static char *
str_replace(const char * s1, const char * s2, char * string)
{
    char * res = NULL;
    size_t nb_entry = 0;
    size_t diff_size = strlen(s2) - strlen(s1);
    size_t size_res;
    const char * p = string;
    char * p_res;
    const char * t;

    while ((t = strstr(p,s1)) != NULL) {
        nb_entry ++;
        p = t + 1;
    }

// OK nous connaissons le nombre d'entree a remplacer
    size_res = strlen(string) + 1 + nb_entry * diff_size;
    res = malloc(size_res);
    p = string;
    p_res = res;
    strcpy(res,"");

    while ((t = strstr(p,s1)) != NULL) {
        strncat(p_res,p,t-p);
        strcat(p_res,s2);
        p_res += (t-p);
        p_res += strlen(s2);
        p = t + strlen(s1);
    }

    sprintf(p_res,"%s",p);

    return res;

}