DCMTK: OFCharacterEncoding Class Reference

DCMTK Version 3.6.9 OFFIS DICOM Toolkit

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Public Types | Public Member Functions | Static Public Member Functions | Private Attributes | List of all members
OFCharacterEncoding Class Reference

A class for managing and converting between different character encodings. More...

## Public Types
enum | ConversionFlags { AbortTranscodingOnIllegalSequence = 1 , DiscardIllegalSequences = 2 , TransliterateIllegalSequences = 4 }
| Constants to control encoder behavior, e.g. regarding illegal character sequences. More...

## Public Member Functions
| OFCharacterEncoding ()
| constructor.
| OFCharacterEncoding (const OFCharacterEncoding &rhs)
| copy constructor.
| ~OFCharacterEncoding ()
| destructor
OFCharacterEncoding & | operator= (const OFCharacterEncoding &rhs)
| copy assignment.
| operator OFBool () const
| check whether this object refers to a valid encoder.
OFBool | operator! () const
| check whether this object does not refer to a valid encoder.
OFBool | operator== (const OFCharacterEncoding &rhs) const
| check whether two OFCharacterEncoding instances refer to the same encoder.
OFBool | operator!= (const OFCharacterEncoding &rhs) const
| check whether two OFCharacterEncoding instances do not refer to the same encoder.
void | clear ()
| clear the internal state.
unsigned | getConversionFlags () const
| get flags controlling converter behavior, e.g. specifying how illegal character sequences should be handled during conversion.
OFCondition | setConversionFlags (const unsigned flags)
| set flags controlling converter behavior, e.g. illegal character sequences should be handled during conversion.
OFCondition | selectEncoding (const OFString &fromEncoding, const OFString &toEncoding)
| select source and destination character encoding for subsequent conversion(s).
OFCondition | convertString (const OFString &fromString, OFString &toString, const OFBool clearMode=OFTrue)
| convert the given string between the selected character encodings.
OFCondition | convertString (const char *fromString, const size_t fromLength, OFString &toString, const OFBool clearMode=OFTrue)
| convert the given string between the selected character encodings.

## Static Public Member Functions
static OFBool | hasDefaultEncoding ()
| determine whether the underlying implementations defines a default encoding.
static OFString | getLocaleEncoding ()
| get the character encoding of the currently set global locale.
static OFBool | supportsConversionFlags (const unsigned flags)
| determine whether the underlying implementation supports the given conversion flags.
static OFBool | isLibraryAvailable ()
| check whether character set conversion is available, e.g. the underlying encoding library is available.
static OFString | getLibraryVersionString ()
| get version information of the underlying character encoding library.
static size_t | countCharactersInUTF8String (const OFString &utf8String)
| count characters in given UTF-8 string and return the resulting number of so-called "code points".

## Private Attributes
OFshared_ptr< Implementation > | TheImplementation
| shared pointer to internal implementation (interface to character encoding library)

## Detailed Description

A class for managing and converting between different character encodings.

The implementation relies on ICONV (native implementation or libiconv) or ICU, depending on the configuration.

Remarks
  An encoder might be shared by copy constructing an OFCharacterEncoding object from an existing one. Both objects will refer to the same encoder once this is done, which will only be destroyed after both objects are, using OFshared_ptr internally.

## Member Enumeration Documentation

## ◆ ConversionFlags

enum OFCharacterEncoding::ConversionFlags

Constants to control encoder behavior, e.g. regarding illegal character sequences.

Currently defined constants may be used to control the implementation's behavior regarding illegal character sequences. An illegal character sequence is a sequence of characters in the source string that is only valid in the context of the source string's character set and has no valid representation in the character set of the destination string. Use these constants to control the transcoding behavior in case an illegal sequence is encountered.

Note
  You may set a single one of the constants as the encoder behavior or even a combination (bitwise OR), however, it depends on the underlying implementation which flags/combinations are supported. Use supportsConversionFlags() to query this information at runtime.

Enumerator
AbortTranscodingOnIllegalSequence | Abort transcoding (returning an error condition) if an illegal sequence is encountered.
DiscardIllegalSequences | Skip over any illegal character sequences that are encountered.
TransliterateIllegalSequences | Replace illegal character sequences with an available representation in the destination character set that somewhat resembles the meaning (i.e. ö -> "o). The actual results may vary depending on the underlying implementation.

## Constructor & Destructor Documentation

## ◆ OFCharacterEncoding() [1/2]

OFCharacterEncoding::OFCharacterEncoding | ( |  | ) |

constructor.

