find_primes.cc

#include <node_api.h>

#define NAPI_CALL(env, call)                                      \
  do                                                              \
  {                                                               \
    napi_status status = (call);                                  \
    if (status != napi_ok)                                        \
    {                                                             \
      const napi_extended_error_info *error_info = NULL;          \
      napi_get_last_error_info((env), &error_info);               \
      bool is_pending;                                            \
      napi_is_exception_pending((env), &is_pending);              \
      if (!is_pending)                                            \
      {                                                           \
        const char *message = (error_info->error_message == NULL) \
                                  ? "empty error message"         \
                                  : error_info->error_message;    \
        napi_throw_error((env), NULL, message);                   \
        return NULL;                                              \
      }                                                           \
    }                                                             \
  } while (0)

int is_prime(int num)
{
  if (num <= 1)
    return 0;
  for (int i = 2; i <= num / 2; i++)
  {
    if (num % i == 0)
    {
      return 0;
    }
  }
  return 1; //if both failed then num is prime
}

int find_prime(int upper_limit)
{
  int largest_prime;

  for (int i = 2; i <= upper_limit; i++)
  {
    if (is_prime(i))
    {
      largest_prime = i;
    }
  }

  return largest_prime;
}


napi_value FindPrimes(napi_env env, napi_callback_info info)
{
  size_t argc = 1;
  napi_value args[1];
  int64_t upper_limit;
  int64_t largest_prime;
  napi_value output;

  NAPI_CALL(env,napi_get_cb_info(env, info, &argc, args, NULL, NULL));

  NAPI_CALL(env,napi_get_value_int64(env, args[0], &upper_limit));

  largest_prime = find_prime(upper_limit);

  NAPI_CALL(env,napi_create_double(env, largest_prime, &output));

  return output;
}

napi_value init(napi_env env, napi_value exports)
{
  napi_value find_primes;

  napi_create_function(env, nullptr, 0, FindPrimes, nullptr, &find_primes);

  return find_primes;
}

NAPI_MODULE(NODE_GYP_MODULE_NAME, init);