From e11e1c4cb8fc9be7f46160ba52cdad8acc433ea7 Mon Sep 17 00:00:00 2001
From: William S Fulton <wsf@fultondesigns.co.uk>
Date: Fri, 19 May 2017 08:15:01 +0100
Subject: [PATCH] C# std::complex wrappers marshalling by value

Change the wrapping to marshall directly to the .net
System.Numerics.Complex type instead of using an intermediate
std::complex .net type.
---
 Lib/csharp/std_complex.i | 57 ++++++++++++++++++++++++----------------
 1 file changed, 35 insertions(+), 22 deletions(-)

diff --git a/Lib/csharp/std_complex.i b/Lib/csharp/std_complex.i
index ac30e1692..0f5b6b921 100644
--- a/Lib/csharp/std_complex.i
+++ b/Lib/csharp/std_complex.i
@@ -2,54 +2,67 @@
 #include <complex>
 %}
 
+%fragment("SwigSystemNumericsComplex", "header") {
+// Identical to the layout of System.Numerics.Complex, but does assume that it is
+// LayoutKind.Sequential on the managed side
+struct SwigSystemNumericsComplex {
+  double real;
+  double imag;
+  SwigSystemNumericsComplex(double r = 0.0, double i = 0.0) : real(r), imag(i) {}
+};
+}
+
 namespace std {
 
 %naturalvar complex;
 
-// An extremely simplified subset of std::complex<> which contains just the
-// methods we need.
 template<typename T>
 class complex
 {
 public:
     complex(T re = T(), T im = T());
-
-    T real() const;
-    T imag() const;
 };
 
-} // namespace std
+}
 
 %define swig_complex_typemaps(T)
-%typemap(cstype) std::complex<T>, const std::complex<T>& "System.Numerics.Complex"
+%typemap(ctype, fragment="SwigSystemNumericsComplex") std::complex<T>, const std::complex<T> & "SwigSystemNumericsComplex"
+%typemap(imtype) std::complex<T>, const std::complex<T> & "System.Numerics.Complex"
+%typemap(cstype) std::complex<T>, const std::complex<T> & "System.Numerics.Complex"
 
-// The casts in "pre" are needed in order to allow creating std::complex<float>
-// from System.Numerics.Complex, which always uses doubles. It relies on the
-// fact that the name of the C++ and C# float/double types are the same.
-%typemap(csin,
-         pre="    var cpp$csinput = new Complex_" #T "((" #T ")$csinput.Real, (" #T ")$csinput.Imaginary);"
-        ) std::complex<T>, const std::complex<T>& "Complex_" #T ".getCPtr(cpp$csinput)"
+%typemap(in) std::complex<T>($*1_ltype temp), const std::complex<T> &($*1_ltype temp)
+%{temp = std::complex< double >($input.real, $input.imag);
+  $1 = &temp;%}
 
-%typemap(csout, excode=SWIGEXCODE) std::complex<T>, const std::complex<T>& {
-    Complex_##T cppret = new Complex_##T($imcall, $owner);$excode
-    return new System.Numerics.Complex(cppret.real(), cppret.imag());
+%typemap(out) std::complex<T>
+%{$result = SwigSystemNumericsComplex($1.real(), $1.imag());%}
+
+%typemap(out) const std::complex<T> &
+%{$result = SwigSystemNumericsComplex($1->real(), $1->imag());%}
+
+%typemap(cstype) std::complex<T>, const std::complex<T> & "System.Numerics.Complex"
+
+%typemap(csin) std::complex<T>, const std::complex<T> & "$csinput"
+
+%typemap(csout, excode=SWIGEXCODE) std::complex<T>, const std::complex<T> & {
+    System.Numerics.Complex ret = $imcall;$excode
+    return ret;
   }
 
-%typemap(csvarin, excode=SWIGEXCODE2) const std::complex<T>& %{
+%typemap(csvarin, excode=SWIGEXCODE2) const std::complex<T> & %{
     set {
-      var cppvalue = new Complex_##T((T)value.Real, (T)value.Imaginary);
       $imcall;$excode
     }
   %}
 
-%typemap(csvarout, excode=SWIGEXCODE2) const std::complex<T>& %{
+%typemap(csvarout, excode=SWIGEXCODE2) const std::complex<T> & %{
     get {
-      var cppret = new Complex_##T($imcall, $owner);$excode
-      return new System.Numerics.Complex(cppret.real(), cppret.imag());
+      System.Numerics.Complex ret = $imcall;$excode
+      return ret;
     }
   %}
 
-%template(Complex_##T) std::complex<T>;
+%template() std::complex<T>;
 %enddef
 
 // By default, typemaps for both std::complex<double> and std::complex<float>