cam: Add a parser for capture scripts

Add a parser class to the cam test application to control the capture
operations through a yaml script.

The capture script currently allow to specify a list of controls and
their associated values to be applied per-frame.

Also add a trivial capture script example to showcase the intended
script structure.

Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>

src/cam/capture_script.h

@@ -0,0 +1,62 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Copyright (C) 2022, Ideas on Board Oy
+ *
+ * capture_script.h - Capture session configuration script
+ */
+
+#pragma once
+
+#include <map>
+#include <memory>
+#include <string>
+
+#include <libcamera/camera.h>
+#include <libcamera/controls.h>
+
+#include <yaml.h>
+
+class CaptureScript
+{
+public:
+	CaptureScript(std::shared_ptr<libcamera::Camera> camera,
+		      const std::string &fileName);
+
+	bool valid() const { return valid_; }
+
+	const libcamera::ControlList &frameControls(unsigned int frame);
+
+private:
+	struct EventDeleter {
+		void operator()(yaml_event_t *event) const
+		{
+			yaml_event_delete(event);
+			delete event;
+		}
+	};
+	using EventPtr = std::unique_ptr<yaml_event_t, EventDeleter>;
+
+	std::map<std::string, const libcamera::ControlId *> controls_;
+	std::map<unsigned int, libcamera::ControlList> frameControls_;
+	std::shared_ptr<libcamera::Camera> camera_;
+	yaml_parser_t parser_;
+	bool valid_;
+
+	EventPtr nextEvent(yaml_event_type_t expectedType = YAML_NO_EVENT);
+	bool checkEvent(const EventPtr &event, yaml_event_type_t expectedType) const;
+	static std::string eventScalarValue(const EventPtr &event);
+	static std::string eventTypeName(yaml_event_type_t type);
+
+	int parseScript(FILE *script);
+
+	int parseFrames();
+	int parseFrame(EventPtr event);
+	int parseControl(EventPtr event, libcamera::ControlList &controls);
+
+	std::string parseScalar();
+
+	void unpackFailure(const libcamera::ControlId *id,
+			   const std::string &repr);
+	libcamera::ControlValue unpackControl(const libcamera::ControlId *id,
+					      const std::string &repr);
+};