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Integrate External C++ Object Methods

This example shows how to use the Legacy Code Tool to integrate legacy C++ object methods.

The Legacy Code Tool allows you to:

  • Provide the legacy function specification.

  • Generate a C++ MEX S-function that is used during simulation to call the legacy code.

  • Compile and build the generated S-function for simulation.

  • Generate a block TLC file and optional rtwmakecfg.m file that is used during code generation to call the legacy code.

Provide the Legacy Function Specification

Functions provided with the Legacy Code Tool take a specific data structure or array of structures as the argument. The data structure is initialized by calling the function legacy_code() using 'initialize' as the first input. After initializing the structure, assign its properties to values corresponding to the legacy code being integrated. For detailed help on the properties, call legacy_code('help'). The definition of the legacy C++ class being used in this example is:

class adder {
  private:
      int int_state;
  public:
      adder();
      int add_one(int increment);
      int get_val();
};

The legacy source code is in the files adder_cpp.h and adder_cpp.cpp.

% rtwdemo_sfun_adder_cpp
def = legacy_code('initialize');
def.SFunctionName = 'rtwdemo_sfun_adder_cpp';
def.StartFcnSpec  = 'createAdder()';
def.OutputFcnSpec = 'int32 y1 = adderOutput(int32 u1)';
def.TerminateFcnSpec = 'deleteAdder()';
def.HeaderFiles   = {'adder_cpp.h'};
def.SourceFiles   = {'adder_cpp.cpp'};
def.IncPaths      = {'rtwdemo_lct_src'};
def.SrcPaths      = {'rtwdemo_lct_src'};
def.Options.language = 'C++';
def.Options.useTlcWithAccel = false;

Generate an S-Function for Simulation

To generate a C-MEX S-function according to the description provided by the input argument 'def', call the function legacy_code() again with the first input set to 'sfcn_cmex_generate'. The S-function calls the legacy functions in simulation. The source code for the S-function is in the file rtwdemo_sfun_adder_cpp.cpp.

legacy_code('sfcn_cmex_generate', def);

Compile the Generated S-Function for Simulation

After you generate the C-MEX S-function source file, to compile the S-function for simulation with Simulink®, call the function legacy_code() again with the first input set to 'compile'.

legacy_code('compile', def);
### Start Compiling rtwdemo_sfun_adder_cpp
    mex('-compatibleArrayDims', '-I/mathworks/devel/bat/Bdoc16a/build/matlab/toolbox/rtw/rtwdemos/rtwdemo_lct_src', '-I/tmp/Bdoc16a_342494_6186/tpb227ff9c_7457_42c7_ad22_0e13480900da', '-c', '-outdir', '/tmp/Bdoc16a_342494_6186/tp6b863895_2406_4b1d_a371_e41247c75ee0', '/mathworks/devel/bat/Bdoc16a/build/matlab/toolbox/rtw/rtwdemos/rtwdemo_lct_src/adder_cpp.cpp')
Building with 'g++'.
MEX completed successfully.
    mex('rtwdemo_sfun_adder_cpp.cpp', '-compatibleArrayDims', '-I/mathworks/devel/bat/Bdoc16a/build/matlab/toolbox/rtw/rtwdemos/rtwdemo_lct_src', '-I/tmp/Bdoc16a_342494_6186/tpb227ff9c_7457_42c7_ad22_0e13480900da', '-cxx', '/tmp/Bdoc16a_342494_6186/tp6b863895_2406_4b1d_a371_e41247c75ee0/adder_cpp.o')
Building with 'g++'.
MEX completed successfully.
### Finish Compiling rtwdemo_sfun_adder_cpp
### Exit

Generate a TLC Block File for Code Generation

After you compile the S-function and use it in simulation, you can call the function legacy_code() again with the first input set to 'sfcn_tlc_generate' in order to generate a TLC block file to support code generation through Simulink® Coder™. If the TLC block file is not created and you try to generate code for a model that includes the S-function, code generation fails. The TLC block file for the S-function is: rtwdemo_sfun_adder_cpp.tlc.

legacy_code('sfcn_tlc_generate', def);

Generate an rtwmakecfg.m File for Code Generation

After you create the TLC block file, you can call the function legacy_code() again with the first input set to 'rtwmakecfg_generate' to generate an rtwmakecfg.m file to support code generation through Simulink® Coder™. If the required source and header files for the S-function are not in the same folder as the S-function, and you want to add these dependencies in the makefile produced during code generation, generate the rtwmakecfg.m file.

legacy_code('rtwmakecfg_generate', def);

Generate a Masked S-Function Block for Calling the Generated S-Function

After you compile the C-MEX S-function source, you can call the function legacy_code() again with the first input set to 'slblock_generate' to generate a masked S-function block that is configured to call that S-function. The software places the block in a new model and it can be copied to an existing model.

% legacy_code('slblock_generate', def);

Show the Generated Integration with Legacy Code

The model rtwdemo_lct_cpp shows integration with the legacy code.

open_system('rtwdemo_lct_cpp')
sim('rtwdemo_lct_cpp')

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