
//	A template function that converts an arbitrary member function pointer into the 
//	simplest possible form of member function pointer, using a supplied 'this' pointer.
//  According to the standard, this can be done legally with reinterpret_cast<>.
//	For (non-standard) compilers which use member function pointers which vary in size 
//  depending on the class, we need to use	knowledge of the internal structure of a 
//  member function pointer, as used by the compiler. Template specialization is used