FlatBuffers 转换数据字节为JSON字符串的格式。

flatbuffers::Parser::Parse 函数

parser->opts.strict_json = true;  置为JSON格式。

头文件：

#pragma once

#include "prerequisites.h"
#include "msg_define_generated.h"
#include "LoggerManager.h"

class MessageDefine final : private boost::noncopyable
{
public:
	MessageDefine() = default;

	~MessageDefine() = default;

	static MessageDefine* instance();

	void initialize();

	std::shared_ptr findSchema(const std::string& name);
	std::shared_ptr findRequestSchema(MSG_DEFINE id);
	std::shared_ptr findReplySchema(MSG_DEFINE id);

	template
	inline const T* parseRequestMessage(MSG_DEFINE id, std::string& message, size_t offset)
	{
		if (message.size() <= offset)
		{
			LOG_WARNING(default, "Schema size < offset, id[{}]", EnumNameMSG_DEFINE(id));
			return nullptr;
		}

		auto parser = MessageDefine::instance()->findRequestSchema(id);
		if (!parser)
		{
			LOG_WARNING(default, "Schema not find, id[{}]", EnumNameMSG_DEFINE(id));
			return nullptr;
		}

		if (!parser->Parse(message.c_str() + offset, nullptr))
		{
			LOG_WARNING(default, "Schema parse failed:{}, id[{}], error:{}", message, EnumNameMSG_DEFINE(id), parser->error_);
			return nullptr;
		}

		flatbuffers::Verifier verifier(parser->builder_.GetBufferPointer(), parser->builder_.GetSize());
		if (verifier.VerifyBuffer(nullptr))
		{
			message.resize(parser->builder_.GetSize() + offset);
			memcpy((char*)(message.c_str() + offset), parser->builder_.GetBufferPointer(), parser->builder_.GetSize());
			return flatbuffers::GetRoot(message.c_str() + offset);
		}
		return nullptr;
	}

	template
	inline const T* parseReplyMessage(MSG_DEFINE id, std::string& message, size_t offset)
	{
		if (message.size() <= offset)
		{
			LOG_WARNING(default, "Schema size < offset, id[{}]", EnumNameMSG_DEFINE(id));
			return nullptr;
		}

		auto parser = MessageDefine::instance()->findReplySchema(id);
		if (!parser)
		{
			LOG_WARNING(default, "Schema not find, id[{}]", EnumNameMSG_DEFINE(id));
			return nullptr;
		}

		if (!parser->Parse(message.c_str() + offset, nullptr))
		{
			LOG_WARNING(default, "Schema parse failed:{}, id[{}]", message, EnumNameMSG_DEFINE(id));
			return nullptr;
		}

		flatbuffers::Verifier verifier(parser->builder_.GetBufferPointer(), parser->builder_.GetSize());
		if (verifier.VerifyBuffer(nullptr))
		{
			message.resize(parser->builder_.GetSize() + offset);
			memcpy((char*)(message.c_str() + offset), parser->builder_.GetBufferPointer(), parser->builder_.GetSize());
			return flatbuffers::GetRoot(message.c_str() + offset);
		}
		return nullptr;
	}
protected:
	bool loadSchemaFile(std::string_view path, const std::string& filename, bool bStrict);

protected:
	std::unordered_map> m_parsers;
	std::unordered_map m_requestIdNames;
	std::unordered_map m_replyIdNames;
};


template
inline const T* json2fb(const std::string& name, const char* message, std::string_view* outMessage)
{
	auto parser = MessageDefine::instance()->findSchema(name);
	if (!parser)
	{
		LOG_WARNING(default, "Schema:{} not find", name);
		return nullptr;
	}

	if (!parser->Parse(message, nullptr))
	{
		LOG_WARNING(default, "Schema:{} parse failed:{}", name, message);
		return nullptr;
	}

