* 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 BreakIterator. 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.
* Match results in the forward direction will match the result matches in
* the backwards direction in the reverse order
*
* SearchIterator provides APIs to specify the starting position
* within the text string to be searched, e.g. setOffset,
* preceding and following. Since the
* starting position will be set as it is specified, please take note that
* there are some danger points 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 getCollator and using the APIs in coll.h.
* Lastly to update StringSearch to the new collator attributes,
* reset() has to be called.
*
* Restriction:
* Consult the SearchIterator documentation for information on
* and examples of how to use instances of this class to implement text
* searching.
*
* Note: No parsing of the text within the CharacterIterator
* will be done during searching for this version. The block of text
* in CharacterIterator will be used as it is.
* @param pattern The text for which this object will search.
* @param text The text iterator in which to search for the pattern.
* @param locale A locale which defines the language-sensitive
* comparison rules used to determine whether text in the
* pattern and target matches. User is responsible for
* the clearing of this object.
* @param breakiter A BreakIterator object used to constrain
* the matches that are found. Matches whose start and end
* indices in the target text are not boundaries as
* determined by the BreakIterator are
* ignored. If this behavior is not desired,
* NULL can be passed in instead.
* @param status for errors if any. If either the length of pattern or
* text is 0 then an U_ILLEGAL_ARGUMENT_ERROR is returned.
* @draft ICU 2.0
*/
StringSearch(const UnicodeString &pattern, CharacterIterator &text,
const Locale &locale,
BreakIterator *breakiter,
UErrorCode &status);
/**
* Creating a StringSearch instance using the argument collator
* language rule set. Note, user retains the ownership of this collator,
* it does not get destroyed during this instance's destruction.
*
* Note: No parsing of the text within the CharacterIterator
* will be done during searching for this version. The block of text
* in CharacterIterator will be used as it is.
* @param pattern The text for which this object will search.
* @param text The text in which to search for the pattern.
* @param coll A RuleBasedCollator object which defines
* the language-sensitive comparison rules used to
* determine whether text in the pattern and target
* matches. User is responsible for the clearing of this
* object.
* @param breakiter A BreakIterator object used to constrain
* the matches that are found. Matches whose start and end
* indices in the target text are not boundaries as
* determined by the BreakIterator are
* ignored. If this behavior is not desired,
* NULL can be passed in instead.
* @param status for errors if any. If either the length of pattern or
* text is 0 then an U_ILLEGAL_ARGUMENT_ERROR is returned.
* @draft ICU 2.0
*/
StringSearch(const UnicodeString &pattern, CharacterIterator &text,
RuleBasedCollator *coll,
BreakIterator *breakiter,
UErrorCode &status);
/**
* Copy constructor that creates a StringSearch instance with the same
* behavior, and iterating over the same text.
* @param that StringSearch instance to be copied.
* @draft ICU 2.0
*/
StringSearch(const StringSearch &that);
/**
* Destructor. Cleans up the search iterator data struct.
* If a collator is created in the constructor, it will be destroyed here.
* @draft ICU 2.0
*/
virtual ~StringSearch(void);
// operator overloading ---------------------------------------------
/**
* Assignment operator. Sets this iterator to have the same behavior,
* and iterate over the same text, as the one passed in.
* @param that instance to be copied.
* @draft ICU 2.0
*/
StringSearch & operator=(const StringSearch &that);
/**
* Equality operator.
* @param that instance to be compared.
* @return TRUE if both instances have the same attributes,
* breakiterators, collators and iterate over the same text
* while looking for the same pattern.
* @draft ICU 2.0
*/
virtual UBool operator==(const SearchIterator &that) const;
// public get and set methods ----------------------------------------
/**
* Sets the index to point to the given position, and clears any state
* that's affected.
*
* 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.
* @param position within the text to be set
* @param status for errors if it occurs
* @draft ICU 2.0
*/
virtual void setOffset(int32_t position, UErrorCode &status);
/**
* Return the current index in the 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.
* @return current index in the text being searched.
* @draft ICU 2.0
*/
virtual int32_t getOffset(void) const;
/**
* Set the target 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 text text string to be searched
* @param status for errors if any. If the text length is 0 then an
* U_ILLEGAL_ARGUMENT_ERROR is returned.
* @draft ICU 2.0
*/
virtual void setText(const UnicodeString &text, UErrorCode &status);
/**
* Set the target 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.
* Note: No parsing of the text within the CharacterIterator
* will be done during searching for this version. The block of text
* in CharacterIterator will be used as it is.
* @param text text string to be searched
* @param status for errors if any. If the text length is 0 then an
* U_ILLEGAL_ARGUMENT_ERROR is returned.
* @draft ICU 2.0
*/
virtual void setText(CharacterIterator &text, UErrorCode &status);
/**
* Gets the collator used for the language rules.
*
* Deleting the returned RuleBasedCollator before calling
* the destructor would cause the string search to fail.
* The destructor will delete the collator if this instance owns it
* @return collator used for string search
* @draft ICU 2.0
*/
RuleBasedCollator * getCollator() const;
/**
* 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 coll collator
* @param status for errors if any
* @draft ICU 2.0
*/
void setCollator(RuleBasedCollator *coll, 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 pattern search pattern to be found
* @param status for errors if any. If the pattern length is 0 then an
* U_ILLEGAL_ARGUMENT_ERROR is returned.
* @draft ICU 2.0
*/
void setPattern(const UnicodeString &pattern, UErrorCode &status);
/**
* Gets the search pattern.
