-rw-r--r-- 1408 djbsort-20180710/int32/portable4/sort.c
#include "int32_sort.h"
#define int32 int32_t

static inline int32 minmax(int32 a,int32 *y)
{
  int32 b = *y;
  int32 ab = b ^ a;
  int32 c = b - a;
  c ^= ab & (c ^ b);
  c >>= 31;
  c &= ab;
  a ^= c;
  *y = b ^ c;
  return a;
}

void int32_sort(int32 *x,long long n)
{
  long long top,p,q,r,i,j;

  if (n < 2) return;
  top = 1;
  while (top < n - top) top += top;

  for (p = top;p >= 1;p >>= 1) {
    i = 0;
    while (i + 2 * p <= n) {
      for (j = i;j < i + p;++j)
        x[j] = minmax(x[j],x + j + p);
      i += 2 * p;
    }
    for (j = i;j < n - p;++j)
      x[j] = minmax(x[j],x + j + p);

    i = 0;
    j = 0;
    for (q = top;q > p;q >>= 1) {
      if (j != i) for (;;) {
        if (j == n - q) goto done;
        int32 a = x[j + p];
        for (r = q;r > p;r >>= 1)
          a = minmax(a,x + j + r);
        x[j + p] = a;
        ++j;
        if (j == i + p) {
          i += 2 * p;
          break;
        }
      }
      while (i + p <= n - q) {
        for (j = i;j < i + p;++j) {
          int32 a = x[j + p];
          for (r = q;r > p;r >>= 1)
            a = minmax(a,x + j + r);
          x[j + p] = a;
        }
        i += 2 * p;
      }
      /* now i + p > n - q */
      j = i;
      while (j < n - q) {
        int32 a = x[j + p];
        for (r = q;r > p;r >>= 1)
          a = minmax(a,x + j + r);
        x[j + p] = a;
        ++j;
      }

      done: ;
    }
  }
}