SqMod/include/sqrat/sqratOverloadMethods.h

//
// SqratOverloadMethods: Overload Methods
//

//
// Copyright (c) 2009 Brandon Jones
//
// This software is provided 'as-is', without any express or implied
// warranty. In no event will the authors be held liable for any damages
// arising from the use of this software.
//
// Permission is granted to anyone to use this software for any purpose,
// including commercial applications, and to alter it and redistribute it
// freely, subject to the following restrictions:
//
//  1. The origin of this software must not be misrepresented; you must not
//  claim that you wrote the original software. If you use this software
//  in a product, an acknowledgment in the product documentation would be
//  appreciated but is not required.
//
//  2. Altered source versions must be plainly marked as such, and must not be
//  misrepresented as being the original software.
//
//  3. This notice may not be removed or altered from any source
//  distribution.
//

#if !defined(_SQRAT_OVERLOAD_METHODS_H_)
#define _SQRAT_OVERLOAD_METHODS_H_

#ifdef SQMOD_PLUGIN_API
    #include <SqAPI.h>
#else
    #include <squirrelex.h>
#endif // SQMOD_PLUGIN_API

#include "sqratTypes.h"
#include "sqratUtil.h"
#include "sqratGlobalMethods.h"
#include "sqratMemberMethods.h"

namespace Sqrat {

/// @cond DEV

//
// Overload name generator
//

class SqOverloadName {
public:

    static void Get(const SQChar* name, int args, string & out) {
        SQChar buf[16] = {'_', 'o'};
        unsigned l = I32ToA(args, &buf[2]);
        out.append(buf, l+2);
        out.push_back('_');
        out.append(name);
    }

    static string Get(const SQChar* name, int args) {
        string out;
        out.reserve(15);
        Get(name, args, out);
        return out;
    }
};


//
// Don't include the overloaded call forwarder into the templated class
//  to avoid duplicating code that doesn't need to be specialized.
//
inline SQInteger OverloadExecutionForwarder(HSQUIRRELVM vm) {
    const SQInteger top = sq_gettop(vm);
    // Get the argument count
    const int argCount = static_cast<int>(top - 2);
    // Subtract environment and base name in free variable^
    const SQChar* funcName;
    SQInteger funcNameSize;
    // Get the un-mangled function name (free variable)
    sq_getstringandsize(vm, -1, &funcName, &funcNameSize);
    // Generate the overload mangled name
    string overloadName;
    overloadName.reserve(funcNameSize+5);
    SqOverloadName::Get(funcName, argCount, overloadName);
    // Pop the un-mangled closure name from the stack so we can replace it later
    sq_poptop(vm); // `funcName` becomes invalid after this
    // Push the overload mangled name on the stack
    sq_pushstring(vm, overloadName.c_str(), static_cast<SQInteger>(overloadName.size()));
    // Lookup the proper overload and get it on the stack
#if !defined (SCRAT_NO_ERROR_CHECKING)
    if (SQ_FAILED(sq_get(vm, 1))) {
        sq_settop(vm, top); // keep the stack size intact
        return sq_throwerror(vm, _SC("wrong number of parameters"));
    }
#else
    sq_get(vm, 1);
#endif
    SQFUNCTION f = nullptr;
    // Get the native closure pointer that we must invoke
    SQRESULT res = sq_getnativeclosurepointer(vm, -1, &f);
    if (SQ_FAILED(res)) {
        return res;
    // Make sure a native closure pointer is available
    } else if (!f) {
        return sq_throwerror(vm, _SC("unable to acquire the proper overload closure"));
    }
    // Attempt to get the free variable containing the native closure pointer on the stack
    sq_getonefreevariable(vm, 0);
    // This is simply a hack to implement a direct call and gain some performance
    // Since both closures expect a free variable we simply replace the free variable
    //  containing closure name with the free variable containing the closure pointer
    sq_settop(vm, top); // keep the stack size intact before invoking the overload
    // Perform a direct call and return the result back to the caller
    return f(vm);
}

