From a2d7181700ac64b8e7a4472ec26dfa253b38f188 Mon Sep 17 00:00:00 2001
From: Lexi Winter <lexi@le-fay.org>
Date: Sat, 28 Jun 2025 19:25:55 +0100
Subject: split nihil into separate modules

---
 nihil.guard/guard.ccm | 51 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 51 insertions(+)
 create mode 100644 nihil.guard/guard.ccm

(limited to 'nihil.guard/guard.ccm')

diff --git a/nihil.guard/guard.ccm b/nihil.guard/guard.ccm
new file mode 100644
index 0000000..c586a20
--- /dev/null
+++ b/nihil.guard/guard.ccm
@@ -0,0 +1,51 @@
+/*
+ * This source code is released into the public domain.
+ */
+
+module;
+
+#include <concepts>
+#include <functional>
+#include <optional>
+#include <utility>
+
+export module nihil.guard;
+
+namespace nihil {
+
+/*
+ * guard: invoke a callable when this object is destroyed; this is similar to
+ * scope_exit from the library fundamentals TS, which LLVM doesn't implement.
+ */
+export template<std::invocable F>
+struct guard final {
+	// Initialise the guard with a callable we will invoke later.
+	guard(F func) : m_func(std::move(func)) {}
+
+	/*
+	 * We are being destroyed, so call the callable.
+	 * If the callable throws, std::terminate() will be called.
+	 */
+	~guard() {
+		if (m_func)
+			std::invoke(*m_func);
+	}
+
+	// Release the guard.  This turns the destructor into a no-op.
+	void release() noexcept {
+		m_func.reset();
+	}
+
+	// Not default-constructible, movable or copyable.
+	guard() = delete;
+	guard(guard const &) = delete;
+	guard(guard &&) noexcept = delete;
+	guard &operator=(guard const &) = delete;
+	guard &operator=(guard &&) noexcept = delete;
+
+private:
+	// The callable to be invoked when we are destroyed.
+	std::optional<F> m_func;
+};
+
+} // namespace nihil
-- 
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