ubidi.h File Reference
C API: BIDI algorithm.
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#include "unicode/utypes.h"
#include "unicode/uchar.h"
Go to the source code of this file.
Detailed Description
C API: BIDI algorithm.
BIDI algorithm for ICU
This is an implementation of the Unicode Bidirectional algorithm. The algorithm is defined in the Unicode Technical Report 9, version 5, also described in The Unicode Standard, Version 3.0 .
General remarks about the API:
In functions with an error code parameter, the pErrorCode
pointer must be valid and the value that it points to must not indicate a failure before the function call. Otherwise, the function returns immediately. After the function call, the value indicates success or failure.
The "limit" of a sequence of characters is the position just after their last character, i.e., one more than that position.
Some of the API functions provide access to "runs". Such a "run" is defined as a sequence of characters that are at the same embedding level after performing the BIDI algorithm.
- Author:
- Markus W. Scherer
- Version:
- 1.0
Sample code for the ICU BIDI API
Rendering a paragraph with the ICU BiDi API
This is (hypothetical) sample code that illustrates how the ICU BiDi API could be used to render a paragraph of text. Rendering code depends highly on the graphics system, therefore this sample code must make a lot of assumptions, which may or may not match any existing graphics system's properties.
The basic assumptions are:
-
Rendering is done from left to right on a horizontal line.
-
A run of single-style, unidirectional text can be rendered at once.
-
Such a run of text is passed to the graphics system with characters (code units) in logical order.
-
The line-breaking algorithm is very complicated and Locale-dependent - and therefore its implementation omitted from this sample code.
*#include
"unicode/ubidi.h"
*
typedef enum {
styleNormal=0, styleSelected=1,
styleBold=2, styleItalics=4,
styleSuper=8, styleSub=16
*} Style;
*
typedef struct { int32_t limit; Style style; } StyleRun;
*
int getTextWidth(
const UChar *text, int32_t start, int32_t limit,
const StyleRun *styleRuns,
int styleRunCount);
*
void getLineBreak(
const UChar *text, int32_t start, int32_t *pLimit,
UBiDi *para,
const StyleRun *styleRuns,
int styleRunStart,
int *pStyleRunLimit,
int *pLineWidth);
*
void startLine(UBiDiDirection textDirection,
int lineWidth);
*
void renderRun(
const UChar *text, int32_t start, int32_t limit,
UBiDiDirection textDirection, Style style);
*
void renderDirectionalRun(
const UChar *text,
int32_t start, int32_t limit,
UBiDiDirection direction,
const StyleRun *styleRuns,
int styleRunCount) {
int i;
if(direction==
UBIDI_LTR) {
int styleLimit;
for(i=0; i<styleRunCount; ++i) {
styleLimit=styleRun[i].limit;
if(start<styleLimit) {
if(styleLimit>limit) { styleLimit=limit; }
renderRun(text, start, styleLimit,
direction, styleRun[i].style);
if(styleLimit==limit) {
break; }
start=styleLimit;
}
}
}
else {
int styleStart;
for(i=styleRunCount-1; i>=0; --i) {
if(i>0) {
styleStart=styleRun[i-1].limit;
}
else {
styleStart=0;
}
if(limit>=styleStart) {
if(styleStart<start) { styleStart=start; }
renderRun(text, styleStart, limit,
direction, styleRun[i].style);
if(styleStart==start) {
break; }
limit=styleStart;
}
}
}
}
void renderLine(UBiDi *line,
const UChar *text,
int32_t start, int32_t limit,
const StyleRun *styleRuns,
int styleRunCount) {
UBiDiDirection direction=
ubidi_getDirection(line);
if(direction!=
UBIDI_MIXED) {
