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 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 during 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('-I/mathworks/devel/bat/BR2020bd/build/matlab/toolbox/rtw/rtwdemos/rtwdemo_lct_src', '-I/tmp/BR2020bd_1444674_32127/publish_examples5/tpffbcdbd5/ex06428671', '-c', '-outdir', '/tmp/BR2020bd_1444674_32127/publish_examples5/tpe277eaa2_14e0_4641_b664_101a9461dbb7', '/mathworks/devel/bat/BR2020bd/build/matlab/toolbox/rtw/rtwdemos/rtwdemo_lct_src/adder_cpp.cpp')
Building with 'g++'.
MEX completed successfully.
    mex('rtwdemo_sfun_adder_cpp.cpp', '-I/mathworks/devel/bat/BR2020bd/build/matlab/toolbox/rtw/rtwdemos/rtwdemo_lct_src', '-I/tmp/BR2020bd_1444674_32127/publish_examples5/tpffbcdbd5/ex06428671', '-cxx', '/tmp/BR2020bd_1444674_32127/publish_examples5/tpe277eaa2_14e0_4641_b664_101a9461dbb7/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. Set the first input to 'sfcn_tlc_generate' to generate a TLC block file that supports 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. Set the first input to 'rtwmakecfg_generate' to generate an rtwmakecfg.m file that supports 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. Set the first input 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. You can copy the block 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')