/*

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

*

*   Copyright (C) 2002-2004, International Business Machines

*   Corporation and others.  All Rights Reserved.

*

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

*   file name:  uiter.h

*   encoding:   US-ASCII

*   tab size:   8 (not used)

*   indentation:4

*

*   created on: 2002jan18

*   created by: Markus W. Scherer

*/

#ifndef __UITER_H__

#define __UITER_H__

/**

 * \file

 * \brief C API: Unicode Character Iteration

 *

 * @see UCharIterator

 */

#include "unicode/utypes.h"

#ifdef XP_CPLUSPLUS

    U_NAMESPACE_BEGIN

    class CharacterIterator;

    class Replaceable;

    U_NAMESPACE_END

#endif

U_CDECL_BEGIN

struct UCharIterator;

typedef struct UCharIterator UCharIterator; /**< C typedef for struct UCharIterator. @stable ICU 2.1 */

/**

 * Origin constants for UCharIterator.getIndex() and UCharIterator.move().

 * @see UCharIteratorMove

 * @see UCharIterator

 * @stable ICU 2.1

 */

typedef enum UCharIteratorOrigin {

    UITER_START, UITER_CURRENT, UITER_LIMIT, UITER_ZERO, UITER_LENGTH

} UCharIteratorOrigin;

/** Constants for UCharIterator. @stable ICU 2.6 */

enum {

    /**

     * Constant value that may be returned by UCharIteratorMove

     * indicating that the final UTF-16 index is not known, but that the move succeeded.

     * This can occur when moving relative to limit or length, or

     * when moving relative to the current index after a setState()

     * when the current UTF-16 index is not known.

     *

     * It would be very inefficient to have to count from the beginning of the text

     * just to get the current/limit/length index after moving relative to it.

     * The actual index can be determined with getIndex(UITER_CURRENT)

     * which will count the UChars if necessary.

     *

     * @stable ICU 2.6

     */

    UITER_UNKNOWN_INDEX=-2

};

/**

 * Constant for UCharIterator getState() indicating an error or

 * an unknown state.

 * Returned by uiter_getState()/UCharIteratorGetState

 * when an error occurs.

 * Also, some UCharIterator implementations may not be able to return

 * a valid state for each position. This will be clearly documented

 * for each such iterator (none of the public ones here).

 *

 * @stable ICU 2.6

 */

#define UITER_NO_STATE ((uint32_t)0xffffffff)

/**

 * Function type declaration for UCharIterator.getIndex().

 *

 * Gets the current position, or the start or limit of the

 * iteration range.

 *

 * This function may perform slowly for UITER_CURRENT after setState() was called,

 * or for UITER_LENGTH, because an iterator implementation may have to count

 * UChars if the underlying storage is not UTF-16.

 *

 * @param iter the UCharIterator structure ("this pointer")

 * @param origin get the 0, start, limit, length, or current index

 * @return the requested index, or U_SENTINEL in an error condition

 *

 * @see UCharIteratorOrigin

 * @see UCharIterator

 * @stable ICU 2.1

 */

typedef int32_t U_CALLCONV

UCharIteratorGetIndex(UCharIterator *iter, UCharIteratorOrigin origin);

/**

 * Function type declaration for UCharIterator.move().

 *

 * Use iter->move(iter, index, UITER_ZERO) like CharacterIterator::setIndex(index).

 *

 * Moves the current position relative to the start or limit of the

 * iteration range, or relative to the current position itself.

 * The movement is expressed in numbers of code units forward

 * or backward by specifying a positive or negative delta.

 * Out of bounds movement will be pinned to the start or limit.

 *

 * This function may perform slowly for moving relative to UITER_LENGTH

 * because an iterator implementation may have to count the rest of the

 * UChars if the native storage is not UTF-16.

 *

 * When moving relative to the limit or length, or

 * relative to the current position after setState() was called,

 * move() may return UITER_UNKNOWN_INDEX (-2) to avoid an inefficient

 * determination of the actual UTF-16 index.

 * The actual index can be determined with getIndex(UITER_CURRENT)

 * which will count the UChars if necessary.

 * See UITER_UNKNOWN_INDEX for details.

