FastDelegates.h

//                      FastDelegate.hpp
//  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.
//      Version 2.0 by Pa�l Jim�nez.
//      Version 2.0.1 by Benjamin YanXiang Huang
//
// 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.
// 06-Feb-13 2.0  * GetMemento is now const
//                * Added hash method that makes use of new unchecked function unsafe_horrible_cast
//                * Removed VC6 code
//                * Use variadic templates (C++11)
//                * Added MakeDelegate for plain function pointers
//                * Use static_assert for compile-time checks (C++11)
// 21-Jan-14 2.0.1* Fixed 2 typos (line 393 & 429) where a static_cast should have been a static_assert. 
// 21-Jun-14 2.0.2* Fixed incorrect union member name in the SimplifyMemFunc struct.

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

#include <cstring> // 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
#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.
    static_assert(sizeof(InputClass)==sizeof(u) && sizeof(InputClass)==sizeof(OutputClass), "Cannot use horrible_cast<>");
    u.in = input;
    return u.out;
}

template <class OutputClass, class InputClass>
inline OutputClass unsafe_horrible_cast(const InputClass input){
    horrible_union<OutputClass, InputClass> u;
    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

typedef void DefaultVoid;

// 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
//  to distinguish between the sizes. Because some compilers don't support partial
//  template specialisation, I use full specialisation of a wrapper struct.

// general case -- don't know how to convert it. Force a compile failure
template <int N>
struct SimplifyMemFunc {
    template <class X, class XFuncType, class GenericMemFuncType>
    inline static GenericClass *Convert(X *pthis, XFuncType function_to_bind,
        GenericMemFuncType &bound_func) {
        // Unsupported member function type -- force a compile failure.
        // (it's illegal to have a array with negative size).
        static_assert(N - 100, "Unsupported member function pointer on this compiler");
        return 0;
    }
};

// For compilers where all member func ptrs are the same size, everything goes here.
// For non-standard compilers, only single_inheritance classes go here.
template <>
struct SimplifyMemFunc<SINGLE_MEMFUNCPTR_SIZE>  {
    template <class X, class XFuncType, class GenericMemFuncType>
    inline static GenericClass *Convert(X *pthis, XFuncType function_to_bind,
            GenericMemFuncType &bound_func) {
#if defined __DMC__
        // Digital Mars doesn't allow you to cast between abitrary PMF's,
        // even though the standard says you can. The 32-bit compiler lets you
        // static_cast through an int, but the DOS compiler doesn't.
        bound_func = horrible_cast<GenericMemFuncType>(function_to_bind);
#else
        bound_func = reinterpret_cast<GenericMemFuncType>(function_to_bind);
#endif
        return reinterpret_cast<GenericClass *>(pthis);
    }
};

////////////////////////////////////////////////////////////////////////////////
//                      Fast Delegates, part 1b:
//
//                  Workarounds for Microsoft and Intel
//
////////////////////////////////////////////////////////////////////////////////


// Compilers with member function pointers which violate the standard (MSVC, Intel, Codeplay),
// need to be treated as a special case.
#ifdef FASTDLGT_MICROSOFT_MFP

// We use unions to perform horrible_casts. I would like to use #pragma pack(push, 1)
// at the start of each function for extra safety, but VC6 seems to ICE
// intermittently if you do this inside a template.

// __multiple_inheritance classes go here
// Nasty hack for Microsoft and Intel (IA32 and Itanium)
template<>
struct SimplifyMemFunc< SINGLE_MEMFUNCPTR_SIZE + sizeof(int) >  {
    template <class X, class XFuncType, class GenericMemFuncType>
    inline static GenericClass *Convert(X *pthis, XFuncType function_to_bind,
        GenericMemFuncType &bound_func) {
        // We need to use a horrible_cast to do this conversion.
        // In MSVC, a multiple inheritance member pointer is internally defined as:
        union {
            XFuncType func;
            struct {
                GenericMemFuncType funcaddress; // points to the actual member function
                int delta;       // #BYTES to be added to the 'this' pointer
            }s;
        } u;
        // Check that the horrible_cast will work
        static_assert(sizeof(function_to_bind)==sizeof(u.s), "Cannot use horrible_cast<>");
        u.func = function_to_bind;
        bound_func = u.s.funcaddress;
        return reinterpret_cast<GenericClass *>(reinterpret_cast<char *>(pthis) + u.s.delta);
    }
};

// virtual inheritance is a real nuisance. It's inefficient and complicated.
// On MSVC and Intel, there isn't enough information in the pointer itself to
// enable conversion to a closure pointer. Earlier versions of this code didn't
// work for all cases, and generated a compile-time error instead.
// But a very clever hack invented by John M. Dlugosz solves this problem.
// My code is somewhat different to his: I have no asm code, and I make no
// assumptions about the calling convention that is used.

