A subclass of BreakIterator whose behavior is specified using a list of rules.
* *There are two kinds of rules, which are separated by semicolons: variable definitions * and regular expressions.
* *A varialbe definition defines a variable name that can be used in subsequent expressions. * It consists of a name preceded by a dollar sign, an equals * sign, and an expression. * A $variable is visible after its definition. * Variable definitions can contain other variables, as * long as those variables have been defined first. Variables are generally used to * make the regular expressions (which can get quite complex) shorter and easier to read. * They typically define either character categories or commonly-used subexpressions.
* *A regular expression uses a subset of the normal Unix regular-expression syntax, and * defines a sequence of characters to be kept together. With one significant exception, the * iterator uses a longest-possible-match algorithm when matching text to regular * expressions. The iterator also treats descriptions containing multiple regular expressions * as if they were ORed together (i.e., as if they were separated by |).
* *The special characters recognized by the regular-expression parser are as follows:
* ***/ class U_COMMON_API RuleBasedBreakIterator : public BreakIterator { protected: /** * The character iterator through which this BreakIterator accesses the text */ CharacterIterator* fText; // // The rule data for this BreakIterator instance // RBBIDataWrapper *fData; UTrie *fCharMappings; // Rule {tag} value for the most recent match. int32_t fLastBreakTag; // // Counter for the number of characters encountered with the "dictionary" // flag set. Normal RBBI iterators don't use it, although the code // for updating it is live. Dictionary Based break iterators (a subclass // of us) access this field directly. // uint32_t fDictionaryCharCount; // // Debugging flag. // static UBool fTrace; private: /** * Class ID */ static const char fgClassID; protected: //======================================================================= // constructors //======================================================================= // This constructor uses the udata interface to create a BreakIterator whose // internal tables live in a memory-mapped file. "image" is a pointer to the // beginning of that file. RuleBasedBreakIterator(UDataMemory* image, UErrorCode &status); // // Constructor from a flattened set of RBBI data in malloced memory. // RulesBasedBreakIterators built from a custom set of rules // are created via this constructor; the rules are compiled // into memory, then the break iterator is constructed here. // // The break iterator adopts the memory, and will // uprv_free() it when done. RuleBasedBreakIterator(RBBIDataHeader* data, UErrorCode &status); friend class RBBIRuleBuilder; friend class BreakIterator; public: /** Default constructor. Creates an empty shell of an iterator, with no * rules or text to iterate over. Object can subsequently be assigned. */ RuleBasedBreakIterator(); /** * Copy constructor. Will produce a break iterator with the same behavior, * and which iterates over the same text, as the one passed in. */ RuleBasedBreakIterator(const RuleBasedBreakIterator& that); /** * Construct a RuleBasedBreakIterator from a set of rules supplied as a string. */ RuleBasedBreakIterator( const UnicodeString &rules, UParseError &parseError, UErrorCode &status); /** * Destructor */ virtual ~RuleBasedBreakIterator(); /** * Assignment operator. Sets this iterator to have the same behavior, * and iterate over the same text, as the one passed in. */ RuleBasedBreakIterator& operator=(const RuleBasedBreakIterator& that); /** * Equality operator. Returns TRUE if both BreakIterators are of the * same class, have the same behavior, and iterate over the same text. */ virtual UBool operator==(const BreakIterator& that) const; /** * Not-equal operator. If operator== returns TRUE, this returns FALSE, * and vice versa. */ UBool operator!=(const BreakIterator& that) const; /** * Returns a newly-constructed RuleBasedBreakIterator with the same * behavior, and iterating over the same text, as this one. * Differs from the copy constructor in that it is polymorphic, and * will correctly clone (copy) a derived class. */ virtual BreakIterator* clone() const; /** * Compute a hash code for this BreakIterator * @return A hash code */ virtual int32_t hashCode(void) const; /** * Returns the description used to create this iterator */ virtual const UnicodeString& getRules(void) const; //======================================================================= // BreakIterator overrides //======================================================================= /** * Return a CharacterIterator over the text being analyzed. This version * of this method returns the actual CharacterIterator we're using internally. * Changing the state of this iterator can have undefined consequences. If * you need to change it, clone it first. * @return An iterator over the text being analyzed. */ virtual const CharacterIterator& getText(void) const; /** * Set the iterator to analyze a new piece of text. This function resets * the current iteration position to the beginning of the text. * @param newText An iterator over the text to analyze. The BreakIterator * takes ownership of the character iterator. The caller MUST NOT delete it! */ virtual void adoptText(CharacterIterator* newText); /** * Set the iterator to analyze a new piece of text. This function resets * the current iteration position to the beginning of the text. * @param newText The text to analyze. */ virtual void setText(const UnicodeString& newText); /** * Sets the current iteration position to the beginning of the text. * (i.e., the CharacterIterator's starting offset). * @return The offset of the beginning of the text. */ virtual int32_t first(void); /** * Sets the current iteration position to the end of the text. * (i.e., the CharacterIterator's ending offset). * @return The text's past-the-end offset. */ virtual int32_t last(void); /** * Advances the iterator either forward or backward the specified number of steps. * Negative values move backward, and positive values move forward. This is * equivalent to repeatedly calling next() or previous(). * @param n The number of steps to move. The sign indicates the direction * (negative is backwards, and positive is forwards). * @return The character offset of the boundary position n boundaries away from * the current one. */ virtual int32_t next(int32_t n); /** * Advances the iterator to the next boundary position. * @return The position of the first boundary after this one. */ virtual int32_t next(void); /** * Advances the iterator backwards, to the last boundary preceding this one. * @return The position of the last boundary position preceding this one. */ virtual