 *

 * @param iter the UCharIterator structure ("this pointer")

 * @param delta can be positive, zero, or negative

 * @param origin move relative to the 0, start, limit, length, or current index

 * @return the new index, or U_SENTINEL on an error condition,

 *         or UITER_UNKNOWN_INDEX when the index is not known.

 *

 * @see UCharIteratorOrigin

 * @see UCharIterator

 * @see UITER_UNKNOWN_INDEX

 * @stable ICU 2.1

 */

typedef int32_t U_CALLCONV

UCharIteratorMove(UCharIterator *iter, int32_t delta, UCharIteratorOrigin origin);

/**

 * Function type declaration for UCharIterator.hasNext().

 *

 * Check if current() and next() can still

 * return another code unit.

 *

 * @param iter the UCharIterator structure ("this pointer")

 * @return boolean value for whether current() and next() can still return another code unit

 *

 * @see UCharIterator

 * @stable ICU 2.1

 */

typedef UBool U_CALLCONV

UCharIteratorHasNext(UCharIterator *iter);

/**

 * Function type declaration for UCharIterator.hasPrevious().

 *

 * Check if previous() can still return another code unit.

 *

 * @param iter the UCharIterator structure ("this pointer")

 * @return boolean value for whether previous() can still return another code unit

 *

 * @see UCharIterator

 * @stable ICU 2.1

 */

typedef UBool U_CALLCONV

UCharIteratorHasPrevious(UCharIterator *iter);

/**

 * Function type declaration for UCharIterator.current().

 *

 * Return the code unit at the current position,

 * or U_SENTINEL if there is none (index is at the limit).

 *

 * @param iter the UCharIterator structure ("this pointer")

 * @return the current code unit

 *

 * @see UCharIterator

 * @stable ICU 2.1

 */

typedef UChar32 U_CALLCONV

UCharIteratorCurrent(UCharIterator *iter);

/**

 * Function type declaration for UCharIterator.next().

 *

 * Return the code unit at the current index and increment

 * the index (post-increment, like s[i++]),

 * or return U_SENTINEL if there is none (index is at the limit).

 *

 * @param iter the UCharIterator structure ("this pointer")

 * @return the current code unit (and post-increment the current index)

 *

 * @see UCharIterator

 * @stable ICU 2.1

 */

typedef UChar32 U_CALLCONV

UCharIteratorNext(UCharIterator *iter);

/**

 * Function type declaration for UCharIterator.previous().

 *

 * Decrement the index and return the code unit from there

 * (pre-decrement, like s[--i]),

 * or return U_SENTINEL if there is none (index is at the start).

 *

 * @param iter the UCharIterator structure ("this pointer")

 * @return the previous code unit (after pre-decrementing the current index)

 *

 * @see UCharIterator

 * @stable ICU 2.1

 */

typedef UChar32 U_CALLCONV

UCharIteratorPrevious(UCharIterator *iter);

/**

 * Function type declaration for UCharIterator.reservedFn().

 * Reserved for future use.

 *

 * @param iter the UCharIterator structure ("this pointer")

 * @param something some integer argument

 * @return some integer

 *

 * @see UCharIterator

 * @stable ICU 2.1

 */

typedef int32_t U_CALLCONV

UCharIteratorReserved(UCharIterator *iter, int32_t something);

/**

 * Function type declaration for UCharIterator.getState().

 *

 * Get the "state" of the iterator in the form of a single 32-bit word.

 * It is recommended that the state value be calculated to be as small as

 * is feasible. For strings with limited lengths, fewer than 32 bits may

 * be sufficient.

 *

 * This is used together with setState()/UCharIteratorSetState

 * to save and restore the iterator position more efficiently than with

 * getIndex()/move().

 *

 * The iterator state is defined as a uint32_t value because it is designed

 * for use in ucol_nextSortKeyPart() which provides 32 bits to store the state

 * of the character iterator.

 *

 * With some UCharIterator implementations (e.g., UTF-8),

 * getting and setting the UTF-16 index with existing functions

 * (getIndex(UITER_CURRENT) followed by move(pos, UITER_ZERO)) is possible but

 * relatively slow because the iterator has to "walk" from a known index

 * to the requested one.

