Avoid using std::cyl_bessel_i

We can't rely on it because it's "optional", and some systems report it at compile time but then fail to load at runtime.
kcat · Aug 27, 2024 · 3261333 · 3261333
1 parent adc4574
commit 3261333
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Showing 2 changed files with 6 additions and 16 deletions.
diff --git a/common/polyphase_resampler.cpp b/common/polyphase_resampler.cpp
@@ -17,10 +17,6 @@ namespace {
 
 constexpr double Epsilon{1e-9};
 
-#if __cpp_lib_math_special_functions >= 201603L
-using std::cyl_bessel_i;
-
-#else
 
 /* The zero-order modified Bessel function of the first kind, used for the
  * Kaiser window.
@@ -33,7 +29,7 @@ using std::cyl_bessel_i;
  * compounding the rounding and precision error), but it's good enough.
  */
 template<typename T, typename U>
-U cyl_bessel_i(T nu, U x)
+constexpr auto cyl_bessel_i(T nu, U x) -> U
 {
     if(nu != T{0})
         throw std::runtime_error{"cyl_bessel_i: nu != 0"};
@@ -57,7 +53,6 @@ U cyl_bessel_i(T nu, U x)
     } while(sum != last_sum);
     return static_cast<U>(sum);
 }
-#endif
 
 /* This is the normalized cardinal sine (sinc) function.
  *
@@ -89,7 +84,7 @@ double Kaiser(const double beta, const double k, const double besseli_0_beta)
 {
     if(!(k >= -1.0 && k <= 1.0))
         return 0.0;
-    return cyl_bessel_i(0, beta * std::sqrt(1.0 - k*k)) / besseli_0_beta;
+    return ::cyl_bessel_i(0, beta * std::sqrt(1.0 - k*k)) / besseli_0_beta;
 }
 
 /* Calculates the size (order) of the Kaiser window.  Rejection is in dB and
@@ -158,7 +153,7 @@ void PPhaseResampler::init(const uint srcRate, const uint dstRate)
     // calculating the left offset to avoid increasing the transition width.
     const uint l{(CalcKaiserOrder(180.0, width)+1) / 2};
     const double beta{CalcKaiserBeta(180.0)};
-    const double besseli_0_beta{cyl_bessel_i(0, beta)};
+    const double besseli_0_beta{::cyl_bessel_i(0, beta)};
     mM = l*2 + 1;
     mL = l;
     mF.resize(mM);

diff --git a/core/bsinc_tables.cpp b/core/bsinc_tables.cpp
@@ -22,10 +22,6 @@ namespace {
 
 using uint = unsigned int;
 
-#if __cpp_lib_math_special_functions >= 201603L
-using std::cyl_bessel_i;
-
-#else
 
 /* The zero-order modified Bessel function of the first kind, used for the
  * Kaiser window.
@@ -38,7 +34,7 @@ using std::cyl_bessel_i;
  * compounding the rounding and precision error), but it's good enough.
  */
 template<typename T, typename U>
-U cyl_bessel_i(T nu, U x)
+constexpr auto cyl_bessel_i(T nu, U x) -> U
 {
     if(nu != T{0})
         throw std::runtime_error{"cyl_bessel_i: nu != 0"};
@@ -62,7 +58,6 @@ U cyl_bessel_i(T nu, U x)
     } while(sum != last_sum);
     return static_cast<U>(sum);
 }
-#endif
 
 /* This is the normalized cardinal sine (sinc) function.
  *
@@ -95,7 +90,7 @@ constexpr double Kaiser(const double beta, const double k, const double besseli_
 {
     if(!(k >= -1.0 && k <= 1.0))
         return 0.0;
-    return cyl_bessel_i(0, beta * std::sqrt(1.0 - k*k)) / besseli_0_beta;
+    return ::cyl_bessel_i(0, beta * std::sqrt(1.0 - k*k)) / besseli_0_beta;
 }
 
 /* Calculates the (normalized frequency) transition width of the Kaiser window.
@@ -165,7 +160,7 @@ struct SIMDALIGN BSincFilterArray {
         using filter_type = std::array<std::array<double,BSincPointsMax>,BSincPhaseCount>;
         auto filter = std::vector<filter_type>(BSincScaleCount);
 
-        const double besseli_0_beta{cyl_bessel_i(0, hdr.beta)};
+        const double besseli_0_beta{::cyl_bessel_i(0, hdr.beta)};
 
         /* Calculate the Kaiser-windowed Sinc filter coefficients for each
          * scale and phase index.