Jump table example using function pointers in C++

jump_table.cpp

#include <cstdio>
using namespace std;

// function table/jump table example

// various functions that need to be jumped to
void fa() {printf("function a\n");}
void fb() {printf("function b\n");}
void fc() {printf("function c\n");}
void fd() {printf("function d\n");}

// array of function pointers to jump to
void (*functions[])() {fa, fb, fc, fd, nullptr};

// jump function calls the callbacks
int jump(const char *choice)
{
    char code = choice[0]; // grab the first character from the input

    if (code == 'Q' || code == 'q') return 0;

    // count the length of function array
    uint func_length = 0;

    while (functions[func_length] != nullptr)
    {
        func_length++;
    }

    // convert ASCII to int
    uint func_no = (int) code -'0';
    func_no--; // the array start is zero

    // pick the function to run
    if (func_no < 0 || func_no >= func_length)
    {
        printf("invalid choice %d\n", func_no);
        return -1;
    }
    else
    {
        functions[func_no]();
        return 0;
    }
}

int main ()
{
    void (*fp)() = fa;
    // identical to
    // void (*fp)() = &func;
    printf("in main\n");
    fp(); // call from function pointer
    // same as calling the pointer explicitly
    // (*fp)();

    // function table jumps
    const int buff_sz = 15;     // input buffer size
    static char resp[buff_sz];  // user input respone buffer

    // read input
    fgets(resp, buff_sz, stdin);

    // jump to function
    (void)jump(resp);
}