 * This takes more time the farther it needs to go.

 *

 * An opaque state value allows an iterator implementation to provide

 * an internal index (UTF-8: the source byte array index) for

 * fast, constant-time restoration.

 *

 * After calling setState(), a getIndex(UITER_CURRENT) may be slow because

 * the UTF-16 index may not be restored as well, but the iterator can deliver

 * the correct text contents and move relative to the current position

 * without performance degradation.

 *

 * Some UCharIterator implementations may not be able to return

 * a valid state for each position, in which case they return UITER_NO_STATE instead.

 * This will be clearly documented for each such iterator (none of the public ones here).

 *

 * @param iter the UCharIterator structure ("this pointer")

 * @return the state word

 *

 * @see UCharIterator

 * @see UCharIteratorSetState

 * @see UITER_NO_STATE

 * @stable ICU 2.6

 */

typedef uint32_t U_CALLCONV

UCharIteratorGetState(const UCharIterator *iter);

/**

 * Function type declaration for UCharIterator.setState().

 *

 * Restore the "state" of the iterator using a state word from a getState() call.

 * The iterator object need not be the same one as for which getState() was called,

 * but it must be of the same type (set up using the same uiter_setXYZ function)

 * and it must iterate over the same string

 * (binary identical regardless of memory address).

 * For more about the state word see UCharIteratorGetState.

 *

 * After calling setState(), a getIndex(UITER_CURRENT) may be slow because

 * the UTF-16 index may not be restored as well, but the iterator can deliver

 * the correct text contents and move relative to the current position

 * without performance degradation.

 *

 * @param iter the UCharIterator structure ("this pointer")

 * @param state the state word from a getState() call

 *              on a same-type, same-string iterator

 * @param pErrorCode Must be a valid pointer to an error code value,

 *                   which must not indicate a failure before the function call.

 *

 * @see UCharIterator

 * @see UCharIteratorGetState

 * @stable ICU 2.6

 */

typedef void U_CALLCONV

UCharIteratorSetState(UCharIterator *iter, uint32_t state, UErrorCode *pErrorCode);

/**

 * C API for code unit iteration.

 * This can be used as a C wrapper around

 * CharacterIterator, Replaceable, or implemented using simple strings, etc.

 *

 * There are two roles for using UCharIterator:

 *

 * A "provider" sets the necessary function pointers and controls the "protected"

 * fields of the UCharIterator structure. A "provider" passes a UCharIterator

 * into C APIs that need a UCharIterator as an abstract, flexible string interface.

 *

 * Implementations of such C APIs are "callers" of UCharIterator functions;

 * they only use the "public" function pointers and never access the "protected"

 * fields directly.

 *

 * The current() and next() functions only check the current index against the

 * limit, and previous() only checks the current index against the start,

 * to see if the iterator already reached the end of the iteration range.

 *

 * The assumption - in all iterators - is that the index is moved via the API,

 * which means it won't go out of bounds, or the index is modified by

 * user code that knows enough about the iterator implementation to set valid

 * index values.

 *

 * UCharIterator functions return code unit values 0..0xffff,

 * or U_SENTINEL if the iteration bounds are reached.

 *

 * @stable ICU 2.1

 */

struct UCharIterator {

    /**

     * (protected) Pointer to string or wrapped object or similar.

     * Not used by caller.

     * @stable ICU 2.1

     */

    const void *context;

    /**

     * (protected) Length of string or similar.

     * Not used by caller.

     * @stable ICU 2.1

     */

    int32_t length;

    /**

     * (protected) Start index or similar.

     * Not used by caller.

     * @stable ICU 2.1

     */

    int32_t start;

    /**

     * (protected) Current index or similar.

     * Not used by caller.

     * @stable ICU 2.1

     */

    int32_t index;

    /**

     * (protected) Limit index or similar.

     * Not used by caller.

     * @stable ICU 2.1

     */

    int32_t limit;

    /**

     * (protected) Used by UTF-8 iterators and possibly others.

     * @stable ICU 2.1

     */

    int32_t reservedField;

    /**

     * (public) Returns the current position or the

     * start or limit index of the iteration range.

