The typedef keyword. Functions, function pointers, and you.

[Cypher]

Because a certain member of the forums (*cough* typedef *cough*) is a retard (apparently me using typdef on functions pointers is impossible and means I must have "shit for brains" -- his words) I figured other people must suffer from the same misconception so I will explain how to use a typedef with functions or function pointers.

Note: These are all REAL WORLD examples from one of my projects, so typedef (the person) can't go "ZOMG THIS NO WORK" because I'm using it right now and it does.

Functions:

When writing a callback system for my console I needed choose a function prototype all the callbacks would follow, I chose the following:

void __cdecl CallbackName(const std::string& Params);

In order to make writing the callback system easier on myself I used 'typedef' to create a type synonym for the callback prototype:

typedef void (__cdecl ConsoleCallback) (const std::string &);

I could then use the type "ConsoleCallback" instead of typing out the ugly type definition I would have to otherwise. An important thing to note is typedef defines a TYPE SYNONYM, meaning the word actually is a type, it is NOT a 'define' that just copy-pastes using the preprocessor before the compiler takes over, the compiler sees "ConsoleCallback" as a type and treats it as such.

You can then use the new type synonym as such:
std::map<std::string,ConsoleCallback*> ConsoleCallbacks;

void __cdecl TestCallback(const std::string&)
{
	;
}

void RegisterConsoleCallback(const std::string& Name, ConsoleCallback* Callback)
{
	ConsoleCallbacks[Name] = Callback;
}

void RegisterCallbacks()
{
	RegisterConsoleCallback("test",&TestCallback);
}

std::string Submit( const char * /*pszArgs*/, CElement * pThis )
{
	std::string sString(pThis->GetString());
	string Command = sString.substr(0, sString.find(" "));
	string Args = sString.substr(sString.find(" ")+1,sString.size());
	std::transform(Command.begin(), Command.end(), Command.begin(), tolower);
	if (ConsoleCallbacks[Command])
	{
		ConsoleCallback* pMyCallback = ConsoleCallbacks[Command];
		(*pMyCallback)(Args);
	}
	else
	{
		WriteOutput("Invalid command.");
	}
	pThis->SetString("");
	return std::string();
}

Function Pointers:

Typedefs are also useful when calling game function from an injected DLL in the form of a function pointer, this is great because you can avoid the use of inline ASM and have the compiler take care of the stack for you (and generate 'better' ASM because there are no __asm blocks that hinder the compiler's optimizer).

Example (from my fishbot, modified, unrelated code removed):

typedef bool (__cdecl * tCastSpellById)(unsigned int SpellId, unsigned int Unk2, unsigned int Unk3, unsigned int Unk4);
tCastSpellById oCastSpellById = 0;

void SetupMiscFunctions()
{
	oCastSpellById = (tCastSpellById)GetRPMgr()->GetFindPattern()->GetAddress("CSpell::CastSpellById");
}

void CastSpell(unsigned int SpellId)
{
	oCastSpellById(SpellId,0,0,0);
}

You can then use the code to cast for example 'Fishing (Apprentice)' which has ID 7620.

Hopefully now everyone can see you CAN use 'typedef' to define function and function pointer type synonyms.

[Remus]

lol nice read.. i understood it all =)

[Shynd]

I'm shit at C/++ and even I considered this within the realm of common knowledge.

[hypnodok]

This looks like its an irc screenshot, is there a mmowned irc channel?

[Gamer]

This looks like its an irc screenshot, is there a mmowned irc channel?

Shoutbox possibly?

[lanman92]

Okay, here's a semi-related question. Let's say I find GetObjByGUID in IDA. It says it has 3 arguments, but I'm thinking two of those are going to be used for the LONGLONG GUID. Which two is it? And what is the other param for?

This was my first thought:

typedef DWORD (__cdecl * tGetObjByGuid)(__int64 GUID, unsigned int unk1);
tGetObjByGUID oGetObjByGUID = 0x46D3C0;

[Cypher]

It would probably be something like this:
typedef CGObject_C* ( __cdecl* tGetObjectByGUID)(unsigned long GuidLow, unsigned long GuidHigh, int FilterMask);

Orrrr. You could replace it with:
typedef CGObject_C* ( __cdecl* tGetObjectByGUID)(WoWGUID FullGuid, int FilterMask);

struct WoWGUID
{
	union
	{
		__int64 FullGuid;
		struct
		{
			unsigned long High;
			unsigned long Low;
		};
		unsigned char Bytes[8]; // Used for packing/unpacking GUIDs in packets (CPacketManager::PackGuid, CPacketManager::UnpackGuid)
	};
};

EDIT:

The screenshot is from the MMOwned shoutbox.

[lanman92]

Ah, thanks Cypher. Should've gone to the wowdev page... Think they have that struct posted. What does the filter do?

[Cypher]

You can filter objects by type (unit, player, gameobject, etc).

[lanman92]

But, if it only returns one object, what's the point of that?

[Shynd]

He's talking about those received by packet-logging.

[lanman92]

Oh. Gotcha.

[Nesox]

Happy new year u mofos, if you live in a gmt+1 zone!

[schlumpf]

And happy new year, if you live in GMT now.

[Cypher]

GUIDs in packets are "packed" to reduce their size. When dealing with packed GUIDs its much easier to treat them as an array of bytes.