/*

**********************************************************************

*   Copyright (C) 1999-2005 IBM Corp. All rights reserved.

**********************************************************************

*   Date        Name        Description

*   12/1/99    rgillam     Complete port from Java.

*   01/13/2000 helena      Added UErrorCode to ctors.

**********************************************************************

*/

#ifndef DBBI_H

#define DBBI_H

#include "unicode/rbbi.h"

#if !UCONFIG_NO_BREAK_ITERATION

/**

 * \file

 * \brief C++ API: Dictionary Based Break Iterator

 */

U_NAMESPACE_BEGIN

/* forward declaration */

class DictionaryBasedBreakIteratorTables;

/**

 * A subclass of RuleBasedBreakIterator that adds the ability to use a dictionary

 * to further subdivide ranges of text beyond what is possible using just the

 * state-table-based algorithm.  This is necessary, for example, to handle

 * word and line breaking in Thai, which doesn't use spaces between words.  The

 * state-table-based algorithm used by RuleBasedBreakIterator is used to divide

 * up text as far as possible, and then contiguous ranges of letters are

 * repeatedly compared against a list of known words (i.e., the dictionary)

 * to divide them up into words.

 *

 * <p>Applications do not normally need to include this header.</p>

 *

 * <p>This class will probably be deprecated in a future release of ICU, and replaced

 *  with a more flexible and capable dictionary based break iterator.  This change

 *  should be invisible to applications, because creation and use of instances of

 *  DictionaryBasedBreakIterator is through the factories and abstract

 *  API on class BreakIterator, which will remain stable.</p>

 *

 * <p>This class is not intended to be subclassed.</p>

 *

 *

 * DictionaryBasedBreakIterator uses the same rule language as RuleBasedBreakIterator,

 * but adds one more special substitution name: <dictionary>.  This substitution

 * name is used to identify characters in words in the dictionary.  The idea is that

 * if the iterator passes over a chunk of text that includes two or more characters

 * in a row that are included in <dictionary>, it goes back through that range and

 * derives additional break positions (if possible) using the dictionary.

 *

 * DictionaryBasedBreakIterator is also constructed with the filename of a dictionary

 * file.  It follows a prescribed search path to locate the dictionary (right now,

 * it looks for it in /com/ibm/text/resources in each directory in the classpath,

 * and won't find it in JAR files, but this location is likely to change).  The

 * dictionary file is in a serialized binary format.  We have a very primitive (and

 * slow) BuildDictionaryFile utility for creating dictionary files, but aren't

 * currently making it public.  Contact us for help.

 * <p>

 * <b> NOTE </b>  The DictionaryBasedIterator class is still under development.  The

 * APIs are not in stable condition yet.

 */

class U_COMMON_API DictionaryBasedBreakIterator : public RuleBasedBreakIterator {

private:

    /**

     * when a range of characters is divided up using the dictionary, the break

     * positions that are discovered are stored here, preventing us from having

     * to use either the dictionary or the state table again until the iterator

     * leaves this range of text

     */

    int32_t* cachedBreakPositions;

    /**

     * The number of elements in cachedBreakPositions

     */

    int32_t numCachedBreakPositions;

    /**

     * if cachedBreakPositions is not null, this indicates which item in the

     * cache the current iteration position refers to

     */

    int32_t positionInCache;

    DictionaryBasedBreakIteratorTables  *fTables;

    /**=======================================================================

     * Create a dictionary based break boundary detection iterator.

     * @param tablesImage The location for the dictionary to be loaded into memory

     * @param dictionaryFilename The name of the dictionary file

     * @param status the error code status

     * @return A dictionary based break detection iterator.  The UErrorCode& status

     * parameter is used to return status information to the user.

     * To check whether the construction succeeded or not, you should check

     * the value of U_SUCCESS(err).  If you wish more detailed information, you

     * can check for informational error results which still indicate success.  For example,

     * U_FILE_ACCESS_ERROR will be returned if the file does not exist.

     * The caller owns the returned object and is responsible for deleting it.

     ======================================================================= */

    DictionaryBasedBreakIterator(UDataMemory* tablesImage, const char* dictionaryFilename, UErrorCode& status);

public:

    //=======================================================================

    // boilerplate

    //=======================================================================

    /**

     * Destructor

     * @stable ICU 2.0

     */

    virtual ~DictionaryBasedBreakIterator();

    /**

     * Default constructor.  Creates an "empty" break iterator.

