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rbbi.h

/*
* Copyright (C) {1999-2001}, International Business Machines Corporation and others. All Rights Reserved.
**********************************************************************
*   Date        Name        Description
*   10/22/99    alan        Creation.
*   11/11/99    rgillam     Complete port from Java.
**********************************************************************
*/

#ifndef RBBI_H
#define RBBI_H

#include "unicode/utypes.h"
#include "unicode/brkiter.h"
#include "unicode/udata.h"

U_NAMESPACE_BEGIN

class RuleBasedBreakIteratorTables;
class BreakIterator;

/**
 * <p>A subclass of BreakIterator whose behavior is specified using a list of rules.</p>
 *
 * <p>There are two kinds of rules, which are separated by semicolons: <i>substitutions</i>
 * and <i>regular expressions.</i></p>
 *
 * <p>A substitution rule defines a name that can be used in place of an expression. It
 * consists of a name, which is a string of characters contained in angle brackets, an equals
 * sign, and an expression. (There can be no whitespace on either side of the equals sign.)
 * To keep its syntactic meaning intact, the expression must be enclosed in parentheses or
 * square brackets. A substitution is visible after its definition, and is filled in using
 * simple textual substitution. Substitution definitions can contain other substitutions, as
 * long as those substitutions have been defined first. Substitutions are generally used to
 * make the regular expressions (which can get quite complex) shorted and easier to read.
 * They typically define either character categories or commonly-used subexpressions.</p>
 *
 * <p>There is one special substitution.&nbsp; If the description defines a substitution
 * called &quot;&lt;ignore&gt;&quot;, the expression must be a [] expression, and the
 * expression defines a set of characters (the &quot;<em>ignore characters</em>&quot;) that
 * will be transparent to the BreakIterator.&nbsp; A sequence of characters will break the
 * same way it would if any ignore characters it contains are taken out.&nbsp; Break
 * positions never occur befoer ignore characters.</p>
 *
 * <p>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 |).</p>
 *
 * <p>The special characters recognized by the regular-expression parser are as follows:</p>
 *
 * <blockquote>
 *   <table border="1" width="100%">
 *     <tr>
 *       <td width="6%">*</td>
 *       <td width="94%">Specifies that the expression preceding the asterisk may occur any number
 *       of times (including not at all).</td>
 *     </tr>
 *     <tr>
 *       <td width="6%">{}</td>
 *       <td width="94%">Encloses a sequence of characters that is optional.</td>
 *     </tr>
 *     <tr>
 *       <td width="6%">()</td>
 *       <td width="94%">Encloses a sequence of characters.&nbsp; If followed by *, the sequence
 *       repeats.&nbsp; Otherwise, the parentheses are just a grouping device and a way to delimit
 *       the ends of expressions containing |.</td>
 *     </tr>
 *     <tr>
 *       <td width="6%">|</td>
 *       <td width="94%">Separates two alternative sequences of characters.&nbsp; Either one
 *       sequence or the other, but not both, matches this expression.&nbsp; The | character can
 *       only occur inside ().</td>
 *     </tr>
 *     <tr>
 *       <td width="6%">.</td>
 *       <td width="94%">Matches any character.</td>
 *     </tr>
 *     <tr>
 *       <td width="6%">*?</td>
 *       <td width="94%">Specifies a non-greedy asterisk.&nbsp; *? works the same way as *, except
 *       when there is overlap between the last group of characters in the expression preceding the
 *       * and the first group of characters following the *.&nbsp; When there is this kind of
 *       overlap, * will match the longest sequence of characters that match the expression before
 *       the *, and *? will match the shortest sequence of characters matching the expression
 *       before the *?.&nbsp; For example, if you have &quot;xxyxyyyxyxyxxyxyxyy&quot; in the text,
 *       &quot;x[xy]*x&quot; will match through to the last x (i.e., &quot;<strong>xxyxyyyxyxyxxyxyx</strong>yy&quot;,
 *       but &quot;x[xy]*?x&quot; will only match the first two xes (&quot;<strong>xx</strong>yxyyyxyxyxxyxyxyy&quot;).</td>
 *     </tr>
 *     <tr>
 *       <td width="6%">[]</td>
 *       <td width="94%">Specifies a group of alternative characters.&nbsp; A [] expression will
 *       match any single character that is specified in the [] expression.&nbsp; For more on the
 *       syntax of [] expressions, see below.</td>
 *     </tr>
 *     <tr>
 *       <td width="6%">/</td>
