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C++ Object Methods as Legacy Functions

This example shows you 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, and

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

Providing 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, you have to assign its properties to values corresponding to the legacy code being integrated. The definition of the legacy C++ class being used in this example is:

class adder {
      int int_state;
      int add_one(int increment);
      int get_val();

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

% sldemo_sfun_adder_cpp
def = legacy_code('initialize');
def.SFunctionName = 'sldemo_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      = {'sldemo_lct_src'};
def.SrcPaths      = {'sldemo_lct_src'};
def.Options.language = 'C++';
def.Options.useTlcWithAccel = false;

Generating and Compiling an S-Function for Use During Simulation

The function legacy_code() is called again with the first input set to 'generate_for_sim' in order to automatically generate and compile the C-MEX S-function according to the description provided by the input argument 'def'. This S-function is used to call the legacy functions in simulation. The source code for the S-function is found in the file sldemo_sfun_adder_cpp.cpp.

legacy_code('generate_for_sim', def);
### Start Compiling sldemo_sfun_adder_cpp
    mex('-I/tmp/Bdoc24a_2528353_1184574/tp1480b6ce/simulink_features-ex93865240/sldemo_lct_src', '-I/tmp/Bdoc24a_2528353_1184574/tp1480b6ce/simulink_features-ex93865240', '-c', '-outdir', '/tmp/Bdoc24a_2528353_1184574/tp376a5392_cc21_4b18_bdf5_9047e5227915', '/tmp/Bdoc24a_2528353_1184574/tp1480b6ce/simulink_features-ex93865240/sldemo_lct_src/adder_cpp.cpp')
Building with 'g++'.
MEX completed successfully.
    mex('sldemo_sfun_adder_cpp.cpp', '-I/tmp/Bdoc24a_2528353_1184574/tp1480b6ce/simulink_features-ex93865240/sldemo_lct_src', '-I/tmp/Bdoc24a_2528353_1184574/tp1480b6ce/simulink_features-ex93865240', '-cxx', '/tmp/Bdoc24a_2528353_1184574/tp376a5392_cc21_4b18_bdf5_9047e5227915/adder_cpp.o')
Building with 'g++'.
MEX completed successfully.
### Finish Compiling sldemo_sfun_adder_cpp
### Exit

Generating an rtwmakecfg.m File for Code Generation

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

Note: Complete this step only if you are going to simulate the model in accelerated mode.

legacy_code('rtwmakecfg_generate', def);

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

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

% legacy_code('slblock_generate', def);

Integration with Legacy Code

The model sldemo_lct_cpp sldemo_lct_cpp shows integration with the legacy code.


See Also