Common interface for all types of values used with metadata. More...

#include <value.hpp>

Inheritance diagram for Exiv2::Value:

[legend]

Public Types
using	UniquePtr = std::unique_ptr< Value >
	Shortcut for a Value auto pointer.

Public Member Functions
Creators
	Value (TypeId typeId)
	Constructor, taking a type id to initialize the base class with.

virtual	~Value ()=default
	Virtual destructor.

Manipulators
virtual int	read (const byte *buf, size_t len, ByteOrder byteOrder)=0
	Read the value from a character buffer. More...

virtual int	read (const std::string &buf)=0
	Set the value from a string buffer. The format of the string corresponds to that of the write() method, i.e., a string obtained through the write() method can be read by this function. More...

virtual int	setDataArea (const byte *buf, size_t len)
	Set the data area, if the value has one by copying (cloning) the buffer pointed to by buf. More...

Accessors
bool	ok_ {true}
	Indicates the status of the previous to<Type> conversion.

TypeId	typeId () const
	Return the type identifier (Exif data format type).

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

virtual size_t	copy (byte *buf, ByteOrder byteOrder) const =0
	Write value to a data buffer. More...

virtual size_t	count () const =0
	Return the number of components of the value.

virtual size_t	size () const =0
	Return the size of the value in bytes.

virtual std::ostream &	write (std::ostream &os) const =0
	Write the value to an output stream. You do not usually have to use this function; it is used for the implementation of the output operator for Value, operator<<(std::ostream &os, const Value &value).

std::string	toString () const
	Return the value as a string. Implemented in terms of write(std::ostream& os) const of the concrete class.

virtual std::string	toString (size_t n) const
	Return the n-th component of the value as a string. The default implementation returns toString(). The behaviour of this method may be undefined if there is no n-th component.

virtual int64_t	toInt64 (size_t n=0) const =0
	Convert the n-th component of the value to an int64_t. The behaviour of this method may be undefined if there is no n-th component. More...

virtual uint32_t	toUint32 (size_t n=0) const =0
	Convert the n-th component of the value to a float. The behaviour of this method may be undefined if there is no n-th component. More...

virtual float	toFloat (size_t n=0) const =0
	Convert the n-th component of the value to a float. The behaviour of this method may be undefined if there is no n-th component. More...

virtual Rational	toRational (size_t n=0) const =0
	Convert the n-th component of the value to a Rational. The behaviour of this method may be undefined if there is no n-th component. More...

virtual size_t	sizeDataArea () const
	Return the size of the data area, 0 if there is none.

virtual DataBuf	dataArea () const
	Return a copy of the data area if the value has one. The caller owns this copy and DataBuf ensures that it will be deleted. More...

bool	ok () const
	Check the ok status indicator. After a to<Type> conversion, this indicator shows whether the conversion was successful.

static UniquePtr	create (TypeId typeId)
	A (simple) factory to create a Value type. More...

	Value (const Value &)=default

Value &	operator= (const Value &)=default
	Assignment operator. Protected so that it can only be used by subclasses but not directly.

Detailed Description

Common interface for all types of values used with metadata.

The interface provides a uniform way to access values independent of their actual C++ type for simple tasks like reading the values from a string or data buffer. For other tasks, like modifying values you may need to downcast it to a specific subclass to access its interface.

Examples: xmpsample.cpp.

Member Function Documentation

◆ copy()

virtual size_t Exiv2::Value::copy	(	byte *	buf,
		ByteOrder	byteOrder
	)		const

pure virtual

Write value to a data buffer.

The user must ensure that the buffer has enough memory. Otherwise the call results in undefined behaviour.

Parameters

buf	Data buffer to write to.
byteOrder	Applicable byte order (little or big endian).

Returns: Number of bytes written.

Implemented in Exiv2::TimeValue, Exiv2::DateValue, Exiv2::XmpValue, Exiv2::StringValueBase, Exiv2::DataValue, Exiv2::ValueType< T >, and Exiv2::CommentValue.

◆ create()

static UniquePtr Exiv2::Value::create ( TypeId typeId )

static

A (simple) factory to create a Value type.

The following Value subclasses are created depending on typeId:

typeId	Value subclass
`invalidTypeId`	DataValue(invalidTypeId)
`unsignedByte`	DataValue(unsignedByte)
`asciiString`	AsciiValue
`string`	StringValue
`unsignedShort`	ValueType < uint16_t >
`unsignedLong`	ValueType < uint32_t >
`unsignedRational`	ValueType < URational >
`invalid6`	DataValue(invalid6)
`undefined`	DataValue
`signedShort`	ValueType < int16_t >
`signedLong`	ValueType < int32_t >
`signedRational`	ValueType < Rational >
`tiffFloat`	ValueType < float >
`tiffDouble`	ValueType < double >
`tiffIfd`	ValueType < uint32_t >
`date`	DateValue
`time`	TimeValue
`comment`	CommentValue
`xmpText`	XmpTextValue
`xmpBag`	XmpArrayValue
`xmpSeq`	XmpArrayValue
`xmpAlt`	XmpArrayValue
`langAlt`	LangAltValue
default	DataValue(typeId)

Parameters

typeId Type of the value.

Returns: Auto-pointer to the newly created Value. The caller owns this copy and the auto-pointer ensures that it will be deleted.

