How to use static in class?

[Bryan Parkoff]

The local variables and local functions are inside class body. You
define a variable to the class "Reg reg;" in the main function. The reg
variable has a pointer. The pointer gives memory address. The memory
address accesses local variable and local function. It is fine design
according to your preferance.
I try to remove a pointer so I let local variable and local function as
global to
access to the memory directly without needing a pointer. I put static
keyword to the local function inside class.
Why can't I put static on func1(), func2(), func3(), and func4()
functions?

Here is an example of x86 instruction and take a look of my source code
below.

00411CEE call Reg::Init (4111A9h) /* Init() function has static -- one x86
instruction */

Reduced x86 instruction helps to increase critical performance in a
loop.

0041328E lea ecx,[reg] /* Init() function has non-static member in class
Reg -- two x86 instructions */
00413291 call Reg::Init (4111FEh)

According to my speed test, extra x86 instruction for the pointer is
slower than one instruction to do direct memory.

/* main.cpp */
class Reg
{
private:
unsigned char a;
unsigned char b;
unsigned char c;

unsigned char funcCycle;

void func1(void);
void func2(void);
void func3(void);
void func4(void);

typedef void (Reg::*pfunc)();
static const pfunc pf[4];

public:
static void Init (void);
static void Run(void);
} _reg;

const Reg::pfunc Reg::pf[4] = { &Reg::func1, &Reg::func2, &Reg::func3,
&Reg::func4 };

void Reg::Init (void)
{
_reg.funcCycle = 0;
}

void Reg::func1(void)
{
_reg.a += 2;
_reg.b += 4;
_reg.c += 8;
}

void Reg::func2(void)
{
_reg.a -= 2;
_reg.b -= 4;
_reg.c -= 8;
}

void Reg::func3(void)
{
_reg.a *= 2;
_reg.b *= 4;
_reg.c *= 8;
}

void Reg::func4(void)
{
_reg.a /= 2;
_reg.b /= 4;
_reg.c /= 8;
}

void Reg::Run(void)
{
(_reg.*pf[_reg.funcCycle])();
_reg.funcCycle++;
_reg.funcCycle &= 3;
}

int main()
{
_reg.Init();

int count = 0;
while (count++ < 10)
_reg.Run();

return 0;
}

--

Yours Truly,
Bryan Parkoff

[Ian Collins]

Bryan Parkoff wrote:

The local variables and local functions are inside class body. You
define a variable to the class "Reg reg;" in the main function. The reg
variable has a pointer. The pointer gives memory address. The memory
address accesses local variable and local function. It is fine design
according to your preferance.
I try to remove a pointer so I let local variable and local function as
global to
access to the memory directly without needing a pointer. I put static
keyword to the local function inside class.
Why can't I put static on func1(), func2(), func3(), and func4()
functions?

I've no idea what you are trying to do, but the only thing preventing
you from declaring the member functions static is

typedef void (Reg::*pfunc)();

followed by

const Reg::pfunc Reg::pf[4] = { &Reg::func1, &Reg::func2, &Reg::func3,
&Reg::func4 };

the type of pfunc is a member function. if you want to use static
member functions, use

typedef void (*pfunc)();

>
/* main.cpp */
class Reg
{
private:
unsigned char a;
unsigned char b;
unsigned char c;

unsigned char funcCycle;

void func1(void);

drop the (void) () is idiomatic C++.

--
Ian Collins.

[Krice]

On 15 huhti, 07:13, "Bryan Parkoff" <[e-mail]:

According to my speed test, extra x86 instruction for the
pointer is slower than one instruction to do direct memory.

If you want that kind of optimization then C++ is probably
wrong language for that purpose. Try assembly.

[Bryan Parkoff]

> According to my speed test, extra x86 instruction for the

>pointer is slower than one instruction to do direct memory.

If you want that kind of optimization then C++ is probably
wrong language for that purpose. Try assembly.

Ian Collins already answered my question in another thread. To do x86
assembly is not the best option. I depend on C++ Compiler for best
optimization. I am satisified with Ian Collins' answer. It does what I
need.

Yours Truly,
Bryan Parkoff