From 6f65580ee025dc473a88d4d1dd0b5148b785ffd7 Mon Sep 17 00:00:00 2001
From: Alex St-Onge <stonge.alex@gmail.com>
Date: Wed, 1 Nov 2023 08:57:45 -0700
Subject: [PATCH] waveguide gates

---
 include/delayline.h        |  3 +++
 include/waveguide_gates.h  | 32 +++++++++++++++++++++++++
 scripts/waveguide_gates.py |  2 --
 src/CMakeLists.txt         |  3 ++-
 src/delayline.cpp          | 12 ++++++++++
 src/waveguide_gates.cpp    | 49 ++++++++++++++++++++++++++++++++++++++
 6 files changed, 98 insertions(+), 3 deletions(-)
 create mode 100644 include/waveguide_gates.h
 create mode 100644 src/waveguide_gates.cpp

diff --git a/include/delayline.h b/include/delayline.h
index da08209..1948ad2 100644
--- a/include/delayline.h
+++ b/include/delayline.h
@@ -69,6 +69,9 @@ class Delayline
     /// @param input Input sample
     void SetIn(float delay, float input);
 
+    float& operator[](size_t index) const;
+    float& operator[](size_t index);
+
   protected:
     const size_t max_size_ = 0;
     const bool reverse_ = false;
diff --git a/include/waveguide_gates.h b/include/waveguide_gates.h
new file mode 100644
index 0000000..ddf5f73
--- /dev/null
+++ b/include/waveguide_gates.h
@@ -0,0 +1,32 @@
+#pragma once
+
+#include "dsp_base.h"
+
+#include "delayline.h"
+
+namespace dsp
+{
+
+class WaveguideGates
+{
+  public:
+    WaveguideGates();
+    ~WaveguideGates() = default;
+
+    void SetDelay(float delay);
+    float GetDelay() const;
+
+    void SetCoeff(float c);
+
+    void Process(Delayline& left_traveling_line, Delayline& right_traveling_line);
+
+  private:
+    float coeff_ = 0.f;
+    float delay_ = 0.f;
+    size_t delay_integer_ = 0;
+    float delay_fractional_ = 0.f;
+    float inv_delay_fractional_ = 0.f;
+    Delayline delay_left_;
+    Delayline delay_right_;
+};
+} // namespace dsp
\ No newline at end of file
diff --git a/scripts/waveguide_gates.py b/scripts/waveguide_gates.py
index b9466c0..549b77f 100644
--- a/scripts/waveguide_gates.py
+++ b/scripts/waveguide_gates.py
@@ -24,8 +24,6 @@ def tick(self, input):
 
         return a + (b - a) * self.delay_frac
 
-
-
 Fs = 48000
 
 # Waveguide Length
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index bc07038..d33113a 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -14,7 +14,8 @@ set(LIB_SOURCES
     sinc_resampler.cpp
     string_ensemble.cpp
     termination.cpp
-    waveguide.cpp)
+    waveguide.cpp
+    waveguide_gates.cpp)
 
 add_library(dsp STATIC ${LIB_SOURCES})
 
diff --git a/src/delayline.cpp b/src/delayline.cpp
index 4482927..9996f68 100644
--- a/src/delayline.cpp
+++ b/src/delayline.cpp
@@ -124,4 +124,16 @@ void Delayline::SetIn(float delay, float input)
     }
 }
 
+float& Delayline::operator[](size_t index) const
+{
+    size_t read_ptr = (write_ptr_ + index) % max_size_;
+    return line_[read_ptr];
+}
+
+float& Delayline::operator[](size_t index)
+{
+    size_t read_ptr = (write_ptr_ + index) % max_size_;
+    return line_[read_ptr];
+}
+
 } // namespace dsp
\ No newline at end of file
diff --git a/src/waveguide_gates.cpp b/src/waveguide_gates.cpp
new file mode 100644
index 0000000..676d600
--- /dev/null
+++ b/src/waveguide_gates.cpp
@@ -0,0 +1,49 @@
+#include "waveguide_gates.h"
+
+namespace dsp
+{
+
+WaveguideGates::WaveguideGates() : delay_left_(8), delay_right_(8)
+{
+}
+
+void WaveguideGates::SetDelay(float delay)
+{
+    delay_ = delay;
+    delay_integer_ = static_cast<int>(delay);
+    delay_fractional_ = delay - delay_integer_;
+    inv_delay_fractional_ = 1.f - delay_fractional_;
+
+    delay_left_.SetDelay(delay_fractional_ * 2.f);
+    delay_right_.SetDelay(inv_delay_fractional_ * 2.f);
+}
+
+float WaveguideGates::GetDelay() const
+{
+    return delay_;
+}
+
+void WaveguideGates::SetCoeff(float c)
+{
+    coeff_ = c;
+}
+
+void WaveguideGates::Process(Delayline& left_traveling_line, Delayline& right_traveling_line)
+{
+    const float kLeftGate = delay_integer_ - 1;
+    const float kRightGate = delay_integer_ + 1;
+
+    float left_input = right_traveling_line.TapOut(kLeftGate);
+    float left_interpolated = delay_left_.Tick(left_input);
+    float left_gate_sample = left_traveling_line.TapOut(delay_integer_);
+    float new_sample = left_gate_sample * (1 - coeff_) + left_interpolated * (coeff_);
+    left_traveling_line.SetIn(delay_integer_, left_interpolated);
+
+    float right_input = left_traveling_line.TapOut(kRightGate);
+    float right_interpolated = delay_right_.Tick(right_input);
+    float right_gate_sample = right_traveling_line.TapOut(delay_integer_);
+    new_sample += right_gate_sample * (1 - coeff_) + right_interpolated * (coeff_);
+    right_traveling_line.SetIn(delay_integer_, right_interpolated);
+}
+
+} // namespace dsp
\ No newline at end of file