Bidi Transformations. More...

#include "unicode/utypes.h"
#include "unicode/ubidi.h"
#include "unicode/uchar.h"
#include "unicode/localpointer.h"

Namespaces
	icu
	File coll.h.

Typedefs
typedef struct UBiDiTransform	UBiDiTransform
	Forward declaration of the `UBiDiTransform` structure that stores information used by the layout transformation engine. More...

Enumerations
enum	UBiDiOrder { UBIDI_LOGICAL = 0, UBIDI_VISUAL }
	`UBiDiOrder` indicates the order of text. More...

enum	UBiDiMirroring { UBIDI_MIRRORING_OFF = 0, UBIDI_MIRRORING_ON }
	`UBiDiMirroring` indicates whether or not characters with the "mirrored" property in RTL runs should be replaced with their mirror-image counterparts. More...

Functions
uint32_t	ubiditransform_transform (UBiDiTransform pBiDiTransform, const UChar src, int32_t srcLength, UChar dest, int32_t destSize, UBiDiLevel inParaLevel, UBiDiOrder inOrder, UBiDiLevel outParaLevel, UBiDiOrder outOrder, UBiDiMirroring doMirroring, uint32_t shapingOptions, UErrorCode pErrorCode)
	Performs transformation of text from the bidi layout defined by the input ordering scheme to the bidi layout defined by the output ordering scheme, and applies character mirroring and Arabic shaping operations. More...

UBiDiTransform *	ubiditransform_open (UErrorCode *pErrorCode)
	Allocates a `UBiDiTransform` object. More...

void	ubiditransform_close (UBiDiTransform *pBidiTransform)
	Deallocates the given `UBiDiTransform` object. More...

Detailed Description

Bidi Transformations.

Definition in file ubiditransform.h.

Typedef Documentation

◆ UBiDiTransform

typedef struct UBiDiTransform UBiDiTransform

Forward declaration of the UBiDiTransform structure that stores information used by the layout transformation engine.

Stable:: ICU 58

Definition at line 112 of file ubiditransform.h.

Enumeration Type Documentation

◆ UBiDiMirroring

enum UBiDiMirroring

UBiDiMirroring indicates whether or not characters with the "mirrored" property in RTL runs should be replaced with their mirror-image counterparts.

See also: UBIDI_DO_MIRRORING; ubidi_setReorderingOptions; ubidi_writeReordered; ubidi_writeReverse

Stable:: ICU 58

Enumerator

UBIDI_MIRRORING_OFF

0: Constant indicating that character mirroring should not be performed.

This is the default.

Stable:: ICU 58

UBIDI_MIRRORING_ON

1: Constant indicating that character mirroring should be performed.

This corresponds to calling ubidi_writeReordered or ubidi_writeReverse with the UBIDI_DO_MIRRORING option bit set.

Stable:: ICU 58

Definition at line 91 of file ubiditransform.h.

◆ UBiDiOrder

enum UBiDiOrder

UBiDiOrder indicates the order of text.

This bidi transformation engine supports all possible combinations (4 in total) of input and output text order:

<logical input, visual output>: unless the output direction is RTL, this corresponds to a normal operation of the Bidi algorithm as described in the Unicode Technical Report and implemented by UBiDi when the reordering mode is set to UBIDI_REORDER_DEFAULT. Visual RTL mode is not supported by UBiDi and is accomplished through reversing a visual LTR string,
<visual input, logical output>: unless the input direction is RTL, this corresponds to an "inverse bidi algorithm" in UBiDi with the reordering mode set to UBIDI_REORDER_INVERSE_LIKE_DIRECT. Visual RTL mode is not not supported by UBiDi and is accomplished through reversing a visual LTR string,
<logical input, logical output>: if the input and output base directions mismatch, this corresponds to the UBiDi implementation with the reordering mode set to UBIDI_REORDER_RUNS_ONLY; and if the input and output base directions are identical, the transformation engine will only handle character mirroring and Arabic shaping operations without reordering,
<visual input, visual output>: this reordering mode is not supported by the UBiDi engine; it implies character mirroring, Arabic shaping, and - if the input/output base directions mismatch - string reverse operations.
See also
ubidi_setInverse

ubidi_setReorderingMode

UBIDI_REORDER_DEFAULT

UBIDI_REORDER_INVERSE_LIKE_DIRECT

UBIDI_REORDER_RUNS_ONLY

Stable:
ICU 58

Enumerator

UBIDI_LOGICAL

0: Constant indicating a logical order.

