+ size_t i = 0, last_char_width[4] = {}, k = 0, j;
+
+ assert(len > 0); /* at least a terminating NUL */
+
+ for (;;) {
+ char four[4];
+ int w;
+
+ if (*s == 0) /* terminating NUL detected? then we are done! */
+ goto done;
+
+ w = cescape_char(*s, four);
+ if (i + w + 1 > len) /* This character doesn't fit into the buffer anymore? In that case let's
+ * ellipsize at the previous location */
+ break;
+
+ /* OK, there was space, let's add this escaped character to the buffer */
+ memcpy(buf + i, four, w);
+ i += w;
+
+ /* And remember its width in the ring buffer */
+ last_char_width[k] = w;
+ k = (k + 1) % 4;
+
+ s++;
+ }
+
+ /* Ellipsation is necessary. This means we might need to truncate the string again to make space for 4
+ * characters ideally, but the buffer is shorter than that in the first place take what we can get */
+ for (j = 0; j < ELEMENTSOF(last_char_width); j++) {
+
+ if (i + 4 <= len) /* nice, we reached our space goal */
+ break;
+
+ k = k == 0 ? 3 : k - 1;
+ if (last_char_width[k] == 0) /* bummer, we reached the beginning of the strings */
+ break;
+
+ assert(i >= last_char_width[k]);
+ i -= last_char_width[k];
+ }
+
+ if (i + 4 <= len) /* yay, enough space */
+ i += write_ellipsis(buf + i, false);
+ else if (i + 3 <= len) { /* only space for ".." */
+ buf[i++] = '.';
+ buf[i++] = '.';
+ } else if (i + 2 <= len) /* only space for a single "." */
+ buf[i++] = '.';
+ else
+ assert(i + 1 <= len);