refactor: move iir_filter to separate compilation unit

pasada-lib/CMakeLists.txt

@@ -2,6 +2,7 @@ project(Pasada_Lib)
 
 SET(PASADA_SRC
         library.cpp
+        iir_filter.cpp
 )
 
 if(PASADA_BUILD_TESTS)

pasada-lib/iir_filter.cpp

@@ -0,0 +1,51 @@
+//
+// Created by david on 02.03.2026.
+//
+
+#include "iir_filter.h"
+
+Buf::Buf(size_t N): size(N), n(0) {
+    data.resize(N);
+    data.assign(N, 0.0);
+}
+void Buf::push(double val) {
+    data[n] = val;
+    n = (n+1) % size;
+}
+
+Filt::Filt(size_t N, size_t shift, size_t offset, std::vector<double> taps): Buf(N), shift(shift), offset(offset), taps(taps) {
+    if (taps.size() != N) throw std::invalid_argument("taps.size() != N");
+}
+double Filt::filter(double val) {
+    this->push(val);
+    return this->peek();
+}
+double Filt::peek() {
+    double sum = 0;
+    for (size_t i = offset; i < this->size; i++) {
+        //size_t n = (this->n - i + shift - 1) % this->size; // unsigned % size ... bad if u is negative
+        size_t n = (this->size + this->n - i + shift - 1) % this->size;
+        //std::cout << " t[" << i << "] * v[" << n << "]" << std::endl;
+        sum += this->data[n] * this->taps[i];
+    }
+    return sum;
+}
+void Filt::push(double val) {
+    Buf::push(val);
+}
+
+IirFilter::IirFilter(std::vector<double> b, std::vector<double> a) : x(b.size(), 0, 0, b), y(a.size(), 1, 1, a) {
+    if (b.size() != a.size()) throw std::invalid_argument("b.size() != a.size()");
+}
+double IirFilter::filter(double val) {
+    //std::cout << "x.filter(" << val << ")" << std::endl;
+    double xv = x.filter(val);
+    //std::cout << "xv=" << xv << std::endl;
+    //std::cout << "y.peek()" << std::endl;
+    double yv = y.peek();
+    //std::cout << "yv=" << yv << std::endl;
+    //std::cout << "---" << std::endl;
+    double yo = xv - yv;
+    y.push(yo);
+    return yo;
+}

pasada-lib/include/iir_filter.h

@@ -0,0 +1,46 @@
+//
+// Created by david on 02.03.2026.
+//
+
+#ifndef PASADASUPERPROJECT_IIR_FILTER_H
+#define PASADASUPERPROJECT_IIR_FILTER_H
+
+#include <utility>
+#include <vector>
+#include <stdexcept>
+
+/** Shift register implemented as a circular buffer. */
+class Buf {
+protected:
+    std::vector<double> data;
+    size_t size;
+    size_t n;
+public:
+    Buf(size_t N);
+    void push(double val);
+};
+
+/** Running filter base. */
+class Filt : Buf {
+protected:
+    std::vector<double> taps;
+    size_t shift;
+    size_t offset;
+public:
+    Filt(size_t N, size_t shift, size_t offset, std::vector<double> taps);
+    double filter(double val);
+    double peek();
+    void push(double val);
+};
+
+/** Running IIR filter. */
+class IirFilter {
+protected:
+    Filt y;
+    Filt x;
+public:
+    IirFilter(std::vector<double> b, std::vector<double> a);
+    double filter(double val);
+};
+
+#endif //PASADASUPERPROJECT_IIR_FILTER_H