Function Pointer

[curlious]

I have a function in my code that I want to return a pointer to a function. The result would then invoke the returned function. How would I set this up? Here is the code for the function that returns one of two pointer to another function.

USHORT * getPixelFormat()
{
	DDPIXELFORMAT ddpixel;

	//clear out structure
	memset(&ddpixel, 0, sizeof(ddpixel));

	//set length
	ddpixel.dwSize = sizeof(ddpixel);

	//use primary surface interface to get pixel format
	lppdsprimary->GetPixelFormat(&ddpixel);

	//determine function corresponding to pixel format
	BOOL RGB = (ddpixel.dwFlags & DDPF_RGB);
	
	// test for mode 5.5.5
	if (RGB & (ddpixel.dwRGBBitCount==15))    
		return RGB16BIT555;                   
	if (RGB & (ddpixel.dwRGBBitCount==16))
		return RGB16BIT565;

	return NULL;
}

Here is more of the code I have tried.

//Prototypes
USHORT * getPixelFormat();
USHORT RGB16BIT555(int r, int g, int b);
USHORT RGB16BIT565(int r, int g, int b);
USHORT (*pfnColor)(int,int,int);			 // pointer to RGBcolor function
.
.
.
	// Determine color function based on pixel format
	
	pfnColor = getPixelFormat();
.
.
.
void Plot_Pixel(int x, int y, int red, int green, int blue, USHORT * video_buffer, int lpitch)
{
	USHORT pixel = (*pfnColor)(red,green,blue);
	video_buffer[x+y*(lpitch>>1)]=pixel;
}

[Salem]

If you want to keep your sanity, make a typedef for the type of the function you want to return a pointer to.

After that, its dead easy

#include <stdio.h>

typedef void (*fp)(void);

void foo ( void ) {
    printf( "This is foo\n" );
}
void bar ( void ) {
    printf( "This is bar\n" );
}

fp chooser ( int which ) {
    if ( which ) {
        return foo;
    } else {
        return bar;
    }
}

int main ( void ) {
    fp one = chooser(0);  // grab a function
    fp two = chooser(1);

    one();  // and call it
    two();

    // combined
    chooser(0)();

    return 0;
}

[curlious]

Thanks Salem, my program compiles now but doesn't work properly.

Basicly I was trying to implement the proper pixel format instead of just assuming 565. When I was making the assumption and using a #define for my RGB value it was working now it will not plot and I am not sure why. I will repost the entire code under the windows section and maybe someone can help me figure out whats going wrong.

Ignore the above, doh I was using the & operator in place of the logical && in two of my tests. Again thanks for the help on the pointer to function aspect