From d6e79c9023ad66986fcfe16caef15d8e8b14a20f Mon Sep 17 00:00:00 2001
From: Chris Robinson <chris.kcat@gmail.com>
Date: Thu, 19 Jan 2023 13:30:00 -0800
Subject: Minor code refactor for the frequency shifter effect

---
 alc/effects/fshifter.cpp | 97 +++++++++++++++++++++++++-----------------------
 1 file changed, 50 insertions(+), 47 deletions(-)

(limited to 'alc/effects/fshifter.cpp')

diff --git a/alc/effects/fshifter.cpp b/alc/effects/fshifter.cpp
index 5d899aed..4bdb53a7 100644
--- a/alc/effects/fshifter.cpp
+++ b/alc/effects/fshifter.cpp
@@ -48,44 +48,47 @@ namespace {
 using uint = unsigned int;
 using complex_d = std::complex<double>;
 
-#define HIL_SIZE 1024
-#define OVERSAMP (1<<2)
+constexpr size_t HilSize{1024};
+constexpr size_t HilHalfSize{HilSize >> 1};
+constexpr size_t OversampleFactor{4};
 
-#define HIL_STEP     (HIL_SIZE / OVERSAMP)
-#define FIFO_LATENCY (HIL_STEP * (OVERSAMP-1))
+static_assert(HilSize%OversampleFactor == 0, "Factor must be a clean divisor of the size");
+constexpr size_t HilStep{HilSize / OversampleFactor};
 
 /* Define a Hann window, used to filter the HIL input and output. */
-std::array<double,HIL_SIZE> InitHannWindow()
-{
-    std::array<double,HIL_SIZE> ret;
-    /* Create lookup table of the Hann window for the desired size, i.e. HIL_SIZE */
-    for(size_t i{0};i < HIL_SIZE>>1;i++)
+struct Windower {
+    alignas(16) std::array<double,HilSize> mData;
+
+    Windower()
     {
-        constexpr double scale{al::numbers::pi / double{HIL_SIZE}};
-        const double val{std::sin((static_cast<double>(i)+0.5) * scale)};
-        ret[i] = ret[HIL_SIZE-1-i] = val * val;
+        /* Create lookup table of the Hann window for the desired size. */
+        for(size_t i{0};i < HilHalfSize;i++)
+        {
+            constexpr double scale{al::numbers::pi / double{HilSize}};
+            const double val{std::sin((static_cast<double>(i)+0.5) * scale)};
+            mData[i] = mData[HilSize-1-i] = val * val;
+        }
     }
-    return ret;
-}
-alignas(16) const std::array<double,HIL_SIZE> HannWindow = InitHannWindow();
+};
+const Windower gWindow{};
 
 
 struct FshifterState final : public EffectState {
     /* Effect parameters */
     size_t mCount{};
     size_t mPos{};
-    uint mPhaseStep[2]{};
-    uint mPhase[2]{};
-    double mSign[2]{};
+    std::array<uint,2> mPhaseStep{};
+    std::array<uint,2> mPhase{};
+    std::array<double,2> mSign{};
 
     /* Effects buffers */
-    double mInFIFO[HIL_SIZE]{};
-    complex_d mOutFIFO[HIL_STEP]{};
-    complex_d mOutputAccum[HIL_SIZE]{};
-    complex_d mAnalytic[HIL_SIZE]{};
-    complex_d mOutdata[BufferLineSize]{};
+    std::array<double,HilSize> mInFIFO{};
+    std::array<complex_d,HilStep> mOutFIFO{};
+    std::array<complex_d,HilSize> mOutputAccum{};
+    std::array<complex_d,HilSize> mAnalytic{};
+    std::array<complex_d,BufferLineSize> mOutdata{};
 
-    alignas(16) float mBufferOut[BufferLineSize]{};
+    alignas(16) FloatBufferLine mBufferOut{};
 
     /* Effect gains for each output channel */
     struct {
@@ -107,15 +110,15 @@ void FshifterState::deviceUpdate(const DeviceBase*, const Buffer&)
 {
     /* (Re-)initializing parameters and clear the buffers. */
     mCount = 0;
-    mPos = FIFO_LATENCY;
+    mPos = HilSize - HilStep;
 
