PbConvertor-C++ convertor between protobuf message and C struct

PbConvertor is used to convert protobuf message to C struct or C struct to protobuf message. PbConvertor is mainly based on protobuf reflection.

Dependency

• C++11 or higher version
• protobuf

Usage

Suppose your *.pb.h, *.pb.cc and C struct definition are prepared.

1. Refer to C struct definition requirements to modify your C struct definition.
2. Add PbConvertor.h and PbConvertor.cpp into your C++ project.
3. Use the following methods in PbConvertor class to convert protobuf message to C struct or C struct to protobuf message.

    /**
     * @brief convert C struct to protobuf message.
     * @param pStruct pointer to C struct.
     * @param pPb pointer to protobuf message.
     * @return whether successful.
     */
    static bool struct2Pb(const char *&pStruct, google::protobuf::Message *pPb);

    /**
     * @brief convert C struct to serialized protobuf message.
     * @param pStruct pointer to C struct.
     * @param pbTypeName protobuf message type name.
     * @param pSerializedPb pointer to serialized protobuf message which must be released by user using delete [].
     * @param serializedPbSize serialized protobuf message size.
     * @return whether successful.
     */
    static bool struct2serializedPb(const char *pStruct, const std::string &pbTypeName, char *&pSerializedPb, size_t &serializedPbSize);

    /**
     * @brief convert protobuf message to C struct.
     * @param pPb pointer to protobuf message.
     * @param stru memory tree related to C struct, and pointer to C struct equals to stru.pMem.
     *        Memory tree must be released by user using stru.release().
     * @return whether successful.
     */
    static bool pb2struct(const google::protobuf::Message *pPb, MemTree &stru);

    /**
     * @brief convert serialized protobuf message to C struct.
     * @param pbTypeName protobuf message type name.
     * @param pSerializedPb pointer to serialized protobuf message.
     * @param serializedPbSize serialized protobuf message size.
     * @param stru memory tree related to C struct, and pointer to C struct equals to stru.pMem.
     *        Memory tree must be released by user using stru.release().
     * @return whether successful.
     */
    static bool serializedPb2struct(const std::string &pbTypeName, const char *pSerializedPb, const size_t serializedPbSize, MemTree &stru);

4. A usage example is provided.

C struct definition requirements

C struct definition must be one byte aligned using #pragma pack(1) and #pragma pack().
C struct member type must correspond to protobuf message field type according to the following table. The other C struct member types not listed in the following table are not allowed.

protobuf message field type	C struct member type
double	double
float	float
int32	int32_t
int64	int64_t
uint32	uint32_t
uint64	uint64_t
bool	bool
string Note: UTF-8 encoding is required.	char * (not char[N]) Note: 1. UTF-8 encoding is required. 2. NULL value of char * member will be converted to "" of the protobuf message string field.
enum	enum : int
message	struct Note: struct member must meet C struct definition requirements.
repeated element_type Note: element_type must meet C struct definition requirements.	element_type * (not element_type[N]) Note: 1. The element amount of the array must be provided by the previous member whose type is int32_t/int64_t/uint32_t/uint64_t. 2. element_type must meet C struct definition requirements.

Attention

Your C++ project must have a multi-threaded configuration, otherwise protobuf will not work well.