add comments to BoringMixer.cpp

Author: Nathan Ho

01-BoringMixer/BoringMixer.cpp

@@ -1,30 +1,52 @@
 #include "SC_PlugIn.h"
 
+// InterfaceTable contains pointers to functions in the host (server).
 static InterfaceTable *ft;
 
+// declare struct to hold unit generator state
 struct BoringMixer : public Unit {
+    // this is blank because this particular ugen is stateless.
+    // in more advanced examples we'll have stuff here.
 };
 
-static void BoringMixer_next(BoringMixer *unit, int inNumSamples);
+// in some older plugins these function declarations are wrapped in 'extern "C" { ... }'
+// no need to do that these days.
+static void BoringMixer_next(BoringMixer* unit, int inNumSamples);
 static void BoringMixer_Ctor(BoringMixer* unit);
 
+// the constructor function is called when a Synth containing this ugen is played.
+// it MUST be named PluginName_Ctor.
+// in later examples, this function will initialize state variables.
 void BoringMixer_Ctor(BoringMixer* unit) {
+    // set a calculation function.
+    // in later examples, we will have multiple calculation functions depending on input and output rates.
     SETCALC(BoringMixer_next);
+    // calculate one sample of output.
+    // this allows plugging into other ugens with initial-rate inputs 
     BoringMixer_next(unit, 1);
 }
 
+// the calculation function can have any name, but this is conventional.
+// this function is called every control period (64 samples is typical)
 void BoringMixer_next(BoringMixer* unit, int inNumSamples) {
 
-    float *left = IN(0);
-    float *right = IN(1);
-    float *out = OUT(0);
+    // IN and OUT are helper macros that return audio-rate input and output buffers.
+    // in SC source code, these buffers are often called "wire bufs" since they are how ugens communicate.
+    float *left = IN(0); // first input
+    float *right = IN(1); // second input
+    float *out = OUT(0); // first output
 
+    // loop through samples
     for (int i = 0; i < inNumSamples; i++) {
         out[i] = (left[i] + right[i]) * 0.5;
     }
 }
 
+// the entry point is called by the host when the plug-in is loaded
 PluginLoad(BoringMixerUGens) {
-    ft = inTable;
+    // InterfaceTable *inTable implicitly given as argument to the load function
+    ft = inTable; // store pointer to InterfaceTable
+    // DefineSimpleUnit is one of four macros defining different kinds of ugens.
+    // In later examples involving memory allocation, we'll see DefineDtorUnit.
     DefineSimpleUnit(BoringMixer);
-}
+}