StringSearch
is a SearchIterator
that provides language-sensitive text searching based on the comparison rules defined in a RuleBasedCollator object.
More...
#include <stsearch.h>
Inheritance diagram for StringSearch:
Public Member Functions | |
StringSearch (const UnicodeString &pattern, const UnicodeString &text, const Locale &locale, BreakIterator *breakiter, UErrorCode &status) | |
Creating a StringSearch instance using the argument locale language rule set. | |
StringSearch (const UnicodeString &pattern, const UnicodeString &text, RuleBasedCollator *coll, BreakIterator *breakiter, UErrorCode &status) | |
Creating a StringSearch instance using the argument collator language rule set. | |
StringSearch (const UnicodeString &pattern, CharacterIterator &text, const Locale &locale, BreakIterator *breakiter, UErrorCode &status) | |
Creating a StringSearch instance using the argument locale language rule set. | |
StringSearch (const UnicodeString &pattern, CharacterIterator &text, RuleBasedCollator *coll, BreakIterator *breakiter, UErrorCode &status) | |
Creating a StringSearch instance using the argument collator language rule set. | |
StringSearch (const StringSearch &that) | |
Copy constructor that creates a StringSearch instance with the same behavior, and iterating over the same text. | |
virtual | ~StringSearch (void) |
Destructor. | |
StringSearch * | clone () const |
Clone this object. | |
StringSearch & | operator= (const StringSearch &that) |
Assignment operator. | |
virtual UBool | operator== (const SearchIterator &that) const |
Equality operator. | |
virtual void | setOffset (int32_t position, UErrorCode &status) |
Sets the index to point to the given position, and clears any state that's affected. | |
virtual int32_t | getOffset (void) const |
Return the current index in the text being searched. | |
virtual void | setText (const UnicodeString &text, UErrorCode &status) |
Set the target text to be searched. | |
virtual void | setText (CharacterIterator &text, UErrorCode &status) |
Set the target text to be searched. | |
RuleBasedCollator * | getCollator () const |
Gets the collator used for the language rules. | |
void | setCollator (RuleBasedCollator *coll, UErrorCode &status) |
Sets the collator used for the language rules. | |
void | setPattern (const UnicodeString &pattern, UErrorCode &status) |
Sets the pattern used for matching. | |
const UnicodeString & | getPattern () const |
Gets the search pattern. | |
virtual void | reset () |
Reset the iteration. | |
virtual SearchIterator * | safeClone (void) const |
Returns a copy of StringSearch with the same behavior, and iterating over the same text, as this one. | |
virtual UClassID | getDynamicClassID () const |
ICU "poor man's RTTI", returns a UClassID for the actual class. | |
Static Public Member Functions | |
static UClassID | getStaticClassID () |
ICU "poor man's RTTI", returns a UClassID for this class. | |
Protected Member Functions | |
virtual int32_t | handleNext (int32_t position, UErrorCode &status) |
Search forward for matching text, starting at a given location. | |
virtual int32_t | handlePrev (int32_t position, UErrorCode &status) |
Search backward for matching text, starting at a given location. |
StringSearch
is a SearchIterator
that provides language-sensitive text searching based on the comparison rules defined in a RuleBasedCollator object.
StringSearch ensures that language eccentricity can be handled, e.g. for the German collator, characters ß and SS will be matched if case is chosen to be ignored. See the "ICU Collation Design Document" for more information.
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:
Let S' be the sub-string of a text string S between the offsets start and end <start, end>.
A pattern string P matches a text string S at the offsets <start, end> if
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.
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:
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.
Consult the SearchIterator
documentation for information on and examples of how to use instances of this class to implement text searching.
UnicodeString target("The quick brown fox jumped over the lazy fox");
UnicodeString pattern("fox");
SearchIterator *iter = new StringSearch(pattern, target);
UErrorCode error = U_ZERO_ERROR;
for (int pos = iter->first(error); pos != USEARCH_DONE;
pos = iter->next(error)) {
printf("Found match at %d pos, length is %d\n", pos,
iter.getMatchLength());
}
Note, StringSearch is not to be subclassed.
Definition at line 136 of file stsearch.h.
