Use a variant to control the modulator effect generator

kcat · Feb 16, 2024 · d81b453 · d81b453
1 parent 8e672fc
commit d81b453
Showing 1 changed file with 44 additions and 44 deletions.
diff --git a/alc/effects/modulator.cpp b/alc/effects/modulator.cpp
@@ -48,42 +48,29 @@ namespace {
 
 using uint = unsigned int;
 
-inline float Sin(uint index, float scale)
-{ return std::sin(static_cast<float>(index) * scale); }
-
-inline float Saw(uint index, float scale)
-{ return static_cast<float>(index)*scale - 1.0f; }
-
-inline float Square(uint index, float scale)
-{ return float(static_cast<float>(index)*scale < 0.5f)*2.0f - 1.0f; }
+struct SinFunc {
+    static auto Get(uint index, float scale) noexcept(noexcept(std::sin(0.0f))) -> float
+    { return std::sin(static_cast<float>(index) * scale); }
+};
 
-inline float One(uint, float)
-{ return 1.0f; }
+struct SawFunc {
+    static constexpr auto Get(uint index, float scale) noexcept -> float
+    { return static_cast<float>(index)*scale - 1.0f; }
+};
 
-struct ModulatorState final : public EffectState {
-    template<float (&func)(uint,float)>
-    void Modulate(size_t todo)
-    {
-        const uint range{mRange};
-        const float scale{mIndexScale};
-        uint index{mIndex};
+struct SquareFunc {
+    static constexpr auto Get(uint index, float scale) noexcept -> float
+    { return float(static_cast<float>(index)*scale < 0.5f)*2.0f - 1.0f; }
+};
 
-        ASSUME(range > 1);
-        ASSUME(todo > 0);
+struct OneFunc {
+    static constexpr auto Get(uint, float) noexcept -> float
+    { return 1.0f; }
+};
 
-        for(size_t i{0};i < todo;)
-        {
-            size_t rem{std::min(todo-i, size_t{range-index})};
-            do {
-                mModSamples[i++] = func(index++, scale);
-            } while(--rem);
-            if(index == range)
-                index = 0;
-        }
-        mIndex = index;
-    }
 
-    void (ModulatorState::*mGenModSamples)(size_t){};
+struct ModulatorState final : public EffectState {
+    std::variant<OneFunc,SinFunc,SawFunc,SquareFunc> mSampleGen;
 
     uint mIndex{0};
     uint mRange{1};
@@ -110,13 +97,6 @@ struct ModulatorState final : public EffectState {
         const al::span<FloatBufferLine> samplesOut) override;
 };
 
-template<>
-void ModulatorState::Modulate<One>(size_t todo)
-{
-    std::fill_n(mModSamples.begin(), todo, 1.0f);
-    mIndex = 0;
-}
-
 void ModulatorState::deviceUpdate(const DeviceBase*, const BufferStorage*)
 {
     for(auto &e : mChans)
@@ -151,27 +131,27 @@ void ModulatorState::update(const ContextBase *context, const EffectSlot *slot,
     if(mRange == 1)
     {
         mIndexScale = 0.0f;
-        mGenModSamples = &ModulatorState::Modulate<One>;
+        mSampleGen.emplace<OneFunc>();
     }
     else if(props.Waveform == ModulatorWaveform::Sinusoid)
     {
         mIndexScale = al::numbers::pi_v<float>*2.0f / static_cast<float>(mRange);
-        mGenModSamples = &ModulatorState::Modulate<Sin>;
+        mSampleGen.emplace<SinFunc>();
     }
     else if(props.Waveform == ModulatorWaveform::Sawtooth)
     {
         mIndexScale = 2.0f / static_cast<float>(mRange-1);
-        mGenModSamples = &ModulatorState::Modulate<Saw>;
+        mSampleGen.emplace<SawFunc>();
     }
-    else /*if(props.Waveform == ModulatorWaveform::Square)*/
+    else if(props.Waveform == ModulatorWaveform::Square)
     {
         /* For square wave, the range should be even (there should be an equal
          * number of high and low samples). An odd number of samples per cycle
          * would need a more complex value generator.
          */
         mRange = (mRange+1) & ~1u;
         mIndexScale = 1.0f / static_cast<float>(mRange-1);
-        mGenModSamples = &ModulatorState::Modulate<Square>;
+        mSampleGen.emplace<SquareFunc>();
     }
 
     float f0norm{props.HighPassCutoff / static_cast<float>(device->Frequency)};
@@ -192,7 +172,27 @@ void ModulatorState::update(const ContextBase *context, const EffectSlot *slot,
 
 void ModulatorState::process(const size_t samplesToDo, const al::span<const FloatBufferLine> samplesIn, const al::span<FloatBufferLine> samplesOut)
 {
-    (this->*mGenModSamples)(samplesToDo);
+    ASSUME(samplesToDo > 0);
+
+    std::visit([this,samplesToDo](auto&& type)
+    {
+        const uint range{mRange};
+        const float scale{mIndexScale};
+        uint index{mIndex};
+
+        ASSUME(range > 1);
+
+        for(size_t i{0};i < samplesToDo;)
+        {
+            size_t rem{std::min(samplesToDo-i, size_t{range-index})};
+            do {
+                mModSamples[i++] = type.Get(index++, scale);
+            } while(--rem);
+            if(index == range)
+                index = 0;
+        }
+        mIndex = index;
+    }, mSampleGen);
 
     auto chandata = mChans.begin();
     for(const auto &input : samplesIn)