From eb957de7f539c3f06df10028f09a58c4017ba4f0 Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Wed, 19 Feb 2020 23:42:04 +0000
Subject: Add Handle, like unique_ptr but for non-pointers

---
 libadhocutil/handle.h                 | 88 +++++++++++++++++++++++++++++++++++
 libadhocutil/unittests/Jamfile.jam    |  8 ++++
 libadhocutil/unittests/testHandle.cpp | 60 ++++++++++++++++++++++++
 3 files changed, 156 insertions(+)
 create mode 100644 libadhocutil/handle.h
 create mode 100644 libadhocutil/unittests/testHandle.cpp

diff --git a/libadhocutil/handle.h b/libadhocutil/handle.h
new file mode 100644
index 0000000..7363183
--- /dev/null
+++ b/libadhocutil/handle.h
@@ -0,0 +1,88 @@
+#ifndef ADHOCUTIL_HANDLE_H
+#define ADHOCUTIL_HANDLE_H
+
+#include <utility>
+#include "c++11Helpers.h"
+
+namespace AdHoc {
+	/// A unique_ptr like construct for non-pointer objects.
+	/// Implements RAII.
+	template<typename T, typename D>
+	class Handle {
+		public:
+			/// Constructs a Handle that owns t, to be tidied with d
+			Handle(T t, D d) noexcept :
+				inst(std::move(t)),
+				deleter(std::move(d)),
+				owning(true)
+			{
+			}
+
+			/// Constructs a Handle that takes over ownership of h
+			Handle(Handle && h) noexcept :
+				inst(std::move(h.inst)),
+				deleter(std::move(h.deleter)),
+				owning(h.owning)
+			{
+				h.owning = false;
+			}
+
+			~Handle()
+			{
+				if (owning) {
+					deleter(inst);
+				}
+			}
+
+			/// Standard special members
+			SPECIAL_MEMBERS_COPY(Handle, delete);
+
+			/// Takes over ownership of h
+			Handle & operator=(Handle && h) noexcept
+			{
+				if (owning) {
+					deleter(inst);
+				}
+				inst = std::move(h.inst);
+				deleter = std::move(h.deleter);
+				owning = h.owning;
+				h.owning = false;
+			}
+
+			/// Returns a reference to the managed object.
+			[[nodiscard]] T & get() noexcept { return inst; }
+			/// Returns a const reference to the managed object.
+			[[nodiscard]] const T & get() const noexcept { return inst; }
+
+			/// Returns a pointer to the managed object.
+			[[nodiscard]] T * operator->() noexcept { return inst; }
+			/// Returns a const pointer to the managed object.
+			[[nodiscard]] const T * operator->() const noexcept { return inst; }
+
+			/// Returns a reference to the managed object.
+			[[nodiscard]] T & operator*() noexcept { return inst; }
+			/// Returns a const reference to the managed object.
+			[[nodiscard]] const T & operator*() const noexcept { return inst; }
+
+			/// Returns a reference to the managed object.
+			// NOLINTNEXTLINE(hicpp-explicit-conversions)
+			operator T &() noexcept { return inst; }
+			/// Returns a const reference to the managed object.
+			// NOLINTNEXTLINE(hicpp-explicit-conversions)
+			operator const T &() const noexcept { return inst; }
+
+		private:
+			T inst;
+			D deleter;
+			bool owning;
+	};
+
+	template<typename T, typename D, typename... Args>
+	Handle<T, D> make_handle(D && d, Args && ... args)
+	{
+		return { T(std::forward<Args>(args)...), std::forward<D>(d) };
+	}
+}
+
+#endif
+
diff --git a/libadhocutil/unittests/Jamfile.jam b/libadhocutil/unittests/Jamfile.jam
index 642ff9b..d62f6da 100644
--- a/libadhocutil/unittests/Jamfile.jam
+++ b/libadhocutil/unittests/Jamfile.jam
@@ -304,3 +304,11 @@ run
 	<library>boost_utf
 	;
 
+run
+	testHandle.cpp
+	: : :
+	<define>BOOST_TEST_DYN_LINK
+	<library>..//adhocutil
+	<library>boost_utf
+	;
+
diff --git a/libadhocutil/unittests/testHandle.cpp b/libadhocutil/unittests/testHandle.cpp
new file mode 100644
index 0000000..e7f52af
--- /dev/null
+++ b/libadhocutil/unittests/testHandle.cpp
@@ -0,0 +1,60 @@
+#define BOOST_TEST_MODULE Handle
+#include <boost/test/unit_test.hpp>
+
+#include <type_traits>
+#include <fcntl.h>
+#include "handle.h"
+
+// Test case base on a file handle
+using T = decltype(STDIN_FILENO);
+using D = decltype(&close);
+static_assert(std::is_trivially_move_constructible_v<T>);
+static_assert(std::is_trivially_move_constructible_v<D>);
+
+using TestHandle = AdHoc::Handle<T, D>;
+
+static_assert(std::is_nothrow_move_constructible_v<TestHandle>);
+static_assert(std::is_nothrow_move_assignable_v<TestHandle>);
+static_assert(!std::is_copy_constructible_v<TestHandle>);
+static_assert(!std::is_copy_assignable_v<TestHandle>);
+
+BOOST_AUTO_TEST_CASE(values)
+{
+	TestHandle th { open("/dev/null", O_RDWR), &close };
+	static_assert(std::is_same_v<T, std::remove_reference_t<decltype(th.get())>>);
+	static_assert(std::is_same_v<T, std::remove_reference_t<decltype(*th)>>);
+	BOOST_REQUIRE_EQUAL(1, write(th, "1", 1));
+}
+
+BOOST_AUTO_TEST_CASE(values_const)
+{
+	const TestHandle cth { open("/dev/null", O_RDWR), &close };
+	static_assert(std::is_same_v<const T, std::remove_reference_t<decltype(cth.get())>>);
+	static_assert(std::is_same_v<const T, std::remove_reference_t<decltype(*cth)>>);
+	BOOST_REQUIRE_EQUAL(1, write(cth, "1", 1));
+}
+
+BOOST_AUTO_TEST_CASE(make)
+{
+	bool closed = false;
+	int fd = -2;
+	const auto doClose = [&](T lfd) {
+		BOOST_CHECK(!closed);
+		BOOST_CHECK_EQUAL(lfd, fd);
+		closed = true;
+		return close(lfd);
+	};
+	{
+		auto th = AdHoc::make_handle<T>(doClose, open("/dev/null", O_RDWR));
+		BOOST_REQUIRE(!closed);
+		BOOST_REQUIRE_EQUAL(1, write(th, "1", 1));
+		auto th2 = std::move(th);
+		BOOST_REQUIRE(!closed);
+		BOOST_REQUIRE_EQUAL(1, write(th2, "1", 1));
+		fd = th2;
+	}
+	BOOST_REQUIRE(closed);
+	BOOST_REQUIRE_EQUAL(-1, write(fd, "1", 1));
+	BOOST_REQUIRE_EQUAL(errno, EBADF);
+}
+
-- 
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