From ef3311ea98ff0ad0689c8becd7c956620830bd27 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?J=C3=BCrgen=20Hock?= <juergen.hock@jurihock.de>
Date: Tue, 28 Nov 2023 22:36:30 +0100
Subject: [PATCH] Use const span to indicate the read-only input #39

---
 cpp/StftPitchShift/Dump.h             |  2 +-
 cpp/StftPitchShift/FFT.h              |  8 ++++----
 cpp/StftPitchShift/Normalizer.h       |  4 ++--
 cpp/StftPitchShift/RFFT.h             | 12 ++++++------
 cpp/StftPitchShift/Resampler.h        | 14 +++++++-------
 cpp/StftPitchShift/STFT.h             | 10 +++++-----
 cpp/StftPitchShift/StftPitchShift.cpp |  8 ++++----
 cpp/StftPitchShift/StftPitchShift.h   |  8 ++++----
 8 files changed, 33 insertions(+), 33 deletions(-)

diff --git a/cpp/StftPitchShift/Dump.h b/cpp/StftPitchShift/Dump.h
index e52dae7..a4bdfb6 100755
--- a/cpp/StftPitchShift/Dump.h
+++ b/cpp/StftPitchShift/Dump.h
@@ -22,7 +22,7 @@ namespace stftpitchshift
     }
 
     template<class T>
-    void operator()(const std::span<T> data)
+    void operator()(const std::span<const T> data)
     {
       if (fileindex < minindex)
       {
diff --git a/cpp/StftPitchShift/FFT.h b/cpp/StftPitchShift/FFT.h
index 226218d..f27731d 100755
--- a/cpp/StftPitchShift/FFT.h
+++ b/cpp/StftPitchShift/FFT.h
@@ -12,11 +12,11 @@ namespace stftpitchshift
 
     virtual ~FFT() {}
 
-    virtual void fft(const std::span<float>  frame, const std::span<std::complex<float>>  dft) = 0;
-    virtual void fft(const std::span<double> frame, const std::span<std::complex<double>> dft) = 0;
+    virtual void fft(const std::span<const float>  frame, const std::span<std::complex<float>>  dft) = 0;
+    virtual void fft(const std::span<const double> frame, const std::span<std::complex<double>> dft) = 0;
 
-    virtual void ifft(const std::span<std::complex<float>>  dft, const std::span<float>  frame) = 0;
-    virtual void ifft(const std::span<std::complex<double>> dft, const std::span<double> frame) = 0;
+    virtual void ifft(const std::span<const std::complex<float>>  dft, const std::span<float>  frame) = 0;
+    virtual void ifft(const std::span<const std::complex<double>> dft, const std::span<double> frame) = 0;
 
   };
 }
diff --git a/cpp/StftPitchShift/Normalizer.h b/cpp/StftPitchShift/Normalizer.h
index 177c27f..6e8ca49 100755
--- a/cpp/StftPitchShift/Normalizer.h
+++ b/cpp/StftPitchShift/Normalizer.h
@@ -15,7 +15,7 @@ class Normalizer
   {
   }
 
-  void calibrate(const std::span<std::complex<T>> data)
+  void calibrate(const std::span<const std::complex<T>> data)
   {
     target = rms(data);
   }
@@ -42,7 +42,7 @@ class Normalizer
 
   T target;
 
-  static T rms(const std::span<std::complex<T>> data)
+  static T rms(const std::span<const std::complex<T>> data)
   {
     // without 1/N and sqrt
 
diff --git a/cpp/StftPitchShift/RFFT.h b/cpp/StftPitchShift/RFFT.h
index e1f9023..ccc144f 100755
--- a/cpp/StftPitchShift/RFFT.h
+++ b/cpp/StftPitchShift/RFFT.h
@@ -119,7 +119,7 @@ namespace stftpitchshift
 
   public:
 
-    void fft(const std::span<T> frame, const std::span<std::complex<T>> dft)
+    void fft(const std::span<const T> frame, const std::span<std::complex<T>> dft)
     {
       assert(dft.size() == frame.size() / 2 + 1);
 
