// To build with Digital Mars C++ Compiler:
//    dmc -mn -WD -o testdll.cpp kernel32.lib
//
// To build with MSVC 2022+:
//   cl.exe /std:c++17 /EHsc /LD testdll.cpp /link /PDBSTRIPPED /out:testdll.dll

#include <malloc.h>

extern "C" __declspec(dllexport) void (*Display)(const char *format, ...) = 0;
extern "C" __declspec(dllexport) double (*EngAtof)(const char **string)   = 0;

union uData {
  bool                   b;
  char                   c;
  unsigned char          uc;
  short                  s;
  unsigned short         us;
  int                    i;
  unsigned int           ui;
  float                  f;
  double                 d;
  long long int          i64;
  unsigned long long int ui64;
  char                  *str;
  unsigned char         *bytes;
};

// int DllMain() must exist and return 1 for a process to load the .DLL
// See https://docs.microsoft.com/en-us/windows/win32/dlls/dllmain for more
// information.
int __stdcall DllMain(void *module, unsigned int reason, void *reserved) {
  return 1;
}

// #undef pin names lest they collide with names in any header file(s) you might
// include.
#undef In
#undef Out

struct InstData {
  double X1Vals[3];
  double fParms[3];
};

void parseFloatStr(const char *str, InstData &inst) {
  for (int i = 0; *str && i < sizeof(inst.X1Vals) / sizeof(inst.X1Vals[0]); i++)
    inst.X1Vals[i] = EngAtof(&str);
}

void getfParms(InstData &inst) {
  const char *fVals[] = {"f1", "f2", "f3"};   // must be lower case
  for (int i = 0; i < sizeof(fVals) / sizeof(fVals[0]); i++) {
    double val     = EngAtof(fVals + i);
    inst.fParms[i] = val;
  }
}

extern "C" __declspec(dllexport) void testdll(
    InstData **opaque, double t, union uData *data) {
  double      In     = data[0].d;     // input
  const char *X1Vals = data[1].str;   // input parameter
  const char *X2Vals = data[2].str;   // input parameter
  double     &Out    = data[3].d;     // output

  InstData *inst = *opaque;
  if (!inst) {
    inst = *opaque = (InstData *)calloc(sizeof(InstData), 1);

    Display("X1Vals Attribute String From Schematic: \"%s\"\n", X1Vals);
    Display("X2Vals Attribute String From Schematic: \"%s\"\n", X2Vals);

    parseFloatStr(X1Vals, *inst);
    Display("Parsed Values From X1Vals Attribute String:\n");
    Display("X1Vals[0]=%f, X1Vals[1]=%f, X1Vals[2]=%f\n", inst->X1Vals[0],
        inst->X1Vals[1], inst->X1Vals[2]);

    getfParms(*inst);
    Display("Param Values Obtained Directly From Schematic:\n");
    Display("Params F1=%f, F2=%f, F3=%f\n", inst->fParms[0], inst->fParms[1],
        inst->fParms[2]);
  }

  Out = In * In;   // do something
}

extern "C" __declspec(dllexport) void Destroy(InstData *inst) { free(inst); }