if(styleRunCount<=1) {
renderRun(text, start, limit, direction, styleRuns[0].style);
}
else {
renderDirectionalRun(text, start, limit,
direction, styleRuns, styleRunCount);
}
}
else {
int32_t count, i, length;
UBiDiLevel level;
count=
ubidi_countRuns(para, pErrorCode);
if(
U_SUCCESS(*pErrorCode)) {
if(styleRunCount<=1) {
Style style=styleRuns[0].style;
for(i=0; i<count; ++i) {
direction=
ubidi_getVisualRun(para, i, &start, &length);
renderRun(text, start, start+length, direction, style);
}
}
else {
int32_t j;
for(i=0; i<count; ++i) {
direction=
ubidi_getVisualRun(line, i, &start, &length);
renderDirectionalRun(text, start, start+length,
direction, styleRuns, styleRunCount);
}
}
}
}
}
*
void renderParagraph(
const UChar *text, int32_t length,
UBiDiDirection textDirection,
const StyleRun *styleRuns,
int styleRunCount,
int lineWidth,
UErrorCode *pErrorCode) {
UBiDi *para;
if(pErrorCode==
NULL ||
U_FAILURE(*pErrorCode) || length<=0) {
return;
}
para=
ubidi_openSized(length, 0, pErrorCode);
if(para==
NULL) {
return; }
ubidi_setPara(para, text, length,
textDirection ? UBIDI_DEFAULT_RTL : UBIDI_DEFAULT_LTR,
NULL, pErrorCode);
if(
U_SUCCESS(*pErrorCode)) {
UBiDiLevel paraLevel=1&
ubidi_getParaLevel(para);
StyleRun styleRun={ length, styleNormal };
int width;
if(styleRuns==
NULL || styleRunCount<=0) {
styleRunCount=1;
styleRuns=&styleRun;
}
width=getTextWidth(text, 0, length, styleRuns, styleRunCount);
if(width<=lineWidth) {
startLine(paraLevel, width);
renderLine(para, text, 0, length,
styleRuns, styleRunCount);
}
else {
UBiDi *line;
line=
ubidi_openSized(length, 0, pErrorCode);
if(line!=
NULL) {
int32_t start=0, limit;
int styleRunStart=0, styleRunLimit;
for(;;) {
limit=length;
styleRunLimit=styleRunCount;
getLineBreak(text, start, &limit, para,
styleRuns, styleRunStart, &styleRunLimit,
&width);
ubidi_setLine(para, start, limit, line, pErrorCode);
if(
U_SUCCESS(*pErrorCode)) {
startLine(paraLevel, width);
renderLine(line, text, start, limit,
styleRuns+styleRunStart,
styleRunLimit-styleRunStart);
}
if(limit==length) {
break; }
start=limit;
styleRunStart=styleRunLimit-1;
if(start>=styleRuns[styleRunStart].limit) {
++styleRunStart;
}
}
ubidi_close(line);
}
}
}
ubidi_close(para);
*}
*
Define Documentation
#define UBIDI_DEFAULT_LTR 0xfe |
|
|
Paragraph level setting.
If there is no strong character, then set the paragraph level to 0 (left-to-right). |
#define UBIDI_DEFAULT_RTL 0xff |
|
|
Paragraph level setting.
If there is no strong character, then set the paragraph level to 1 (right-to-left). |
#define UBIDI_DO_MIRRORING 2 |
|
#define UBIDI_INSERT_LRM_FOR_NUMERIC 4 |
|
#define UBIDI_KEEP_BASE_COMBINING 1 |
|
#define UBIDI_LEVEL_OVERRIDE 0x80 |
|
|
Bit flag for level input.
Overrides directional properties. |
#define UBIDI_MAX_EXPLICIT_LEVEL 61 |
|
|
Maximum explicit embedding level.
(The maximum resolved level can be up to UBIDI_MAX_EXPLICIT_LEVEL+1 ). |
#define UBIDI_OUTPUT_REVERSE 16 |
|
|
option bit for ubidi_writeReordered(): write the output in reverse order
This has the same effect as calling ubidi_writeReordered() first without this option, and then calling ubidi_writeReverse() without mirroring. Doing this in the same step is faster and avoids a temporary buffer. An example for using this option is output to a character terminal that is designed for RTL scripts and stores text in reverse order.
- See also:
- ubidi_writeReordered
|
#define UBIDI_REMOVE_BIDI_CONTROLS 8 |
|
Typedef Documentation
|
UBiDiLevel is the type of the level values in this BiDi implementation.