int32_t previous(void); /** * Sets the iterator to refer to the first boundary position following * the specified position. * @offset The position from which to begin searching for a break position. * @return The position of the first break after the current position. */ virtual int32_t following(int32_t offset); /** * Sets the iterator to refer to the last boundary position before the * specified position. * @offset The position to begin searching for a break from. * @return The position of the last boundary before the starting position. */ virtual int32_t preceding(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". * @param offset the offset to check. * @return True if "offset" is a boundary position. */ virtual UBool isBoundary(int32_t offset); /** * Returns the current iteration position. * @return The current iteration position. */ virtual int32_t current(void) const; /** * Return the status from the break rule that determined the most recently * returned break position. The values appear in the rule source * within brackets, {123}, for example. For rules that do not specify a * status, a default value of 0 is returned. */ virtual int32_t getRuleStatus() const; /** * Returns a unique class ID POLYMORPHICALLY. Pure virtual override. * This method is to implement a simple version of RTTI, since not all * C++ compilers support genuine RTTI. Polymorphic operator==() and * clone() methods call this method. * * @return The class ID for this object. All objects of a * given class have the same class ID. Objects of * other classes have different class IDs. */ inline virtual UClassID getDynamicClassID(void) const; /** * Returns the class ID for this class. This is useful only for * comparing to a return value from getDynamicClassID(). For example: * * Base* polymorphic_pointer = createPolymorphicObject(); * if (polymorphic_pointer->getDynamicClassID() == * Derived::getStaticClassID()) ... * * @return The class ID for all objects of this class. */ inline static UClassID getStaticClassID(void); virtual BreakIterator * createBufferClone(void *stackBuffer, int32_t &BufferSize, UErrorCode &status); /** * Return the binary form of compiled break rules, * which can then be used to create a new break iterator at some * time in the future. Creating a break iterator in this way * is much faster than building one from the source form of the * break rules. * * The binary data is can only be used with the same version of ICU * and on the same platform type (processor endian-ness) * * @return A pointer to the binary (compiled) rule data. The storage * belongs to the RulesBasedBreakIterator object, no the * caller, and must not be modified or deleted. */ virtual const uint8_t *getBinaryRules(uint32_t &length); #ifdef RBBI_DEBUG void debugDumpTables() const; #endif protected: //======================================================================= // implementation //======================================================================= /** * This method is the actual implementation of the next() method. All iteration * vectors through here. This method initializes the state machine to state 1 * and advances through the text character by character until we reach the end * of the text or the state machine transitions to state 0. We update our return * value every time the state machine passes through a possible end state. */ virtual int32_t handleNext(void); /** * This method backs the iterator back up to a "safe position" in the text. * This is a position that we know, without any context, must be a break position. * The various calling methods then iterate forward from this safe position to * the appropriate position to return. (For more information, see the description * of buildBackwardsStateTable() in RuleBasedBreakIterator.Builder.) */ virtual int32_t handlePrevious(void); /** * Dumps caches and performs other actions associated with a complete change * in text or iteration position. This function is a no-op in RuleBasedBreakIterator, * but subclasses can and do override it. */ virtual void reset(void); /** * Return true if the category lookup for this char * indicates that it is in the set of dictionary lookup chars. * This function is intended for use by dictionary based break iterators. */ virtual UBool isDictionaryChar(UChar32); /** * Common initialization function, used by constructors and bufferClone. * (Also used by DictionaryBasedBreakIterator::createBufferClone().) */ void init(); }; //---------------------------------------------------------------------------------- // // Inline Functions Definitions ... // //---------------------------------------------------------------------------------- inline UBool RuleBasedBreakIterator::operator!=(const BreakIterator& that) const { return !operator==(that); } inline UClassID RuleBasedBreakIterator::getDynamicClassID(void) const { return RuleBasedBreakIterator::getStaticClassID(); } inline UClassID RuleBasedBreakIterator::getStaticClassID(void) { return (UClassID)(&fgClassID); } U_NAMESPACE_END #endif*
** ** *Specifies that the expression preceding the asterisk may occur any number * of times (including not at all). ** *() *Encloses a sequence of characters. If followed by *, the sequence * repeats. Otherwise, the parentheses are just a grouping device and a way to delimit * the ends of expressions containing |. ** *| *Separates two alternative sequences of characters. Either one * sequence or the other, but not both, matches this expression. ** *. *Matches any character. ** *[] *Specify a set of characters. A [] expression will * match any single character that is specified in the [] expression. For more on the * syntax of [] expressions, see the ICU User Guide description of UnicodeSet. ** */ *Specifies where the break position should go if text matches this * expression. (e.g., "[a-z]*/[:Zs:]*1" will match if the iterator sees a run * of letters, followed by a run of whitespace, followed by a digit, but the break position * will actually go before the whitespace). Expressions that don't contain / put the * break position at the end of the matching text. ** *\ *Escape character. The \ itself is ignored, but causes the next * character to be treated as literal character. Except for letters and numbers, * characters in the ASCII range must be escaped to be considered as literals. ** *! *If ! appears at the beginning of a regular expression, it tells the regexp * parser that this expression specifies the backwards-iteration behavior of the iterator, * and not its normal iteration behavior. The backwards rules must move the * iterator to a safe position at or before the previous break position; forwards rules * will then be used to find the exact previous position ** *(all others) *All other characters are treated as literal characters, which must match * the corresponding character(s) in the text exactly. *