// In VC++ and ICL, a virtual_inheritance member pointer
// is internally defined as:
struct MicrosoftVirtualMFP {
    void (GenericClass::*codeptr)(); // points to the actual member function
    int delta;      // #bytes to be added to the 'this' pointer
    int vtable_index; // or 0 if no virtual inheritance
};
// The CRUCIAL feature of Microsoft/Intel MFPs which we exploit is that the
// m_codeptr member is *always* called, regardless of the values of the other
// members. (This is *not* true for other compilers, eg GCC, which obtain the
// function address from the vtable if a virtual function is being called).
// Dlugosz's trick is to make the codeptr point to a probe function which
// returns the 'this' pointer that was used.

// Define a generic class that uses virtual inheritance.
// It has a trival member function that returns the value of the 'this' pointer.
struct GenericVirtualClass : virtual public GenericClass
{
    typedef GenericVirtualClass * (GenericVirtualClass::*ProbePtrType)();
    GenericVirtualClass * GetThis() { return this; }
};

// __virtual_inheritance classes go here
template <>
struct SimplifyMemFunc<SINGLE_MEMFUNCPTR_SIZE + 2*sizeof(int) >
{

    template <class X, class XFuncType, class GenericMemFuncType>
    inline static GenericClass *Convert(X *pthis, XFuncType function_to_bind,
        GenericMemFuncType &bound_func) {
        union {
            XFuncType func;
            GenericClass* (X::*ProbeFunc)();
            MicrosoftVirtualMFP s;
        } u;
        u.func = function_to_bind;
        bound_func = reinterpret_cast<GenericMemFuncType>(u.s.codeptr);
        union {
            GenericVirtualClass::ProbePtrType virtfunc;
            MicrosoftVirtualMFP s;
        } u2;
        // Check that the horrible_cast<>s will work
        static_assert(sizeof(function_to_bind)==sizeof(u.s) && sizeof(function_to_bind)==sizeof(u.ProbeFunc) && sizeof(u2.virtfunc)==sizeof(u2.s), "Cannot use horrible_cast<>");
        /*typedef int ERROR_CantUsehorrible_cast[sizeof(function_to_bind)==sizeof(u.s)
            && sizeof(function_to_bind)==sizeof(u.ProbeFunc)
            && sizeof(u2.virtfunc)==sizeof(u2.s) ? 1 : -1];*/
   // Unfortunately, taking the address of a MF prevents it from being inlined, so
   // this next line can't be completely optimised away by the compiler.
        u2.virtfunc = &GenericVirtualClass::GetThis;
        u.s.codeptr = u2.s.codeptr;
        return (pthis->*u.ProbeFunc)();
    }
};

// Nasty hack for Microsoft and Intel (IA32 and Itanium)
// unknown_inheritance classes go here
// This is probably the ugliest bit of code I've ever written. Look at the casts!
// There is a compiler bug in MSVC6 which prevents it from using this code.
template <>
struct SimplifyMemFunc<SINGLE_MEMFUNCPTR_SIZE + 3*sizeof(int) >
{
    template <class X, class XFuncType, class GenericMemFuncType>
    inline static GenericClass *Convert(X *pthis, XFuncType function_to_bind,
            GenericMemFuncType &bound_func) {
        // The member function pointer is 16 bytes long. We can't use a normal cast, but
        // we can use a union to do the conversion.
        union {
            XFuncType func;
            // In VC++ and ICL, an unknown_inheritance member pointer
            // is internally defined as:
            struct {
                GenericMemFuncType funcaddress; // points to the actual member function
                int delta;      // #bytes to be added to the 'this' pointer
                int vtordisp;       // #bytes to add to 'this' to find the vtable
                int vtable_index; // or 0 if no virtual inheritance
            } s;
        } u;
        // Check that the horrible_cast will work
        static_assert(sizeof(XFuncType)==sizeof(u.s), "Cannot use horrible_cast<>");
        //typedef int ERROR_CantUsehorrible_cast[sizeof(XFuncType)==sizeof(u.s)? 1 : -1];
        u.func = function_to_bind;
        bound_func = u.s.funcaddress;
        int virtual_delta = 0;
        if (u.s.vtable_index) { // Virtual inheritance is used
            // First, get to the vtable.
            // It is 'vtordisp' bytes from the start of the class.
            const int * vtable = *reinterpret_cast<const int *const*>(
                reinterpret_cast<const char *>(pthis) + u.s.vtordisp );