     * Such an iterator can subsequently be assigned to.

     * @return the newly created DictionaryBaseBreakIterator.

     * @stable ICU 2.0

     */

     DictionaryBasedBreakIterator();

     /**

      * Copy constructor.

      * @param other The DictionaryBasedBreakIterator to be copied.

      * @return the newly created DictionaryBasedBreakIterator.

      * @stable ICU 2.0

      */

     DictionaryBasedBreakIterator(const DictionaryBasedBreakIterator &other);

    /**

     * Assignment operator.

     * @param that The object to be copied.

     * @return the newly set DictionaryBasedBreakIterator.

     * @stable ICU 2.0

     */

    DictionaryBasedBreakIterator& operator=(const DictionaryBasedBreakIterator& that);

    /**

     * Returns a newly-constructed RuleBasedBreakIterator with the same

     * behavior, and iterating over the same text, as this one.

     * @return Returns a newly-constructed RuleBasedBreakIterator.

     * @stable ICU 2.0

     */

    virtual BreakIterator* clone(void) const;

    //=======================================================================

    // BreakIterator overrides

    //=======================================================================

    /**

     * Advances the iterator backwards, to the last boundary preceding this one.

     * @return The position of the last boundary position preceding this one.

     * @stable ICU 2.0

     */

    virtual int32_t previous(void);

    /**

     * Sets the iterator to refer to the first boundary position following

     * the specified position.

     * @param offset The position from which to begin searching for a break position.

     * @return The position of the first break after the current position.

     * @stable ICU 2.0

     */

    virtual int32_t following(int32_t offset);

    /**

     * Sets the iterator to refer to the last boundary position before the

     * specified position.

     * @param offset The position to begin searching for a break from.

     * @return The position of the last boundary before the starting position.

     * @stable ICU 2.0

     */

    virtual int32_t preceding(int32_t offset);

    /**

     * 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.

     * @stable ICU 2.0

     */

    static UClassID U_EXPORT2 getStaticClassID(void);

    /**

     * 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.

     * @stable ICU 2.0

     */

    virtual UClassID getDynamicClassID(void) const;

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.

     * @internal

     */

    virtual int32_t handleNext(void);

    /**

     * removes the cache of break positions (usually in response to a change in

     * position of some sort)

     * @internal

     */

    virtual void reset(void);

    /**

     *  init    Initialize a dbbi.  Common routine for use by constructors.

     *  @internal

     */

    void init();

    /**

     * @param stackBuffer user allocated space for the new clone. If NULL new memory will be allocated.

     * If buffer is not large enough, new memory will be allocated.

     * @param BufferSize reference to size of allocated space.

     * If BufferSize == 0, a sufficient size for use in cloning will

     * be returned ('pre-flighting')

     * If BufferSize is not enough for a stack-based safe clone,

     * new memory will be allocated.

     * @param status to indicate whether the operation went on smoothly or there were errors

     *  An informational status value, U_SAFECLONE_ALLOCATED_ERROR, is used if any allocations were

     *  necessary.

     * @return pointer to the new clone

     * @internal

     */

    virtual BreakIterator *  createBufferClone(void *stackBuffer,

                                               int32_t &BufferSize,

                                               UErrorCode &status);

private:

    /**

     * This is the function that actually implements the dictionary-based

     * algorithm.  Given the endpoints of a range of text, it uses the

     * dictionary to determine the positions of any boundaries in this

     * range.  It stores all the boundary positions it discovers in

     * cachedBreakPositions so that we only have to do this work once

     * for each time we enter the range.

     * @param startPos The start position of a range of text

     * @param endPos The end position of a range of text

     * @param status The error code status

     */

    void divideUpDictionaryRange(int32_t startPos, int32_t endPos, UErrorCode &status);

    /*

     * HSYS : Please revisit with Rich, the ctors of the DBBI class is currently

     * marked as private.

     */

    friend class DictionaryBasedBreakIteratorTables;

    friend class BreakIterator;

};

U_NAMESPACE_END

#endif /* #if !UCONFIG_NO_BREAK_ITERATION */

#endif