@@ -147,7 +147,7 @@ namespace stftpitchshift
       }
     }
 
-    void ifft(const std::span<std::complex<T>> dft, const std::span<T> frame)
+    void ifft(const std::span<const std::complex<T>> dft, const std::span<T> frame)
     {
       assert(dft.size() == frame.size() / 2 + 1);
 
@@ -237,22 +237,22 @@ namespace stftpitchshift
 
   public:
 
-    void fft(const std::span<float> frame, const std::span<std::complex<float>> dft) override
+    void fft(const std::span<const float> frame, const std::span<std::complex<float>> dft) override
     {
       precision.f.fft(frame, dft);
     }
 
-    void fft(const std::span<double> frame, const std::span<std::complex<double>> dft) override
+    void fft(const std::span<const double> frame, const std::span<std::complex<double>> dft) override
     {
       precision.d.fft(frame, dft);
     }
 
-    void ifft(const std::span<std::complex<float>> dft, const std::span<float> frame) override
+    void ifft(const std::span<const std::complex<float>> dft, const std::span<float> frame) override
     {
       precision.f.ifft(dft, frame);
     }
 
-    void ifft(const std::span<std::complex<double>> dft, const std::span<double> frame) override
+    void ifft(const std::span<const std::complex<double>> dft, const std::span<double> frame) override
     {
       precision.d.ifft(dft, frame);
     }
diff --git a/cpp/StftPitchShift/Resampler.h b/cpp/StftPitchShift/Resampler.h
index b808f9a..e8d336b 100755
--- a/cpp/StftPitchShift/Resampler.h
+++ b/cpp/StftPitchShift/Resampler.h
@@ -35,7 +35,7 @@ namespace stftpitchshift
       linear<T>(x, x);
     }
 
-    void linear(const std::span<T> x,
+    void linear(const std::span<const T> x,
                 const std::span<T> y) const
     {
       linear<T>(x, y);
@@ -46,14 +46,14 @@ namespace stftpitchshift
       linear<std::complex<T>>(x, x);
     }
 
-    void linear(const std::span<std::complex<T>> x,
+    void linear(const std::span<const std::complex<T>> x,
                 const std::span<std::complex<T>> y) const
     {
       linear<std::complex<T>>(x, y);
     }
 
-    void bilinear(const std::span<T> x0,
-                  const std::span<T> x1,
+    void bilinear(const std::span<const T> x0,
+                  const std::span<const T> x1,
                   const std::span<T> y) const
     {
       assert(x0.size() == y.size());
@@ -71,8 +71,8 @@ namespace stftpitchshift
       }
     }
 
-    void bilinear(const std::span<std::complex<T>> x0,
-                  const std::span<std::complex<T>> x1,
+    void bilinear(const std::span<const std::complex<T>> x0,
+                  const std::span<const std::complex<T>> x1,
                   const std::span<std::complex<T>> y) const
     {
       assert(x0.size() == y.size());
@@ -95,7 +95,7 @@ namespace stftpitchshift
     double value;
 
     template<class V>
-    void linear(const std::span<V> x,
+    void linear(const std::span<const V> x,
                 const std::span<V> y) const
     {
       assert(x.size() == y.size());
diff --git a/cpp/StftPitchShift/STFT.h b/cpp/StftPitchShift/STFT.h
index 704e8ca..4432cdb 100755
--- a/cpp/StftPitchShift/STFT.h
+++ b/cpp/StftPitchShift/STFT.h
@@ -78,7 +78,7 @@ namespace stftpitchshift
       buffer.freq.resize(buffer.size / 2 + 1);
     }
 
-    void operator()(const std::span<T> input, const std::span<T> output, const std::function<void(std::span<std::complex<T>> dft)> callback)
+    void operator()(const std::span<const T> input, const std::span<T> output, const std::function<void(std::span<std::complex<T>> dft)> callback)
     {
       const size_t samples = (std::min)(input.size(), output.size());
 
