erl_nif のメモ（その２）

その１の、その後。

nif.c

# include <stdio.h>
# include <string.h>
# include <errno.h>

# define UNUSED(p) (void)(p)

// -- --

typedef struct {
  int id;
} nif_t;

// -- --

static ERL_NIF_TERM open(ErlNifEnv *env, int argc, const ERL_NIF_TERM *argv) {

  if (1 == argc &&
      enif_is_number(env, argv[0])) {

    int id = 0;
    enif_get_int(env, argv[0], &id);

    ERL_NIF_TERM term;

    nif_t *resource = (nif_t *)enif_make_new_binary(env, sizeof(nif_t), &term);

    if (NULL != resource) {

      resource->id = id;

      printf("open: resource=%ld, id=%d\r\n", (long)resource, resource->id);

      return enif_make_tuple2(env,
                              enif_make_atom(env, "ok"),
                              term);
    } else {

      return enif_make_tuple2(env,
                              enif_make_atom(env, "error"),
                              enif_make_string(env, "enomem", ERL_NIF_LATIN1));
    }
  }

  return enif_make_badarg(env);
}

static ERL_NIF_TERM close(ErlNifEnv *env, int argc, const ERL_NIF_TERM *argv) {

  if (1 == argc) {

    ErlNifBinary bin;

    if (enif_inspect_binary(env, argv[0], &bin) && sizeof(nif_t) == bin.size) {

      ERL_NIF_TERM term;

      nif_t *resource = (nif_t *)enif_make_new_binary(env, sizeof(nif_t), &term);

      memcpy(resource, bin.data, bin.size);

      printf("close: resource=%ld, id=%d\r\n", (long)resource, resource->id);

      return enif_make_atom(env, "ok");
    }
  }

  return enif_make_badarg(env);
}

// -- --

static ErlNifFunc funcs[] = {
  {"open", 1, open},
  {"close", 1, close},
};

static int load(ErlNifEnv *env, void **priv_data, ERL_NIF_TERM load_info) {

  UNUSED(env), UNUSED(load_info);

  *priv_data = NULL;

  return 0;
}

/*
 */
ERL_NIF_INIT(nif, funcs, load, NULL, NULL, NULL);

Erlang R16B03-1 (erts-5.10.4) [source] [64-bit] [smp:4:4] [async-threads:10] [hipe] [kernel-poll:false] [dtrace]

Eshell V5.10.4  (abort with ^G)
1> 
1> {ok,B} = nif:open(123).
open: resource=444388128, id=123
{ok,<<123,0,0,0>>}
2> nif:close(B).
close: resource=444424072, id=123
ok
3> q().

crypto を真似て。戻りの binary が <<>> でないのも良い。