It holds an embedding level and indicates the visual direction by its bit 0 (even/odd value).
It can also hold non-level values for the paraLevel and embeddingLevels arguments of ubidi_setPara() ; there:
-
bit 7 of an
embeddingLevels[] value indicates whether the using application is specifying the level of a character to override whatever the BiDi implementation would resolve it to.
-
paraLevel can be set to the pesudo-level values UBIDI_DEFAULT_LTR and UBIDI_DEFAULT_RTL .
- See also:
- ubidi_setPara
The related constants are not real, valid level values. UBIDI_DEFAULT_XXX can be used to specify a default for the paragraph level for when the ubidi_setPara() function shall determine it but there is no strongly typed character in the input.
Note that the value for UBIDI_DEFAULT_LTR is even and the one for UBIDI_DEFAULT_RTL is odd, just like with normal LTR and RTL level values - these special values are designed that way. Also, the implementation assumes that UBIDI_MAX_EXPLICIT_LEVEL is odd.
- See also:
- UBIDI_DEFAULT_LTR
UBIDI_DEFAULT_RTL
UBIDI_LEVEL_OVERRIDE
UBIDI_MAX_EXPLICIT_LEVEL
|
Enumeration Type Documentation
|
UBiDiDirection values indicate the text direction.
- Enumeration values:
-
UBIDI_LTR |
All left-to-right text.
This is a 0 value. |
UBIDI_RTL |
All right-to-left text.
This is a 1 value. |
UBIDI_MIXED |
Mixed-directional text.
|
|
Function Documentation
U_CAPI void U_EXPORT2 ubidi_close |
( |
UBiDi * |
pBiDi |
) |
|
|
U_CAPI int32_t U_EXPORT2 ubidi_countRuns |
( |
UBiDi * |
pBiDi, |
|
|
UErrorCode * |
pErrorCode |
|
) |
|
|
|
Get the number of runs.
This function may invoke the actual reordering on the UBiDi object, after ubidi_setPara() may have resolved only the levels of the text. Therefore, ubidi_countRuns() may have to allocate memory, and may fail doing so.
- Parameters:
-
| pBiDi | is the paragraph or line UBiDi object. |
| pErrorCode | must be a valid pointer to an error code value, which must not indicate a failure before the function call. |
- Returns:
- The number of runs.
|
|
Get the directionality of the text.
- Parameters:
-
| pBiDi | is the paragraph or line UBiDi object. |
- Returns:
- A
UBIDI_XXX value that indicates if the entire text represented by this object is unidirectional, and which direction, or if it is mixed-directional.
- See also:
- UBiDiDirection
|
U_CAPI int32_t U_EXPORT2 ubidi_getLength |
( |
const UBiDi * |
pBiDi |
) |
|
|
|
Get the length of the text.
- Parameters:
-
| pBiDi | is the paragraph or line UBiDi object. |
- Returns:
- The length of the text that the UBiDi object was created for.
|
U_CAPI UBiDiLevel U_EXPORT2 ubidi_getLevelAt |
( |
const UBiDi * |
pBiDi, |
|
|
int32_t |
charIndex |
|
) |
|
|
|
Get the level for one character.
- Parameters:
-
| pBiDi | is the paragraph or line UBiDi object. |
| charIndex | the index of a character. |
- Returns:
- The level for the character at charIndex.
- See also:
- UBiDiLevel
|
|
Get an array of levels for each character.
Note that this function may allocate memory under some circumstances, unlike ubidi_getLevelAt() .
- Parameters:
-
| pBiDi | is the paragraph or line UBiDi object. |
| pErrorCode | must be a valid pointer to an error code value, which must not indicate a failure before the function call. |
- Returns:
- The levels array for the text, or
NULL if an error occurs.
- See also:
- UBiDiLevel
|
U_CAPI int32_t U_EXPORT2 ubidi_getLogicalIndex |
( |
UBiDi * |
pBiDi, |
|
|
int32_t |
visualIndex, |
|
|
UErrorCode * |
pErrorCode |
|
) |
|
|
|
Get the logical text position from a visual position.
