contracts: add EmptyConstructor contract

contracts/Cargo.toml

@@ -7,6 +7,7 @@ members = [
     "counter",
     "debugger",
     "double_counter",
+    "empty_constructor",
     "eventer",
     "everest",
     "fallible_counter",

contracts/empty_constructor/Cargo.toml

@@ -0,0 +1,15 @@
+[package]
+name = "empty_constructor"
+version = "0.1.0"
+authors = [
+    "Eduardo Leegwater Simões <[email protected]>",
+]
+edition = "2021"
+
+license = "MPL-2.0"
+
+[dependencies]
+piecrust-uplink = { path = "../../piecrust-uplink", features = ["abi", "dlmalloc"] }
+
+[lib]
+crate-type = ["cdylib", "rlib"]

contracts/empty_constructor/src/lib.rs

@@ -0,0 +1,56 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+//
+// Copyright (c) DUSK NETWORK. All rights reserved.
+
+//! Contract that provides and example use of the constructor.
+
+#![no_std]
+
+use piecrust_uplink as uplink;
+
+/// Struct that describes the state of the Constructor contract
+pub struct EmptyConstructor {
+    value: u8,
+}
+
+impl EmptyConstructor {
+    pub fn init(&mut self) {
+        self.value = 0x10;
+    }
+}
+
+/// State of the EmptyConstructor contract
+static mut STATE: EmptyConstructor = EmptyConstructor { value: 0x00 };
+
+impl EmptyConstructor {
+    /// Read the value of the constructor contract state
+    pub fn read_value(&self) -> u8 {
+        self.value
+    }
+
+    /// Increment the value  by 1
+    pub fn increment(&mut self) {
+        let value = self.value + 1;
+        self.value = value;
+    }
+}
+
+/// Expose `EmptyConstructor::read_value()` to the host
+#[no_mangle]
+unsafe fn read_value(arg_len: u32) -> u32 {
+    uplink::wrap_call(arg_len, |_: ()| STATE.read_value())
+}
+
+/// Expose `EmptyConstructor::increment()` to the host
+#[no_mangle]
+unsafe fn increment(arg_len: u32) -> u32 {
+    uplink::wrap_call(arg_len, |_: ()| STATE.increment())
+}
+
+/// Expose `EmptyConstructor::init()` to the host
+#[no_mangle]
+unsafe fn init(arg_len: u32) -> u32 {
+    uplink::wrap_call(arg_len, |()| STATE.init())
+}