1 files changed, 107 insertions, 0 deletions
diff --git a/nihil/argv.ccm b/nihil/argv.ccm
new file mode 100644
index 0000000..a9c254e
--- /dev/null
+++ b/nihil/argv.ccm
@@ -0,0 +1,107 @@
+/*
+ * This source code is released into the public domain.
+ */
+
+module;
+
+#include <memory>
+#include <ranges>
+#include <string>
+#include <vector>
+
+export module nihil:argv;
+
+namespace nihil {
+
+/*
+ * argv: stores a null-terminated array of nul-terminated C strings.
+ * argv::data() is suitable for passing to ::execv().
+ *
+ * Create an argv using argv::from_range(), which takes a range of
+ * string-like objects.
+ */
+
+export struct argv {
+	/*
+	 * Create a new argv from a range.
+	 */
+	static auto from_range(std::ranges::range auto &&args) -> argv
+	{
+		auto ret = argv{};
+
+		for (auto &&arg : args)
+			ret._add_arg(std::string_view(arg));
+
+		ret._args.push_back(nullptr);
+		return ret;
+	}
+
+	template<typename T>
+	static auto from_args(std::initializer_list<T> &&args)
+	{
+		return from_range(std::move(args));
+	}
+
+	argv(argv &&) noexcept = default;
+	auto operator=(this argv &, argv &&other) -> argv& = default;
+
+	// Not copyable.  TODO: for completeness, it probably should be.
+	argv(argv const &) = delete;
+	auto operator=(this argv &, argv const &other) -> argv& = delete;
+
+	~argv()
+	{
+		for (auto *arg : _args)
+			delete[] arg;
+	}
+
+	// Access the stored arguments.
+	auto data(this argv const &self) -> char const * const *
+	{
+		return self._args.data();
+	}
+
+	auto data(this argv &self) -> char * const *
+	{
+		return self._args.data();
+	}
+
+	auto size(this argv const &self)
+	{
+		return self._args.size();
+	}
+
+	// Range access
+	auto begin(this argv const &self)
+	{
+		return self._args.begin();
+	}
+
+	auto end(this argv const &self)
+	{
+		return self._args.end();
+	}
+
+private:
+	// Use the from_range() factory method to create new instances.
+	argv() = default;
+
+	// The argument pointers, including the null terminator.
+	std::vector<char *> _args;
+
+	// Add a new argument to the array.
+	auto _add_arg(this argv &self, std::string_view arg) -> void
+	{
+		// Create a nul-terminated C string.
+		auto ptr = std::make_unique<char[]>(arg.size() + 1);
+		std::ranges::copy(arg, ptr.get());
+		ptr[arg.size()] = '\0';
+
+		// Ensure we won't throw when emplacing the pointer.
+		self._args.reserve(self._args.size() + 1);
+		self._args.emplace_back(ptr.release());
+	}
+};
+
+} // namespace nihil
+