If such a mapping is used many times on the same UBiDi object, then calling ubidi_getVisualMap() is more efficient.
This is the inverse function to ubidi_getVisualIndex() .
- Parameters:
-
| pBiDi | is the paragraph or line UBiDi object. |
| visualIndex | is the visual position of a character. |
| pErrorCode | must be a valid pointer to an error code value, which must not indicate a failure before the function call. |
- Returns:
- The index of this character in the text.
- See also:
- ubidi_getVisualMap
ubidi_getVisualIndex
|
U_CAPI void U_EXPORT2 ubidi_getLogicalMap |
( |
UBiDi * |
pBiDi, |
|
|
int32_t * |
indexMap, |
|
|
UErrorCode * |
pErrorCode |
|
) |
|
|
|
Get a logical-to-visual index map (array) for the characters in the UBiDi (paragraph or line) object.
- Parameters:
-
| pBiDi | is the paragraph or line UBiDi object. |
| indexMap | is a pointer to an array of ubidi_getLength() indexes which will reflect the reordering of the characters. The array does not need to be initialized. |
The index map will result in indexMap[logicalIndex]==visualIndex .
- Parameters:
-
| pErrorCode | must be a valid pointer to an error code value, which must not indicate a failure before the function call. |
- See also:
- ubidi_getVisualMap
ubidi_getVisualIndex
|
U_CAPI void U_EXPORT2 ubidi_getLogicalRun |
( |
const UBiDi * |
pBiDi, |
|
|
int32_t |
logicalStart, |
|
|
int32_t * |
pLogicalLimit, |
|
|
UBiDiLevel * |
pLevel |
|
) |
|
|
|
Get a logical run.
This function returns information about a run and is used to retrieve runs in logical order.
This is especially useful for line-breaking on a paragraph.
- Parameters:
-
| pBiDi | is the paragraph or line UBiDi object. |
| logicalStart | is the first character of the run. |
| pLogicalLimit | will receive the limit of the run. The l-value that you point to here may be the same expression (variable) as the one for logicalStart . This pointer can be NULL if this value is not necessary. |
| pLevel | will receive the level of the run. This pointer can be NULL if this value is not necessary. |
|
|
Get the paragraph level of the text.
- Parameters:
-
| pBiDi | is the paragraph or line UBiDi object. |
- Returns:
- The paragraph level.
- See also:
- UBiDiLevel
|
U_CAPI const UChar* U_EXPORT2 ubidi_getText |
( |
const UBiDi * |
pBiDi |
) |
|
|
|
Get the pointer to the text.
- Parameters:
-
| pBiDi | is the paragraph or line UBiDi object. |
- Returns:
- The pointer to the text that the UBiDi object was created for.
- See also:
- ubidi_setPara
ubidi_setLine
|
U_CAPI int32_t U_EXPORT2 ubidi_getVisualIndex |
( |
UBiDi * |
pBiDi, |
|
|
int32_t |
logicalIndex, |
|
|
UErrorCode * |
pErrorCode |
|
) |
|
|
|
Get the visual position from a logical text position.
If such a mapping is used many times on the same UBiDi object, then calling ubidi_getLogicalMap() is more efficient.
Note that in right-to-left runs, this mapping places modifier letters before base characters and second surrogates before first ones.
- Parameters:
-
| pBiDi | is the paragraph or line UBiDi object. |
| logicalIndex | is the index of a character in the text. |
| pErrorCode | must be a valid pointer to an error code value, which must not indicate a failure before the function call. |
- Returns:
- The visual position of this character.
- See also:
- ubidi_getLogicalMap
ubidi_getLogicalIndex
|
U_CAPI void U_EXPORT2 ubidi_getVisualMap |
( |
UBiDi * |
pBiDi, |
|
|
int32_t * |
indexMap, |
|
|
UErrorCode * |
pErrorCode |
|
) |
|
|
|
Get a visual-to-logical index map (array) for the characters in the UBiDi (paragraph or line) object.
