How to parse Simulink Coder system hierarchy from generated source code

/**
 * [...]
 * 
 *  Here is the system hierarchy for this model
 *  [...]
 *  '<S27>'  : 'MySimulinkModel/MyImportantSubsystem'
 *  [...]
 */

#include <clang-c/Index.h>
#include <iostream>
#include <vector>
#include <string>
#include <cstring>
#include <functional>
#include <regex>
#include <unordered_map>
#include <sstream>
#include <fstream>
#include <rapidjson/document.h>
#include <rapidjson/writer.h>
#include <rapidjson/stringbuffer.h>
#include <rapidjson/filewritestream.h>
#include <rapidjson/prettywriter.h>

void extractCommentBlocks(CXTranslationUnit unit, std::function<void(const std::string&, unsigned, unsigned)> processor) {
    CXSourceRange range = clang_getCursorExtent(clang_getTranslationUnitCursor(unit));
    CXToken *tokens;
    unsigned numTokens;
    
    clang_tokenize(unit, range, &tokens, &numTokens);
    
    for (unsigned i = 0; i < numTokens; ++i) {
        CXTokenKind tokenKind = clang_getTokenKind(tokens[i]);
        if (tokenKind == CXToken_Comment) {
            CXString tokenSpelling = clang_getTokenSpelling(unit, tokens[i]);
            CXSourceLocation location = clang_getTokenLocation(unit, tokens[i]);
            
            unsigned line, column;
            CXFile file;
            clang_getFileLocation(location, &file, &line, &column, nullptr);
            
            std::string comment = clang_getCString(tokenSpelling);
            processor(comment, line, column);
            
            clang_disposeString(tokenSpelling);
        }
    }
    
    clang_disposeTokens(unit, tokens, numTokens);
}

int main(int argc, char *argv[]) {
    if (argc != 3) {
        std::cerr << "Usage: " << argv[0] << " <source_file> <output_json_file>" << std::endl;
        return 1;
    }

    CXIndex index = clang_createIndex(0, 0);
    const char *filename = argv[1];
    const char *outputFile = argv[2];

    CXTranslationUnit unit = clang_parseTranslationUnit(index, filename, nullptr, 0, nullptr, 0, CXTranslationUnit_None);
    if (unit == nullptr) {
        std::cerr << "Failed to parse translation unit: " << filename << std::endl;
        return 1;
    }

    CXCursor cursor = clang_getTranslationUnitCursor(unit);
    std::unordered_map<std::string, std::string> hierarchyMap;
    std::regex pattern(R"('\<([S]\d+)\>' : '([^']+)')");
    
    extractCommentBlocks(unit, [&hierarchyMap, &pattern](const std::string& comment, unsigned line, unsigned column) {
        if(comment.find("Here is the system hierarchy for this model") != std::string::npos) {
            std::cout << "Found system hierarchy comment." << std::endl;
            std::cout << "Comment at line " << line << ", column " << column << ": " 
            << comment << std::endl;

            // Parse each line in the comment using regex
            std::istringstream stream(comment);
            std::string line_text;
            while (std::getline(stream, line_text)) {
                std::smatch matches;
                if (std::regex_search(line_text, matches, pattern)) {
                    std::string sNumber = matches[1].str();
                    std::string path = matches[2].str();
                    hierarchyMap[sNumber] = path;
                }
            }
        }
    });

    // Print all entries in the map
    std::cout << "\nExtracted hierarchy entries:" << std::endl;
    for (const auto& entry : hierarchyMap) {
        std::cout << entry.first << " -> " << entry.second << std::endl;
    }

    // Generate JSON output using RapidJSON
    rapidjson::Document document;
    document.SetObject();
    rapidjson::Document::AllocatorType& allocator = document.GetAllocator();
    
    rapidjson::Value hierarchyObject(rapidjson::kObjectType);
    
    for (const auto& entry : hierarchyMap) {
        rapidjson::Value key(entry.first.c_str(), allocator);
        rapidjson::Value value(entry.second.c_str(), allocator);
        hierarchyObject.AddMember(key, value, allocator);
    }
    
    document.AddMember("hierarchy", hierarchyObject, allocator);
    
    // Write to file
    FILE* fp = fopen(outputFile, "wb");
    if (!fp) {
        std::cerr << "Failed to open output file: " << outputFile << std::endl;
        clang_disposeTranslationUnit(unit);
        clang_disposeIndex(index);
        return 1;
    }
    
    char writeBuffer[65536];
    rapidjson::FileWriteStream os(fp, writeBuffer, sizeof(writeBuffer));
    rapidjson::PrettyWriter<rapidjson::FileWriteStream> writer(os);
    document.Accept(writer);
    fclose(fp);

    std::cout << "JSON output written to: " << outputFile << std::endl;

    clang_disposeTranslationUnit(unit);
    clang_disposeIndex(index);
    return 0;
}

g++ test.cpp -o parse_hierarchy -std=c++17 -I/usr/lib/llvm-19/include -L/usr/lib/llvm-19/lib -lclang

./parse_hierarchy my_model.h output.json

{
    "hierarchy": {
        "<S27>": "MySimulinkModel/MyImportantSubsystem",
        ...
    }
}