            // 'vtable_index' tells us where in the table we should be looking.
            virtual_delta = u.s.vtordisp + *reinterpret_cast<const int *>(
                reinterpret_cast<const char *>(vtable) + u.s.vtable_index);
        }
        // The int at 'virtual_delta' gives us the amount to add to 'this'.
        // Finally we can add the three components together. Phew!
        return reinterpret_cast<GenericClass *>(
            reinterpret_cast<char *>(pthis) + u.s.delta + virtual_delta);
    };
};

#endif // MS/Intel hacks

}  // namespace detail

////////////////////////////////////////////////////////////////////////////////
//                      Fast Delegates, part 2:
//
//  Define the delegate storage, and cope with static functions
//
////////////////////////////////////////////////////////////////////////////////

// DelegateMemento -- an opaque structure which can hold an arbitary delegate.
// It knows nothing about the calling convention or number of arguments used by
// the function pointed to.
// It supplies comparison operators so that it can be stored in STL collections.
// It cannot be set to anything other than null, nor invoked directly:
//   it must be converted to a specific delegate.

// Implementation:
// There are two possible implementations: the Safe method and the Evil method.
//              DelegateMemento - Safe version
//
// This implementation is standard-compliant, but a bit tricky.
// A static function pointer is stored inside the class.
// Here are the valid values:
// +-- Static pointer --+--pThis --+-- pMemFunc-+-- Meaning------+
// |   0                |  0       |   0        | Empty          |
// |   !=0              |(dontcare)|  Invoker   | Static function|
// |   0                |  !=0     |  !=0*      | Method call    |
// +--------------------+----------+------------+----------------+
//  * For Metrowerks, this can be 0. (first virtual function in a
//       single_inheritance class).
// When stored stored inside a specific delegate, the 'dontcare' entries are replaced
// with a reference to the delegate itself. This complicates the = and == operators
// for the delegate class.

//              DelegateMemento - Evil version
//
// For compilers where data pointers are at least as big as code pointers, it is
// possible to store the function pointer in the this pointer, using another
// horrible_cast. In this case the DelegateMemento implementation is simple:
// +--pThis --+-- pMemFunc-+-- Meaning---------------------+
// |    0     |  0         | Empty                         |
// |  !=0     |  !=0*      | Static function or method call|
// +----------+------------+-------------------------------+
//  * For Metrowerks, this can be 0. (first virtual function in a
//       single_inheritance class).
// Note that the Sun C++ and MSVC documentation explicitly state that they
// support static_cast between void * and function pointers.

class DelegateMemento {
protected:
    // the data is protected, not private, because many
    // compilers have problems with template friends.
    typedef void (detail::GenericClass::*GenericMemFuncType)(); // arbitrary MFP.
    detail::GenericClass *m_pthis;
    GenericMemFuncType m_pFunction;

