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ubrk.h File Reference

C API: BreakIterator. More...

#include "unicode/utypes.h"

Go to the source code of this file.

Defines

#define UBRK_DONE   ((int32_t) -1)
 Value indicating all text boundaries have been returned.
#define U_BRK_SAFECLONE_BUFFERSIZE   512

Typedefs

typedef void * UBreakIterator
 A text-break iterator.
typedef enum UBreakIteratorType UBreakIteratorType

Enumerations

enum  UBreakIteratorType {
  UBRK_CHARACTER, UBRK_WORD, UBRK_LINE, UBRK_SENTENCE,
  UBRK_TITLE
}
 The possible types of text boundaries. More...

Functions

U_CAPI UBreakIterator *U_EXPORT2 ubrk_open (UBreakIteratorType type, const char *locale, const UChar *text, int32_t textLength, UErrorCode *status)
 Open a new UBreakIterator for locating text boundaries for a specified locale.
U_CAPI UBreakIterator *U_EXPORT2 ubrk_openRules (const UChar *rules, int32_t rulesLength, const UChar *text, int32_t textLength, UErrorCode *status)
 Open a new UBreakIterator for locating text boundaries using specified breaking rules.
U_CAPI UBreakIterator *U_EXPORT2 ubrk_safeClone (const UBreakIterator *bi, void *stackBuffer, int32_t *pBufferSize, UErrorCode *status)
 Thread safe cloning operation.
U_CAPI void U_EXPORT2 ubrk_close (UBreakIterator *bi)
 Close a UBreakIterator.
U_CAPI void U_EXPORT2 ubrk_setText (UBreakIterator *bi, const UChar *text, int32_t textLength, UErrorCode *status)
 Sets an existing iterator to point to a new piece of text .
U_CAPI int32_t U_EXPORT2 ubrk_current (const UBreakIterator *bi)
 Determine the most recently-returned text boundary.
U_CAPI int32_t U_EXPORT2 ubrk_next (UBreakIterator *bi)
 Determine the text boundary following the current text boundary.
U_CAPI int32_t U_EXPORT2 ubrk_previous (UBreakIterator *bi)
 Determine the text boundary preceding the current text boundary.
U_CAPI int32_t U_EXPORT2 ubrk_first (UBreakIterator *bi)
 Determine the index of the first character in the text being scanned.
U_CAPI int32_t U_EXPORT2 ubrk_last (UBreakIterator *bi)
 Determine the index immediately beyond the last character in the text being scanned.
U_CAPI int32_t U_EXPORT2 ubrk_preceding (UBreakIterator *bi, int32_t offset)
 Determine the text boundary preceding the specified offset.
U_CAPI int32_t U_EXPORT2 ubrk_following (UBreakIterator *bi, int32_t offset)
 Determine the text boundary following the specified offset.
U_CAPI const char *U_EXPORT2 ubrk_getAvailable (int32_t index)
 Get a locale for which text breaking information is available.
U_CAPI int32_t U_EXPORT2 ubrk_countAvailable (void)
 Determine how many locales have text breaking information available.
U_CAPI UBool U_EXPORT2 ubrk_isBoundary (UBreakIterator *bi, int32_t offset)
 Returns true if the specfied position is a boundary position.


Detailed Description

C API: BreakIterator.

BreakIterator C API

The BreakIterator C API defines methods for finding the location of boundaries in text. Pointer to a UBreakIterator maintain a current position and scan over text returning the index of characters where boundaries occur.

Line boundary analysis determines where a text string can be broken when line-wrapping. The mechanism correctly handles punctuation and hyphenated words.

Sentence boundary analysis allows selection with correct interpretation of periods within numbers and abbreviations, and trailing punctuation marks such as quotation marks and parentheses.

Word boundary analysis is used by search and replace functions, as well as within text editing applications that allow the user to select words with a double click. Word selection provides correct interpretation of punctuation marks within and following words. Characters that are not part of a word, such as symbols or punctuation marks, have word-breaks on both sides.

Character boundary analysis allows users to interact with characters as they expect to, for example, when moving the cursor through a text string. Character boundary analysis provides correct navigation of through character strings, regardless of how the character is stored. For example, an accented character might be stored as a base character and a diacritical mark. What users consider to be a character can differ between languages.

Title boundary analysis locates all positions, typically starts of words, that should be set to Title Case when title casing the text.

This is the interface for all text boundaries.