Will create an OFCharacterEncoding instance that does not refer to an encoder.

Referenced by OFCharacterEncoding(), operator!=(), operator=(), and operator==().

## ◆ OFCharacterEncoding() [2/2]

OFCharacterEncoding::OFCharacterEncoding | ( | const OFCharacterEncoding & | rhs | ) |

copy constructor.

Will share the encoder of another OFCharacterEncoding instance.

Parameters

  rhs | another OFCharacterEncoding instance.

References OFCharacterEncoding().

## Member Function Documentation

## ◆ clear()

void OFCharacterEncoding::clear | ( |  | ) |

clear the internal state.

This resets the converter and potentially frees all used resources (if this is the last OFCharacterEncoding instance referring to the encoder).

## ◆ convertString() [1/2]

OFCondition OFCharacterEncoding::convertString | ( | const char * | fromString,
|  | const size_t | fromLength,
|  | OFString & | toString,
|  | const OFBool | clearMode = OFTrue )

convert the given string between the selected character encodings.

That means selectEncoding() has to be called prior to this method. Since the length of the input string has to be specified explicitly, the string can contain more than one NULL byte.

Parameters

  fromString | input string to be converted (using the source character encoding). A NULL pointer is regarded as an empty string.
  fromLength | length of the input string (number of bytes without the trailing NULL byte)
  toString | reference to variable where the converted string (using the destination character encoding) is stored (or appended, see parameter 'clearMode')
  clearMode | flag indicating whether to clear the variable 'toString' before appending the converted string

Returns
  status, EC_Normal if successful, an error code otherwise

## ◆ convertString() [2/2]

OFCondition OFCharacterEncoding::convertString | ( | const OFString & | fromString,
|  | OFString & | toString,
|  | const OFBool | clearMode = OFTrue )

convert the given string between the selected character encodings.

That means selectEncoding() has to be called prior to this method.

Parameters

  fromString | input string to be converted (using the source character encoding)
  toString | reference to variable where the converted string (using the destination character encoding) is stored (or appended, see parameter 'clearMode')
  clearMode | flag indicating whether to clear the variable 'toString' before appending the converted string

Returns
  status, EC_Normal if successful, an error code otherwise

## ◆ countCharactersInUTF8String()

static size_t OFCharacterEncoding::countCharactersInUTF8String | ( | const OFString & | utf8String | ) |
| static

count characters in given UTF-8 string and return the resulting number of so-called "code points".

Please note that invalid UTF-8 encodings are not handled properly. ASCII strings (7-bit) are also supported, although OFString::length() is probably much faster.

Parameters

  utf8String | valid character string with UTF-8 encoding

Returns
  number of characters (code points) in given UTF-8 string

## ◆ getConversionFlags()

unsigned OFCharacterEncoding::getConversionFlags | ( |  | ) | const

get flags controlling converter behavior, e.g. specifying how illegal character sequences should be handled during conversion.

Note
  This method will always return 0 if no encoder was selected using selectEncoding() before calling it.

Returns
  a combination the IllegalSequenceMode constants (bitwise or) that is currently set or 0 if the current mode cannot be determined.

## ◆ getLibraryVersionString()

static OFString OFCharacterEncoding::getLibraryVersionString | ( |  | ) |
| static

get version information of the underlying character encoding library.

Typical output format: "LIBICONV, Version 1.14". If character encoding is not available the output is: "<no character encoding library available>"

Returns
  name and version number of the character encoding library

## ◆ getLocaleEncoding()

static OFString OFCharacterEncoding::getLocaleEncoding | ( |  | ) |
| static

get the character encoding of the currently set global locale.

Remarks
  Calling this function might be rather exhaustive depending on employed character set conversion library. Caching the result might therefore be recommended.

Note
  The result may be an empty string, if the name of the current encoding cannot be determined.

Returns
  the current locale's character encoding

## ◆ hasDefaultEncoding()

static OFBool OFCharacterEncoding::hasDefaultEncoding | ( |  | ) |
| static

determine whether the underlying implementations defines a default encoding.

Most implementations define a default encoding, i.e. one can pass an empty string as the toEncoding and/or fromEncoding argument(s) of selectEncoding() to select the current locale's encoding. However, some iconv implementations inside the C standard library do not understand this.

Warning
  Using getLocaleEncoding() instead of an empty string argument in this case typically won't work, since the implementations that don't define a default encoding typically also don't support determining the current locale's encoding.

