ircd::util: Start an env var convenience suite.

include/ircd/util/env.h

@@ -0,0 +1,38 @@
+// Matrix Construct
+//
+// Copyright (C) Matrix Construct Developers, Authors & Contributors
+// Copyright (C) 2016-2018 Jason Volk <jason@zemos.net>
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice is present in all copies. The
+// full license for this software is available in the LICENSE file.
+
+#pragma once
+#define HAVE_IRCD_UTIL_ENV_H
+
+namespace ircd::util
+{
+	string_view getenv(const string_view &);
+}
+
+inline ircd::string_view
+ircd::util::getenv(const string_view &key)
+{
+	if(unlikely(size(key) > 127))
+		throw std::runtime_error
+		{
+			"getenv(): variable key is too long."
+		};
+
+	// Ensure the key is null terminated for the std:: call.
+	char keystr[128];
+	const size_t len{copy(keystr, key)};
+	keystr[std::min(len, sizeof(keystr) - 1)] = '\0';
+	const string_view var
+	{
+		std::getenv(keystr)
+	};
+
+	return var;
+}

include/ircd/util/util.h

@@ -36,6 +36,7 @@ namespace ircd
 #include "reentrance.h"
 #include "enum.h"
 #include "syscall.h"
+#include "env.h"
 #include "va_rtti.h"
 #include "unique_iterator.h"
 #include "instance_list.h"