#if !defined(FASTDELEGATE_USESTATICFUNCTIONHACK)
    typedef void (*GenericFuncPtr)(); // arbitrary code pointer
    GenericFuncPtr m_pStaticFunction;
#endif

public:
#if !defined(FASTDELEGATE_USESTATICFUNCTIONHACK)
    DelegateMemento() : m_pthis(0), m_pFunction(0), m_pStaticFunction(0) {};
    void clear() {
        m_pthis=0; m_pFunction=0; m_pStaticFunction=0;
    }
#else
    DelegateMemento() : m_pthis(0), m_pFunction(0) {};
    void clear() {  m_pthis=0; m_pFunction=0;   }
#endif
public:
#if !defined(FASTDELEGATE_USESTATICFUNCTIONHACK)
    inline bool IsEqual (const DelegateMemento &x) const{
        // We have to cope with the static function pointers as a special case
        if (m_pFunction!=x.m_pFunction) return false;
        // the static function ptrs must either both be equal, or both be 0.
        if (m_pStaticFunction!=x.m_pStaticFunction) return false;
        if (m_pStaticFunction!=0) return m_pthis==x.m_pthis;
        else return true;
    }
#else // Evil Method
    inline bool IsEqual (const DelegateMemento &x) const{
        return m_pthis==x.m_pthis && m_pFunction==x.m_pFunction;
    }
#endif
    // Provide a strict weak ordering for DelegateMementos.
    inline bool IsLess(const DelegateMemento &right) const {
        // deal with static function pointers first
#if !defined(FASTDELEGATE_USESTATICFUNCTIONHACK)
        if (m_pStaticFunction !=0 || right.m_pStaticFunction!=0)
                return m_pStaticFunction < right.m_pStaticFunction;
#endif
        if (m_pthis !=right.m_pthis) return m_pthis < right.m_pthis;
    // There are no ordering operators for member function pointers,
    // but we can fake one by comparing each byte. The resulting ordering is
    // arbitrary (and compiler-dependent), but it permits storage in ordered STL containers.
        return std::memcmp(&m_pFunction, &right.m_pFunction, sizeof(m_pFunction)) < 0;

    }
    // Provide a simple hashing method.
    inline size_t Hash() const {
        return reinterpret_cast<size_t>(m_pthis) ^ detail::unsafe_horrible_cast<size_t>(m_pFunction);
    }
    // BUGFIX (Mar 2005):
    // We can't just compare m_pFunction because on Metrowerks,
    // m_pFunction can be zero even if the delegate is not empty!
    inline bool operator ! () const     // Is it bound to anything?
    { return m_pthis==0 && m_pFunction==0; }
    inline bool empty() const       // Is it bound to anything?
    { return m_pthis==0 && m_pFunction==0; }
public:
    DelegateMemento & operator = (const DelegateMemento &right)  {
        SetMementoFrom(right);
        return *this;
    }
    inline bool operator <(const DelegateMemento &right) {
        return IsLess(right);
    }
    inline bool operator >(const DelegateMemento &right) {
        return right.IsLess(*this);
    }
    DelegateMemento (const DelegateMemento &right)  :
        m_pthis(right.m_pthis), m_pFunction(right.m_pFunction)
#if !defined(FASTDELEGATE_USESTATICFUNCTIONHACK)
        , m_pStaticFunction (right.m_pStaticFunction)
#endif
        {}
protected:
    void SetMementoFrom(const DelegateMemento &right)  {
        m_pFunction = right.m_pFunction;
        m_pthis = right.m_pthis;
#if !defined(FASTDELEGATE_USESTATICFUNCTIONHACK)
        m_pStaticFunction = right.m_pStaticFunction;
#endif
    }
};


//                      ClosurePtr<>
//
// A private wrapper class that adds function signatures to DelegateMemento.
// It's the class that does most of the actual work.
// The signatures are specified by:
// GenericMemFunc: must be a type of GenericClass member function pointer.
// StaticFuncPtr:  must be a type of function pointer with the same signature
//                 as GenericMemFunc.
// UnvoidStaticFuncPtr: is the same as StaticFuncPtr, except on VC6
//                 where it never returns void (returns DefaultVoid instead).

// An outer class, FastDelegateN<>, handles the invoking and creates the
// necessary typedefs.
// This class does everything else.

namespace detail {

template < class GenericMemFunc, class StaticFuncPtr, class UnvoidStaticFuncPtr>
class ClosurePtr : public DelegateMemento {
public:
    // These functions are for setting the delegate to a member function.

