#include <iostream>
#include <cstdio>

#define w2c(x) ( (char) ((x) & 0x00FF) )
#define is_uri_ch(x) ( ((x)>32) && ((x)<128) ) // uwaga! nie odporne na skutki uboczne

using namespace std;

void _hex2_(wchar_t in, char* out) {
    static char lookup[] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F' };
    int tmp; tmp = in & 0x000000FF; int first = tmp / 16; int second = tmp % 16;
    out[0] = lookup[first]; out[1] = lookup[second];
}

void hex(wchar_t* in, char* out, int max) {
    int i=0, max2=max-3, j=0;
    while(in[i]!=0) {
        if (j<max2) {
            if (is_uri_ch(in[i])) { out[j] = w2c(in[i]); ++j; }
            else { out[j] = '%'; _hex2_(in[i], out+j+1); j+=3; }
        }
        ++i;
    }
    out[j+1] = 0;
}


int main() {
    char buf[100];
    wchar_t uri[] = L"gżegżółka";
    hex(uri, buf, 100);
    cout << buf << endl;
    getchar();
    return 0;
}