Porting of C++ code with specialized templates to C language [closed] - c++

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I have many very similar functions like
void someLargeFulction1(args)
{
IDENTICAL CODE
DIFFERENT CODE 1
IDENTICAL CODE
}
//---------------------------//
//---------------------------//
void someLargeFulctionN(args)
{
IDENTICAL CODE
DIFFERENT CODE N
IDENTICAL CODE
}
All these functions differs only in DIFFERENT CODE N part (this is a shot series of floating point operations). Since most of the someLargeFulctionN codes is identical, I wont to avoid code replication because this greatly complicates code maintenance. Reducing reps is my major goal. Unfortunately, I can not organize DIFFERENT CODE as function call and pass this functions as a someLargeFulction argument due to critical performance impact - DIFFERENT CODE performed much faster than a typical function call, excluding the case of call inlining by compiler. I would not like to organize someLargeFulctionN as macro definition (which however is the possible solution).
In the C++ programming language I have very simple and useful solution - template functions. I can do something like:
template <int N>
void someLargeFulction(args)
{
IDENTICAL CODE
differentCode<N>();
IDENTICAL CODE
}
And specialize differentCode() function for all variants. For all tested compilers (g++, MVSC) it works great! The compiler always inlines a differentCode call and I have the necessary number of someLargeFulction variants. The problem is that now I need to port this code to С98. For solve the problem directly, I need to create a full number of someLargeFulction copies, this is a bad decision. Using a macro-definition with someLargeFulction implementation acceptable, but not desirable. What other options do you see?

Answer 1

Something like :
#include <stdio.h>
#define doIt(OP,a,b) do##OP(a,b)
#define performTmpl(OP,a,b,c) { for (int i=0; i<10; i++) a[i]=doIt(OP,b[i],c[i]); }
enum { ADD, SUB };
int doADD(int a,int b) { return a+b; }
int doSUB(int a,int b) { return a-b; }
int main() {
printf("%d\n",doIt(ADD,5,4));
printf("%d\n",doIt(SUB,5,4));
int x[10], y[10]={1,2,3,4,5,6,7,8,9,10}, z[10]={1,1,1,1,1,1,1,1,1,1};
performTmpl(ADD,x,y,z);
for (int i=0; i<10; i++) printf("%d\n",x[i]);
}