	flatbuffers::Verifier verifier(parser->builder_.GetBufferPointer(), parser->builder_.GetSize());
	if (verifier.VerifyBuffer(nullptr))
	{
		if (outMessage)
			*outMessage = std::string_view(reinterpret_cast(parser->builder_.GetBufferPointer()), parser->builder_.GetSize());
		return flatbuffers::GetRoot(parser->builder_.GetBufferPointer());
	}
	return nullptr;
}

inline bool bin2json(const std::string& name, const void* message, std::string& jsongen)
{
	auto parser = MessageDefine::instance()->findSchema(name);
	if (!parser)
	{
		LOG_WARNING(default, "Schema:{} not find", name);
		return false;
	}

	if (!GenerateText(*parser, message, &jsongen))
	{
		LOG_WARNING(default, "Schema:{} Couldn't serialize parsed data to JSON", name);
		return false;
	}
	return true;
}

源文件：

#include "MessageDefine.h"
#include "ConfigLoader.h"
#include "MessageDefineConfig_generated.h"

MessageDefine* MessageDefine::instance()
{
	thread_local std::unique_ptr tl_instance;
	if (!tl_instance)
	{
		tl_instance = std::make_unique();
		tl_instance->initialize();
	}
	return tl_instance.get();
}

void MessageDefine::initialize()
{
	TConfigLoader cfgMessageDefine;
	if (!cfgMessageDefine.parse("common/MessageDefineConfig.fbs", "config/MessageDefineConfig.json"))
	{
		return;
	}

	auto cfg = cfgMessageDefine.data;
	for (auto item : *cfg->items())
	{
		auto path = item->path()->string_view();
		if (item->names())
		{
			for (auto name : *item->names())
			{
				loadSchemaFile(path, name->str(), true);
			}
		}
		if (item->no_strict_names())
		{
			for (auto name : *item->no_strict_names())
			{
				loadSchemaFile(path, name->str(), false);
			}
		}
	}
	for (auto item : *cfg->request_id_names())
	{
		m_requestIdNames[item->id()] = item->name()->str();
	}
	for (auto item : *cfg->reply_id_names())
	{
		m_replyIdNames[item->id()] = item->name()->str();
	}
}

bool MessageDefine::loadSchemaFile(std::string_view path, const std::string& filename, bool bStrict)
{
	if (m_parsers.find(filename) != m_parsers.end())
		return true;

	// load FlatBuffer schema (.fbs)
	std::string schemafile;
	std::string schemafilename = fmt::format(path, filename);
	bool ok = flatbuffers::LoadFile(schemafilename.c_str(), false, &schemafile);
	if (!ok)
	{
		LOG_ERROR(network, "couldn't load schemafilename:{}", filename);
		return false;
	}

	// parse schema first, so we can use it to parse the data after
	auto parser = std::make_shared();
	const char* include_directories[] = { "../../fbs", nullptr };
	ok = parser->Parse(schemafile.c_str(), include_directories);
	if (!ok)
	{
		LOG_ERROR(network, "parse schemafilename:{} failed: {}", filename, parser->error_);
		return false;
	}

	if (bStrict)
	{
		parser->opts.strict_json = true;
	}

	m_parsers.emplace(filename, parser);
	return true;
}

std::shared_ptr MessageDefine::findSchema(const std::string& name)
{
	if (auto it = m_parsers.find(name); it != m_parsers.end())
	{
		it->second->builder_.Clear();
		return it->second;
	}
	return nullptr;
}

std::shared_ptr MessageDefine::findRequestSchema(MSG_DEFINE id)
{
	if (auto it = m_requestIdNames.find(id); it != m_requestIdNames.end())
	{
		return findSchema(it->second);
	}
	return nullptr;
}

std::shared_ptr MessageDefine::findReplySchema(MSG_DEFINE id)
{
	if (auto it = m_replyIdNames.find(id); it != m_replyIdNames.end())
	{
		return findSchema(it->second);
	}
	return nullptr;
}