 *       <td width="94%">Specifies where the break position should go if text matches this
 *       expression.&nbsp; (e.g., &quot;[a-z]&#42;/[:Zs:]*1&quot; 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).&nbsp; Expressions that don't contain / put the
 *       break position at the end of the matching text.</td>
 *     </tr>
 *     <tr>
 *       <td width="6%"></td>
 *       <td width="94%">Escape character.&nbsp; The \ itself is ignored, but causes the next
 *       character to be treated as literal character.&nbsp; This has no effect for many
 *       characters, but for the characters listed above, this deprives them of their special
 *       meaning.&nbsp; (There are no special escape sequences for Unicode characters, or tabs and
 *       newlines; these are all handled by a higher-level protocol.&nbsp; In a Java string,
 *       &quot;\n&quot; will be converted to a literal newline character by the time the
 *       regular-expression parser sees it.&nbsp; Of course, this means that \ sequences that are
 *       visible to the regexp parser must be written as \\ when inside a Java string.)&nbsp; All
 *       characters in the ASCII range except for letters, digits, and control characters are
 *       reserved characters to the parser and must be preceded by \ even if they currently don't
 *       mean anything.</td>
 *     </tr>
 *     <tr>
 *       <td width="6%">!</td>
 *       <td width="94%">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.&nbsp; This is generally only used in situations
 *       where the automatically-generated backwards-iteration brhavior doesn't produce
 *       satisfactory results and must be supplemented with extra client-specified rules.</td>
 *     </tr>
 *     <tr>
 *       <td width="6%"><em>(all others)</em></td>
 *       <td width="94%">All other characters are treated as literal characters, which must match
 *       the corresponding character(s) in the text exactly.</td>
 *     </tr>
 *   </table>
 * </blockquote>
 *
 * <p>Within a [] expression, a number of other special characters can be used to specify
 * groups of characters:</p>
 *
 * <blockquote>
 *   <table border="1" width="100%">
 *     <tr>
 *       <td width="6%">-</td>
 *       <td width="94%">Specifies a range of matching characters.&nbsp; For example
 *       &quot;[a-p]&quot; matches all lowercase Latin letters from a to p (inclusive).&nbsp; The -
 *       sign specifies ranges of continuous Unicode numeric values, not ranges of characters in a
 *       language's alphabetical order: &quot;[a-z]&quot; doesn't include capital letters, nor does
 *       it include accented letters such as a-umlaut.</td>
 *     </tr>
 *     <tr>
 *       <td width="6%">::</td>
 *       <td width="94%">A pair of colons containing a one- or two-letter code matches all
 *       characters in the corresponding Unicode category.&nbsp; The two-letter codes are the same
 *       as the two-letter codes in the Unicode database (for example, &quot;[:Sc::Sm:]&quot;
 *       matches all currency symbols and all math symbols).&nbsp; Specifying a one-letter code is
 *       the same as specifying all two-letter codes that begin with that letter (for example,
 *       &quot;[:L:]&quot; matches all letters, and is equivalent to
 *       &quot;[:Lu::Ll::Lo::Lm::Lt:]&quot;).&nbsp; Anything other than a valid two-letter Unicode
 *       category code or a single letter that begins a Unicode category code is illegal within
 *       colons.</td>
 *     </tr>
 *     <tr>
 *       <td width="6%">[]</td>
 *       <td width="94%">[] expressions can nest.&nbsp; This has no effect, except when used in
 *       conjunction with the ^ token.</td>
 *     </tr>
 *     <tr>
 *       <td width="6%">^</td>
 *       <td width="94%">Excludes the character (or the characters in the [] expression) following
 *       it from the group of characters.&nbsp; For example, &quot;[a-z^p]&quot; matches all Latin
 *       lowercase letters except p.&nbsp; &quot;[:L:^[\u4e00-\u9fff]]&quot; matches all letters
 *       except the Han ideographs.</td>
 *     </tr>
 *     <tr>
 *       <td width="6%"><em>(all others)</em></td>
 *       <td width="94%">All other characters are treated as literal characters.&nbsp; (For
 *       example, &quot;[aeiou]&quot; specifies just the letters a, e, i, o, and u.)</td>
 *     </tr>
 *   </table>
 * </blockquote>
 *
 * <p>For a more complete explanation, see <a
 * href="http://www.ibm.com/developerworks/unicode/library/boundaries/boundaries.html">http://www.ibm.com/developerworks/unicode/library/boundaries/boundaries.html</a>.
 * &nbsp; For examples, see the resource data (which is annotated).</p>
 *
 * @author Richard Gillam
 */
00186 class U_COMMON_API RuleBasedBreakIterator : public BreakIterator {

