/*

* Copyright (C) 1999-2005, International Business Machines Corporation and others.

* All Rights Reserved.

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

*   Date        Name        Description

*   11/17/99    aliu        Creation.

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

*/

#ifndef UNIFILT_H

#define UNIFILT_H

#include "unicode/unifunct.h"

#include "unicode/unimatch.h"

/**

 * \file 

 * \brief C++ API: Unicode Filter

 */

U_NAMESPACE_BEGIN

/**

 * U_ETHER is used to represent character values for positions outside

 * a range.  For example, transliterator uses this to represent

 * characters outside the range contextStart..contextLimit-1.  This

 * allows explicit matching by rules and UnicodeSets of text outside a

 * defined range.

 * @draft ICU 3.0

 */

#define U_ETHER ((UChar)0xFFFF)

/**

 *

 * <code>UnicodeFilter</code> defines a protocol for selecting a

 * subset of the full range (U+0000 to U+10FFFF) of Unicode characters.

 * Currently, filters are used in conjunction with classes like {@link

 * Transliterator} to only process selected characters through a

 * transformation.

 *

 * <p>Note: UnicodeFilter currently stubs out two pure virtual methods

 * of its base class, UnicodeMatcher.  These methods are toPattern()

 * and matchesIndexValue().  This is done so that filter classes that

 * are not actually used as matchers -- specifically, those in the

 * UnicodeFilterLogic component, and those in tests -- can continue to

 * work without defining these methods.  As long as a filter is not

 * used in an RBT during real transliteration, these methods will not

 * be called.  However, this breaks the UnicodeMatcher base class

 * protocol, and it is not a correct solution.

 *

 * <p>In the future we may revisit the UnicodeMatcher / UnicodeFilter

 * hierarchy and either redesign it, or simply remove the stubs in

 * UnicodeFilter and force subclasses to implement the full

 * UnicodeMatcher protocol.

 *

 * @see UnicodeFilterLogic

 * @stable ICU 2.0

 */

class U_COMMON_API UnicodeFilter : public UnicodeFunctor, public UnicodeMatcher {

public:

    /**

     * Destructor

     * @stable ICU 2.0

     */

    virtual ~UnicodeFilter();

    /**

     * Returns <tt>true</tt> for characters that are in the selected

     * subset.  In other words, if a character is <b>to be

     * filtered</b>, then <tt>contains()</tt> returns

     * <b><tt>false</tt></b>.

     * @stable ICU 2.0

     */

    virtual UBool contains(UChar32 c) const = 0;

    /**

     * UnicodeFunctor API.  Cast 'this' to a UnicodeMatcher* pointer

     * and return the pointer.

     * @stable ICU 2.4

     */

    virtual UnicodeMatcher* toMatcher() const;

    /**

     * Implement UnicodeMatcher API.

     * @stable ICU 2.4

     */

    virtual UMatchDegree matches(const Replaceable& text,

                                 int32_t& offset,

                                 int32_t limit,

                                 UBool incremental);

    /**

     * UnicodeFunctor API.  Nothing to do.

     * @stable ICU 2.4

     */

    virtual void setData(const TransliterationRuleData*);

    /**

     * ICU "poor man's RTTI", returns a UClassID for the actual class.

     *

     * @stable ICU 2.2

     */

    virtual UClassID getDynamicClassID() const = 0;

    /**

     * ICU "poor man's RTTI", returns a UClassID for this class.

     *

     * @stable ICU 2.2

     */

    static UClassID U_EXPORT2 getStaticClassID();

protected:

    /*

     * Since this class has pure virtual functions,

     * a constructor can't be used.

     * @stable ICU 2.0

     */

/*    UnicodeFilter();*/

};

/*inline UnicodeFilter::UnicodeFilter() {}*/

U_NAMESPACE_END

#endif