Examples:

Helper function to output text

 
    void printTextRange(UChar* str, int32_t start, int32_t end ) {
         UChar* result;
         UChar* temp;
         const char* res;
         temp=(UChar*)malloc(sizeof(UChar) * ((u_strlen(str)-start)+1));
         result=(UChar*)malloc(sizeof(UChar) * ((end-start)+1));
         u_strcpy(temp, &str[start]);
         u_strncpy(result, temp, end-start);
         res=(char*)malloc(sizeof(char) * (u_strlen(result)+1));
         u_austrcpy(res, result);
         printf("%s\n", res);
    }
Print each element in order:
 
    void printEachForward( UBreakIterator* boundary, UChar* str) {
       int32_t end;
       int32_t start = ubrk_first(boundary);
       for (end = ubrk_next(boundary)); end != UBRK_DONE; start = end, end = ubrk_next(boundary)) {
             printTextRange(str, start, end );
         }
    }
Print each element in reverse order:
 
    void printEachBackward( UBreakIterator* boundary, UChar* str) {
       int32_t start;
       int32_t end = ubrk_last(boundary);
       for (start = ubrk_previous(boundary); start != UBRK_DONE;  end = start, start =ubrk_previous(boundary)) {
             printTextRange( str, start, end );
         }
    }
Print first element
 
    void printFirst(UBreakIterator* boundary, UChar* str) {
        int32_t end;
        int32_t start = ubrk_first(boundary);
        end = ubrk_next(boundary);
        printTextRange( str, start, end );
    }
Print last element
 
    void printLast(UBreakIterator* boundary, UChar* str) {
        int32_t start;
        int32_t end = ubrk_last(boundary);
        start = ubrk_previous(boundary);
        printTextRange(str, start, end );
    }
Print the element at a specified position
 
    void printAt(UBreakIterator* boundary, int32_t pos , UChar* str) {
        int32_t start;
        int32_t end = ubrk_following(boundary, pos);
        start = ubrk_previous(boundary);
        printTextRange(str, start, end );
    }
Creating and using text boundaries
 
       void BreakIterator_Example( void ) {
           UBreakIterator* boundary;
           UChar *stringToExamine;
           stringToExamine=(UChar*)malloc(sizeof(UChar) * (strlen("Aaa bbb ccc. Ddd eee fff.")+1) );
           u_uastrcpy(stringToExamine, "Aaa bbb ccc. Ddd eee fff.");
           printf("Examining: "Aaa bbb ccc. Ddd eee fff.");

           //print each sentence in forward and reverse order
           boundary = ubrk_open(UBRK_SENTENCE, "en_us", stringToExamine, u_strlen(stringToExamine), &status);
           printf("----- forward: -----------\n");
           printEachForward(boundary, stringToExamine);
           printf("----- backward: ----------\n");
           printEachBackward(boundary, stringToExamine);
           ubrk_close(boundary);

           //print each word in order
           boundary = ubrk_open(UBRK_WORD, "en_us", stringToExamine, u_strlen(stringToExamine), &status);
           printf("----- forward: -----------\n");
           printEachForward(boundary, stringToExamine);
           printf("----- backward: ----------\n");
           printEachBackward(boundary, stringToExamine);
           //print first element
           printf("----- first: -------------\n");
           printFirst(boundary, stringToExamine);
           //print last element
           printf("----- last: --------------\n");
           printLast(boundary, stringToExamine);
           //print word at charpos 10
           printf("----- at pos 10: ---------\n");
           printAt(boundary, 10 , stringToExamine);

           ubrk_close(boundary);
       }

Typedef Documentation

typedef void* UBreakIterator
 

A text-break iterator.

For usage in C programs.


Enumeration Type Documentation

enum UBreakIteratorType
 

The possible types of text boundaries.

Enumeration values:
UBRK_CHARACTER  Character breaks.
UBRK_WORD  Word breaks.
UBRK_LINE  Line breaks.
UBRK_SENTENCE  Sentence breaks.
UBRK_TITLE  Title Case breaks.


Function Documentation

U_CAPI void U_EXPORT2 ubrk_close UBreakIterator bi  ) 
 

Close a UBreakIterator.

Once closed, a UBreakIterator may no longer be used.

Parameters:
bi The break iterator to close.

U_CAPI int32_t U_EXPORT2 ubrk_countAvailable void   ) 
 

Determine how many locales have text breaking information available.

This function is most useful as determining the loop ending condition for calls to {ubrk_getAvailable}.

Returns:
The number of locales for which text breaking information is available.
See also:
ubrk_getAvailable

U_CAPI int32_t U_EXPORT2 ubrk_current const UBreakIterator bi  ) 
 

Determine the most recently-returned text boundary.

Parameters:
bi The break iterator to use.
Returns:
The character index most recently returned by {ubrk_next}, {ubrk_previous}, {ubrk_first}, or {ubrk_last}.

U_CAPI int32_t U_EXPORT2 ubrk_first UBreakIterator bi  ) 
 

Determine the index of the first character in the text being scanned.

This is not always the same as index 0 of the text.

Parameters:
bi The break iterator to use.
Returns:
The character index of the first character in the text being scanned.
See also:
ubrk_last

U_CAPI int32_t U_EXPORT2 ubrk_following UBreakIterator bi,
int32_t  offset
 

Determine the text boundary following the specified offset.