protected:
    /**
     * A token used as a character-category value to identify ignore characters
     */
00192     static const int8_t UBRK_IGNORE;
    friend class DictionaryBasedBreakIteratorTables;

private:
    /**
     * The state number of the starting state
     */
00199     static const int16_t START_STATE;

    /**
     * The state-transition value indicating "stop"
     */
00204     static const int16_t STOP_STATE;

protected:
    /**
     * The character iterator through which this BreakIterator accesses the text
     */
00210     CharacterIterator* text;

    /**
     * The data tables this iterator uses to determine the break positions
     */
00215     RuleBasedBreakIteratorTables* tables;

private:
    /**
     * Class ID
     */
00221     static const char fgClassID;
/*
 * HSYS: To be revisited, once the ctor are made public.
 */
 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);

 public:
    /**
     * Copy constructor.  Will produce a collator with the same behavior,
     * and which iterates over the same text, as the one passed in.
     */
    RuleBasedBreakIterator(const RuleBasedBreakIterator& that);

    //=======================================================================
    // boilerplate
    //=======================================================================

    /**
     * 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.
     */
    virtual BreakIterator* clone(void) 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;

#ifdef ICU_ENABLE_DEPRECATED_BREAKITERATOR
    /**
     * Returns a newly-created CharacterIterator that the caller is to take
     * ownership of.
     * @deprecated This will be removed after 2000-Dec-31.
     * THIS FUNCTION SHOULD NOT BE HERE.  IT'S HERE BECAUSE BreakIterator DEFINES
     * IT AS PURE VIRTUAL, FORCING RBBI TO IMPLEMENT IT.  IT SHOULD BE REMOVED
     * FROM *BOTH* CLASSES.  Use getText() instead.
     */
    virtual CharacterIterator* createText(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 The text to analyze.
     * @deprecated
     * THIS FUNCTION SHOULD NOT BE HERE.  IT'S HERE BECAUSE BreakIterator DEFINES
     * IT AS PURE VIRTUAL, FORCING RBBI TO IMPLEMENT IT.  IT SHOULD BE REMOVED
     * FROM *BOTH* CLASSES. Use the other setText() instead.
     */
    virtual void setText(const UnicodeString* newText);
#endif

    /**
     * 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;

    /**
     * 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);
#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);

private:

    /**
     * Constructs a RuleBasedBreakIterator that uses the already-created
     * tables object that is passed in as a parameter.
     */
    RuleBasedBreakIterator(RuleBasedBreakIteratorTables* adoptTables);

    friend class BreakIterator;

};

00478 inline UBool RuleBasedBreakIterator::operator!=(const BreakIterator& that) const {
    return !operator==(that);
}

00482 inline UClassID RuleBasedBreakIterator::getDynamicClassID(void) const {
    return RuleBasedBreakIterator::getStaticClassID();
}

00486 inline UClassID RuleBasedBreakIterator::getStaticClassID(void) {
    return (UClassID)(&fgClassID);
}

U_NAMESPACE_END

#endif

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