re-write CLI argument parsing for testability

tools/cliutil.h

@@ -0,0 +1,58 @@
+/**
+ * Copyright - See the COPYRIGHT that is included with this distribution.
+ * pvxs is distributed subject to a Software License Agreement found
+ * in file LICENSE that is included with this distribution.
+ */
+
+#ifndef CLIUTIL_H
+#define CLIUTIL_H
+
+#include <vector>
+#include <string>
+#include <stdexcept>
+#include <map> // for std::pair
+
+#include <utilpvt.h>
+
+namespace pvxs {
+
+struct ArgVal {
+    std::string value;
+    bool defined = false;
+
+    ArgVal() = default;
+    ArgVal(std::nullptr_t) {}
+    ArgVal(const std::string& value) :value(value), defined(true) {}
+    ArgVal(const char* value) :value(value), defined(true) {}
+
+    inline explicit
+    operator bool() const { return defined; }
+
+    inline
+    const std::string& operator*() const {
+        if(defined)
+            return value;
+        throw std::logic_error("Undefined argument value");
+    }
+
+    template<typename V>
+    inline
+    V as() const {
+        return parseTo<V>(**this);
+    }
+};
+
+bool operator==(const ArgVal& rhs, const ArgVal& lhs);
+
+struct GetOpt {
+    GetOpt(int argc, char *argv[], const char *spec);
+
+    const char *argv0;
+    std::vector<std::string> positional;
+    std::vector<std::pair<char, ArgVal>> arguments;
+    bool success = false;
+};
+
+} // namespace pvxs
+
+#endif // CLIUTIL_H