     *

     * @see UCharIteratorGetIndex

     * @stable ICU 2.1

     */

    UCharIteratorGetIndex *getIndex;

    /**

     * (public) Moves the current position relative to the start or limit of the

     * iteration range, or relative to the current position itself.

     * The movement is expressed in numbers of code units forward

     * or backward by specifying a positive or negative delta.

     *

     * @see UCharIteratorMove

     * @stable ICU 2.1

     */

    UCharIteratorMove *move;

    /**

     * (public) Check if current() and next() can still

     * return another code unit.

     *

     * @see UCharIteratorHasNext

     * @stable ICU 2.1

     */

    UCharIteratorHasNext *hasNext;

    /**

     * (public) Check if previous() can still return another code unit.

     *

     * @see UCharIteratorHasPrevious

     * @stable ICU 2.1

     */

    UCharIteratorHasPrevious *hasPrevious;

    /**

     * (public) Return the code unit at the current position,

     * or U_SENTINEL if there is none (index is at the limit).

     *

     * @see UCharIteratorCurrent

     * @stable ICU 2.1

     */

    UCharIteratorCurrent *current;

    /**

     * (public) Return the code unit at the current index and increment

     * the index (post-increment, like s[i++]),

     * or return U_SENTINEL if there is none (index is at the limit).

     *

     * @see UCharIteratorNext

     * @stable ICU 2.1

     */

    UCharIteratorNext *next;

    /**

     * (public) Decrement the index and return the code unit from there

     * (pre-decrement, like s[--i]),

     * or return U_SENTINEL if there is none (index is at the start).

     *

     * @see UCharIteratorPrevious

     * @stable ICU 2.1

     */

    UCharIteratorPrevious *previous;

    /**

     * (public) Reserved for future use. Currently NULL.

     *

     * @see UCharIteratorReserved

     * @stable ICU 2.1

     */

    UCharIteratorReserved *reservedFn;

    /**

     * (public) Return the state of the iterator, to be restored later with setState().

     * This function pointer is NULL if the iterator does not implement it.

     *

     * @see UCharIteratorGet

     * @stable ICU 2.6

     */

    UCharIteratorGetState *getState;

    /**

     * (public) Restore the iterator state from the state word from a call

     * to getState().

     * This function pointer is NULL if the iterator does not implement it.

     *

     * @see UCharIteratorSet

     * @stable ICU 2.6

     */

    UCharIteratorSetState *setState;

};

/**

 * Helper function for UCharIterator to get the code point

 * at the current index.

 *

 * Return the code point that includes the code unit at the current position,

 * or U_SENTINEL if there is none (index is at the limit).

 * If the current code unit is a lead or trail surrogate,

 * then the following or preceding surrogate is used to form

 * the code point value.

 *

 * @param iter the UCharIterator structure ("this pointer")

 * @return the current code point

 *

 * @see UCharIterator

 * @see U16_GET

 * @see UnicodeString::char32At()

 * @stable ICU 2.1

 */

U_STABLE UChar32 U_EXPORT2

uiter_current32(UCharIterator *iter);

/**

 * Helper function for UCharIterator to get the next code point.

 *

 * Return the code point at the current index and increment

 * the index (post-increment, like s[i++]),

 * or return U_SENTINEL if there is none (index is at the limit).

 *

 * @param iter the UCharIterator structure ("this pointer")

 * @return the current code point (and post-increment the current index)

 *

 * @see UCharIterator

 * @see U16_NEXT

 * @stable ICU 2.1

 */

U_STABLE UChar32 U_EXPORT2

uiter_next32(UCharIterator *iter);

/**

 * Helper function for UCharIterator to get the previous code point.

 *

 * Decrement the index and return the code point from there

 * (pre-decrement, like s[--i]),

 * or return U_SENTINEL if there is none (index is at the start).

 *

 * @param iter the UCharIterator structure ("this pointer")

 * @return the previous code point (after pre-decrementing the current index)

 *

 * @see UCharIterator

 * @see U16_PREV

 * @stable ICU 2.1

 */

U_STABLE UChar32 U_EXPORT2

uiter_previous32(UCharIterator *iter);