StringSearch::StringSearch | ( | const UnicodeString & | pattern, | |
const UnicodeString & | text, | |||
const Locale & | locale, | |||
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 during destruction
pattern | The text for which this object will search. | |
text | The text in which to search for the pattern. | |
locale | A locale which defines the language-sensitive comparison rules used to determine whether text in the pattern and target matches. | |
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. | |
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. |
StringSearch::StringSearch | ( | const UnicodeString & | pattern, | |
const UnicodeString & | text, | |||
RuleBasedCollator * | coll, | |||
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.
pattern | The text for which this object will search. | |
text | The text in which to search for the pattern. | |
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. | |
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. | |
status | for errors if any. If either the length of pattern or text is 0 then an U_ILLEGAL_ARGUMENT_ERROR is returned. |
StringSearch::StringSearch | ( | const UnicodeString & | pattern, | |
CharacterIterator & | text, | |||
const Locale & | locale, | |||
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 during 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.
pattern | The text for which this object will search. | |
text | The text iterator in which to search for the pattern. | |
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. | |
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. | |
status | for errors if any. If either the length of pattern or text is 0 then an U_ILLEGAL_ARGUMENT_ERROR is returned. |
StringSearch::StringSearch | ( | const UnicodeString & | pattern, | |
CharacterIterator & | text, | |||
RuleBasedCollator * | coll, | |||
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.
pattern | The text for which this object will search. | |
text | The text in which to search for the pattern. | |
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. | |
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. | |
status | for errors if any. If either the length of pattern or text is 0 then an U_ILLEGAL_ARGUMENT_ERROR is returned. |
StringSearch::StringSearch | ( | const StringSearch & | that | ) |
Copy constructor that creates a StringSearch instance with the same behavior, and iterating over the same text.
that | StringSearch instance to be copied. |
virtual StringSearch::~StringSearch | ( | void | ) | [virtual] |
Destructor.
Cleans up the search iterator data struct. If a collator is created in the constructor, it will be destroyed here.
StringSearch* StringSearch::clone | ( | ) | const |
Clone this object.
Clones can be used concurrently in multiple threads. If an error occurs, then NULL is returned. The caller must delete the clone.
StringSearch& StringSearch::operator= | ( | const StringSearch & | that | ) |
Assignment operator.
Sets this iterator to have the same behavior, and iterate over the same text, as the one passed in.
that | instance to be copied. |
virtual UBool StringSearch::operator== | ( | const SearchIterator & | that | ) | const [virtual] |
Equality operator.
that | instance to be compared. |
Reimplemented from SearchIterator.
virtual void StringSearch::setOffset | ( | int32_t | position, | |
UErrorCode & | status | |||
) | [virtual] |
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.
position | within the text to be set. If position is less than or greater than the text range for searching, an U_INDEX_OUTOFBOUNDS_ERROR will be returned | |
status | for errors if it occurs |
Implements SearchIterator.
virtual int32_t StringSearch::getOffset | ( | void | ) | const [virtual] |
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), USEARCH_DONE is returned.
Implements SearchIterator.
virtual void StringSearch::setText | ( | const UnicodeString & | text, | |
UErrorCode & | status | |||
) | [virtual] |
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.
text | text string to be searched | |
status | for errors if any. If the text length is 0 then an U_ILLEGAL_ARGUMENT_ERROR is returned. |
Reimplemented from SearchIterator.
virtual void StringSearch::setText | ( | CharacterIterator & | text, | |
UErrorCode & | status | |||
) | [virtual] |
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.
text | text string to be searched | |
status | for errors if any. If the text length is 0 then an U_ILLEGAL_ARGUMENT_ERROR is returned. |
Reimplemented from SearchIterator.
RuleBasedCollator* StringSearch::getCollator | ( | ) | const |
Gets the collator used for the language rules.
Caller may modify but must not delete the RuleBasedCollator
! Modifications to this collator will affect the original collator passed in to the StringSearch>
constructor or to setCollator, if any.
void StringSearch::setCollator | ( | RuleBasedCollator * | coll, | |
UErrorCode & | status | |||
) |
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.
coll | collator | |
status | for errors if any |
void StringSearch::setPattern | ( | const UnicodeString & | pattern, | |
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.
pattern | search pattern to be found | |
status | for errors if any. If the pattern length is 0 then an U_ILLEGAL_ARGUMENT_ERROR is returned. |
const UnicodeString& StringSearch::getPattern | ( | ) | const |
virtual void StringSearch::reset | ( | ) | [virtual] |
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.
Reimplemented from SearchIterator.
virtual SearchIterator* StringSearch::safeClone | ( | void | ) | const [virtual] |
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.
Implements SearchIterator.
virtual UClassID StringSearch::getDynamicClassID | ( | ) | const [virtual] |
static UClassID StringSearch::getStaticClassID | ( | ) | [static] |
virtual int32_t StringSearch::handleNext | ( | int32_t | position, | |
UErrorCode & | status | |||
) | [protected, virtual] |
Search forward for matching text, starting at a given location.
Clients should not call this method directly; instead they should call SearchIterator#next.
If a match is found, this method returns the index at which the match starts and calls 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 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.
position | The index in the target text at which the search starts | |
status | for errors if any occurs |
Implements SearchIterator.
virtual int32_t StringSearch::handlePrev | ( | int32_t | position, | |
UErrorCode & | status | |||
) | [protected, virtual] |
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 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 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.
position | The index in the target text at which the search starts. | |
status | for errors if any occurs |
Implements SearchIterator.