4 files changed, 250 insertions, 0 deletions

diff --git a/include/libcamera/internal/meson.build b/include/libcamera/internal/meson.build
index 1c5eef9c..7533b075 100644
--- a/include/libcamera/internal/meson.build
+++ b/include/libcamera/internal/meson.build
@@ -41,6 +41,7 @@ libcamera_internal_headers = files([
     'v4l2_pixelformat.h',
     'v4l2_subdevice.h',
     'v4l2_videodevice.h',
+    'yaml_emitter.h',
     'yaml_parser.h',
 ])
 
diff --git a/include/libcamera/internal/yaml_emitter.h b/include/libcamera/internal/yaml_emitter.h
new file mode 100644
index 00000000..f8df5265
--- /dev/null
+++ b/include/libcamera/internal/yaml_emitter.h
@@ -0,0 +1,61 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2024, Ideas On Board Oy
+ *
+ * libcamera YAML emitter helper
+ */
+
+#pragma once
+
+#include <map>
+#include <memory>
+#include <string>
+
+#include <libcamera/base/class.h>
+#include <libcamera/base/file.h>
+
+#include <yaml.h>
+
+namespace libcamera {
+
+class File;
+class YamlEvent;
+
+class YamlEmitter final
+{
+public:
+	~YamlEmitter();
+
+	static std::unique_ptr<YamlEmitter> create(std::string &path);
+
+	int emit(std::map<std::string, std::string>);
+	int emit(const std::string &scalar);
+
+private:
+	LIBCAMERA_DISABLE_COPY(YamlEmitter);
+
+	class Emitter
+	{
+	public:
+		Emitter() = default;
+		~Emitter();
+
+		void init(File *file);
+
+		int emit(YamlEvent *event);
+
+	private:
+		void logError();
+
+		yaml_emitter_t emitter_;
+	};
+
+	YamlEmitter() = default;
+
+	void init();
+
+	std::unique_ptr<File> file_;
+	Emitter emitter_;
+};
+
+} /* namespace libcamera */
diff --git a/src/libcamera/meson.build b/src/libcamera/meson.build
index aa9ab029..5b8af410 100644
--- a/src/libcamera/meson.build
+++ b/src/libcamera/meson.build
@@ -51,6 +51,7 @@ libcamera_internal_sources = files([
     'v4l2_pixelformat.cpp',
     'v4l2_subdevice.cpp',
     'v4l2_videodevice.cpp',
+    'yaml_emitter.cpp',
     'yaml_parser.cpp',
 ])
 
