MindConnect Library – Replacing MCL Modules¶

Agent developers can provide custom implementations for the following modules and configure MCL build to use custom implementations in place of the default implementations.

HTTP Client¶

LibCurl is set as the default HTTP client library in MCL which can be replaced by implementing the functions declared in mcl_core/include/mcl_core/mcl_http_client.h. Default implementation is located in mcl_core/src/http_client/curl/http_client_libcurl.c. Note that default http client implementation depends on OpenSSL for TLS.

An alternative implementation of http client is also distributed in mcl_core/src/http_client/basic/ directory which uses tcp sockets and depends on mbedtls as the tls library. To use this basic http client instead of curl, you can follow the instructions below as if you provided it as your own implementation.

You may place your implementation in:

a) a subfolder under mcl_core/src/http_client/ so that the directory structure looks like:

+-- mcl_core
    +-- src
        +-- http_client
            +-- basic
            +-- curl
            +-- <your_implementation_folder>
                +-- <your_source_file(s)>
                +-- CMakeLists.txt

In this case, MCL can be configured to use the alternative implementation by setting -DMCL_HTTP_CLIENT=<your_implementation_folder> when building MCL.

b) any place out of MCL project so that the directory structure looks like:

+-- mcl_core
    +-- src
        +-- http_client
            +-- basic
            +-- curl

+-- <any_place_out_of_MCL>
    +-- <your_implementation_folder>
        +-- <your_source_file(s)>
        +-- CMakeLists.txt

In this case, MCL can be configured to use the alternative implementation by setting -DMCL_HTTP_CLIENT=<absolute_path_to_your_implementation_folder> when building MCL.

If you are using CMake to build MCL, you also need to provide CMakeLists.txt file within your alternative implementation directory. CMakeLists.txt file must set the parameters MCL_HTTP_CLIENT_INCLUDE_DIRECTORIES, MCL_HTTP_CLIENT_LIBRARIES and MCL_HTTP_CLIENT_SOURCES for PARENT_SCOPE. Typical CMakeLists.txt would look like:

SET(MCL_HTTP_CLIENT_INCLUDE_DIRECTORIES <directory_to_include> <another_directory_to_include> PARENT_SCOPE)
SET(MCL_HTTP_CLIENT_LIBRARIES <library_to_be_linked> <another_library_to_be_linked> PARENT_SCOPE)
SET(MCL_HTTP_CLIENT_SOURCES <your_source_file> <your_another_source_file> PARENT_SCOPE)

If you are using CMake to build MCL, and your alternative implementation depends on another library, do not forget to add the directory (with contents including headers and the binaries) of that library to CMAKE_PREFIX_PATH option when building MCL.

Crypto¶

OpenSSL is set as the default cryptography library in MCL which can be replaced by implementing the functions declared in mcl_core/src/security.h. Default implementation is located in mcl_core/src/crypto/openssl/security_libcrypto.c.

An alternative implementation of security interface is also distributed in mcl_core/src/crypto/mbedtls/ directory which uses mbedtls as the cryptography library. To use mbedtls instead of openssl as the security interface, you can follow the instructions below as if you provided it as your own implementation.

You may place your implementation in:

a) a subfolder under mcl_core/src/crypto/ so that the directory structure looks like:

+-- mcl_core
    +-- src
        +-- crypto
            +-- mbedtls
            +-- openssl
            +-- <your_implementation_folder>
                +-- <your_source_file(s)>
                +-- CMakeLists.txt

In this case, MCL can be configured to use the alternative implementation by setting -DMCL_CRYPTO=<your_implementation_folder> when building MCL.

b) any place out of MCL project so that the directory structure looks like:

+-- mcl_core
    +-- src
        +-- crypto
            +-- mbedtls
            +-- openssl

+-- <any_place_out_of_MCL>
    +-- <your_implementation_folder>
        +-- <your_source_file(s)>
        +-- CMakeLists.txt

In this case, MCL can be configured to use the alternative implementation by setting -DMCL_CRYPTO=<absolute_path_to_your_implementation_folder> when building MCL.

If you are using CMake to build MCL, you also need to provide CMakeLists.txt file within your alternative implementation directory. CMakeLists.txt file must set the parameters MCL_CRYPTO_INCLUDE_DIRECTORIES, MCL_CRYPTO_LIBRARIES and MCL_CRYPTO_SOURCES for PARENT_SCOPE. Typical CMakeLists.txt would look like:

SET(MCL_CRYPTO_INCLUDE_DIRECTORIES <directory_to_include> <another_directory_to_include> PARENT_SCOPE)
SET(MCL_CRYPTO_LIBRARIES <library_to_be_linked> <another_library_to_be_linked> PARENT_SCOPE)
SET(MCL_CRYPTO_SOURCES <your_source_file> <your_another_source_file> PARENT_SCOPE)

If you are using CMake to build MCL, and your alternative implementation depends on another library, do not forget to add the directory (with contents including headers and the binaries) of that library to CMAKE_PREFIX_PATH option when building MCL.

