#include "git-compat-util.h"

/*

 * A merge sort implementation, simplified from the qsort implementation

 * by Mike Haertel, which is a part of the GNU C Library.

 */

static void msort_with_tmp(void *b, size_t n, size_t s,

         int (*cmp)(const void *, const void *),

         char *t)

{

  char *tmp;

  char *b1, *b2;

  size_t n1, n2;

  if (n <= 1)

    return;

  n1 = n / 2;

  n2 = n - n1;

  b1 = b;

  b2 = (char *)b + (n1 * s);

  msort_with_tmp(b1, n1, s, cmp, t);

  msort_with_tmp(b2, n2, s, cmp, t);

  tmp = t;

  while (n1 > 0 && n2 > 0) {

    if (cmp(b1, b2) <= 0) {

      memcpy(tmp, b1, s);

      tmp += s;

      b1 += s;

      --n1;

    } else {

      memcpy(tmp, b2, s);

      tmp += s;

      b2 += s;

      --n2;

    }

  }

  if (n1 > 0)

    memcpy(tmp, b1, n1 * s);

  memcpy(b, t, (n - n2) * s);

}

void git_stable_qsort(void *b, size_t n, size_t s,

          int (*cmp)(const void *, const void *))

{

  const size_t size = st_mult(n, s);

  char *tmp;

  tmp = xmalloc(size);

  msort_with_tmp(b, n, s, cmp, tmp);

  free(tmp);

}