From be6c84ee7492cd713c280e7944d94a720cf16d22 Mon Sep 17 00:00:00 2001
From: Peter M <petermm@gmail.com>
Date: Sun, 22 Sep 2024 21:51:43 +0200
Subject: [PATCH] System.ex monotonic_time/1 system_time/1

Carbon copy from elixir with :native time unit removed, as it's not supported by current erlang implementation.

Signed-off-by: Peter M <petermm@gmail.com>
---
 libs/exavmlib/lib/CMakeLists.txt |  1 +
 libs/exavmlib/lib/System.ex      | 50 ++++++++++++++++++++++++++++++++
 2 files changed, 51 insertions(+)
 create mode 100644 libs/exavmlib/lib/System.ex

diff --git a/libs/exavmlib/lib/CMakeLists.txt b/libs/exavmlib/lib/CMakeLists.txt
index 70749cfef..80c33f9b0 100644
--- a/libs/exavmlib/lib/CMakeLists.txt
+++ b/libs/exavmlib/lib/CMakeLists.txt
@@ -49,6 +49,7 @@ set(ELIXIR_MODULES
     Process
     Protocol.UndefinedError
     Range
+    System
     Tuple
 
     ArithmeticError
diff --git a/libs/exavmlib/lib/System.ex b/libs/exavmlib/lib/System.ex
new file mode 100644
index 000000000..97f64eb61
--- /dev/null
+++ b/libs/exavmlib/lib/System.ex
@@ -0,0 +1,50 @@
+#
+# This file is part of elixir-lang.
+#
+# Copyright 2012-2024 Elixir Contributors
+# https://github.com/elixir-lang/elixir/blob/v1.17/lib/elixir/lib/system.ex
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+
+defmodule System do
+  @type time_unit ::
+          :second
+          | :millisecond
+          | :microsecond
+
+  @doc """
+  Returns the current monotonic time in the given time unit.
+
+  This time is monotonically increasing and starts in an unspecified
+  point in time.
+  """
+  @spec monotonic_time(time_unit) :: integer
+  def monotonic_time(unit) do
+    :erlang.monotonic_time(unit)
+  end
+
+  @doc """
+  Returns the current system time in the given time unit.
+
+  It is the VM view of the `os_time/0`. They may not match in
+  case of time warps although the VM works towards aligning
+  them. This time is not monotonic.
+  """
+  @spec system_time(time_unit) :: integer
+  def system_time(unit) do
+    :erlang.system_time(unit)
+  end
+end