table.c

/**
 * https://news.ycombinator.com/item?id=8737349
 *
 */
 
#include <stdlib.h>

#define SIZE 1024


static int (**hnew())[2] {
  return calloc(sizeof(int**), SIZE);
}

static void hdel(int (**e)[2]) {
  for (int i = 0; i < SIZE; i++) free(e[i]); free(e);
}

static int (**hget(int (**t)[2], int k))[2] {
  for (int h = k & (SIZE - 1); **t && ***t != k; h = ((h + 1) & (SIZE - 1)), t += h);
  return t;
}

static void hset(int (**t)[2], int k, int v) {
  for (int (**a)[2] = hget(t, k); !*a && (*a=malloc(sizeof(**t))); (**a)[0]=k,(**a)[1]=v);
}


// TEST DRIVER

#include <stdio.h>


int main() {
  int (**table)[2] = hnew();

  hset(table, 10, 20);
  hset(table, 20, 30);
  hset(table, 30, 40);

  int (**a)[2] = hget(table, 10);
  int (**b)[2] = hget(table, 20);
  int (**c)[2] = hget(table, 30);

  printf("%d:%d\n", (**a)[0], (**a)[1]);
  printf("%d:%d\n", (**b)[0], (**b)[1]);
  printf("%d:%d\n", (**c)[0], (**c)[1]);

  hdel(table);
}