lib: stdio/qsort: Refactor, fixes GCC-4.6.4.

* lib/stdlib/qsort.c (qswap): Refactor.
(qpart): Add "lo" parametor, use "hi" instead of
count.  Refactor.
(qsort): Move to...
(_qsort): ...this, and refactor.
(qsort): New function.

lib/stdlib/qsort.c

@@ -19,62 +19,62 @@
  * along with GNU Mes.  If not, see <http://www.gnu.org/licenses/>.
  */
 
-#include <stdlib.h>
-#include <string.h>
+/* See: https://en.wikipedia.org/wiki/Quicksort */
 
-void
-qswap (void *a, void *b, size_t size)
+#include <stdlib.h>
+
+static void
+qswap (char *a, char *b, size_t size)
 {
-  char *pa = a;
-  char *pb = b;
-  do
-  {
-    char tmp = *pa;
-    *pa++ = *pb;
-    *pb++ = tmp;
-  } while (--size > 0);
+  while (size-- > 0)
+    {
+      char tmp = *a;
+      *a++ = *b;
+      *b++ = tmp;
+    }
 }
 
-size_t
-qpart (void *base, size_t count, size_t size, int (*compare) (void const *, void const *))
+static size_t
+qpart (char *base, size_t lo, size_t hi, size_t size,
+       int (*compare) (void const *, void const *))
 {
-  void *p = base + count * size;
-  size_t i = 0;
-  for (size_t j = 0; j < count; j++)
+  char *pivot = base + hi * size;
+  size_t i = lo;
+
+  for (size_t j = lo; j < hi; j++)
     {
-      int c = compare (base + j * size, p);
-      if (c < 0)
+      char *pj = base + j * size;
+      if (pj != pivot && compare (pj, pivot) < 0)
         {
-#if 1                           //__x86_64__
-          qswap (base + i * size, base + j * size, size);
-#else
-          int p1 = base + i * size;
-          int p2 = base + j * size;
-          qswap (p1, p2, size);
-#endif
+          void *pi = base + i * size;
+          qswap (pi, pj, size);
           i++;
         }
-      else if (c == 0)
-        i++;
     }
-  if (compare (base + count * size, base + i * size) < 0)
-    qswap (base + i * size, base + count * size, size);
+
+  char *pi = base + i * size;
+  qswap (pi, pivot, size);
+
   return i;
 }
 
-void
-qsort (void *base, size_t count, size_t size, int (*compare) (void const *, void const *))
+static void
+_qsort (void *base, size_t lo, size_t hi, size_t size,
+        int (*compare) (void const *, void const *))
 {
-  if (count > 1)
-    {
-      int p = qpart (base, count - 1, size, compare);
-      qsort (base, p, size, compare);
-#if 1                           //__x86_64__
-      qsort (base + p * size, count - p, size, compare);
-#else
-      int p1 = base + p * size;
-      int p2 = count - p;
-      qsort (p1, p2, size, compare);
-#endif
-    }
+  if (lo >= hi)
+    return;
+  size_t pi = qpart (base, lo, hi, size, compare);
+  if (pi > 0)
+    _qsort (base, lo, pi - 1, size, compare);
+  _qsort (base, pi + 1, hi, size, compare);
+}
+
+void
+qsort (void *base, size_t count, size_t size,
+       int (*compare) (void const *, void const *))
+{
+  if (count <= 1)
+    return;
+  _qsort (base, 0, count - 1, size, compare);
 }