- Parameters:
-
| pBiDi | is the paragraph or line UBiDi object. |
| indexMap | is a pointer to an array of ubidi_getLength() indexes which will reflect the reordering of the characters. The array does not need to be initialized. |
The index map will result in indexMap[visualIndex]==logicalIndex .
- Parameters:
-
| pErrorCode | must be a valid pointer to an error code value, which must not indicate a failure before the function call. |
- See also:
- ubidi_getLogicalMap
ubidi_getLogicalIndex
|
U_CAPI UBiDiDirection U_EXPORT2 ubidi_getVisualRun |
( |
UBiDi * |
pBiDi, |
|
|
int32_t |
runIndex, |
|
|
int32_t * |
pLogicalStart, |
|
|
int32_t * |
pLength |
|
) |
|
|
|
Get one run's logical start, length, and directionality, which can be 0 for LTR or 1 for RTL.
In an RTL run, the character at the logical start is visually on the right of the displayed run. The length is the number of characters in the run.
ubidi_countRuns() should be called before the runs are retrieved.
- Parameters:
-
| pBiDi | is the paragraph or line UBiDi object. |
| runIndex | is the number of the run in visual order, in the range [0..ubidi_countRuns(pBiDi)-1] . |
| pLogicalStart | is the first logical character index in the text. The pointer may be NULL if this index is not needed. |
| pLength | is the number of characters (at least one) in the run. The pointer may be NULL if this is not needed. |
- Returns:
- the directionality of the run,
UBIDI_LTR==0 or UBIDI_RTL==1 , never UBIDI_MIXED .
- See also:
- ubidi_countRuns
Example:
int32_t i, count= ubidi_countRuns(pBiDi),
logicalStart, visualIndex=0, length;
for(i=0; i<count; ++i) {
if( UBIDI_LTR== ubidi_getVisualRun(pBiDi, i, &logicalStart, &length)) {
do {
show_char(text[logicalStart++], visualIndex++);
} while(--length>0);
} else {
logicalStart+=length;
do {
show_char(text[--logicalStart], visualIndex++);
} while(--length>0);
}
}
*
Note that in right-to-left runs, code like this places modifier letters before base characters and second surrogates before first ones. |
U_CAPI void U_EXPORT2 ubidi_invertMap |
( |
const int32_t * |
srcMap, |
|
|
int32_t * |
destMap, |
|
|
int32_t |
length |
|
) |
|
|
|
Invert an index map.
The one-to-one index mapping of the first map is inverted and written to the second one.
- Parameters:
-
| srcMap | is an array with length indexes which define the original mapping. |
| destMap | is an array with length indexes which will be filled with the inverse mapping. |
| length | is the length of each array. |
|
U_CAPI UBool U_EXPORT2 ubidi_isInverse |
( |
UBiDi * |
pBiDi |
) |
|
|
U_CAPI UBiDi* U_EXPORT2 ubidi_open |
( |
void |
|
) |
|
|
|
Allocate a UBiDi structure.
Such an object is initially empty. It is assigned the BiDi properties of a paragraph by ubidi_setPara() or the BiDi properties of a line of a paragraph by ubidi_setLine() .
This object can be reused for as long as it is not deallocated by calling ubidi_close() .
ubidi_set() will allocate additional memory for internal structures as necessary.
- Returns:
- An empty
UBiDi object.
|
U_CAPI UBiDi* U_EXPORT2 ubidi_openSized |
( |
int32_t |
maxLength, |
|
|
int32_t |
maxRunCount, |
|
|
UErrorCode * |
pErrorCode |
|
) |
|
|
|
Allocate a UBiDi structure with preallocated memory for internal structures.
This function provides a UBiDi object like ubidi_open() with no arguments, but it also preallocates memory for internal structures according to the sizings supplied by the caller.
Subsequent functions will not allocate any more memory, and are thus guaranteed not to fail because of lack of memory.
The preallocation can be limited to some of the internal memory by setting some values to 0 here. That means that if, e.g., maxRunCount cannot be reasonably predetermined and should not be set to maxLength (the only failproof value) to avoid wasting memory, then maxRunCount could be set to 0 here and the internal structures that are associated with it will be allocated on demand, just like with ubidi_open() .
