Factors string serialisation with \n\r conversion out of the Apple II and reuses it with the Oric.

Machines/Utility/StringSerialiser.cpp

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+//
+//  StringSerialiser.cpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 13/05/2018.
+//  Copyright © 2018 Thomas Harte. All rights reserved.
+//
+
+#include "StringSerialiser.hpp"
+
+using namespace Utility;
+
+StringSerialiser::StringSerialiser(const std::string &source, bool use_linefeed_only) {
+	if(!use_linefeed_only) {
+		input_string_ = source;
+	} else {
+		input_string_.reserve(source.size());
+
+		// Commute any \ns that are not immediately after \rs to \rs; remove the rest.
+		bool saw_carriage_return = false;
+		for(auto character: source) {
+			if(character != '\n') {
+				input_string_.push_back(character);
+			} else {
+				if(!saw_carriage_return) {
+					input_string_.push_back('\r');
+				}
+			}
+			saw_carriage_return = character == '\r';
+		}
+	}
+}
+
+uint8_t StringSerialiser::head() {
+	if(input_string_pointer_ == input_string_.size())
+		return '\0';
+	return static_cast<uint8_t>(input_string_[input_string_pointer_]);
+}
+
+bool StringSerialiser::advance() {
+	if(input_string_pointer_ != input_string_.size()) {
+		++input_string_pointer_;
+		return input_string_pointer_ != input_string_.size();
+	}
+	return false;
+}