    // Here's the clever bit: we convert an arbitrary member function into a
    // standard form. XMemFunc should be a member function of class X, but I can't
    // enforce that here. It needs to be enforced by the wrapper class.
    template < class X, class XMemFunc >
    inline void bindmemfunc(X *pthis, XMemFunc function_to_bind ) {
        m_pthis = SimplifyMemFunc< sizeof(function_to_bind) >
            ::Convert(pthis, function_to_bind, m_pFunction);
#if !defined(FASTDELEGATE_USESTATICFUNCTIONHACK)
        m_pStaticFunction = 0;
#endif
    }
    // For const member functions, we only need a const class pointer.
    // Since we know that the member function is const, it's safe to
    // remove the const qualifier from the 'this' pointer with a const_cast.
    // VC6 has problems if we just overload 'bindmemfunc', so we give it a different name.
    template < class X, class XMemFunc>
    inline void bindconstmemfunc(const X *pthis, XMemFunc function_to_bind) {
        m_pthis= SimplifyMemFunc< sizeof(function_to_bind) >
            ::Convert(const_cast<X*>(pthis), function_to_bind, m_pFunction);
#if !defined(FASTDELEGATE_USESTATICFUNCTIONHACK)
        m_pStaticFunction = 0;
#endif
    }
#ifdef FASTDELEGATE_GCC_BUG_8271    // At present, GCC doesn't recognize constness of MFPs in templates
    template < class X, class XMemFunc>
    inline void bindmemfunc(const X *pthis, XMemFunc function_to_bind) {
        bindconstmemfunc(pthis, function_to_bind);
#if !defined(FASTDELEGATE_USESTATICFUNCTIONHACK)
        m_pStaticFunction = 0;
#endif
    }
#endif
    // These functions are required for invoking the stored function
    inline GenericClass *GetClosureThis() const { return m_pthis; }
    inline GenericMemFunc GetClosureMemPtr() const { return reinterpret_cast<GenericMemFunc>(m_pFunction); }

// There are a few ways of dealing with static function pointers.
// There's a standard-compliant, but tricky method.
// There's also a straightforward hack, that won't work on DOS compilers using the
// medium memory model. It's so evil that I can't recommend it, but I've
// implemented it anyway because it produces very nice asm code.

#if !defined(FASTDELEGATE_USESTATICFUNCTIONHACK)

//              ClosurePtr<> - Safe version
//
// This implementation is standard-compliant, but a bit tricky.
// I store the function pointer inside the class, and the delegate then
// points to itself. Whenever the delegate is copied, these self-references
// must be transformed, and this complicates the = and == operators.
public:
    // The next two functions are for operator ==, =, and the copy constructor.
    // We may need to convert the m_pthis pointers, so that
    // they remain as self-references.
    template< class DerivedClass >
    inline void CopyFrom (DerivedClass *pParent, const DelegateMemento &x) {
        SetMementoFrom(x);
        if (m_pStaticFunction!=0) {
            // transform self references...
            m_pthis=reinterpret_cast<GenericClass *>(pParent);
        }
    }
    // For static functions, the 'static_function_invoker' class in the parent
    // will be called. The parent then needs to call GetStaticFunction() to find out
    // the actual function to invoke.
    template < class DerivedClass, class ParentInvokerSig >
    inline void bindstaticfunc(DerivedClass *pParent, ParentInvokerSig static_function_invoker,
                StaticFuncPtr function_to_bind ) {
        if (function_to_bind==0) { // cope with assignment to 0
            m_pFunction=0;
        } else {
            bindmemfunc(pParent, static_function_invoker);
        }
        m_pStaticFunction=reinterpret_cast<GenericFuncPtr>(function_to_bind);
    }
    inline UnvoidStaticFuncPtr GetStaticFunction() const {
        return reinterpret_cast<UnvoidStaticFuncPtr>(m_pStaticFunction);
    }
#else

//              ClosurePtr<> - Evil version
//
// For compilers where data pointers are at least as big as code pointers, it is
// possible to store the function pointer in the this pointer, using another
// horrible_cast. Invocation isn't any faster, but it saves 4 bytes, and
// speeds up comparison and assignment. If C++ provided direct language support
// for delegates, they would produce asm code that was almost identical to this.
// Note that the Sun C++ and MSVC documentation explicitly state that they
// support static_cast between void * and function pointers.

