+static inline char *
+med3(char *a, char *b, char *c, cmp_t *cmp, void *thunk)
+{
+ return CMP(thunk, a, b) < 0 ?
+ (CMP(thunk, b, c) < 0 ? b : (CMP(thunk, a, c) < 0 ? c : a ))
+ :(CMP(thunk, b, c) > 0 ? b : (CMP(thunk, a, c) < 0 ? a : c ));
+}
+
+
+void qsort_r_fallback(void *a, size_t n, size_t es, void *thunk, cmp_t *cmp)
+{
+ char *pa, *pb, *pc, *pd, *pl, *pm, *pn;
+ size_t d1, d2;
+ int cmp_result;
+ int swap_cnt;
+
+loop:
+ swap_cnt = 0;
+ if (n < 7) {
+ for (pm = (char *)a + es; pm < (char *)a + n * es; pm += es)
+ for (pl = pm;
+ pl > (char *)a && CMP(thunk, pl - es, pl) > 0;
+ pl -= es)
+ swapfunc(pl, pl - es, es);
+ return;
+ }
+ pm = (char *)a + (n / 2) * es;
+ if (n > 7) {
+ pl = a;
+ pn = (char *)a + (n - 1) * es;
+ if (n > 40) {
+ size_t d = (n / 8) * es;
+
+ pl = med3(pl, pl + d, pl + 2 * d, cmp, thunk);
+ pm = med3(pm - d, pm, pm + d, cmp, thunk);
+ pn = med3(pn - 2 * d, pn - d, pn, cmp, thunk);
+ }
+ pm = med3(pl, pm, pn, cmp, thunk);
+ }
+ swapfunc(a, pm, es);
+ pa = pb = (char *)a + es;
+
+ pc = pd = (char *)a + (n - 1) * es;
+ for (;;) {
+ while (pb <= pc && (cmp_result = CMP(thunk, pb, a)) <= 0) {
+ if (cmp_result == 0) {
+ swap_cnt = 1;
+ swapfunc(pa, pb, es);
+ pa += es;
+ }
+ pb += es;
+ }
+ while (pb <= pc && (cmp_result = CMP(thunk, pc, a)) >= 0) {
+ if (cmp_result == 0) {
+ swap_cnt = 1;
+ swapfunc(pc, pd, es);
+ pd -= es;
+ }
+ pc -= es;
+ }
+ if (pb > pc)
+ break;
+ swapfunc(pb, pc, es);
+ swap_cnt = 1;
+ pb += es;
+ pc -= es;
+ }
+ if (swap_cnt == 0) { /* Switch to insertion sort */
+ for (pm = (char *)a + es; pm < (char *)a + n * es; pm += es)
+ for (pl = pm;
+ pl > (char *)a && CMP(thunk, pl - es, pl) > 0;
+ pl -= es)
+ swapfunc(pl, pl - es, es);
+ return;
+ }
+
+ pn = (char *)a + n * es;
+ d1 = MIN(pa - (char *)a, pb - pa);
+ vecswap(a, pb - d1, d1);
+ d1 = MIN(pd - pc, pn - pd - es);
+ vecswap(pb, pn - d1, d1);
+
+ d1 = pb - pa;
+ d2 = pd - pc;
+ if (d1 <= d2) {
+ /* Recurse on left partition, then iterate on right partition */
+ if (d1 > es) {
+ qsort_r_fallback(a, d1 / es, es, thunk, cmp);
+ }
+ if (d2 > es) {
+ /* Iterate rather than recurse to save stack space */
+ /* qsort(pn - d2, d2 / es, es, cmp); */
+ a = pn - d2;
+ n = d2 / es;
+ goto loop;
+ }
+ } else {
+ /* Recurse on right partition, then iterate on left partition */
+ if (d2 > es) {
+ qsort_r_fallback(pn - d2, d2 / es, es, thunk, cmp);
+ }
+ if (d1 > es) {
+ /* Iterate rather than recurse to save stack space */
+ /* qsort(a, d1 / es, es, cmp); */
+ n = d1 / es;
+ goto loop;
+ }
+ }
+}