sort.h

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#pragma once
 
#include <assert.h>
#include <stdlib.h>
 
static _Thread_local int (*gv_sort_compar)(const void *, const void *, void *);
static _Thread_local void *gv_sort_arg;
 
static inline int gv_sort_compar_wrapper(const void *a, const void *b) {
  assert(gv_sort_compar != NULL && "no comparator set in gv_sort");
  return gv_sort_compar(a, b, gv_sort_arg);
}
 
static inline void gv_sort(void *base, size_t nmemb, size_t size,
                           int (*compar)(const void *, const void *, void *),
                           void *arg) {
  assert(gv_sort_compar == NULL && gv_sort_arg == NULL &&
         "unsupported recursive call to gv_sort");
 
  gv_sort_compar = compar;
  gv_sort_arg = arg;
 
  if (nmemb > 1) {
    qsort(base, nmemb, size, gv_sort_compar_wrapper);
  }
 
  gv_sort_compar = NULL;
  gv_sort_arg = NULL;
}
 
static inline int sort_place_cmp(const void *a, const void *b, void *context) {
  const int *const x = a;
  const int *const y = b;
  const double *const place = context;
 
  if (place[*x] < place[*y]) {
    return -1;
  }
  if (place[*x] > place[*y]) {
    return 1;
  }
  return 0;
}
 
static inline void sort_place(double *place, int *ordering, size_t size) {
  gv_sort(ordering, size, sizeof(ordering[0]), sort_place_cmp, place);
}