mutt_qsort_r.c

#include <assert.h>
#include <stdio.h>
#include <stdlib.h>

// void qsort  (void *base, size_t nmemb, size_t size, int (*compar)(const void *, const void *));
// void qsort_r(void *base, size_t nmemb, size_t size, int (*compar)(const void *, const void *, void *), void *arg);

typedef int (*qsort_compar_t)  (const void *a, const void *b);
typedef int (*qsort_r_compar_t)(const void *a, const void *b, void *arg);

static qsort_r_compar_t global_compar = NULL;
static void            *global_data   = NULL;

static int relay_compar(const void *a, const void *b)
{
  return global_compar(a, b, global_data);
}

void mutt_qsort_r(void *base, size_t nmemb, size_t size, qsort_r_compar_t compar, void *arg)
{
  assert((global_compar == NULL) && (global_data == NULL));
  global_compar = compar;
  global_data = arg;
  qsort(base, nmemb, size, relay_compar);
  global_compar = NULL;
  global_data = NULL;
}