//
// Don't include the overloaded call forwarder into the templated class
//  to avoid duplicating code that doesn't need to be specialized.
//
inline SQInteger OverloadConstructionForwarder(HSQUIRRELVM vm) {
    const SQInteger top = sq_gettop(vm);
    // Get the argument count
    const int argCount = static_cast<int>(top - 2);
    // Subtract environment and base name in free variable^
    const SQChar* funcName;
    SQInteger funcNameSize;
    // Get the un-mangled function name (free variable)
    sq_getstringandsize(vm, -1, &funcName, &funcNameSize);
    // Generate the overload mangled name
    string overloadName;
    overloadName.reserve(funcNameSize+5);
    SqOverloadName::Get(funcName, argCount, overloadName);
    // Push the overload mangled name on the stack
    sq_pushstring(vm, overloadName.c_str(), static_cast<SQInteger>(overloadName.size()));
    // Lookup the proper overload and get it on the stack
#if !defined (SCRAT_NO_ERROR_CHECKING)
    if (SQ_FAILED(sq_get(vm, 1))) {
        sq_settop(vm, top); // keep the stack size intact
        return sq_throwerrorf(vm, _SC("wrong number of parameters. no such constructor overload: `%s`"), overloadName.data());
    }
#else
    sq_get(vm, 1);
#endif
    SQFUNCTION f = nullptr;
    // Get the native closure pointer that we must invoke
    SQRESULT res = sq_getnativeclosurepointer(vm, -1, &f);
    if (SQ_FAILED(res)) {
        return res;
    // Make sure a native closure pointer is available
    } else if (!f) {
        return sq_throwerror(vm, _SC("unable to acquire the proper overload closure"));
    }
    // Restore the stack size by removing the overload closure object
    sq_poptop(vm);
    // Pop the un-mangled closure name from the stack
    // The constructor doesn't expect any free variables
    //sq_poptop(vm); // `funcName` becomes invalid after this
    // Perform a direct call and store the result
    SQRESULT r = f(vm);
    // Keep the stack size intact before leaving
    sq_settop(vm, top);
    // Return the result back to the caller
    return r;
}

//
// Squirrel Overload Functions
//

template <class R>
class SqOverload {
public:

    static SQInteger Func(HSQUIRRELVM vm) {
        return OverloadExecutionForwarder(vm);
    }
};


//
// void return specialization
//

template <>
class SqOverload<void> {
public:

    static SQInteger Func(HSQUIRRELVM vm) {
        return OverloadExecutionForwarder(vm);
    }
};

// Global Overloaded Function Resolver
template <class R,class... A> SQFUNCTION SqGlobalOverloadedFunc(R (* /*method*/)(A...)) {
    return SqGlobal<R>::template GetProxy<2, true, A...>();
}

// Global Overloaded Function Resolver
template <class R,class... A> SQFUNCTION SqGlobalOverloadedFunc(R& (* /*method*/)(A...)) {
    return SqGlobal<R&>::template GetProxy<2, true, A...>();
}

// Member Global Overloaded Function Resolver
template <class R,class T,class... A> SQFUNCTION SqMemberGlobalOverloadedFunc(R (* /*method*/)(T, A...)) {
    return SqGlobal<R>::template GetProxy<1, true, T, A...>();
}

// Member Global Overloaded Function Resolver
template <class R,class T,class... A> SQFUNCTION SqMemberGlobalOverloadedFunc(R& (* /*method*/)(T, A...)) {
    return SqGlobal<R&>::template GetProxy<1, true, T, A...>();
}

// Member Overloaded Function Resolver
template <class C, class R,class... A> SQFUNCTION SqMemberOverloadedFunc(R (C::* /*method*/)(A...)) {
    return SqMember<C,R>::template GetProxy<true, A...>();
}

// Member Overloaded Function Resolver
template <class C, class R,class... A> SQFUNCTION SqMemberOverloadedFunc(R (C::* /*method*/)(A...) const) {
    return SqMember<C,R>::template GetProxyC<true, A...>();
}

// Member Overloaded Function Resolver
template <class C, class R,class... A> SQFUNCTION SqMemberOverloadedFunc(R& (C::* /*method*/)(A...)) {
    return SqMember<C,R&>::template GetProxy<true, A...>();
}

// Member Overloaded Function Resolver
template <class C, class R,class... A> SQFUNCTION SqMemberOverloadedFunc(R& (C::* /*method*/)(A...) const) {
    return SqMember<C,R&>::template GetProxyC<true, A...>();
}

//
// Overload handler resolver
//

template <class R>
inline SQFUNCTION SqOverloadFunc(R (* /*method*/)) {
    return &SqOverload<R>::Func;
}

template <class R, class... A>
inline SQFUNCTION SqOverloadFunc(R (* /*method*/)(A...)) {
    return &SqOverload<R>::Func;
}

template <class C, class R>
inline SQFUNCTION SqOverloadFunc(R (C::* /*method*/)) {
    return &SqOverload<R>::Func;
}

template <class C, class R>
inline SQFUNCTION SqOverloadFunc(R (C::* /*method*/)() const ) {
    return &SqOverload<R>::Func;
}

template <class C, class R, class... A>
inline SQFUNCTION SqOverloadFunc(R (C::* /*method*/)(A...) ) {
    return &SqOverload<R>::Func;
}

template <class C, class R, class... A>
inline SQFUNCTION SqOverloadFunc(R (C::* /*method*/)(A...) const ) {
    return &SqOverload<R>::Func;
}

//
// Query argument count
//
template <class R, class... Args>
inline int SqGetArgCount(R (* /*method*/)(Args...)) {
    return sizeof...(Args);
}

//
// Query member function argument count
//
template <class C, class R, class... Args>
inline int SqGetArgCount(R (C::* /*method*/)(Args...)) {
    return sizeof...(Args);
}

//
// Query const member function argument count
//
template <class C, class R, class... Args>
inline int SqGetArgCount(R (C::* /*method*/)(Args...) const) {
    return sizeof...(Args);
}

/// @endcond

}

#endif