RAII classes for udunits

include/udunitscpp.h

@@ -0,0 +1,94 @@
+#pragma once
+#include "MString.h"
+#include <udunits2.h>
+
+using michlib::MString;
+
+class UtUnit
+{
+ static ut_system* system;
+ static size_t     count;
+
+ ut_unit* unit;
+
+ class ConverterRAII
+ {
+  cv_converter* cnv;
+
+  ConverterRAII()                     = delete;
+  ConverterRAII(const ConverterRAII&) = delete;
+
+  public:
+  ConverterRAII(ConverterRAII&&) = default;
+
+  ConverterRAII(const ut_unit* fr, const ut_unit* to): cnv(ut_get_converter(fr, to))
+  {
+   /*
+   auto* frc = ut_clone(fr);
+   auto* toc = ut_clone(to);
+   cnv       = ut_get_converter(frc, toc);
+   if(frc != nullptr) ut_free(frc);
+   if(toc != nullptr) ut_free(toc);
+   */
+  }
+  ~ConverterRAII()
+  {
+   if(cnv != nullptr) cv_free(cnv);
+  }
+
+  explicit operator bool() const { return cnv != nullptr; }
+  float    operator()(float v) const { return cnv == nullptr ? v : cv_convert_float(cnv, v); }
+  double   operator()(double v) const { return cnv == nullptr ? v : cv_convert_float(cnv, v); }
+ };
+
+ static void ReadSystem()
+ {
+  if(system == nullptr)
+  {
+   auto oldhandler = ut_set_error_message_handler(ut_ignore);
+   system          = ut_read_xml(nullptr);
+   ut_set_error_message_handler(oldhandler);
+  }
+ }
+
+ static void DestroySystem()
+ {
+  if(system != nullptr) ut_free_system(system);
+  system = nullptr;
+ }
+
+ UtUnit()              = delete;
+ UtUnit(const UtUnit&) = delete;
+
+ public:
+ UtUnit(UtUnit&&) = default;
+
+ UtUnit(const MString& desc)
+ {
+  ReadSystem();
+  unit = ut_parse(system, desc.Buf(), UT_UTF8);
+  if(unit != nullptr) count++;
+ }
+
+ ~UtUnit()
+ {
+  if(unit != nullptr)
+  {
+   count--;
+   ut_free(unit);
+   unit = nullptr;
+  }
+  if(count == 0) DestroySystem();
+ }
+
+ explicit operator bool() const { return unit != nullptr; }
+
+ bool operator==(const UtUnit& u) const { return ut_compare(unit, u.unit) == 0; }
+
+ bool Compatible(const UtUnit& u) const { return ut_are_convertible(unit, u.unit) != 0; }
+
+ auto Converter(const UtUnit& u) const { return ConverterRAII{unit, u.unit}; }
+};
+
+inline bool Compatible(const UtUnit& u1, const UtUnit& u2) { return u1.Compatible(u2); }
+inline auto Converter(const UtUnit& fr, const UtUnit& to) { return fr.Converter(to); }

src/udunitscpp.cpp

@@ -0,0 +1,5 @@
+#define MICHLIB_NOSOURCE
+#include "udunitscpp.h"
+
+ut_system* UtUnit::system = nullptr;
+size_t     UtUnit::count  = 0;