1 files changed, 45 insertions, 0 deletions
diff --git a/nihil.posix/posix.getenv.cc b/nihil.posix/posix.getenv.cc
new file mode 100644
index 0000000..36df950
--- /dev/null
+++ b/nihil.posix/posix.getenv.cc
@@ -0,0 +1,45 @@
+
+/*
+ * This source code is released into the public domain.
+ */
+
+module;
+
+#include <cstdint>
+#include <expected>
+#include <string>
+#include <system_error>
+#include <vector>
+
+#include <unistd.h>
+
+module nihil.posix;
+
+import nihil.error;
+
+namespace nihil {
+
+auto getenv(std::string_view varname) -> std::expected<std::string, error>
+{
+	// 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(error(std::errc(errno)));
+	}
+}
+
+} // namespace nihil