@@ -96,7 +96,7 @@ namespace stftpitchshift
         timers.loop.tic();
         for (size_t hop = 0; (hop + buffer.size) < samples; hop += hopsize)
         {
-          const std::span<T> src = input.subspan(hop, buffer.size);
+          const std::span<const T> src = input.subspan(hop, buffer.size);
           const std::span<T> dst = output.subspan(hop, buffer.size);
 
           timers.analysis.tic();
@@ -124,7 +124,7 @@ namespace stftpitchshift
       {
         for (size_t hop = 0; (hop + buffer.size) < samples; hop += hopsize)
         {
-          const std::span<T> src = input.subspan(hop, buffer.size);
+          const std::span<const T> src = input.subspan(hop, buffer.size);
           const std::span<T> dst = output.subspan(hop, buffer.size);
 
           reject(src, buffer.time, window.analysis);
@@ -182,7 +182,7 @@ namespace stftpitchshift
       fft->ifft(dft, frame);
     }
 
-    inline void reject(const std::span<T> input, const std::span<T> frame, const std::span<T> window) const
+    inline void reject(const std::span<const T> input, const std::span<T> frame, const std::span<T> window) const
     {
       for (size_t i = 0; i < window.size(); ++i)
       {
@@ -190,7 +190,7 @@ namespace stftpitchshift
       }
     }
 
-    inline void inject(const std::span<T> output, const std::span<T> frame, const std::span<T> window) const
+    inline void inject(const std::span<T> output, const std::span<const T> frame, const std::span<T> window) const
     {
       for (size_t i = 0; i < window.size(); ++i)
       {
diff --git a/cpp/StftPitchShift/StftPitchShift.cpp b/cpp/StftPitchShift/StftPitchShift.cpp
index cc0ac8d..c9d193f 100755
--- a/cpp/StftPitchShift/StftPitchShift.cpp
+++ b/cpp/StftPitchShift/StftPitchShift.cpp
@@ -74,7 +74,7 @@ StftPitchShift::StftPitchShift(
 }
 
 void StftPitchShift::shiftpitch(
-  const std::span<float> input,
+  const std::span<const float> input,
   const std::span<float> output,
   const double factor,
   const double quefrency,
@@ -91,7 +91,7 @@ void StftPitchShift::shiftpitch(
 }
 
 void StftPitchShift::shiftpitch(
-  const std::span<double> input,
+  const std::span<const double> input,
   const std::span<double> output,
   const double factor,
   const double quefrency,
@@ -108,7 +108,7 @@ void StftPitchShift::shiftpitch(
 }
 
 void StftPitchShift::shiftpitch(
-  const std::span<float> input,
+  const std::span<const float> input,
   const std::span<float> output,
   const std::vector<double>& factors,
   const double quefrency,
@@ -133,7 +133,7 @@ void StftPitchShift::shiftpitch(
 }
 
 void StftPitchShift::shiftpitch(
-  const std::span<double> input,
+  const std::span<const double> input,
   const std::span<double> output,
   const std::vector<double>& factors,
   const double quefrency,
diff --git a/cpp/StftPitchShift/StftPitchShift.h b/cpp/StftPitchShift/StftPitchShift.h
index 18571ed..10495b4 100755
--- a/cpp/StftPitchShift/StftPitchShift.h
+++ b/cpp/StftPitchShift/StftPitchShift.h
@@ -85,7 +85,7 @@ namespace stftpitchshift
      * @param distortion The fractional timbre shifting factor.
      */
     void shiftpitch(
-      const std::span<float> input,
+      const std::span<const float> input,
       const std::span<float> output,
       const double factor = 1,
       const double quefrency = 0,
@@ -99,7 +99,7 @@ namespace stftpitchshift
      * @param distortion The fractional timbre shifting factor.
      */
     void shiftpitch(
-      const std::span<double> input,
+      const std::span<const double> input,
       const std::span<double> output,
       const double factor = 1,
       const double quefrency = 0,
@@ -113,7 +113,7 @@ namespace stftpitchshift
      * @param distortion The fractional timbre shifting factor.
      */
     void shiftpitch(
-      const std::span<float> input,
+      const std::span<const float> input,
       const std::span<float> output,
       const std::vector<double>& factors,
       const double quefrency = 0,
@@ -127,7 +127,7 @@ namespace stftpitchshift
      * @param distortion The fractional timbre shifting factor.
      */
     void shiftpitch(
-      const std::span<double> input,
+      const std::span<const double> input,
       const std::span<double> output,
       const std::vector<double>& factors,
       const double quefrency = 0,