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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>
/*! \brief A view into an attribute value. The class does not take the ownership of the data.
*
* Audacity internally uses regular XML and an internal binary XML-like format.
* Binary format extends the possible XML types to support integers and floating point values,
* not just the string values.
*
* This class represents the attribute value for both text and binary XML formats.
*
* Class has a number of Get overloads, that allow to read the value with the required data type.
*
* Integer-based types can be read from the view if it was initialized by an integer value or with a
* string_view that is a textual representation of an integer value. To avoid runtime data loss it is not
* possible to read an integer from the floating point values. Boundary checks are always performed.
* If the type is not large enough to store the value, Get fails.
*
* Floating point values can be read from the view, if it is initialized using floating point, integer or
* a compatible string value. Conversion from Float to Double is forbidden.
*
* String values can be read only if the view was created using a string_view.
* However there are ToString() and ToWString() methods that allow conversion from any type to string.
* Null type is represented by an empty string.
*/
class XML_API XMLAttributeValueView final
{
public:
//! Type of the value represented by the XMLAttributeValueView.
enum class Type
{
Null, //!< The value is not initialized.
SignedInteger, //!< The value is a signed integer.
UnsignedInteger, //!< The value is an unsigned integer.
Float, //!< The value is a single precision floating point value.
Double, //!< The value is a double precision floating point value.
StringView //!< The value is a string_view.
};
//! Construct an uninitialized view of type Null
XMLAttributeValueView() = default;
XMLAttributeValueView(const XMLAttributeValueView&) = default;
XMLAttributeValueView(XMLAttributeValueView&&) = default;
XMLAttributeValueView& operator = (const XMLAttributeValueView&) = default;
XMLAttributeValueView& operator = (XMLAttributeValueView&&) = default;
//! Construct a view of type UnsignedInteger from the value.
explicit XMLAttributeValueView(bool value) noexcept;
//! Construct a view of type SignedInteger from the value.
explicit XMLAttributeValueView(short value) noexcept;
//! Construct a view of type UnsignedInteger from the value.
explicit XMLAttributeValueView(unsigned short value) noexcept;
//! Construct a view of type SignedInteger from the value.
explicit XMLAttributeValueView(int value) noexcept;
//! Construct a view of type UnsignedInteger from the value.
explicit XMLAttributeValueView(unsigned int value) noexcept;
//! Construct a view of type SignedInteger from the value.
explicit XMLAttributeValueView(long value) noexcept;
//! Construct a view of type UnsignedInteger from the value.
explicit XMLAttributeValueView(unsigned long value) noexcept;
//! Construct a view of type SignedInteger from the value.
explicit XMLAttributeValueView(long long value) noexcept;
//! Construct a view of type UnsignedInteger from the value.
explicit XMLAttributeValueView(unsigned long long value) noexcept;
//! Construct a view of type Float from the value.
explicit XMLAttributeValueView(float value) noexcept;
//! Construct a view of type Double from the value.
explicit XMLAttributeValueView(double value) noexcept;
//! Construct a view of type StringView from the value.
explicit XMLAttributeValueView(const std::string_view& value) noexcept;
//! Get the view type.
Type GetType() const noexcept;
//! Check if view is Null.
bool IsNull() const noexcept;
//! Check if view has the SignedInteger type.
bool IsSignedInteger() const noexcept;
//! Check if view has the UnsignedInteger type.
bool IsUnsignedInteger() const noexcept;
//! Check if view has the Float type.
bool IsFloat() const noexcept;
//! Check if view has the Double type.
bool IsDouble() const noexcept;
//! Check if view has the StringView type.
bool IsStringView() const noexcept;
//! Try to get a boolean value from the view.
bool TryGet(bool& value) const noexcept;
//! Try to get a short value from the view.
bool TryGet(short& value) const noexcept;
//! Try to get an unsigned short value from the view.
bool TryGet(unsigned short& value) const noexcept;
//! Try to get an int value from the view.
bool TryGet(int& value) const noexcept;
//! Try to get an unsigned int value from the view.
bool TryGet(unsigned int& value) const noexcept;
//! Try to get a long value from the view.
bool TryGet(long& value) const noexcept;
//! Try to get an unsigned long value from the view.
bool TryGet(unsigned long& value) const noexcept;
//! Try to get a long long value from the view.
bool TryGet(long long& value) const noexcept;
//! Try to get an unsigned long long value from the view.
bool TryGet(unsigned long long& value) const noexcept;
//! Try to get a float value from the view.
bool TryGet(float& value) const noexcept;
//! Try to get a double value from the view.
bool TryGet(double& value) const noexcept;
//! Try to get a string_view value from the view.
bool TryGet(std::string_view& value) const noexcept;
//! Returns the value if there is a viable conversion, default value otherwise
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;
}
//! Convert the view value to an UTF8 string.
std::string ToString() const;
//! Convert the view value to wxString.
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 };
};
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