Returns
  OFTrue if a default encoding is defined and empty strings are valid arguments to selectEncoding(), OFFalse otherwise.

## ◆ isLibraryAvailable()

static OFBool OFCharacterEncoding::isLibraryAvailable | ( |  | ) |
| static

check whether character set conversion is available, e.g. the underlying encoding library is available.

If not, no conversion between different character encodings will be possible (apart from the Windows-specific wide character conversion functions).

Returns
  OFTrue if character set conversion is possible, OFFalse otherwise

## ◆ operator OFBool()

OFCharacterEncoding::operator OFBool | ( |  | ) | const

check whether this object refers to a valid encoder.

Returns
  OFTrue if this refers to a valid encoder, OFFalse otherwise.

## ◆ operator!()

OFBool OFCharacterEncoding::operator! | ( |  | ) | const

check whether this object does not refer to a valid encoder.

Returns
  OFFalse if this refers to a valid encoder, OFTrue otherwise.

## ◆ operator!=()

OFBool OFCharacterEncoding::operator!= | ( | const OFCharacterEncoding & | rhs | ) | const

check whether two OFCharacterEncoding instances do not refer to the same encoder.

Note
  This only tests if both objects refer to the exactly same encoder, originating from one and the same call to selectEncoding(). The result will be OFTrue if both encoders were constructed independently of each other, even if exactly the same parameters were used.

Parameters

  rhs | another OFCharacterEncoding instance.

Returns
  OFFalse if both instances refer to the same encoder, OFTrue otherwise.

References OFCharacterEncoding().

## ◆ operator=()

OFCharacterEncoding & OFCharacterEncoding::operator= | ( | const OFCharacterEncoding & | rhs | ) |

copy assignment.

Effectively calls clear() and then shares the encoder of another OFCharacterEncoding instance.

Parameters

  rhs | another OFCharacterEncoding instance.

Returns
  reference to this object

References OFCharacterEncoding().

## ◆ operator==()

OFBool OFCharacterEncoding::operator== | ( | const OFCharacterEncoding & | rhs | ) | const

check whether two OFCharacterEncoding instances refer to the same encoder.

Note
  This only tests if both objects refer to the exactly same encoder, originating from one and the same call to selectEncoding(). The result will be OFFalse if both encoders were constructed independently of each other, even if exactly the same parameters were used.

Parameters

  rhs | another OFCharacterEncoding instance.

Returns
  OFTrue if both instances refer to the same encoder, OFFalse otherwise.

References OFCharacterEncoding().

## ◆ selectEncoding()

OFCondition OFCharacterEncoding::selectEncoding | ( | const OFString & | fromEncoding,
|  | const OFString & | toEncoding )

select source and destination character encoding for subsequent conversion(s).

The encoding names can be found in the documentation of the underlying implementation (e.g. libiconv). Typical names are "ASCII", "ISO-8859-1" and "UTF-8". An empty string denotes the encoding of the current locale (see getLocaleEncoding()).

Parameters

  fromEncoding | name of the source character encoding
  toEncoding | name of the destination character encoding

Returns
  status, EC_Normal if successful, an error code otherwise

## ◆ setConversionFlags()

OFCondition OFCharacterEncoding::setConversionFlags | ( | const unsigned | flags | ) |

set flags controlling converter behavior, e.g. illegal character sequences should be handled during conversion.

Precondition
  An encoding has been selected by successfully calling OFCharacterEncoding::selectEncoding(), i.e. OFCharacterEncoding::isLibraryAvailable() and *this evaluate to OFTrue.

Parameters

  flags | the conversion flags that shall be used, a combination of the OFCharacterEncoding::ConversionFlags constants, e.g. TransliterateIllegalSequences | DiscardIllegalSequences.

Returns
  EC_Normal if the flags were set, an error code otherwise, i.e. if the flags are not supported by the underlying implementation.

See also
  OFCharacterEncoding::supportsConversionFlags()

## ◆ supportsConversionFlags()

static OFBool OFCharacterEncoding::supportsConversionFlags | ( | const unsigned | flags | ) |
| static

determine whether the underlying implementation supports the given conversion flags.

Parameters

  flags | the flags to query, a combination of OFCharacterEncoding::ConversionFlags constants, e.g. TransliterateIllegalSequences | DiscardIllegalSequences.

Returns
  OFTrue if the given flags are supported, OFFalse if not or support is unknown.

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

- ofstd/include/dcmtk/ofstd/ofchrenc.h

Generated on Sat Mar 1 2025 for DCMTK Version 3.6.9 by Doxygen 1.13.2