+ front = string;
+ back = string + off2;
+ front_len = off1;
+ replacement_len = strlen (replacement);
+ back_len = strlen (back);
+
+ if (front_len >= buflen) {
+ front_len = buflen - 1;
+ replacement_len = 0;
+ back_len = 0;
+ } else if ((front_len + replacement_len) >= buflen) {
+ replacement_len = buflen - (front_len + 1);
+ back_len = 0;
+ } else if ((front_len + replacement_len + back_len) >= buflen) {
+ back_len = buflen - (front_len + replacement_len + 1);
+ } else {
+ buflen = front_len + replacement_len + back_len + 1;
+ }
+ assert ((front_len + replacement_len + back_len) == (buflen - 1));