* The algorithm implemented is a modified form of the Boyer Moore's search. * For more information see * * "Efficient Text Searching in Java", published in Java Report * in February, 1999, for further information on the algorithm. *
* There are 2 match options for selection:
* This search has APIs similar to that of other text iteration mechanisms
* such as the break iterators in ubrk.h. Using these
* APIs, it is easy to scan through text looking for all occurances of
* a given pattern. This search iterator allows changing of direction by
* calling a reset followed by a next or previous.
* Though a direction change can occur without calling reset first,
* this operation comes with some speed penalty.
* Generally, match results in the forward direction will match the result
* matches in the backwards direction in the reverse order
*
* usearch.h provides APIs to specify the starting position
* within the text string to be searched, e.g. usearch_setOffset,
* usearch_preceding and usearch_following. Since the
* starting position will be set as it is specified, please take note that
* there are some dangerous positions which the search may render incorrect
* results:
*
* A breakiterator can be used if only matches at logical breaks are desired.
* Using a breakiterator will only give you results that exactly matches the
* boundaries given by the breakiterator. For instance the pattern "e" will
* not be found in the string "\u00e9" if a character break iterator is used.
*
* Options are provided to handle overlapping matches.
* E.g. In English, overlapping matches produces the result 0 and 2
* for the pattern "abab" in the text "ababab", where else mutually
* exclusive matches only produce the result of 0.
*
* Though collator attributes will be taken into consideration while
* performing matches, there are no APIs here for setting and getting the
* attributes. These attributes can be set by getting the collator
* from usearch_getCollator and using the APIs in ucol.h.
* Lastly to update String Search to the new collator attributes,
* usearch_reset() has to be called.
*
* Restriction:
* Example of use:
* Use usearch_getMatchedLength to get the matched string length.
* @param strsrch search iterator data struct
* @return index to a substring within the text string that is being
* searched.
* @draft ICU 2.0
*/
U_CAPI int32_t U_EXPORT2 usearch_getMatchedStart(
const UStringSearch *strsrch);
/**
* Returns the length of text in the string which matches the search pattern.
* This call returns a valid result only after a successful call to
* {@link #usearch_first}, {@link #usearch_next},
* {@link #usearch_previous}, or {@link #usearch_last}.
* Just after construction, or after a searching method returns
* USEARCH_DONE, this method will return 0.
* @param strsrch search iterator data struct
* @return The length of the match in the string text, or 0 if there is no
* match currently.
* @draft ICU 2.0
*/
U_CAPI int32_t U_EXPORT2 usearch_getMatchedLength(
const UStringSearch *strsrch);
/**
* Returns the text that was matched by the most recent call to
* {@link #usearch_first}, {@link #usearch_next},
* {@link #usearch_previous}, or {@link #usearch_last}.
* If the iterator is not pointing at a valid match (e.g. just after
* construction or after USEARCH_DONE has been returned, returns
* an empty string. If result is not large enough to store the matched text,
* result will be filled with the partial text and an U_BUFFER_OVERFLOW_ERROR
* will be returned in status. result will be null-terminated whenever
* possible. If the buffer fits the matched text exactly, a null-termination
* is not possible, then a U_STRING_NOT_TERMINATED_ERROR set in status.
* Pre-flighting can be either done with length = 0 or the API
* usearch_getMatchLength().
* @param strsrch search iterator data struct
* @param result UChar buffer to store the matched string
* @param resultCapacity length of the result buffer
* @param status error returned if result is not large enough
* @return exact length of the matched text, not counting the null-termination
* @draft ICU 2.0
*/
U_CAPI int32_t U_EXPORT2 usearch_getMatchedText(const UStringSearch *strsrch,
UChar *result,
int32_t resultCapacity,
UErrorCode *status);
/**
* Set the BreakIterator that will be used to restrict the points at which
* matches are detected.