Examples: addmoddel.cpp, and xmpsample.cpp.

◆ dataArea()

virtual DataBuf Exiv2::Value::dataArea ( ) const

virtual

Return a copy of the data area if the value has one. The caller owns this copy and DataBuf ensures that it will be deleted.

Values may have a data area, which can contain additional information besides the actual value. This method is used to access such a data area.

Returns: A DataBuf containing a copy of the data area or an empty DataBuf if the value does not have a data area assigned.

Reimplemented in Exiv2::ValueType< T >.

◆ read() [1/2]

virtual int Exiv2::Value::read	(	const byte *	buf,
		size_t	len,
		ByteOrder	byteOrder
	)

pure virtual

Read the value from a character buffer.

Parameters

buf	Pointer to the data buffer to read from
len	Number of bytes in the data buffer
byteOrder	Applicable byte order (little or big endian).

Returns: 0 if successful.

Implemented in Exiv2::TimeValue, Exiv2::DateValue, Exiv2::XmpValue, Exiv2::StringValueBase, Exiv2::DataValue, Exiv2::ValueType< T >, and Exiv2::CommentValue.

◆ read() [2/2]

virtual int Exiv2::Value::read ( const std::string & buf )

pure virtual

Set the value from a string buffer. The format of the string corresponds to that of the write() method, i.e., a string obtained through the write() method can be read by this function.

Parameters

buf	The string to read from.

Returns: 0 if successful.

Implemented in Exiv2::CommentValue, Exiv2::XmpValue, Exiv2::ValueType< T >, Exiv2::TimeValue, Exiv2::DateValue, Exiv2::LangAltValue, Exiv2::XmpArrayValue, Exiv2::XmpTextValue, Exiv2::AsciiValue, Exiv2::StringValueBase, and Exiv2::DataValue.

◆ setDataArea()

virtual int Exiv2::Value::setDataArea	(	const byte *	buf,
		size_t	len
	)

virtual

Set the data area, if the value has one by copying (cloning) the buffer pointed to by buf.

Values may have a data area, which can contain additional information besides the actual value. This method is used to set such a data area.

Parameters

buf	Pointer to the source data area
len	Size of the data area

Returns: Return -1 if the value has no data area, else 0.

Reimplemented in Exiv2::ValueType< T >.

◆ toFloat()

virtual float Exiv2::Value::toFloat ( size_t n = 0 ) const

pure virtual

Convert the n-th component of the value to a float. The behaviour of this method may be undefined if there is no n-th component.

Returns: The converted value.

Implemented in Exiv2::ValueType< T >, Exiv2::TimeValue, Exiv2::DateValue, Exiv2::LangAltValue, Exiv2::XmpArrayValue, Exiv2::XmpTextValue, Exiv2::StringValueBase, Exiv2::DataValue, Exiv2::ValueType< T >, and Exiv2::ValueType< T >.

Examples: xmpsample.cpp.

◆ toInt64()

virtual int64_t Exiv2::Value::toInt64 ( size_t n = 0 ) const

pure virtual

Convert the n-th component of the value to an int64_t. The behaviour of this method may be undefined if there is no n-th component.

Returns: The converted value.

Implemented in Exiv2::ValueType< T >, Exiv2::TimeValue, Exiv2::DateValue, Exiv2::LangAltValue, Exiv2::XmpArrayValue, Exiv2::XmpTextValue, Exiv2::StringValueBase, Exiv2::DataValue, Exiv2::ValueType< T >, Exiv2::ValueType< T >, Exiv2::ValueType< T >, and Exiv2::ValueType< T >.

Examples: xmpsample.cpp.

◆ toRational()

virtual Rational Exiv2::Value::toRational ( size_t n = 0 ) const

pure virtual

Convert the n-th component of the value to a Rational. The behaviour of this method may be undefined if there is no n-th component.

Returns: The converted value.

Implemented in Exiv2::ValueType< T >, Exiv2::TimeValue, Exiv2::DateValue, Exiv2::LangAltValue, Exiv2::XmpArrayValue, Exiv2::XmpTextValue, Exiv2::StringValueBase, Exiv2::DataValue, Exiv2::ValueType< T >, Exiv2::ValueType< T >, Exiv2::ValueType< T >, and Exiv2::ValueType< T >.

Examples: xmpsample.cpp.

◆ toUint32()

virtual uint32_t Exiv2::Value::toUint32 ( size_t n = 0 ) const

pure virtual

Convert the n-th component of the value to a float. The behaviour of this method may be undefined if there is no n-th component.

Returns: The converted value.

Implemented in Exiv2::ValueType< T >, Exiv2::TimeValue, Exiv2::DateValue, Exiv2::LangAltValue, Exiv2::XmpArrayValue, Exiv2::XmpTextValue, Exiv2::StringValueBase, Exiv2::DataValue, Exiv2::ValueType< T >, Exiv2::ValueType< T >, Exiv2::ValueType< T >, and Exiv2::ValueType< T >.

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

value.hpp

Public Types

Public Member Functions

Accessors

Detailed Description

Member Function Documentation

◆ copy()

◆ create()

◆ dataArea()

◆ read() [1/2]

◆ read() [2/2]

◆ setDataArea()

◆ toFloat()

◆ toInt64()

◆ toRational()

◆ toUint32()