diff --git a/src/libcamera/yaml_emitter.cpp b/src/libcamera/yaml_emitter.cpp
new file mode 100644
index 00000000..5683d1d4
--- /dev/null
+++ b/src/libcamera/yaml_emitter.cpp
@@ -0,0 +1,187 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2024, Ideas On Board Oy
+ *
+ * libcamera YAML emitter helper
+ */
+
+#include "libcamera/internal/yaml_emitter.h"
+
+#include <libcamera/base/log.h>
+#include <libcamera/base/span.h>
+
+/**
+ * \file yaml_emitter.h
+ * \brief A YAML emitter helper
+ */
+
+namespace libcamera {
+
+LOG_DEFINE_CATEGORY(YamlEmitter)
+
+namespace {
+
+int yamlWrite(void *data, unsigned char *buffer, size_t size)
+{
+	File *file = static_cast<File *>(data);
+
+	Span<unsigned char> buf{ buffer, size };
+	ssize_t ret = file->write(buf);
+	if (ret < 0)
+		return 0;
+
+	return 1;
+}
+
+} /* namespace */
+
+class YamlEvent
+{
+public:
+	static std::unique_ptr<YamlEvent> create();
+
+	const yaml_event_t *event() const
+	{
+		return &event_;
+	}
+
+	yaml_event_t *event()
+	{
+		return &event_;
+	}
+
+private:
+	YamlEvent() = default;
+
+	yaml_event_t event_;
+};
+
+std::unique_ptr<YamlEvent> YamlEvent::create()
+{
+	struct Deleter : std::default_delete<YamlEvent> {
+		void operator()(YamlEvent *yamlEvent)
+		{
+			yaml_event_delete(yamlEvent->event());
+		}
+	};
+
+	return std::unique_ptr<YamlEvent>(new YamlEvent(), Deleter());
+}
+
+YamlEmitter::Emitter::~Emitter()
+{
+	yaml_emitter_delete(&emitter_);
+}
+
+void YamlEmitter::Emitter::init(File *file)
+{
+	yaml_emitter_initialize(&emitter_);
+	yaml_emitter_set_output(&emitter_, yamlWrite, file);
+}
+
+void YamlEmitter::Emitter::logError()
+{
+	switch (emitter_.error) {
+	case YAML_MEMORY_ERROR:
+		LOG(YamlEmitter, Error)
+			<< "Memory error: Not enough memory for emitting";
+		break;
+
+	case YAML_WRITER_ERROR:
+		LOG(YamlEmitter, Error)
+			<< "Writer error: " << emitter_.problem;
+		break;
+
+	case YAML_EMITTER_ERROR:
+		LOG(YamlEmitter, Error)
+			<< "Emitter error: " << emitter_.problem;
+		break;
+
+	default:
+		LOG(YamlEmitter, Error) << "Internal problem";
+		break;
+	}
+}
+
+int YamlEmitter::Emitter::emit(YamlEvent *event)
+{
+	int ret = yaml_emitter_emit(&emitter_, event->event());
+	if (!ret) {
+		logError();
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+YamlEmitter::~YamlEmitter()
+{
+	std::unique_ptr<YamlEvent> event = YamlEvent::create();
+
+	yaml_document_end_event_initialize(event->event(), 0);
+	emitter_.emit(event.get());
+
+	yaml_stream_end_event_initialize(event->event());
+	emitter_.emit(event.get());
+}
+
+void YamlEmitter::init()
+{
+	emitter_.init(file_.get());
+
+	std::unique_ptr<YamlEvent> event = YamlEvent::create();
+
+	yaml_stream_start_event_initialize(event->event(), YAML_UTF8_ENCODING);
+	emitter_.emit(event.get());
+
+	yaml_document_start_event_initialize(event->event(), NULL, NULL,
+					     NULL, 0);
+	emitter_.emit(event.get());
+}
+
+std::unique_ptr<YamlEmitter> YamlEmitter::create(std::string &path)
+{
+	YamlEmitter *emitter = new YamlEmitter();
+
+	emitter->file_ = std::make_unique<File>(path);
+	emitter->file_->open(File::OpenModeFlag::WriteOnly);
+
+	emitter->init();
+
+	return std::unique_ptr<YamlEmitter>(emitter);
+}
+
+int YamlEmitter::emit(std::map<std::string, std::string> map)
+{
+	std::unique_ptr<YamlEvent> event = YamlEvent::create();
+
+	auto iter = map.begin();
+
+	yaml_mapping_start_event_initialize(event->event(), NULL, NULL,
+					    true, YAML_BLOCK_MAPPING_STYLE);
+	emitter_.emit(event.get());
+
+	emit(iter->first);
+	emit(iter->second);
+
+	yaml_mapping_end_event_initialize(event->event());
+	emitter_.emit(event.get());
+
+	return 0;
+}
+
+int YamlEmitter::emit(const std::string &scalar)
+{
+	const unsigned char *value = reinterpret_cast<const unsigned char *>
+				     (scalar.c_str());
+	std::unique_ptr<YamlEvent> event = YamlEvent::create();
+
+	yaml_scalar_event_initialize(event->event(), NULL, NULL, value,
+				     scalar.length(), true, false,
+				     YAML_PLAIN_SCALAR_STYLE);
+	emitter_.emit(event.get());
+
+	return 0;
+}
+
+} /* namespace libcamera */