- Parameters:
-
| maxLength | is the maximum paragraph or line length that internal memory will be preallocated for. An attempt to associate this object with a longer text will fail, unless this value is 0, which leaves the allocation up to the implementation. |
| maxRunCount | is the maximum anticipated number of same-level runs that internal memory will be preallocated for. An attempt to access visual runs on an object that was not preallocated for as many runs as the text was actually resolved to will fail, unless this value is 0, which leaves the allocation up to the implementation. |
The number of runs depends on the actual text and maybe anywhere between 1 and maxLength . It is typically small.
- Parameters:
-
| pErrorCode | must be a valid pointer to an error code value, which must not indicate a failure before the function call. |
- Returns:
- An empty
UBiDi object with preallocated memory.
|
U_CAPI void U_EXPORT2 ubidi_reorderLogical |
( |
const UBiDiLevel * |
levels, |
|
|
int32_t |
length, |
|
|
int32_t * |
indexMap |
|
) |
|
|
|
This is a convenience function that does not use a UBiDi object.
It is intended to be used for when an application has determined the levels of objects (character sequences) and just needs to have them reordered (L2). This is equivalent to using ubidi_getLogicalMap on a UBiDi object.
- Parameters:
-
| levels | is an array with length levels that have been determined by the application. |
| length | is the number of levels in the array, or, semantically, the number of objects to be reordered. It must be length>0 . |
| indexMap | is a pointer to an array of length indexes which will reflect the reordering of the characters. The array does not need to be initialized. |
The index map will result in indexMap[logicalIndex]==visualIndex . |
U_CAPI void U_EXPORT2 ubidi_reorderVisual |
( |
const UBiDiLevel * |
levels, |
|
|
int32_t |
length, |
|
|
int32_t * |
indexMap |
|
) |
|
|
|
This is a convenience function that does not use a UBiDi object.
It is intended to be used for when an application has determined the levels of objects (character sequences) and just needs to have them reordered (L2). This is equivalent to using ubidi_getVisualMap on a UBiDi object.
- Parameters:
-
| levels | is an array with length levels that have been determined by the application. |
| length | is the number of levels in the array, or, semantically, the number of objects to be reordered. It must be length>0 . |
| indexMap | is a pointer to an array of length indexes which will reflect the reordering of the characters. The array does not need to be initialized. |
The index map will result in indexMap[visualIndex]==logicalIndex . |
U_CAPI void U_EXPORT2 ubidi_setInverse |
( |
UBiDi * |
pBiDi, |
|
|
UBool |
isInverse |
|
) |
|
|
|
Modify the operation of the BiDi algorithm such that it approximates an "inverse BiDi" algorithm.
This function must be called before ubidi_setPara() .
The normal operation of the BiDi algorithm as described in the Unicode Technical Report is to take text stored in logical (keyboard, typing) order and to determine the reordering of it for visual rendering. Some legacy codepages store text in visual order, and for operations with standard, Unicode-based algorithms, the text needs to be transformed to logical order. This is effectively the inverse algorithm of the described BiDi algorithm. Note that there is no standard algorithm for this "inverse BiDi" and that the current implementation provides only an approximation of "inverse BiDi".
With isInverse set to TRUE , this function changes the behavior of some of the subsequent functions in a way that they can be used for the inverse BiDi algorithm. Specifically, runs of text with numeric characters will be treated in a special way and may need to be surrounded with LRM characters when they are written in reordered sequence.
Output runs should be retrieved using ubidi_getVisualRun() . Since the actual input for "inverse BiDi" is visually ordered text and ubidi_getVisualRun() gets the reordered runs, these are actually the runs of the logically ordered output.