    template< class DerivedClass >
    inline void CopyFrom (DerivedClass * /*pParent*/, const DelegateMemento &right) {
        SetMementoFrom(right);
    }
    // For static functions, the 'static_function_invoker' class in the parent
    // will be called. The parent then needs to call GetStaticFunction() to find out
    // the actual function to invoke.
    // ******** EVIL, EVIL CODE! *******
    template <  class DerivedClass, class ParentInvokerSig>
    inline void bindstaticfunc(DerivedClass *pParent, ParentInvokerSig static_function_invoker,
                StaticFuncPtr function_to_bind) {
        if (function_to_bind==0) { // cope with assignment to 0
            m_pFunction=0;
        } else {
           // We'll be ignoring the 'this' pointer, but we need to make sure we pass
           // a valid value to bindmemfunc().
            bindmemfunc(pParent, static_function_invoker);
        }

        // WARNING! Evil hack. We store the function in the 'this' pointer!
        // Ensure that there's a compilation failure if function pointers
        // and data pointers have different sizes.
        // If you get this error, you need to #undef FASTDELEGATE_USESTATICFUNCTIONHACK.
        static_assert(sizeof(GenericClass *)==sizeof(function_to_bind), "Cannot use evil method");
        m_pthis = horrible_cast<GenericClass *>(function_to_bind);
        // MSVC, SunC++ and DMC accept the following (non-standard) code:
//      m_pthis = static_cast<GenericClass *>(static_cast<void *>(function_to_bind));
        // BCC32, Comeau and DMC accept this method. MSVC7.1 needs __int64 instead of long
//      m_pthis = reinterpret_cast<GenericClass *>(reinterpret_cast<long>(function_to_bind));
    }
    // ******** EVIL, EVIL CODE! *******
    // This function will be called with an invalid 'this' pointer!!
    // We're just returning the 'this' pointer, converted into
    // a function pointer!
    inline UnvoidStaticFuncPtr GetStaticFunction() const {
        // Ensure that there's a compilation failure if function pointers
        // and data pointers have different sizes.
        // If you get this error, you need to #undef FASTDELEGATE_USESTATICFUNCTIONHACK.
        static_assert(sizeof(UnvoidStaticFuncPtr)==sizeof(this), "Cannot use evil method");
        return horrible_cast<UnvoidStaticFuncPtr>(this);
    }
#endif // !defined(FASTDELEGATE_USESTATICFUNCTIONHACK)

    // Does the closure contain this static function?
    inline bool IsEqualToStaticFuncPtr(StaticFuncPtr funcptr){
        if (funcptr==0) return empty();
    // For the Evil method, if it doesn't actually contain a static function, this will return an arbitrary
    // value that is not equal to any valid function pointer.
        else return funcptr==reinterpret_cast<StaticFuncPtr>(GetStaticFunction());
    }
};


} // namespace detail

////////////////////////////////////////////////////////////////////////////////
//                      Fast Delegates, part 3:
//
//              Wrapper classes to ensure type safety
//
////////////////////////////////////////////////////////////////////////////////


// Once we have the member function conversion templates, it's easy to make the
// wrapper classes. So that they will work with as many compilers as possible,
// the classes are of the form
//   FastDelegate3<int, char *, double>
// They can cope with any combination of parameters. The max number of parameters
// allowed is 8, but it is trivial to increase this limit.
// Note that we need to treat const member functions seperately.
// All this class does is to enforce type safety, and invoke the delegate with
// the correct list of parameters.

// Because of the weird rule about the class of derived member function pointers,
// you sometimes need to apply a downcast to the 'this' pointer.
// This is the reason for the use of "implicit_cast<X*>(pthis)" in the code below.
// If CDerivedClass is derived from CBaseClass, but doesn't override SimpleVirtualFunction,
// without this trick you'd need to write:
//      MyDelegate(static_cast<CBaseClass *>(&d), &CDerivedClass::SimpleVirtualFunction);
// but with the trick you can write
//      MyDelegate(&d, &CDerivedClass::SimpleVirtualFunction);

// RetType is the type the compiler uses in compiling the template. For VC6,
// it cannot be void. DesiredRetType is the real type which is returned from
// all of the functions. It can be void.

