From 5d9ffddfe118c9f2356a79df63cc2019cdcb16f8 Mon Sep 17 00:00:00 2001
From: Borislav Stanimirov <b.stanimirov@abv.bg>
Date: Tue, 16 Jul 2024 19:30:23 +0300
Subject: [PATCH] new library: generator, wip

---
 include/itlib/generator.hpp | 125 ++++++++++++++++++++++++++++++++++++
 test/CMakeLists.txt         |   8 ++-
 test/t-generator-20.cpp     |   5 ++
 3 files changed, 136 insertions(+), 2 deletions(-)
 create mode 100644 include/itlib/generator.hpp
 create mode 100644 test/t-generator-20.cpp

diff --git a/include/itlib/generator.hpp b/include/itlib/generator.hpp
new file mode 100644
index 0000000..fc08b90
--- /dev/null
+++ b/include/itlib/generator.hpp
@@ -0,0 +1,125 @@
+// itlib-generator v1.00
+//
+// Simple coroutine generator class for C++20 and later
+//
+// SPDX-License-Identifier: MIT
+// MIT License:
+// Copyright(c) 2024 Borislav Stanimirov
+//
+// Permission is hereby granted, free of charge, to any person obtaining
+// a copy of this software and associated documentation files(the
+// "Software"), to deal in the Software without restriction, including
+// without limitation the rights to use, copy, modify, merge, publish,
+// distribute, sublicense, and / or sell copies of the Software, and to
+// permit persons to whom the Software is furnished to do so, subject to
+// the following conditions :
+//
+// The above copyright notice and this permission notice shall be
+// included in all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+// NONINFRINGEMENT.IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+//
+//
+//                  VERSION HISTORY
+//
+//  1.00 (2024-07-xx) Initial release
+//
+//
+//                  DOCUMENTATION
+//
+// Simply include this file wherever you need.
+// It defines the class generator which allows you to write simple coroutine-
+// based generators.
+//
+// Example:
+//
+// itlib::generator<int> range(int begin, int end) {
+//     for (int i = begin; i < end; ++i) {
+//        co_yield i;
+//     }
+// }
+// ...
+// for (int i : range(0, 10)) {
+//    std::cout << i << std::endl;
+// }
+//
+//                  TESTS
+//
+// You can find unit tests in the official repo:
+// https://github.com/iboB/itlib/blob/master/test/
+//
+#pragma once
+#include <coroutine>
+#include <type_traits>
+#include <optional>
+
+namespace itlib {
+
+namespace genimpl {
+// tempting to include expected here so we could have optional of ref and
+// ditch the T& specialization
+// ... but we promised to make standalone libs
+
+template <typename T>
+class val_holder : public std::optional<T> {};
+
+template <typename T>
+class val_holder<T&> {
+    T* val = nullptr;
+public:
+    void emplace(T& v) noexcept { val = &v; }
+    void reset() noexcept { val = nullptr; }
+    T& operator*() noexcept { return *val; }
+    bool has_value() const noexcept { return val != nullptr; }
+    explicit operator bool() const noexcept { return has_value(); }
+};
+
+} // namespace genimpl
+
+template <typename T>
+class generator {
+public:
+    using value_ret_t = std::conditional_t<std::is_reference_v<T>, T, const T&>;
+
+    class promise_type {
+        genimpl::val_holder<T> m_val;
+    public:
+        promise_type() noexcept = default;
+
+        ~promise_type() = default;
+        generator get_return_object() noexcept {
+            return generator{std::coroutine_handle<promise_type>::from_promise(*this)};
+        }
+        std::suspend_always initial_suspend() noexcept { return {}; }
+        std::suspend_always final_suspend() noexcept { return {}; }
+        std::suspend_always yield_value(T value) noexcept { // assume T is noexcept move constructible
+            m_val = std::move(value);
+            return {};
+        }
+        void return_void() noexcept {}
+        void unhandled_exception() { throw; }
+
+        value_ret_t val() const noexcept {
+            return *m_val;
+        }
+    };
+
+    ~generator() {
+        if (m_handle) m_handle.destroy();
+    }
+
+    // std::optional interface
+    genimpl::val_holder<T> next() {}
+private:
+    using handle_t = std::coroutine_handle<promise_type>;
+    handle_t m_handle;
+    explicit generator(handle_t handle) noexcept : m_handle(handle) {}
+};
+
+} // namespace itlib
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index a09435c..916732f 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -1,9 +1,12 @@
+# Copyright (c) Borislav Stanimirov
+# SPDX-License-Identifier: MIT
+#
 cmake_minimum_required(VERSION 3.16 FATAL_ERROR)
 
 include(./get_cpm.cmake)
 
-CPMAddPackage(gh:iboB/icm@1.4.4)
-CPMAddPackage(gh:iboB/doctest-util@0.1.1)
+CPMAddPackage(gh:iboB/icm@1.5.1)
+CPMAddPackage(gh:iboB/doctest-util@0.1.2)
 
 include(${icm_SOURCE_DIR}/icm_build_failure_testing.cmake)
 
@@ -58,6 +61,7 @@ add_itlib_test(dynamic_bitset)
 add_itlib_test(expected)
 add_itlib_test(flat_map)
 add_itlib_test(flat_set)
+add_itlib_test(generator)
 add_itlib_test(make_ptr)
 add_itlib_test(memory_view)
 add_itlib_test(mem_streambuf)
diff --git a/test/t-generator-20.cpp b/test/t-generator-20.cpp
new file mode 100644
index 0000000..f12f8f1
--- /dev/null
+++ b/test/t-generator-20.cpp
@@ -0,0 +1,5 @@
+// Copyright (c) Borislav Stanimirov
+// SPDX-License-Identifier: MIT
+//
+#include <itlib/generator.hpp>
+#include <doctest/doctest.h>
\ No newline at end of file