From 3365b3e5afa17edb1c6f095306a00dea56d8b00c Mon Sep 17 00:00:00 2001
From: Jesper Louis Andersen <jesper.louis.andersen@gmail.com>
Date: Tue, 18 Nov 2014 23:35:59 +0100
Subject: [PATCH] Provide a way to get at the typical constants for the public
 key box.

---
 c_src/enacl_nif.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/c_src/enacl_nif.c b/c_src/enacl_nif.c
index adcbb31..5772d39 100644
--- a/c_src/enacl_nif.c
+++ b/c_src/enacl_nif.c
@@ -2,11 +2,14 @@
 
 #include <sodium.h>
 
+/* Errors */
 static
 ERL_NIF_TERM nacl_error_tuple(ErlNifEnv *env, char *error_atom) {
 	return enif_make_tuple2(env, enif_make_atom(env, "error"), enif_make_atom(env, error_atom));
 }
 
+/* Helper functions (Hashing, String Equality, ...) */
+
 static
 ERL_NIF_TERM enif_crypto_hash(ErlNifEnv *env, int argc, ERL_NIF_TERM const argv[]) {
 	ErlNifBinary input;
@@ -25,6 +28,22 @@ ERL_NIF_TERM enif_crypto_hash(ErlNifEnv *env, int argc, ERL_NIF_TERM const argv[
 	return enif_make_binary(env, &result);
 }
 
+/* Public-key cryptography */
+static
+ERL_NIF_TERM enif_crypto_box_NONCEBYTES(ErlNifEnv *env, int argc, ERL_NIF_TERM const argv[]) {
+	return enif_make_int64(env, crypto_box_NONCEBYTES);
+}
+
+static
+ERL_NIF_TERM enif_crypto_box_ZEROBYTES(ErlNifEnv *env, int argc, ERL_NIF_TERM const argv[]) {
+	return enif_make_int64(env, crypto_box_ZEROBYTES);
+}
+
+static
+ERL_NIF_TERM enif_crypto_box_BOXZEROBYTES(ErlNifEnv *env, int argc, ERL_NIF_TERM const argv[]) {
+	return enif_make_int64(env, crypto_box_BOXZEROBYTES);
+}
+
 static
 ERL_NIF_TERM enif_crypto_box_keypair(ErlNifEnv *env, int argc, ERL_NIF_TERM const argv[]) {
 	ErlNifBinary pk, sk;
@@ -46,7 +65,11 @@ ERL_NIF_TERM enif_crypto_box_keypair(ErlNifEnv *env, int argc, ERL_NIF_TERM cons
 	return enif_make_tuple3(env, enif_make_atom(env, "ok"), enif_make_binary(env, &pk), enif_make_binary(env, &sk));
 }
 
+/* Tie the knot to the Erlang world */
 static ErlNifFunc nif_funcs[] = {
+	{"crypto_box_NONCEBYTES", 0, enif_crypto_box_NONCEBYTES},
+	{"crypto_box_ZEROBYTES", 0, enif_crypto_box_ZEROBYTES},
+	{"crypto_box_BOXZEROBYTES", 0, enif_crypto_box_BOXZEROBYTES},
 	{"crypto_box_keypair", 0, enif_crypto_box_keypair},
 	{"crypto_hash", 1, enif_crypto_hash, ERL_NIF_DIRTY_JOB_CPU_BOUND}
 };