Add vehicle graph core: .vhg loader, logic and cab blocks, -graph-run and -graph-catalog

vehicle/graph/graph_format.h

@@ -0,0 +1,58 @@
+/*
+This Source Code Form is subject to the
+terms of the Mozilla Public License, v.
+2.0. If a copy of the MPL was not
+distributed with this file, You can
+obtain one at
+http://mozilla.org/MPL/2.0/.
+*/
+
+#pragma once
+
+#include "vehicle/graph/graph_types.h"
+
+#include <string>
+#include <string_view>
+#include <utility>
+#include <vector>
+
+namespace vgraph
+{
+
+using named_value = std::pair<std::string, param_value>;
+
+struct node_desc
+{
+	std::string id;
+	std::string type;
+	std::string title;
+	std::vector<named_value> params; // as stored in the file; checked against the catalog when the graph is compiled
+};
+
+struct connection_desc
+{
+	std::string from_node;
+	std::string from_port;
+	std::string to_node;
+	std::string to_port;
+};
+
+// content of a .vhg file, before it's checked against the block catalog
+struct document
+{
+	std::string name;
+	// when enabled, blocks with low voltage ports simulate the voltages and currents of the control circuits.
+	// when disabled, low voltage connections are ignored and the apparatus behaves as if always powered
+	bool low_voltage_simulation{false};
+	std::vector<named_value> body; // parameters of the vehicle body (mass, dimensions, axles...); used by the simulator integration
+	std::vector<std::pair<std::string, int>> profiles; // standard interfaces used by the vehicle, with their versions
+	std::vector<node_desc> nodes;
+	std::vector<connection_desc> connections;
+};
+
+// parses the content of a .vhg file. problems are appended to the diagnostics; returns false on errors
+bool parse_document(std::string const &Text, document &Document, std::vector<diagnostic> &Diagnostics);
+// reads and parses the specified .vhg file
+bool load_document(std::string const &Path, document &Document, std::vector<diagnostic> &Diagnostics);
+
+} // namespace vgraph