File Utility¶

MCL uses standard C Library as the default file utility for file operations which can be replaced by implementing the functions declared in mcl_core/include/mcl_core/mcl_file_util.h. Default implementation is located in mcl_core/src/file_util/standard/file_util.c.

You may place your implementation in:

a) a subfolder under mcl_core/src/file_util/ so that the directory structure looks like:

+-- mcl_core
    +-- src
        +-- file_util
            +-- standard
            +-- <your_implementation_folder>
                +-- <your_source_file(s)>
                +-- CMakeLists.txt

In this case, MCL can be configured to use the alternative implementation by setting -DMCL_FILE_UTIL=<your_implementation_folder> when building MCL.

b) any place out of MCL project so that the directory structure looks like:

+-- mcl_core
    +-- src
        +-- file_util
            +-- standard

+-- <any_place_out_of_MCL>
    +-- <your_implementation_folder>
        +-- <your_source_file(s)>
        +-- CMakeLists.txt

In this case, MCL can be configured to use the alternative implementation by setting -DMCL_FILE_UTIL=<absolute_path_to_your_implementation_folder> when building MCL.

If you are using CMake to build MCL, you also need to provide CMakeLists.txt file within your alternative implementation directory. CMakeLists.txt file must set the parameters MCL_FILE_UTIL_INCLUDE_DIRECTORIES, MCL_FILE_UTIL_LIBRARIES and MCL_FILE_UTIL_SOURCES for PARENT_SCOPE. Typical CMakeLists.txt would look like:

SET(MCL_FILE_UTIL_INCLUDE_DIRECTORIES <directory_to_include> <another_directory_to_include> PARENT_SCOPE)
SET(MCL_FILE_UTIL_LIBRARIES <library_to_be_linked> <another_library_to_be_linked> PARENT_SCOPE)
SET(MCL_FILE_UTIL_SOURCES <your_source_file> <your_another_source_file> PARENT_SCOPE)

If you are using CMake to build MCL, and your alternative implementation depends on another library, do not forget to add the directory (with contents including headers and the binaries) of that library to CMAKE_PREFIX_PATH option when building MCL.

Memory¶

MCL uses standard C Library as the default utility for memory operations which can be replaced by implementing the functions declared in mcl_core/include/mcl_core/mcl_memory.h. Default implementation is located in mcl_core/src/memory/standard/memory.c.

You may place your implementation in:

a) a subfolder under mcl_core/src/memory/ so that the directory structure looks like:

+-- mcl_core
    +-- src
        +-- memory
            +-- standard
            +-- <your_implementation_folder>
                +-- <your_source_file(s)>
                +-- CMakeLists.txt

In this case, MCL can be configured to use the alternative implementation by setting -DMCL_MCL_MEMORY=<your_implementation_folder> when building MCL.

b) any place out of MCL project so that the directory structure looks like:

+-- mcl_core
    +-- src
        +-- memory
            +-- standard

+-- <any_place_out_of_MCL>
    +-- <your_implementation_folder>
        +-- <your_source_file(s)>
        +-- CMakeLists.txt

In this case, MCL can be configured to use the alternative implementation by setting -DMCL_MEMORY=<absolute_path_to_your_implementation_folder> when building MCL.

If you are using CMake to build MCL, you also need to provide CMakeLists.txt file within your alternative implementation directory. CMakeLists.txt file must set the parameters MCL_MEMORY_INCLUDE_DIRECTORIES, MCL_MEMORY_LIBRARIES and MCL_MEMORY_SOURCES for PARENT_SCOPE. Typical CMakeLists.txt would look like:

SET(MCL_MEMORY_INCLUDE_DIRECTORIES <directory_to_include> <another_directory_to_include> PARENT_SCOPE)
SET(MCL_MEMORY_LIBRARIES <library_to_be_linked> <another_library_to_be_linked> PARENT_SCOPE)
SET(MCL_MEMORY_SOURCES <your_source_file> <your_another_source_file> PARENT_SCOPE)

If you are using CMake to build MCL, and your alternative implementation depends on another library, do not forget to add the directory (with contents including headers and the binaries) of that library to CMAKE_PREFIX_PATH option when building MCL.