// Implicit conversion to "bool" is achieved using the safe_bool idiom,
// using member data pointers (MDP). This allows "if (dg)..." syntax
// Because some compilers (eg codeplay) don't have a unique value for a zero
// MDP, an extra padding member is added to the SafeBool struct.
// Some compilers (eg VC6) won't implicitly convert from 0 to an MDP, so
// in that case the static function constructor is not made explicit; this
// allows "if (dg==0) ..." to compile.

template <typename RetType, typename... Args>
class FastDelegateImpl {
private:
    typedef typename detail::DefaultVoidToVoid<RetType>::type DesiredRetType;
    typedef DesiredRetType (*StaticFunctionPtr)(Args...);
    typedef RetType (*UnvoidStaticFunctionPtr)(Args...);
    typedef RetType (detail::GenericClass::*GenericMemFn)(Args...);
    typedef detail::ClosurePtr<GenericMemFn, StaticFunctionPtr, UnvoidStaticFunctionPtr> ClosureType;
    ClosureType m_Closure;
public:
    // Typedefs to aid generic programming
    typedef FastDelegateImpl type;

    // Construction and comparison functions
    FastDelegateImpl() { clear(); }
    FastDelegateImpl(const FastDelegateImpl &x) {
        m_Closure.CopyFrom(this, x.m_Closure); }
    void operator = (const FastDelegateImpl &x)  {
        m_Closure.CopyFrom(this, x.m_Closure); }
    bool operator ==(const FastDelegateImpl &x) const {
        return m_Closure.IsEqual(x.m_Closure);  }
    bool operator !=(const FastDelegateImpl &x) const {
        return !m_Closure.IsEqual(x.m_Closure); }
    bool operator <(const FastDelegateImpl &x) const {
        return m_Closure.IsLess(x.m_Closure);   }
    bool operator >(const FastDelegateImpl &x) const {
        return x.m_Closure.IsLess(m_Closure);   }
    // Binding to non-const member functions
    template < typename X, typename Y >
    FastDelegateImpl(Y *pthis, DesiredRetType (X::* function_to_bind)(Args... args) ) {
        m_Closure.bindmemfunc(detail::implicit_cast<X*>(pthis), function_to_bind); }
    template < typename X, typename Y >
    inline void bind(Y *pthis, DesiredRetType (X::* function_to_bind)(Args... args)) {
        m_Closure.bindmemfunc(detail::implicit_cast<X*>(pthis), function_to_bind);  }
    // Binding to const member functions.
    template < typename X, typename Y >
    FastDelegateImpl(const Y *pthis, DesiredRetType (X::* function_to_bind)(Args... args) const) {
        m_Closure.bindconstmemfunc(detail::implicit_cast<const X*>(pthis), function_to_bind);   }
    template < typename X, typename Y >
    inline void bind(const Y *pthis, DesiredRetType (X::* function_to_bind)(Args... args) const) {
        m_Closure.bindconstmemfunc(detail::implicit_cast<const X *>(pthis), function_to_bind);  }
    // Static functions. We convert them into a member function call.
    // This constructor also provides implicit conversion
    FastDelegateImpl(DesiredRetType (*function_to_bind)(Args... args) ) {
        bind(function_to_bind); }
    // for efficiency, prevent creation of a temporary
    void operator = (DesiredRetType (*function_to_bind)(Args... args) ) {
        bind(function_to_bind); }
    inline void bind(DesiredRetType (*function_to_bind)(Args... args)) {
        m_Closure.bindstaticfunc(this, &FastDelegateImpl::InvokeStaticFunction,
            function_to_bind); }
    // Invoke the delegate
    RetType operator() (Args... args) const {
    return (m_Closure.GetClosureThis()->*(m_Closure.GetClosureMemPtr()))(args...); }
    // Implicit conversion to "bool" using the safe_bool idiom
private:
    typedef struct SafeBoolStruct {
        int a_data_pointer_to_this_is_0_on_buggy_compilers;
        StaticFunctionPtr m_nonzero;
    } UselessTypedef;
    typedef StaticFunctionPtr SafeBoolStruct::*unspecified_bool_type;
public:
    operator unspecified_bool_type() const {
        return empty()? 0: &SafeBoolStruct::m_nonzero;
    }
    // necessary to allow ==0 to work despite the safe_bool idiom
    inline bool operator==(StaticFunctionPtr funcptr) {
        return m_Closure.IsEqualToStaticFuncPtr(funcptr);   }
    inline bool operator!=(StaticFunctionPtr funcptr) {
        return !m_Closure.IsEqualToStaticFuncPtr(funcptr);    }
    inline bool operator ! () const {   // Is it bound to anything?
            return !m_Closure; }
    inline bool empty() const   {
            return !m_Closure; }
    void clear() { m_Closure.clear();}
    // Conversion to and from the DelegateMemento storage class
    const DelegateMemento & GetMemento() const { return m_Closure; }
    void SetMemento(const DelegateMemento &any) { m_Closure.CopyFrom(this, any); }