-    std::fill(std::begin(mPhaseStep),   std::end(mPhaseStep),   0u);
-    std::fill(std::begin(mPhase),       std::end(mPhase),       0u);
-    std::fill(std::begin(mSign),        std::end(mSign),        1.0);
-    std::fill(std::begin(mInFIFO),      std::end(mInFIFO),      0.0);
-    std::fill(std::begin(mOutFIFO),     std::end(mOutFIFO),     complex_d{});
-    std::fill(std::begin(mOutputAccum), std::end(mOutputAccum), complex_d{});
-    std::fill(std::begin(mAnalytic),    std::end(mAnalytic),    complex_d{});
+    mPhaseStep.fill(0u);
+    mPhase.fill(0u);
+    mSign.fill(1.0);
+    mInFIFO.fill(0.0);
+    mOutFIFO.fill(complex_d{});
+    mOutputAccum.fill(complex_d{});
+    mAnalytic.fill(complex_d{});
 
     for(auto &gain : mGains)
     {
@@ -172,7 +175,7 @@ void FshifterState::process(const size_t samplesToDo, const al::span<const Float
 {
     for(size_t base{0u};base < samplesToDo;)
     {
-        size_t todo{minz(HIL_STEP-mCount, samplesToDo-base)};
+        size_t todo{minz(HilStep-mCount, samplesToDo-base)};
 
         /* Fill FIFO buffer with samples data */
         const size_t pos{mPos};
@@ -185,33 +188,33 @@ void FshifterState::process(const size_t samplesToDo, const al::span<const Float
         mCount = count;
 
         /* Check whether FIFO buffer is filled */
-        if(mCount < HIL_STEP) break;
+        if(mCount < HilStep) break;
         mCount = 0;
-        mPos = (mPos+HIL_STEP) & (HIL_SIZE-1);
+        mPos = (mPos+HilStep) & (HilSize-1);
 
         /* Real signal windowing and store in Analytic buffer */
-        for(size_t src{mPos}, k{0u};src < HIL_SIZE;++src,++k)
-            mAnalytic[k] = mInFIFO[src]*HannWindow[k];
-        for(size_t src{0u}, k{HIL_SIZE-mPos};src < mPos;++src,++k)
-            mAnalytic[k] = mInFIFO[src]*HannWindow[k];
+        for(size_t src{mPos}, k{0u};src < HilSize;++src,++k)
+            mAnalytic[k] = mInFIFO[src]*gWindow.mData[k];
+        for(size_t src{0u}, k{HilSize-mPos};src < mPos;++src,++k)
+            mAnalytic[k] = mInFIFO[src]*gWindow.mData[k];
 
         /* Processing signal by Discrete Hilbert Transform (analytical signal). */
         complex_hilbert(mAnalytic);
 
         /* Windowing and add to output accumulator */
-        for(size_t dst{mPos}, k{0u};dst < HIL_SIZE;++dst,++k)
-            mOutputAccum[dst] += 2.0/OVERSAMP*HannWindow[k]*mAnalytic[k];
-        for(size_t dst{0u}, k{HIL_SIZE-mPos};dst < mPos;++dst,++k)
-            mOutputAccum[dst] += 2.0/OVERSAMP*HannWindow[k]*mAnalytic[k];
+        for(size_t dst{mPos}, k{0u};dst < HilSize;++dst,++k)
+            mOutputAccum[dst] += 2.0/OversampleFactor*gWindow.mData[k]*mAnalytic[k];
+        for(size_t dst{0u}, k{HilSize-mPos};dst < mPos;++dst,++k)
+            mOutputAccum[dst] += 2.0/OversampleFactor*gWindow.mData[k]*mAnalytic[k];
 
         /* Copy out the accumulated result, then clear for the next iteration. */
-        std::copy_n(mOutputAccum + mPos, HIL_STEP, mOutFIFO);
-        std::fill_n(mOutputAccum + mPos, HIL_STEP, complex_d{});
+        std::copy_n(mOutputAccum.cbegin() + mPos, HilStep, mOutFIFO.begin());
+        std::fill_n(mOutputAccum.begin() + mPos, HilStep, complex_d{});
     }
 
     /* Process frequency shifter using the analytic signal obtained. */
-    float *RESTRICT BufferOut{mBufferOut};
-    for(int c{0};c < 2;++c)
+    float *RESTRICT BufferOut{al::assume_aligned<16>(mBufferOut.data())};
+    for(size_t c{0};c < 2;++c)
     {
         const uint phase_step{mPhaseStep[c]};
         uint phase_idx{mPhase[c]};
-- 
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