From 7358bb6777d1f3d110882c3cd54caa7ea5713c4a Mon Sep 17 00:00:00 2001
From: Benedikt Reinartz <filmor@gmail.com>
Date: Mon, 11 Mar 2024 23:18:10 +0100
Subject: [PATCH] Add `Env::is_process_alive` and `LocalPid::is_alive`

---
 rustler/src/types/local_pid.rs                 | 11 +++++++++++
 rustler_tests/lib/rustler_test.ex              |  1 +
 rustler_tests/native/rustler_test/src/lib.rs   |  1 +
 .../native/rustler_test/src/test_env.rs        | 10 +++++++---
 rustler_tests/test/env_test.exs                | 18 ++++++++++++++++++
 5 files changed, 38 insertions(+), 3 deletions(-)

diff --git a/rustler/src/types/local_pid.rs b/rustler/src/types/local_pid.rs
index 437569ae..9babda8b 100644
--- a/rustler/src/types/local_pid.rs
+++ b/rustler/src/types/local_pid.rs
@@ -15,6 +15,11 @@ impl LocalPid {
     pub fn from_c_arg(erl_nif_pid: ErlNifPid) -> Self {
         LocalPid { c: erl_nif_pid }
     }
+
+    /// Check whether the given process is alive
+    pub fn is_alive(self, env: Env) -> bool {
+        env.is_process_alive(self)
+    }
 }
 
 impl<'a> Decoder<'a> for LocalPid {
@@ -48,4 +53,10 @@ impl<'a> Env<'a> {
             c: unsafe { pid.assume_init() },
         }
     }
+
+    /// Checks whether the given process is alive
+    pub fn is_process_alive(self, pid: LocalPid) -> bool {
+        let res = unsafe { rustler_sys::enif_is_process_alive(self.as_c_arg(), pid.as_c_arg()) };
+        res != 0
+    }
 }
diff --git a/rustler_tests/lib/rustler_test.ex b/rustler_tests/lib/rustler_test.ex
index ce63a45d..9a7c9b63 100644
--- a/rustler_tests/lib/rustler_test.ex
+++ b/rustler_tests/lib/rustler_test.ex
@@ -87,6 +87,7 @@ defmodule RustlerTest do
   def send_all(_, _), do: err()
   def send(_, _), do: err()
   def whereis_pid(_), do: err()
+  def is_process_alive(_), do: err()
   def sublists(_), do: err()
 
   def tuple_echo(_), do: err()
diff --git a/rustler_tests/native/rustler_test/src/lib.rs b/rustler_tests/native/rustler_test/src/lib.rs
index a7a4f700..594da3d1 100644
--- a/rustler_tests/native/rustler_test/src/lib.rs
+++ b/rustler_tests/native/rustler_test/src/lib.rs
@@ -63,6 +63,7 @@ rustler::init!(
         test_env::send_all,
         test_env::send,
         test_env::whereis_pid,
+        test_env::is_process_alive,
         test_env::sublists,
         test_codegen::tuple_echo,
         test_codegen::record_echo,
diff --git a/rustler_tests/native/rustler_test/src/test_env.rs b/rustler_tests/native/rustler_test/src/test_env.rs
index c50b31e8..06dd63d6 100644
--- a/rustler_tests/native/rustler_test/src/test_env.rs
+++ b/rustler_tests/native/rustler_test/src/test_env.rs
@@ -24,9 +24,13 @@ pub fn send<'a>(env: Env<'a>, pid: LocalPid, msg: Term<'a>) -> Atom {
 }
 
 #[rustler::nif]
-pub fn whereis_pid<'a>(env: Env<'a>, term: Term<'a>) -> Term<'a> {
-    let result = env.whereis_pid(term);
-    result.encode(env)
+pub fn whereis_pid<'a>(env: Env<'a>, term: Term<'a>) -> Option<LocalPid> {
+    env.whereis_pid(term)
+}
+
+#[rustler::nif]
+pub fn is_process_alive(env: Env, pid: LocalPid) -> bool {
+    env.is_process_alive(pid)
 }
 
 #[rustler::nif]
diff --git a/rustler_tests/test/env_test.exs b/rustler_tests/test/env_test.exs
index d0f16e0b..972f096e 100644
--- a/rustler_tests/test/env_test.exs
+++ b/rustler_tests/test/env_test.exs
@@ -68,6 +68,24 @@ defmodule RustlerTest.EnvTest do
     assert nil == RustlerTest.whereis_pid(:not_a_registered_name)
   end
 
+  test "is_process_alive" do
+    assert true == RustlerTest.is_process_alive(self())
+
+    task =
+      Task.async(fn ->
+        receive do
+          :exit -> :ok
+        end
+      end)
+
+    assert true == RustlerTest.is_process_alive(task.pid)
+
+    send(task.pid, :exit)
+    Task.await(task)
+    
+    assert false == RustlerTest.is_process_alive(task.pid)
+  end
+
   test "send_error" do
     task =
       Task.async(fn ->