private:    // Invoker for static functions
    RetType InvokeStaticFunction(Args... args) const {
    return (*(m_Closure.GetStaticFunction()))(args...); }
};

////////////////////////////////////////////////////////////////////////////////
//                      Fast Delegates, part 4:
//
//              FastDelegate<> class (Original author: Jody Hagins)
//  Allows boost::function style syntax like:
//          FastDelegate< double (int, long) >
// instead of:
//          FastDelegate2< int, long, double >
//
////////////////////////////////////////////////////////////////////////////////

#ifdef FASTDELEGATE_ALLOW_FUNCTION_TYPE_SYNTAX

// Declare FastDelegate as a class template.  It will be specialized
// later for all number of arguments.
template <typename Signature>
class FastDelegate;

template <typename RetType, typename... Args>
class FastDelegate<RetType (Args...)>
  // Inherit from FastDelegate1 so that it can be treated just like a FastDelegate1
  : public FastDelegateImpl < RetType, Args... >
{
public:
  // Make using the base type a bit easier via typedef.
  typedef FastDelegateImpl < RetType, Args... > BaseType;

  // Allow users access to the specific type of this delegate.
  typedef FastDelegate SelfType;

  // Mimic the base class constructors.
  FastDelegate() : BaseType() { }

  template < typename X, typename Y >
  FastDelegate(Y * pthis,
    RetType (X::* function_to_bind)( Args... args ))
    : BaseType(pthis, function_to_bind)  { }

  template < typename X, typename Y >
  FastDelegate(const Y *pthis,
      RetType (X::* function_to_bind)( Args... args ) const)
    : BaseType(pthis, function_to_bind)
  {  }

  FastDelegate(RetType (*function_to_bind)( Args... args ))
    : BaseType(function_to_bind)  { }
  void operator = (const BaseType &x)  {
        *static_cast<BaseType*>(this) = x; }
};

#endif //FASTDELEGATE_ALLOW_FUNCTION_TYPE_SYNTAX

////////////////////////////////////////////////////////////////////////////////
//                      Fast Delegates, part 5:
//
//              MakeDelegate() helper function
//
//          MakeDelegate(&x, &X::func) returns a fastdelegate of the type
//          necessary for calling x.func() with the correct number of arguments.
//          This makes it possible to eliminate many typedefs from user code.
//
////////////////////////////////////////////////////////////////////////////////

// Also declare overloads of a MakeDelegate() global function to
// reduce the need for typedefs.
// We need seperate overloads for const and non-const member functions.
// Also, because of the weird rule about the class of derived member function pointers,
// implicit downcasts may need to be applied later to the 'this' pointer.
// That's why two classes (X and Y) appear in the definitions. Y must be implicitly
// castable to X.

template <typename RetType, typename... Args>
FastDelegate<RetType (Args...)> MakeDelegate(RetType (*func)(Args...)) {
    return FastDelegate<RetType (Args...)>(func);
}

template <typename RetType, typename X, typename Y, typename... Args>
FastDelegate<RetType (Args...)> MakeDelegate(Y* x, RetType (X::*func)(Args...)) {
    return FastDelegate<RetType (Args...)>(x, func);
}

template <typename RetType, typename X, typename Y, typename... Args>
FastDelegate<RetType (Args...)> MakeDelegate(Y* x, RetType (X::*func)(Args...) const) {
    return FastDelegate<RetType (Args...)>(x, func);
}

// clean up after ourselves...
#undef FASTDLGT_RETTYPE

} // namespace fastdelegate

#endif // !defined(FASTDELEGATE_HPP)