This is the default for input text.

Stable:: ICU 58

UBIDI_VISUAL

1: Constant indicating a visual order.

This is a default for output text.

Stable:: ICU 58

Definition at line 68 of file ubiditransform.h.

Function Documentation

◆ ubiditransform_close()

void ubiditransform_close ( UBiDiTransform * pBidiTransform )

Deallocates the given UBiDiTransform object.

Stable:: ICU 58

◆ ubiditransform_open()

UBiDiTransform* ubiditransform_open ( UErrorCode * pErrorCode )

Allocates a UBiDiTransform object.

This object can be reused, e.g. with different ordering schemes, mirroring or shaping options.

Note:The object can only be reused in the same thread. All other threads should allocate a new UBiDiTransform object before using it.

Example of usage:

  UErrorCode errorCode = U_ZERO_ERROR;
  // Open a new UBiDiTransform.
  UBiDiTransform* transform = ubiditransform_open(&errorCode);
  // Run a transformation.
  ubiditransform_transform(transform,
           text1, -1, text2, -1,
           UBIDI_RTL, UBIDI_LOGICAL,
           UBIDI_LTR, UBIDI_VISUAL,
           UBIDI_MIRRORING_ON,
           U_SHAPE_DIGITS_EN2AN,
           &errorCode);
  // Do something with the output text and invoke another transformation using
  //   that text as input.
  ubiditransform_transform(transform,
           text2, -1, text3, -1,
           UBIDI_LTR, UBIDI_VISUAL,
           UBIDI_RTL, UBIDI_VISUAL,
           UBIDI_MIRRORING_ON,
           0, &errorCode);
*

The UBiDiTransform object must be deallocated by calling ubiditransform_close().

Returns: An empty UBiDiTransform object.

Stable:: ICU 58

◆ ubiditransform_transform()

uint32_t ubiditransform_transform	(	UBiDiTransform *	pBiDiTransform,
		const UChar *	src,
		int32_t	srcLength,
		UChar *	dest,
		int32_t	destSize,
		UBiDiLevel	inParaLevel,
		UBiDiOrder	inOrder,
		UBiDiLevel	outParaLevel,
		UBiDiOrder	outOrder,
		UBiDiMirroring	doMirroring,
		uint32_t	shapingOptions,
		UErrorCode *	pErrorCode
	)

Performs transformation of text from the bidi layout defined by the input ordering scheme to the bidi layout defined by the output ordering scheme, and applies character mirroring and Arabic shaping operations.

In terms of UBiDi, such a transformation implies:

calling ubidi_setReorderingMode as needed (when the reordering mode is other than normal),
calling ubidi_setInverse as needed (when text should be transformed from a visual to a logical form),
resolving embedding levels of each character in the input text by calling ubidi_setPara,
reordering the characters based on the computed embedding levels, also performing character mirroring as needed, and streaming the result to the output, by calling ubidi_writeReordered,
performing Arabic digit and letter shaping on the output text by calling u_shapeArabic.

An "ordering scheme" encompasses the base direction and the order of text, and these characteristics must be defined by the caller for both input and output explicitly .

There are 36 possible combinations of <input, output> ordering schemes, which are partially supported by UBiDi already. Examples of the currently supported combinations:

<Logical LTR, Visual LTR>: this is equivalent to calling ubidi_setPara with paraLevel == UBIDI_LTR,
<Logical RTL, Visual LTR>: this is equivalent to calling ubidi_setPara with paraLevel == UBIDI_RTL,
<Logical Default ("Auto") LTR, Visual LTR>: this is equivalent to calling ubidi_setPara with paraLevel == UBIDI_DEFAULT_LTR,
<Logical Default ("Auto") RTL, Visual LTR>: this is equivalent to calling ubidi_setPara with paraLevel == UBIDI_DEFAULT_RTL,
<Visual LTR, Logical LTR>: this is equivalent to calling ubidi_setInverse(UBiDi*, TRUE) and then ubidi_setPara with paraLevel == UBIDI_LTR,
<Visual LTR, Logical RTL>: this is equivalent to calling ubidi_setInverse(UBiDi*, TRUE) and then ubidi_setPara with paraLevel == UBIDI_RTL.