* @param strsrch search iterator data struct
* @param breakiter A BreakIterator that will be used to restrict the points
* at which matches are detected. If a match is found, but
* the match's start or end index is not a boundary as
* determined by the BreakIterator, the match will
* be rejected and another will be searched for.
* If this parameter is NULL, no break detection is
* attempted.
* @param status for errors if it occurs
* @see #usearch_getBreakIterator
* @draft ICU 2.0
*/
U_CAPI void U_EXPORT2 usearch_setBreakIterator(UStringSearch *strsrch,
UBreakIterator *breakiter,
UErrorCode *status);
/**
* Returns the BreakIterator that is used to restrict the points at which
* matches are detected. This will be the same object that was passed to the
* constructor or to usearch_setBreakIterator. Note that
* NULL
* is a legal value; it means that break detection should not be attempted.
* @param strsrch search iterator data struct
* @return break iterator used
* @see #usearch_setBreakIterator
* @draft ICU 2.0
*/
U_CAPI const UBreakIterator * U_EXPORT2 usearch_getBreakIterator(
const UStringSearch *strsrch);
/**
* Set the string text to be searched. Text iteration will hence begin at the
* start of the text string. This method is useful if you want to re-use an
* iterator to search for the same pattern within a different body of text.
* @param strsrch search iterator data struct
* @param text new string to look for match
* @param textlength length of the new string, -1 for null-termination
* @param status for errors if it occurs. If text is NULL, or textlength is 0
* then an U_ILLEGAL_ARGUMENT_ERROR is returned with no change
* done to strsrch.
* @see #usearch_getText
* @draft ICU 2.0
*/
U_CAPI void U_EXPORT2 usearch_setText( UStringSearch *strsrch,
const UChar *text,
int32_t textlength,
UErrorCode *status);
/**
* Return the string text to be searched.
* @param strsrch search iterator data struct
* @param length returned string text length
* @return string text
* @see #usearch_setText
* @draft ICU 2.0
*/
U_CAPI const UChar * U_EXPORT2 usearch_getText(const UStringSearch *strsrch,
int32_t *length);
/**
* Gets the collator used for the language rules.
*
* Deleting the returned UCollator before calling
* usearch_close would cause the string search to fail.
* usearch_close will delete the collator if this search owns it.
* @param strsrch search iterator data struct
* @return collator
* @draft ICU 2.0
*/
U_CAPI UCollator * U_EXPORT2 usearch_getCollator(
const UStringSearch *strsrch);
/**
* Sets the collator used for the language rules. User retains the ownership
* of this collator, thus the responsibility of deletion lies with the user.
* This method causes internal data such as Boyer-Moore shift tables to
* be recalculated, but the iterator's position is unchanged.
* @param strsrch search iterator data struct
* @param collator to be used
* @param status for errors if it occurs
* @draft ICU 2.0
*/
U_CAPI void U_EXPORT2 usearch_setCollator( UStringSearch *strsrch,
const UCollator *collator,
UErrorCode *status);
/**
* Sets the pattern used for matching.
* Internal data like the Boyer Moore table will be recalculated, but the
* iterator's position is unchanged.
* @param strsrch search iterator data struct
* @param pattern string
* @param patternlength pattern length, -1 for null-terminated string
* @param status for errors if it occurs. If text is NULL, or textlength is 0
* then an U_ILLEGAL_ARGUMENT_ERROR is returned with no change
* done to strsrch.
* @draft ICU 2.0
*/
U_CAPI void U_EXPORT2 usearch_setPattern( UStringSearch *strsrch,
const UChar *pattern,
int32_t patternlength,
UErrorCode *status);
/**
* Gets the search pattern
* @param strsrch search iterator data struct
* @param length return length of the pattern, -1 indicates that the pattern
* is null-terminated
* @return pattern string
* @draft ICU 2.0
*/
U_CAPI const UChar * U_EXPORT2 usearch_getPattern(
const UStringSearch *strsrch,
int32_t *length);
/* methods ------------------------------------------------------------- */
/**
* Returns the first index at which the string text matches the search
* pattern.