- Parameters:
-
| pBiDi | is a UBiDi object. |
| isInverse | specifies "forward" or "inverse" BiDi operation |
- See also:
- ubidi_setPara
ubidi_writeReordered
|
U_CAPI void U_EXPORT2 ubidi_setLine |
( |
const UBiDi * |
pParaBiDi, |
|
|
int32_t |
start, |
|
|
int32_t |
limit, |
|
|
UBiDi * |
pLineBiDi, |
|
|
UErrorCode * |
pErrorCode |
|
) |
|
|
|
ubidi_setLine() sets a UBiDi to contain the reordering information, especially the resolved levels, for all the characters in a line of text.
This line of text is specified by referring to a UBiDi object representing this information for a paragraph of text, and by specifying a range of indexes in this paragraph.
In the new line object, the indexes will range from 0 to limit-start .
This is used after calling ubidi_setPara() for a paragraph, and after line-breaking on that paragraph. It is not necessary if the paragraph is treated as a single line.
After line-breaking, rules (L1) and (L2) for the treatment of trailing WS and for reordering are performed on a UBiDi object that represents a line.
Important: pLineBiDi shares data with pParaBiDi . You must destroy or reuse pLineBiDi before pParaBiDi . In other words, you must destroy or reuse the UBiDi object for a line before the object for its parent paragraph.
The text pointer that was stored in pParaBiDi is also copied, and start is added to it so that it points to the beginning of the line for this object.
- Parameters:
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| pParaBiDi | is the parent paragraph object. |
| start | is the line's first index into the paragraph text. |
| limit | is just behind the line's last index into the paragraph text (its last index +1).
It must be 0<=start<=limit<= paragraph length. |
| pLineBiDi | is the object that will now represent a line of the paragraph. |
| pErrorCode | must be a valid pointer to an error code value, which must not indicate a failure before the function call. |
- See also:
- ubidi_setPara
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Perform the Unicode BiDi algorithm.
It is defined in the Unicode Technical Report 9, version 5, also described in The Unicode Standard, Version 3.0 .
This function takes a single plain text paragraph with or without externally specified embedding levels from <quote>styled text and computes the left-right-directionality of each character.
If the entire paragraph consists of text of only one direction, then the function may not perform all the steps described by the algorithm, i.e., some levels may not be the same as if all steps were performed. This is not relevant for unidirectional text.
For example, in pure LTR text with numbers the numbers would get a resolved level of 2 higher than the surrounding text according to the algorithm. This implementation may set all resolved levels to the same value in such a case.
The text must be externally split into separate paragraphs (rule P1). Paragraph separators (B) should appear at most at the very end.
- Parameters:
-
| pBiDi | A UBiDi object allocated with ubidi_open() which will be set to contain the reordering information, especially the resolved levels for all the characters in text . |
| text | is a pointer to the single-paragraph text that the BiDi algorithm will be performed on (step (P1) of the algorithm is performed externally). The text must be (at least) length long. This pointer is stored in the UBiDi object and can be retrieved with ubidi_getText() . |
| length | is the length of the text; if length==-1 then the text must be zero-terminated. |
| paraLevel | specifies the default level for the paragraph; it is typically 0 (LTR) or 1 (RTL). If the function shall determine the paragraph level from the text, then paraLevel can be set to either UBIDI_DEFAULT_LTR or UBIDI_DEFAULT_RTL ; if there is no strongly typed character, then the desired default is used (0 for LTR or 1 for RTL). Any other value between 0 and UBIDI_MAX_EXPLICIT_LEVEL is also valid, with odd levels indicating RTL. |
| embeddingLevels | (in) may be used to preset the embedding and override levels, ignoring characters like LRE and PDF in the text. A level overrides the directional property of its corresponding (same index) character if the level has the UBIDI_LEVEL_OVERRIDE bit set. |
Except for that bit, it must be paraLevel<=embeddingLevels[]<=UBIDI_MAX_EXPLICIT_LEVEL .
Caution: A copy of this pointer, not of the levels, will be stored in the UBiDi object; the embeddingLevels array must not be deallocated before the UBiDi structure is destroyed or reused, and the embeddingLevels should not be modified to avoid unexpected results on subsequent BiDi operations. However, the ubidi_setPara() and ubidi_setLine() functions may modify some or all of the levels.
After the UBiDi object is reused or destroyed, the caller must take care of the deallocation of the embeddingLevels array.
