// Automatically generated C++ file on Thu Feb  5 23:09:50 2026
//
// To build with Digital Mars C++ Compiler:
//
//    dmc -mn -WD -o my_first_block.cpp kernel32.lib

#include <malloc.h>

extern "C" __declspec(dllexport) void (*bzero)(void *ptr, unsigned int count)   = 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
#undef CLK

struct sMY_FIRST_BLOCK
{
  // declare the structure here
  bool lastCLK;   // Previous clock state for edge detection
  float Z1;       // First delay element (y[n-1])
  float Z2;       // Second delay element (y[n-2])
};

extern "C" __declspec(dllexport) void my_first_block(struct sMY_FIRST_BLOCK **opaque, double t, union uData *data)
{
   double  IN  = data[0].d; // input
   bool    CLK = data[1].b; // input
   double &OUT = data[2].d; // output

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

// Implement module evaluation code here:

   // IIR filter coefficients (hard-coded)
   double A0 = -0.5;
   double A1 = 0.9;

   // Process on clock edge
   if (CLK & CLK != inst->lastCLK){
      // 2nd-order IIR filter difference equation: y[n] = x[n] - a1*y[n-1] - a2*y[n-2]
      OUT = IN - inst->Z1 * A0 - inst->Z2 * A1;

      // Update delay line: shift previous outputs
      inst->Z2 = inst->Z1; // Move y[n-1] to y[n-2]
      inst->Z1 = OUT;      // Store current output as y[n-1]
   }

   // Store current clock state for next edge detection
   inst->lastCLK = CLK;

}

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