* The iterator is adjusted so that its current index (as returned by
* {@link #usearch_getOffset}) is the match position if one was found.
* If a match is not found, USEARCH_DONE will be returned and
* the iterator will be adjusted to the index USEARCH_DONE.
* @param strsrch search iterator data struct
* @param status for errors if it occurs
* @return The character index of the first match, or
* USEARCH_DONE if there are no matches.
* @draft ICU 2.0
*/
U_CAPI int32_t U_EXPORT2 usearch_first(UStringSearch *strsrch,
UErrorCode *status);
/**
* Returns the first index greater than position at which the string
* text
* matches the search pattern. The iterator is adjusted so that its current
* index (as returned by {@link #usearch_getOffset}) is the match position if
* one was found.
* If a match is not found, USEARCH_DONE will be returned and
* the iterator will be adjusted to the index USEARCH_DONE
*
* Search positions that may render incorrect results are highlighted in the
* header comments.
* @param strsrch search iterator data struct
* @param position to start the search at
* @param status for errors if it occurs
* @return The character index of the first match following pos,
* or USEARCH_DONE if there are no matches.
* @draft ICU 2.0
*/
U_CAPI int32_t U_EXPORT2 usearch_following(UStringSearch *strsrch,
int32_t position,
UErrorCode *status);
/**
* Returns the last index in the target text at which it matches the search
* pattern. The iterator is adjusted so that its current
* index (as returned by {@link #usearch_getOffset}) is the match position if
* one was found.
* If a match is not found, USEARCH_DONE will be returned and
* the iterator will be adjusted to the index USEARCH_DONE.
* @param strsrch search iterator data struct
* @param status for errors if it occurs
* @return The index of the first match, or USEARCH_DONE if there
* are no matches.
* @draft ICU 2.0
*/
U_CAPI int32_t U_EXPORT2 usearch_last(UStringSearch *strsrch,
UErrorCode *status);
/**
* Returns the first index less than position at which the string text
* matches the search pattern. The iterator is adjusted so that its current
* index (as returned by {@link #usearch_getOffset}) is the match position if
* one was found.
* If a match is not found, USEARCH_DONE will be returned and
* the iterator will be adjusted to the index USEARCH_DONE
*
* Search positions that may render incorrect results are highlighted in the
* header comments.
* @param strsrch search iterator data struct
* @param position index position the search is to begin at
* @param status for errors if it occurs
* @return The character index of the first match preceding pos,
* or USEARCH_DONE if there are no matches.
* @draft ICU 2.0
*/
U_CAPI int32_t U_EXPORT2 usearch_preceding(UStringSearch *strsrch,
int32_t position,
UErrorCode *status);
/**
* Returns the index of the next point at which the string text matches the
* search pattern, starting from the current position.
* The iterator is adjusted so that its current
* index (as returned by {@link #usearch_getOffset}) is the match position if
* one was found.
* If a match is not found, USEARCH_DONE will be returned and
* the iterator will be adjusted to the index USEARCH_DONE
* @param strsrch search iterator data struct
* @param status for errors if it occurs
* @return The index of the next match after the current position, or
* USEARCH_DONE if there are no more matches.
* @see #usearch_first
* @draft ICU 2.0
*/
U_CAPI int32_t U_EXPORT2 usearch_next(UStringSearch *strsrch,
UErrorCode *status);
/**
* Returns the index of the previous point at which the string text matches
* the search pattern, starting at the current position.
* The iterator is adjusted so that its current
* index (as returned by {@link #usearch_getOffset}) is the match position if
* one was found.
* If a match is not found, USEARCH_DONE will be returned and
* the iterator will be adjusted to the index USEARCH_DONE
* @param strsrch search iterator data struct
* @param status for errors if it occurs
* @return The index of the previous match before the current position,
* or USEARCH_DONE if there are no more matches.
