1 files changed, 47 insertions, 0 deletions
diff --git a/modules/getenv.ccm b/modules/getenv.ccm
new file mode 100644
index 0000000..7397b79
--- /dev/null
+++ b/modules/getenv.ccm
@@ -0,0 +1,47 @@
+/*
+ * This source code is released into the public domain.
+ */
+
+module;
+
+#include <cstdint>
+#include <expected>
+#include <string>
+#include <system_error>
+#include <vector>
+
+#include <unistd.h>
+
+export module nihil:getenv;
+
+namespace nihil {
+
+/*
+ * Find a variable by the given name in the environment by calling getenv_r().
+ */
+
+export auto getenv(std::string_view varname)
+	-> std::expected<std::string, std::error_code>
+{
+	// Start with a buffer of this size, and double it every iteration.
+	constexpr auto bufinc = std::size_t{1024};
+
+	auto cvarname = std::string(varname);
+	auto buf = std::vector<char>(bufinc);
+	for (;;) {
+		auto const ret = ::getenv_r(cvarname.c_str(),
+					    buf.data(), buf.size());
+
+		if (ret == 0)
+			return {std::string(buf.data())};
+
+		if (ret == -1 && errno == ERANGE) {
+			buf.resize(buf.size() * 2);
+			continue;
+		}
+
+		return std::unexpected(std::make_error_code(std::errc(errno)));
+	}
+}
+
+} // namespace nihil