* @return pattern used for matching
* @draft ICU 2.0
*/
const UnicodeString & getPattern() const;
// public methods ----------------------------------------------------
/**
* 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.
* @draft ICU 2.0
*/
virtual void reset();
/**
* Returns a copy of StringSearch with the same behavior, and
* iterating over the same text, as this one. Note that all data will be
* replicated, except for the user-specified collator and the
* breakiterator.
* @return cloned object
* @draft ICU 2.0
*/
virtual SearchIterator * safeClone(void) const;
protected:
// protected method -------------------------------------------------
/**
* Search forward for matching text, starting at a given location.
* Clients should not call this method directly; instead they should
* call {@link SearchIterator#next}.
*
* If a match is found, this method returns the index at which the match
* starts and calls {@link SearchIterator#setMatchLength} with the number
* of characters in the target text that make up the match. If no match
* is found, the method returns USEARCH_DONE.
*
* The StringSearch is adjusted so that its current index
* (as returned by {@link #getOffset}) is the match position if one was
* found.
* If a match is not found, USEARCH_DONE will be returned and
* the StringSearch will be adjusted to the index USEARCH_DONE.
* @param position The index in the target text at which the search
* starts
* @param status for errors if any occurs
* @return The index at which the matched text in the target starts, or
* USEARCH_DONE if no match was found.
*/
virtual int32_t handleNext(int32_t position, UErrorCode &status);
/**
* Search backward for matching text, starting at a given location.
* Clients should not call this method directly; instead they should call
* SearchIterator.previous(), which this method overrides.
*
* If a match is found, this method returns the index at which the match
* starts and calls {@link SearchIterator#setMatchLength} with the number
* of characters in the target text that make up the match. If no match
* is found, the method returns USEARCH_DONE.
*
* The StringSearch is adjusted so that its current index
* (as returned by {@link #getOffset}) is the match position if one was
* found.
* If a match is not found, USEARCH_DONE will be returned and
* the StringSearch will be adjusted to the index USEARCH_DONE.
* @param position The index in the target text at which the search
* starts.
* @param status for errors if any occurs
* @return The index at which the matched text in the target starts, or
* USEARCH_DONE if no match was found.
*/
virtual int32_t handlePrev(int32_t position, UErrorCode &status);
private :
// private data members ----------------------------------------------
/**
* RuleBasedCollator, contains exactly the same UCollator * in m_strsrch_
*/
RuleBasedCollator m_collator_;
/**
* Pattern text
*/
UnicodeString m_pattern_;
/**
* Corresponding collation rules
*/
UnicodeString m_collation_rules_;
/**
* String search struct data
*/
UStringSearch *m_strsrch_;
};
U_NAMESPACE_END
#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,
* StringSearch does not guarantee the results for option 1.
*
* @see SearchIterator
* @see RuleBasedCollator
* @since ICU 2.0
*/
class U_I18N_API StringSearch : public SearchIterator
{
public:
// public constructors and destructors --------------------------------
/**
* Creating a StringSearch instance using the argument locale
* language rule set. A collator will be created in the process, which
* will be owned by this instance and will be deleted in during
* destruction
* @param pattern The text for which this object will search.
* @param text The text in which to search for the pattern.
* @param locale A locale which defines the language-sensitive
* comparison rules used to determine whether text in the
* pattern and target matches.
* @param breakiter A BreakIterator object used to constrain
* the matches that are found. Matches whose start and end
* indices in the target text are not boundaries as
* determined by the BreakIterator are
* ignored. If this behavior is not desired,
* NULL can be passed in instead.
* @param status for errors if any. If pattern or text is NULL, or if
* either the length of pattern or text is 0 then an
* U_ILLEGAL_ARGUMENT_ERROR is returned.
* @draft ICU 2.0
*/
StringSearch(const UnicodeString &pattern, const UnicodeString &text,
const Locale &locale,
BreakIterator *breakiter,
UErrorCode &status);
/**
* Creating a StringSearch instance using the argument collator
* language rule set. Note, user retains the ownership of this collator,
* it does not get destroyed during this instance's destruction.
* @param pattern The text for which this object will search.
* @param text The text in which to search for the pattern.
* @param coll A RuleBasedCollator object which defines
* the language-sensitive comparison rules used to
* determine whether text in the pattern and target
* matches. User is responsible for the clearing of this
* object.
* @param breakiter A BreakIterator object used to constrain
* the matches that are found. Matches whose start and end
* indices in the target text are not boundaries as
* determined by the BreakIterator are
* ignored. If this behavior is not desired,
* NULL can be passed in instead.
* @param status for errors if any. If either the length of pattern or
* text is 0 then an U_ILLEGAL_ARGUMENT_ERROR is returned.
* @draft ICU 2.0
*/
StringSearch(const UnicodeString &pattern,
const UnicodeString &text,
RuleBasedCollator *coll,
BreakIterator *breakiter,
UErrorCode &status);
/**
* Creating a StringSearch instance using the argument locale
* language rule set. A collator will be created in the process, which
* will be owned by this instance and will be deleted in during
* destruction
*
* UnicodeString target("The quick brown fox jumped over the lazy fox");
* UnicodeString pattern("fox");
*
* SearchIterator *iter = new StringSearch(pattern, target);
*
* for (int pos = iter->first(); pos != USEARCH_DONE;
* pos = iter->next()) {
* printf("Found match at %d pos, length is %d\n", pos,
* iter.getMatchLength());
* }
*