All combinations that involve the Visual RTL scheme are unsupported by UBiDi, for instance:

<Logical LTR, Visual RTL>,
<Visual RTL, Logical RTL>.

Example of usage of the transformation engine:

  UChar text1[] = {'a', 'b', 'c', 0x0625, '1', 0};
  UChar text2[] = {'a', 'b', 'c', 0x0625, '1', 0};
  UErrorCode errorCode = U_ZERO_ERROR;
  // Run a transformation.
  ubiditransform_transform(pBidiTransform,
           text1, -1, text2, -1,
           UBIDI_LTR, UBIDI_VISUAL,
           UBIDI_RTL, UBIDI_LOGICAL,
           UBIDI_MIRRORING_OFF,
           U_SHAPE_DIGITS_AN2EN | U_SHAPE_DIGIT_TYPE_AN_EXTENDED,
           &errorCode);
  // Do something with text2.
   text2[4] = '2';
  // Run a reverse transformation.
  ubiditransform_transform(pBidiTransform,
           text2, -1, text1, -1,
           UBIDI_RTL, UBIDI_LOGICAL,
           UBIDI_LTR, UBIDI_VISUAL,
           UBIDI_MIRRORING_OFF,
           U_SHAPE_DIGITS_EN2AN | U_SHAPE_DIGIT_TYPE_AN_EXTENDED,
           &errorCode);
*

Parameters

pBiDiTransform A pointer to a UBiDiTransform object allocated with ubiditransform_open() or NULL.

This object serves for one-time setup to amortize initialization overheads. Use of this object is not thread-safe. All other threads should allocate a new UBiDiTransform object by calling ubiditransform_open() before using it. Alternatively, a caller can set this parameter to NULL, in which case the object will be allocated by the engine on the fly.

Parameters

src	A pointer to the text that the Bidi layout transformations will be performed on.

Note: the text must be (at least) srcLength long.

Parameters

srcLength	The length of the text, in number of UChars. If `length == -1` then the text must be zero-terminated.
dest	A pointer to where the processed text is to be copied.
destSize	The size of the `dest` buffer, in number of UChars. If the `U_SHAPE_LETTERS_UNSHAPE` option is set, then the destination length could be as large as `srcLength * 2`. Otherwise, the destination length will not exceed `srcLength`. If the caller reserves the last position for zero-termination, it should be excluded from `destSize`.

destSize == -1 is allowed and makes sense when dest was holds some meaningful value, e.g. that of src. In this case dest must be zero-terminated.

Parameters

inParaLevel	A base embedding level of the input as defined in `ubidi_setPara` documentation for the `paraLevel` parameter.
inOrder	An order of the input, which can be one of the `UBiDiOrder` values.
outParaLevel	A base embedding level of the output as defined in `ubidi_setPara` documentation for the `paraLevel` parameter.
outOrder	An order of the output, which can be one of the `UBiDiOrder` values.
doMirroring	Indicates whether or not to perform character mirroring, and can accept one of the `UBiDiMirroring` values.
shapingOptions	Arabic digit and letter shaping options defined in the ushape.h documentation.

Note: Direction indicator options are computed by the transformation engine based on the effective ordering schemes, so user-defined direction indicators will be ignored.

Parameters

pErrorCode A pointer to an error code value.

Returns: The destination length, i.e. the number of UChars written to dest. If the transformation fails, the return value will be 0 (and the error code will be written to pErrorCode).

See also: UBiDiLevel; UBiDiOrder; UBiDiMirroring; ubidi_setPara; u_shapeArabic

Stable:: ICU 58

Namespaces

Typedefs

Enumerations

Functions

Detailed Description

Typedef Documentation

◆ UBiDiTransform

Enumeration Type Documentation

◆ UBiDiMirroring

◆ UBiDiOrder

Function Documentation

◆ ubiditransform_close()

◆ ubiditransform_open()

◆ ubiditransform_transform()