XMLAttributeValueView.h

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/**********************************************************************
 
  Audacity: A Digital Audio Editor
 
  XMLAttributeValueView.h
 
  Dmitry Vedenko
 
**********************************************************************/
 
#pragma once
 
#include <cstdint>
#include <stdexcept>
#include <string>
#include <string_view>
#include <limits>
 
#include <wx/string.h>
 
class XML_API XMLAttributeValueView final
{
public:
   enum class Type
   {
      Null, 
      SignedInteger, 
      UnsignedInteger, 
      Float, 
      Double, 
      StringView 
   };
 
   XMLAttributeValueView() = default;
 
   XMLAttributeValueView(const XMLAttributeValueView&) = default;
   XMLAttributeValueView(XMLAttributeValueView&&) = default;
 
   XMLAttributeValueView& operator = (const XMLAttributeValueView&) = default;
   XMLAttributeValueView& operator = (XMLAttributeValueView&&) = default;
 
   explicit XMLAttributeValueView(bool value) noexcept;
   explicit XMLAttributeValueView(short value) noexcept;
   explicit XMLAttributeValueView(unsigned short value) noexcept;
   explicit XMLAttributeValueView(int value) noexcept;
   explicit XMLAttributeValueView(unsigned int value) noexcept;
   explicit XMLAttributeValueView(long value) noexcept;
   explicit XMLAttributeValueView(unsigned long value) noexcept;
   explicit XMLAttributeValueView(long long value) noexcept;
   explicit XMLAttributeValueView(unsigned long long value) noexcept;
   explicit XMLAttributeValueView(float value) noexcept;
   explicit XMLAttributeValueView(double value) noexcept;
   explicit XMLAttributeValueView(const std::string_view& value) noexcept;
 
   Type GetType() const noexcept;
 
   bool IsNull() const noexcept;
 
   bool IsSignedInteger() const noexcept;
   bool IsUnsignedInteger() const noexcept;
   bool IsFloat() const noexcept;
   bool IsDouble() const noexcept;
   bool IsStringView() const noexcept;
 
   bool TryGet(bool& value) const noexcept;
   bool TryGet(short& value) const noexcept;
   bool TryGet(unsigned short& value) const noexcept;
   bool TryGet(int& value) const noexcept;
   bool TryGet(unsigned int& value) const noexcept;
   bool TryGet(long& value) const noexcept;
   bool TryGet(unsigned long& value) const noexcept;
   bool TryGet(long long& value) const noexcept;
   bool TryGet(unsigned long long& value) const noexcept;
   bool TryGet(float& value) const noexcept;
   bool TryGet(double& value) const noexcept;
   bool TryGet(std::string_view& value) const noexcept;
 
   template<typename T>
   T Get(T defaultValue = {}) const noexcept
   {
      // TryGet only modifies the value if conversion is possible,
      // so just reuse the defaultValue
      (void) TryGet(defaultValue);
      return defaultValue;
   }
   std::string ToString() const;
   wxString ToWString() const;
 
private:
   template <typename ResultType>
   bool TryGetInteger(ResultType& value) const noexcept;
   // std::variant requires macOS 10.14, which is significantly higher than
   // the current target
   union
   {
      int64_t mInteger;
      double  mDouble;
      float   mFloat;
 
      struct  
      {
         const char* Data;
         size_t Length;
      } mStringView;
   };
 
   Type mType { Type::Null };
};