From 5dd58c558258512b662c060959a419805025cf62 Mon Sep 17 00:00:00 2001
From: Benedikt Reinartz <filmor@gmail.com>
Date: Sun, 13 Oct 2024 08:54:23 +0200
Subject: [PATCH] Add reference type and `make_ref` call

---
 rustler/src/lib.rs                            |  2 +-
 rustler/src/types/mod.rs                      |  9 +++-
 rustler/src/types/reference.rs                | 52 +++++++++++++++++++
 rustler_tests/lib/rustler_test.ex             |  1 +
 .../native/rustler_test/src/test_env.rs       |  9 +++-
 rustler_tests/test/env_test.exs               |  9 ++++
 6 files changed, 78 insertions(+), 4 deletions(-)
 create mode 100644 rustler/src/types/reference.rs

diff --git a/rustler/src/lib.rs b/rustler/src/lib.rs
index d1335526..159e7dc7 100644
--- a/rustler/src/lib.rs
+++ b/rustler/src/lib.rs
@@ -39,7 +39,7 @@ mod term;
 pub use crate::term::Term;
 pub use crate::types::{
     Atom, Binary, Decoder, Encoder, ErlOption, ListIterator, LocalPid, MapIterator, NewBinary,
-    OwnedBinary,
+    OwnedBinary, Reference,
 };
 
 #[cfg(feature = "big_integer")]
diff --git a/rustler/src/types/mod.rs b/rustler/src/types/mod.rs
index 52c141cf..c3f11ced 100644
--- a/rustler/src/types/mod.rs
+++ b/rustler/src/types/mod.rs
@@ -2,8 +2,6 @@ use crate::{Env, Error, NifResult, Term};
 
 #[macro_use]
 pub mod atom;
-pub mod i128;
-pub mod path;
 pub use crate::types::atom::Atom;
 
 pub mod binary;
@@ -32,6 +30,13 @@ pub mod tuple;
 pub mod local_pid;
 pub use self::local_pid::LocalPid;
 
+#[doc(hidden)]
+pub mod reference;
+pub use self::reference::Reference;
+
+pub mod i128;
+pub mod path;
+
 pub mod truthy;
 
 pub mod elixir_struct;
diff --git a/rustler/src/types/reference.rs b/rustler/src/types/reference.rs
new file mode 100644
index 00000000..bdce7f5c
--- /dev/null
+++ b/rustler/src/types/reference.rs
@@ -0,0 +1,52 @@
+use std::ops::Deref;
+
+use crate::{Decoder, Encoder, Env, Error, NifResult, Term};
+
+use crate::sys::enif_make_ref;
+
+#[derive(PartialEq, Eq, Clone, Copy)]
+pub struct Reference<'a>(Term<'a>);
+
+impl<'a> Deref for Reference<'a> {
+    type Target = Term<'a>;
+
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+impl<'a> Into<Term<'a>> for Reference<'a> {
+    fn into(self) -> Term<'a> {
+        self.0
+    }
+}
+
+impl<'a> TryFrom<Term<'a>> for Reference<'a> {
+    type Error = Error;
+
+    fn try_from(term: Term<'a>) -> Result<Self, Self::Error> {
+        if term.is_ref() {
+            Ok(Reference(term))
+        } else {
+            Err(Error::BadArg)
+        }
+    }
+}
+
+impl<'a> Decoder<'a> for Reference<'a> {
+    fn decode(term: Term<'a>) -> NifResult<Self> {
+        term.try_into()
+    }
+}
+
+impl<'a> Encoder for Reference<'a> {
+    fn encode<'b>(&self, env: Env<'b>) -> Term<'b> {
+        self.0.encode(env)
+    }
+}
+
+impl<'a> Env<'a> {
+    pub fn make_ref(self) -> Reference<'a> {
+        unsafe { Reference(Term::new(self, enif_make_ref(self.as_c_arg()))) }
+    }
+}
diff --git a/rustler_tests/lib/rustler_test.ex b/rustler_tests/lib/rustler_test.ex
index b2c2232f..bfebade6 100644
--- a/rustler_tests/lib/rustler_test.ex
+++ b/rustler_tests/lib/rustler_test.ex
@@ -103,6 +103,7 @@ defmodule RustlerTest do
   def whereis_pid(_), do: err()
   def is_process_alive(_), do: err()
   def sublists(_), do: err()
+  def make_refs(), do: err()
 
   def tuple_echo(_), do: err()
   def record_echo(_), do: err()
diff --git a/rustler_tests/native/rustler_test/src/test_env.rs b/rustler_tests/native/rustler_test/src/test_env.rs
index 06dd63d6..99f9da4f 100644
--- a/rustler_tests/native/rustler_test/src/test_env.rs
+++ b/rustler_tests/native/rustler_test/src/test_env.rs
@@ -2,7 +2,7 @@ use rustler::env::{OwnedEnv, SavedTerm, SendError};
 use rustler::types::atom;
 use rustler::types::list::ListIterator;
 use rustler::types::LocalPid;
-use rustler::{Atom, Encoder, Env, NifResult, Term};
+use rustler::{Atom, Encoder, Env, NifResult, Reference, Term};
 use std::thread;
 
 // Send a message to several PIDs.
@@ -84,3 +84,10 @@ pub fn sublists<'a>(env: Env<'a>, list: Term<'a>) -> NifResult<Atom> {
 
     Ok(atom::ok())
 }
+
+#[rustler::nif]
+fn make_refs<'a>(env: Env<'a>) -> (bool, Reference<'a>, Reference<'a>) {
+    let first = env.make_ref();
+    let second = env.make_ref();
+    (first != second, first, second)
+}
diff --git a/rustler_tests/test/env_test.exs b/rustler_tests/test/env_test.exs
index 29c06acc..6e016bbd 100644
--- a/rustler_tests/test/env_test.exs
+++ b/rustler_tests/test/env_test.exs
@@ -104,4 +104,13 @@ defmodule RustlerTest.EnvTest do
     assert :error == RustlerTest.send(task.pid, :msg)
     assert :error == RustlerTest.send(task.pid, :msg)
   end
+
+  test "make_ref" do
+    {different, ref1, ref2} = RustlerTest.make_refs()
+
+    assert different
+    assert is_reference(ref1)
+    assert is_reference(ref2)
+    assert ref1 != ref2
+  end
 end