The embeddingLevels array must be at least length long.
- Parameters:
-
| pErrorCode | must be a valid pointer to an error code value, which must not indicate a failure before the function call. |
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U_CAPI int32_t U_EXPORT2 ubidi_writeReordered |
( |
UBiDi * |
pBiDi, |
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UChar * |
dest, |
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int32_t |
destSize, |
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uint16_t |
options, |
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UErrorCode * |
pErrorCode |
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) |
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Take a UBiDi object containing the reordering information for one paragraph or line of text as set by ubidi_setPara() or ubidi_setLine() and write a reordered string to the destination buffer.
This function preserves the integrity of characters with multiple code units and (optionally) modifier letters. Characters in RTL runs can be replaced by mirror-image characters in the destination buffer. Note that "real" mirroring has to be done in a rendering engine by glyph selection and that for many "mirrored" characters there are no Unicode characters as mirror-image equivalents. There are also options to insert or remove BiDi control characters; see the description of the destSize and options parameters and of the option bit flags.
- Parameters:
-
| pBiDi | A pointer to a UBiDi object that is set by ubidi_setPara() or ubidi_setLine() and contains the reordering information for the text that it was defined for, as well as a pointer to that text. |
The text was aliased (only the pointer was stored without copying the contents) and must not have been modified since the ubidi_setPara() call.
- Parameters:
-
| dest | A pointer to where the reordered text is to be copied. The source text and dest[destSize] must not overlap. |
| destSize | The size of the dest buffer, in number of UChars. If the UBIDI_INSERT_LRM_FOR_NUMERIC option is set, then the destination length could be as large as ubidi_getLength(pBiDi)+2*ubidi_countRuns(pBiDi) . If the UBIDI_REMOVE_BIDI_CONTROLS option is set, then the destination length may be less than ubidi_getLength(pBiDi) . If none of these options is set, then the destination length will be exactly ubidi_getLength(pBiDi) . |
| options | A bit set of options for the reordering that control how the reordered text is written. The options include mirroring the characters on a code point basis and inserting LRM characters, which is used especially for transforming visually stored text to logically stored text (although this is still an imperfect implementation of an "inverse BiDi" algorithm because it uses the "forward BiDi" algorithm at its core). |
| pErrorCode | must be a valid pointer to an error code value, which must not indicate a failure before the function call. |
- Returns:
- The length of the output string.
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U_CAPI int32_t U_EXPORT2 ubidi_writeReverse |
( |
const UChar * |
src, |
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int32_t |
srcLength, |
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UChar * |
dest, |
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int32_t |
destSize, |
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uint16_t |
options, |
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UErrorCode * |
pErrorCode |
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) |
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Reverse a Right-To-Left run of Unicode text.
This function preserves the integrity of characters with multiple code units and (optionally) modifier letters. Characters can be replaced by mirror-image characters in the destination buffer. Note that "real" mirroring has to be done in a rendering engine by glyph selection and that for many "mirrored" characters there are no Unicode characters as mirror-image equivalents. There are also options to insert or remove BiDi control characters.
This function is the implementation for reversing RTL runs as part of ubidi_writeReordered() . For detailed descriptions of the parameters, see there. Since no BiDi controls are inserted here, the output string length will never exceed srcLength .
- See also:
- ubidi_writeReordered
- Parameters:
-
| src | A pointer to the RTL run text. |
| srcLength | The length of the RTL run. |
| dest | A pointer to where the reordered text is to be copied. src[srcLength] and dest[destSize] must not overlap. |
| destSize | The size of the dest buffer, in number of UChars. If the UBIDI_REMOVE_BIDI_CONTROLS option is set, then the destination length may be less than srcLength . If this option is not set, then the destination length will be exactly srcLength . |
| options | A bit set of options for the reordering that control how the reordered text is written. See ubidi_writeReordered() . |
| pErrorCode | must be a valid pointer to an error code value, which must not indicate a failure before the function call. |
- Returns:
- The length of the output string.
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Generated on Fri Aug 13 09:53:50 2004 for ICU 2.1 by
1.3.7