* @draft ICU 2.0
*/
U_CAPI int32_t U_EXPORT2 usearch_previous(UStringSearch *strsrch,
UErrorCode *status);
/**
* Reset the iteration.
* Search will begin at the start of the text string if a forward iteration
* is initiated before a backwards iteration. Otherwise if a backwards
* iteration is initiated before a forwards iteration, the search will begin
* at the end of the text string.
* @param strsrch search iterator data struct
* @draft ICU 2.0
*/
U_CAPI void U_EXPORT2 usearch_reset(UStringSearch *strsrch);
#endif
* Let S' be the sub-string of a text string S between the offsets start and
* end
* A pattern string P matches a text string S at the offsets
* option 1. Some canonical equivalent of P matches some canonical equivalent
* of S'
* option 2. P matches S' and if P starts or ends with a combining mark,
* there exists no non-ignorable combining mark before or after S’
* in S respectively.
*
* Option 2. will be the default·
*
*
* Currently there are no composite characters that consists of a
* character with combining class > 0 before a character with combining
* class == 0. However, if such a character exists in the future, the
* search mechanism does not guarantee the results for option 1.
*
*
*
* @since ICU 2.0
*/
/**
* DONE is returned by previous() and next() after all valid matches have
* been returned, and by first() and last() if there are no matches at all.
*/
#define USEARCH_DONE -1
/**
* Data structure for searching
*/
struct UStringSearch;
typedef struct UStringSearch UStringSearch;
typedef enum {
/** Option for overlapping matches */
USEARCH_OVERLAP,
/**
Option for canonical matches. option 1 in header documentation.
The default value will be USEARCH_OFF
*/
USEARCH_CANONICAL_MATCH,
USEARCH_ATTRIBUTE_COUNT
} USearchAttribute;
typedef enum {
/** default value for any USearchAttribute */
USEARCH_DEFAULT = -1,
/** value for USEARCH_OVERLAP and USEARCH_CANONICAL_MATCH */
USEARCH_OFF,
/** value for USEARCH_OVERLAP and USEARCH_CANONICAL_MATCH */
USEARCH_ON,
USEARCH_ATTRIBUTE_VALUE_COUNT
} USearchAttributeValue;
/* open and close ------------------------------------------------------ */
/**
* Creating a search iterator data struct using the argument locale language
* rule set. A collator will be created in the process, which will be owned by
* this search and will be deleted in usearch_close.
* @param pattern for matching
* @param patternlength length of the pattern, -1 for null-termination
* @param text text string
* @param textlength length of the text string, -1 for null-termination
* @param locale name of locale for the rules to be used
* @param breakiter A BreakIterator that will be used to restrict the points
* at which matches are detected. If a match is found, but
* the match's start or end index is not a boundary as
* determined by the BreakIterator, the match will
* be rejected and another will be searched for.
* If this parameter is NULL, no break detection is
* attempted.
* @param status for errors if it occurs. If pattern or text is NULL, or if
* patternlength or textlength is 0 then an
* U_ILLEGAL_ARGUMENT_ERROR is returned.
* @return search iterator data structure, or NULL if there is an error.
* @draft ICU 2.0
*/
U_CAPI UStringSearch * U_EXPORT2 usearch_open(const UChar *pattern,
int32_t patternlength,
const UChar *text,
int32_t textlength,
const char *locale,
UBreakIterator *breakiter,
UErrorCode *status);
/**
* Creating a search iterator data struct using the argument collator language
* rule set. Note, user retains the ownership of this collator, thus the
* responsibility of deletion lies with the user.
* @param pattern for matching
* @param patternlength length of the pattern, -1 for null-termination
* @param text text string
* @param textlength length of the text string, -1 for null-termination
* @param collator used for the language rules
* @param breakiter A BreakIterator that will be used to restrict the points
* at which matches are detected. If a match is found, but
* the match's start or end index is not a boundary as
* determined by the BreakIterator, the match will
* be rejected and another will be searched for.
