From d9bcd96276431278c71bb8b524465580c320ec69 Mon Sep 17 00:00:00 2001
From: Christopher Herb <chrisherb@outlook.com>
Date: Fri, 7 Jul 2023 14:42:10 +0200
Subject: [PATCH] added generic voice allocator

---
 synth/note_event.h      |  25 +++++++
 synth/voice_allocator.h | 148 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 173 insertions(+)
 create mode 100644 synth/note_event.h
 create mode 100644 synth/voice_allocator.h

diff --git a/synth/note_event.h b/synth/note_event.h
new file mode 100644
index 0000000..5051e5c
--- /dev/null
+++ b/synth/note_event.h
@@ -0,0 +1,25 @@
+#pragma once
+
+namespace trnr::lib::synth {
+
+enum note_event_type {
+    note_on = 0,
+    note_off
+};
+
+class note_event {
+public:
+    note_event_type type;
+    int midi_note;
+    float velocity;
+    int offset;
+
+    note_event(note_event_type type, int _midi_note, float _velocity, int _offset)
+        : type { type }
+        , midi_note { _midi_note }
+        , velocity { _velocity }
+        , offset { _offset }
+    {
+    }
+};
+}
diff --git a/synth/voice_allocator.h b/synth/voice_allocator.h
new file mode 100644
index 0000000..a19cbe1
--- /dev/null
+++ b/synth/voice_allocator.h
@@ -0,0 +1,148 @@
+#pragma once
+#include <vector>
+#include "note_event.h"
+
+namespace trnr::lib::synth {
+
+template <typename t_voice>
+class voice_allocator {
+public:
+    std::vector<t_voice> voices;
+    
+    voice_allocator(const double& _samplerate)
+        : samplerate { _samplerate }
+        , voices(8, t_voice(_samplerate))
+    {
+    }
+
+    void set_voice_count(const int& voice_count)
+    {
+        voices.resize(voice_count, voices.at(0));
+    }
+
+    void note_on(const note_event& event)
+    {
+        t_voice* voice = get_free_voice(event.midi_note);
+
+        if (voice == nullptr) {
+            voice = steal_voice();
+        }
+
+        if (voice != nullptr) {
+            voice->note_on(event.midi_note, event.velocity);
+        }
+    }
+
+    void note_off(const note_event& event)
+    {
+        for (auto it = voices.begin(); it != voices.end(); it++) {
+            if ((*it).MidiNote == event.midi_note) {
+                (*it).note_off();
+            }
+        }
+    }
+
+    void access(std::function<void(t_voice&)> f)
+    {
+        std::for_each(voices.begin(), voices.end(), f);
+    }
+
+    void process_samples(double** _outputs, int _start_index, int _block_size)
+    {
+        for (int s = _start_index; s < _start_index + _block_size; s++) {
+
+            process_events(s);
+
+            float voices_signal = 0.;
+            std::for_each(voices.begin(), voices.end(), [&voices_signal](t_voice& voice) { voices_signal += (voice.ProcessSample() / 3.); });
+
+            _outputs[0][s] = voices_signal;
+            _outputs[1][s] = voices_signal;
+        }
+    }
+
+    void add_event(note_event event)
+    {
+        input_queue.push_back(event);
+    }
+
+    bool voices_active()
+    {
+        bool voices_active = false;
+
+        for (auto it = voices.begin(); it != voices.end(); it++) {
+            bool busy = (*it).is_busy();
+            voices_active |= busy;
+        }
+
+        return voices_active;
+    }
+
+    void set_samplerate(double _samplerate)
+    {
+        this->samplerate = _samplerate;
+        for (int i = 0; i < voices.size(); i++) {
+            voices.at(i).set_samplerate(_samplerate);
+        }
+    }
+
+private:
+    double samplerate;
+    std::vector<note_event> input_queue;
+
+    t_voice* get_free_voice(float frequency)
+    {
+        t_voice* voice = nullptr;
+
+        for (auto it = voices.begin(); it != voices.end(); it++) {
+            if (!(*it).is_busy()) {
+                voice = &*it;
+            }
+        }
+
+        return voice;
+    }
+
+    t_voice* steal_voice()
+    {
+        t_voice* free_voice = nullptr;
+
+        for (auto it = voices.begin(); it != voices.end(); it++) {
+            if (!(*it).gate) {
+                free_voice = &*it;
+                break;
+            }
+        }
+
+        if (free_voice == nullptr) {
+            free_voice = &voices.at(0);
+        }
+
+        return free_voice;
+    }
+
+    void process_events(int _start_index)
+    {
+        auto iterator = input_queue.begin();
+        while (iterator != input_queue.end()) {
+
+            note_event& event = *iterator;
+            if (event.offset == _start_index) {
+
+                switch (event.type) {
+                case note_event_type::note_on:
+                    note_on(event);
+                    break;
+                case note_event_type::note_off:
+                    note_off(event);
+                    break;
+                }
+
+                iterator = input_queue.erase(iterator);
+            } else {
+                iterator++;
+            }
+        }
+    }
+};
+}
\ No newline at end of file