Exiv2::Xmpdatum Class Reference

Information related to an XMP property. An XMP metadatum consists of an XmpKey and a Value and provides methods to manipulate these. More...

#include <xmp_exiv2.hpp>

Inheritance diagram for Exiv2::Xmpdatum:

Public Member Functions
Creators
	Xmpdatum (const XmpKey &key, const Value *pValue=nullptr)
	Constructor for new tags created by an application. The Xmpdatum is created from a key / value pair. Xmpdatum copies (clones) the value if one is provided. Alternatively, a program can create an 'empty' Xmpdatum with only a key and set the value using setValue(). More...
	Xmpdatum (const Xmpdatum &rhs)
	Copy constructor.
	~Xmpdatum () override
	Destructor.
Manipulators
Xmpdatum &	operator= (const Xmpdatum &rhs)
	Assignment operator.
Xmpdatum &	operator= (const std::string &value)
	Assign std::string value to the Xmpdatum. Calls setValue(const std::string&).
template<typename T >
Xmpdatum &	operator= (const T &value)
	Assign a value of any type with an output operator to the Xmpdatum. Calls operator=(const std::string&).
Xmpdatum &	operator= (const Value &value)
	Assign Value value to the Xmpdatum. Calls setValue(const Value*).
void	setValue (const Value *pValue) override
	Set the value. This method copies (clones) the value pointed to by pValue.
int	setValue (const std::string &value) override
	Set the value to the string value. Uses Value::read(const std::string&). If the Xmpdatum does not have a Value yet, then a Value of the correct type for this Xmpdatum is created. If the key is unknown, a XmpTextValue is used as default. Return 0 if the value was read successfully.
Public Member Functions inherited from Exiv2::Metadatum
virtual	~Metadatum ()=default
	Destructor.
std::string	print (const ExifData *pMetadata=nullptr) const
	Write the interpreted value to a string. More...
uint32_t	toUint32 (size_t n=0) const
	Return the n-th component of the value converted to uint32_t.

Accessors
size_t	copy (byte *buf, ByteOrder byteOrder) const override
	Not implemented. Calling this method will raise an exception.
std::ostream &	write (std::ostream &os, const ExifData *pMetadata=nullptr) const override
	Write the interpreted value to an output stream, return the stream. More...
std::string	key () const override
	Return the key of the Xmpdatum. The key is of the form 'Xmp.prefix.property'. Note however that the key is not necessarily unique, i.e., an XmpData object may contain multiple metadata with the same key.
const char *	familyName () const override
	Return the name of the metadata family (which is also the first part of the key)
std::string	groupName () const override
	Return the (preferred) schema namespace prefix.
std::string	tagName () const override
	Return the property name.
std::string	tagLabel () const override
	Return a label for the tag.
std::string	tagDesc () const override
	Return a description for the tag.
uint16_t	tag () const override
	Properties don't have a tag number. Return 0.
TypeId	typeId () const override
	Return the type id of the value.
const char *	typeName () const override
	Return the name of the type.
size_t	typeSize () const override
	The Exif typeSize doesn't make sense here. Return 0.
size_t	count () const override
	Return the number of components in the value.
size_t	size () const override
	Return the size of the value in bytes.
std::string	toString () const override
	Return the value as a string.
std::string	toString (size_t n) const override
	Return the n-th component of the value converted to a string. The behaviour of the method is undefined if there is no n-th component.
int64_t	toInt64 (size_t n=0) const override
	Return the n-th component of the value converted to int64_t. The return value is -1 if the value is not set and the behaviour of the method is undefined if there is no n-th component.
float	toFloat (size_t n=0) const override
	Return the n-th component of the value converted to float. The return value is -1 if the value is not set and the behaviour of the method is undefined if there is no n-th component.
Rational	toRational (size_t n=0) const override
	Return the n-th component of the value converted to Rational. The return value is -1/1 if the value is not set and the behaviour of the method is undefined if there is no n-th component.
Value::UniquePtr	getValue () const override
	Return an auto-pointer to a copy (clone) of the value. The caller owns this copy and the auto-poiner ensures that it will be deleted. More...
const Value &	value () const override
	Return a constant reference to the value. More...

Additional Inherited Members
Protected Member Functions inherited from Exiv2::Metadatum
Metadatum &	operator= (const Metadatum &)=default
	Assignment operator. Protected so that it can only be used by subclasses but not directly.
	Metadatum ()=default
	Metadatum (const Metadatum &)=default

Detailed Description

Information related to an XMP property. An XMP metadatum consists of an XmpKey and a Value and provides methods to manipulate these.

Constructor & Destructor Documentation

Xmpdatum()

Exiv2::Xmpdatum::Xmpdatum ( const XmpKey &  key, const Value *  pValue = nullptr  )

explicit

Constructor for new tags created by an application. The Xmpdatum is created from a key / value pair. Xmpdatum copies (clones) the value if one is provided. Alternatively, a program can create an 'empty' Xmpdatum with only a key and set the value using setValue().

Parameters

key	The key of the Xmpdatum.
pValue	Pointer to a Xmpdatum value.

Exceptions

Error

if the key cannot be parsed and converted to a known schema namespace prefix and property name.

Member Function Documentation

getValue()

Value::UniquePtr Exiv2::Xmpdatum::getValue ( ) const

overridevirtual

Return an auto-pointer to a copy (clone) of the value. The caller owns this copy and the auto-poiner ensures that it will be deleted.

This method is provided for users who need full control over the value. A caller may, e.g., downcast the pointer to the appropriate subclass of Value to make use of the interface of the subclass to set or modify its contents.

Returns

An auto-pointer containing a pointer to a copy (clone) of the value, 0 if the value is not set.

Implements Exiv2::Metadatum.

value()

const Value& Exiv2::Xmpdatum::value ( ) const

overridevirtual

Return a constant reference to the value.

This method is provided mostly for convenient and versatile output of the value which can (to some extent) be formatted through standard stream manipulators. Do not attempt to write to the value through this reference. An Error is thrown if the value is not set; as an alternative to catching it, one can use count() to check if there is any data before calling this method.

Returns

A constant reference to the value.

Exceptions

Error

if the value is not set.

Implements Exiv2::Metadatum.

Referenced by operator=().

write()

std::ostream& Exiv2::Xmpdatum::write ( std::ostream &  os, const ExifData *  pMetadata = nullptr  ) const

overridevirtual

Write the interpreted value to an output stream, return the stream.

The method takes an optional pointer to a metadata container. Pretty-print functions may use that to refer to other metadata as it is sometimes not sufficient to know only the value of the metadatum that should be interpreted. Thus, it is advisable to always call this method with a pointer to the metadata container if possible.

This functionality is currently only implemented for Exif tags. The pointer is ignored when used to write IPTC datasets or XMP properties.

Without the optional metadata pointer, you do not usually have to use this function; it is used for the implementation of the output operator for Metadatum, operator<<(std::ostream &os, const Metadatum &md).

See also print(), which prints the interpreted value to a string.

Implements Exiv2::Metadatum.

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The documentation for this class was generated from the following file:

• xmp_exiv2.hpp