* If this parameter is NULL, no break detection is
* attempted.
* @param status for errors if it occurs. If collator, pattern or text is NULL,
* or if patternlength or textlength is 0 then an
* U_ILLEGAL_ARGUMENT_ERROR is returned.
* @return search iterator data structure, or NULL if there is an error.
* @draft ICU 2.0
*/
U_CAPI UStringSearch * U_EXPORT2 usearch_openFromCollator(
const UChar *pattern,
int32_t patternlength,
const UChar *text,
int32_t textlength,
const UCollator *collator,
UBreakIterator *breakiter,
UErrorCode *status);
/**
* Destroying and cleaning up the search iterator data struct.
* If a collator is created in usearch_open, it will be destroyed here.
* @param searchiter data struct to clean up
* @draft ICU 2.0
*/
U_CAPI void U_EXPORT2 usearch_close(UStringSearch *strsrch);
/* get and set methods -------------------------------------------------- */
/**
* Sets the current position in the text string which the next search will
* start from. Clears previous states.
* This method takes the argument index and sets the position in the text
* string accordingly without checking if the index is pointing to a
* valid starting point to begin searching.
* Search positions that may render incorrect results are highlighted in the
* header comments
* @param strsrch search iterator data struct
* @param position position to start next search from.
* @param status error status if any.
* @draft ICU 2.0
*/
U_CAPI void U_EXPORT2 usearch_setOffset(UStringSearch *strsrch,
int32_t position,
UErrorCode *status);
/**
* Return the current index in the string text being searched.
* If the iteration has gone past the end of the text (or past the beginning
* for a backwards search), {@link #USEARCH_DONE} is returned.
* @param strsrch search iterator data struct
* @draft ICU 2.0
*/
U_CAPI int32_t U_EXPORT2 usearch_getOffset(const UStringSearch *strsrch);
/**
* Sets the text searching attributes located in the enum USearchAttribute
* with values from the enum USearchAttributeValue.
* USEARCH_DEFAULT can be used for all attributes for resetting.
* @param strsrch search iterator data struct
* @param attribute text attribute to be set
* @param value text attribute value
* @param status for errors if it occurs
* @see #usearch_getAttribute
* @draft ICU 2.0
*/
U_CAPI void U_EXPORT2 usearch_setAttribute(UStringSearch *strsrch,
USearchAttribute attribute,
USearchAttributeValue value,
UErrorCode *status);
/**
* Gets the text searching attributes.
* @param strsrch search iterator data struct
* @param attribute text attribute to be retrieve
* @return text attribute value
* @see #usearch_setAttribute
* @draft ICU 2.0
*/
U_CAPI USearchAttributeValue U_EXPORT2 usearch_getAttribute(
const UStringSearch *strsrch,
USearchAttribute attribute);
/**
* Returns the index to the match in the text string that was searched.
* This call returns a valid result only after a successful call to
* {@link #usearch_first}, {@link #usearch_next},
* {@link #usearch_previous}, or {@link #usearch_last}.
* Just after construction, or after a searching method returns
* USEARCH_DONE, this method will return USEARCH_DONE.
*
* char *tgtstr = "The quick brown fox jumped over the lazy fox";
* char *patstr = "fox";
* UChar target[64];
* UChar pattern[16];
* UErrorCode status = U_ZERO_ERROR;
* u_uastrcpy(target, tgtstr);
* u_uastrcpy(pattern, patstr);
*
* UStringSearch *search = usearch_open(pattern, -1, target, -1, "en_US",
* &status);
* if (U_SUCCESS(status)) {
* for (int pos = usearch_first(search, &status);
* pos != USEARCH_DONE;
* pos = usearch_next(search, &status)) {
* printf("Found match at %d pos, length is %d\n", pos,
* usearch_getMatchLength(search));
* }
* }
*