// Automatically generated C++ file on Mon Aug 19 07:36:46 2024
//
// To build with Digital Mars C++ Compiler:
//
//    dmc -mn -WD swopampx.cpp kernel32.lib

#include <malloc.h>

extern "C" __declspec(dllexport) int (*Display)(const char *format, ...) = 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;
}

void bzero(void *ptr, unsigned int count) {
  unsigned char *first = (unsigned char *)ptr;
  unsigned char *last  = first + count;
  while (first < last) *first++ = '\0';
}

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

struct sSWOPAMPX {
  // declare the structure here
  double lastOut;
};

extern "C" __declspec(dllexport) void swopampx(
    struct sSWOPAMPX **opaque, double t, union uData *data) {
  // Implement module evaluation code here:
  double  inP = data[0].d;   // input
  double  inN = data[1].d;   // input
  double  A   = data[2].d;   // input parameter
  double &out = data[3].d;   // output

  if (!*opaque) {
    *opaque = (struct sSWOPAMPX *)malloc(sizeof(struct sSWOPAMPX));
    bzero(*opaque, sizeof(struct sSWOPAMPX));
  }
  struct sSWOPAMPX *inst = *opaque;

  // Implement module evaluation code here:
  out           = A * (inP - inN);
  inst->lastOut = out;
}

extern "C" __declspec(dllexport) void Trunc(struct sSWOPAMPX *inst, double t,
    union uData *data,
    double *timestep) {   // limit the timestep to a tolerance if the circuit
                          // causes a change in struct sSWOPAMPX
  const double ttol = 1e-5;   // 1ns default tolerance

  // this is a simplistic approach to limiting timestep based on a hard-coded
  // max output voltage change.  a more sophisticated approach might save the
  // timestamp (t) in the evaluation function, calculate the slope, and base the
  // returned timestep on the slope....
  const double maxVoltChange = 0.075;

  if (*timestep > ttol) {
    struct sSWOPAMPX tmp = *inst;
    swopampx(&(&tmp), t, data);
    // we're deliberately fixing only the rising edge for demo purposes
    double vChange = tmp.lastOut - inst->lastOut;

    if (vChange > maxVoltChange) { *timestep = ttol; }
  }
}

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