The value returned is always greater than offset, or UBRK_DONE.

Parameters:
bi The break iterator to use.
offset The offset to begin scanning.
Returns:
The text boundary following offset, or UBRK_DONE.
See also:
ubrk_preceding

U_CAPI const char* U_EXPORT2 ubrk_getAvailable int32_t  index  ) 
 

Get a locale for which text breaking information is available.

A UBreakIterator in a locale returned by this function will perform the correct text breaking for the locale.

Parameters:
index The index of the desired locale.
Returns:
A locale for which number text breaking information is available, or 0 if none.
See also:
ubrk_countAvailable

U_CAPI UBool U_EXPORT2 ubrk_isBoundary UBreakIterator bi,
int32_t  offset
 

Returns true if the specfied position is a boundary position.

As a side effect, leaves the iterator pointing to the first boundary position at or after "offset".

Parameters:
bi The break iterator to use.
offset the offset to check.
Returns:
True if "offset" is a boundary position.

U_CAPI int32_t U_EXPORT2 ubrk_last UBreakIterator bi  ) 
 

Determine the index immediately beyond the last character in the text being scanned.

This is not the same as the last character.

Parameters:
bi The break iterator to use.
Returns:
The character offset immediately beyond the last character in the text being scanned.
See also:
ubrk_first

U_CAPI int32_t U_EXPORT2 ubrk_next UBreakIterator bi  ) 
 

Determine the text boundary following the current text boundary.

Parameters:
bi The break iterator to use.
Returns:
The character index of the next text boundary, or UBRK_DONE if all text boundaries have been returned.
See also:
ubrk_previous

U_CAPI UBreakIterator* U_EXPORT2 ubrk_open UBreakIteratorType  type,
const char *  locale,
const UChar text,
int32_t  textLength,
UErrorCode status
 

Open a new UBreakIterator for locating text boundaries for a specified locale.

A UBreakIterator may be used for detecting character, line, word, and sentence breaks in text.

Parameters:
type The type of UBreakIterator to open: one of UBRK_CHARACTER, UBRK_WORD, UBRK_LINE, UBRK_SENTENCE
locale The locale specifying the text-breaking conventions.
text The text to be iterated over.
textLength The number of characters in text, or -1 if null-terminated.
status A UErrorCode to receive any errors.
Returns:
A UBreakIterator for the specified locale.
See also:
ubrk_openRules

U_CAPI UBreakIterator* U_EXPORT2 ubrk_openRules const UChar rules,
int32_t  rulesLength,
const UChar text,
int32_t  textLength,
UErrorCode status
 

Open a new UBreakIterator for locating text boundaries using specified breaking rules.

The rule syntax is ... (TBD)

Parameters:
rules A set of rules specifying the text breaking conventions.
rulesLength The number of characters in rules, or -1 if null-terminated.
text The text to be iterated over.
textLength The number of characters in text, or -1 if null-terminated.
status A UErrorCode to receive any errors.
Returns:
A UBreakIterator for the specified rules.
See also:
ubrk_open

U_CAPI int32_t U_EXPORT2 ubrk_preceding UBreakIterator bi,
int32_t  offset
 

Determine the text boundary preceding the specified offset.

The value returned is always smaller than offset, or UBRK_DONE.

Parameters:
bi The break iterator to use.
offset The offset to begin scanning.
Returns:
The text boundary preceding offset, or UBRK_DONE.
See also:
ubrk_following

U_CAPI int32_t U_EXPORT2 ubrk_previous UBreakIterator bi  ) 
 

Determine the text boundary preceding the current text boundary.

Parameters:
bi The break iterator to use.
Returns:
The character index of the preceding text boundary, or UBRK_DONE if all text boundaries have been returned.
See also:
ubrk_next

U_CAPI UBreakIterator* U_EXPORT2 ubrk_safeClone const UBreakIterator bi,
void *  stackBuffer,
int32_t *  pBufferSize,
UErrorCode status
 

Thread safe cloning operation.

Parameters:
bi iterator to be cloned
stackBuffer user allocated space for the new clone. If NULL new memory will be allocated. If buffer is not large enough, new memory will be allocated. Clients can use the U_BRK_SAFECLONE_BUFFERSIZE. This will probably be enough to avoid memory allocations.
pBufferSize pointer to size of allocated space. If *pBufferSize == 0, a sufficient size for use in cloning will be returned ('pre-flighting') If *pBufferSize is not enough for a stack-based safe clone, new memory will be allocated.
status to indicate whether the operation went on smoothly or there were errors An informational status value, U_SAFECLONE_ALLOCATED_ERROR, is used if any allocations were necessary.
Returns:
pointer to the new clone ICU 1.8


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