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 // © 2016 and later: Unicode, Inc. and others.
 // License & terms of use: http://www.unicode.org/copyright.html
 /*
 *******************************************************************************
 *
 *   Copyright (C) 2002-2011 International Business Machines
 *   Corporation and others.  All Rights Reserved.
 *
 *******************************************************************************
 *   file name:  uiter.h
 *   encoding:   UTF-8
 *   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"
 
 #if U_SHOW_CPLUSPLUS_API
     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_CAPI 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_CAPI 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_CAPI UChar32 U_EXPORT2
 uiter_previous32(UCharIterator *iter);
 
 /**
  * Get the "state" of the iterator in the form of a single 32-bit word.
  * This is a convenience function that calls iter->getState(iter)
  * if iter->getState is not NULL;
  * if it is NULL or any other error occurs, then UITER_NO_STATE is returned.
  *
  * 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 UCharIteratorGetState
  * @see UITER_NO_STATE
  * @stable ICU 2.6
  */
 U_CAPI uint32_t U_EXPORT2
 uiter_getState(const UCharIterator *iter);
 
 /**
  * Restore the "state" of the iterator using a state word from a getState() call.
  * This is a convenience function that calls iter->setState(iter, state, pErrorCode)
  * if iter->setState is not NULL; if it is NULL, then U_UNSUPPORTED_ERROR is set.
  *
  * @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 UCharIteratorSetState
  * @stable ICU 2.6
  */
 U_CAPI void U_EXPORT2
 uiter_setState(UCharIterator *iter, uint32_t state, UErrorCode *pErrorCode);
 
 /**
  * Set up a UCharIterator to iterate over a string.
  *
  * Sets the UCharIterator function pointers for iteration over the string s
  * with iteration boundaries start=index=0 and length=limit=string length.
  * The "provider" may set the start, index, and limit values at any time
  * within the range 0..length.
  * The length field will be ignored.
  *
  * The string pointer s is set into UCharIterator.context without copying
  * or reallocating the string contents.
  *
  * getState() simply returns the current index.
  * move() will always return the final index.
  *
  * @param iter UCharIterator structure to be set for iteration
  * @param s String to iterate over
  * @param length Length of s, or -1 if NUL-terminated
  *
  * @see UCharIterator
  * @stable ICU 2.1
  */
 U_CAPI void U_EXPORT2
 uiter_setString(UCharIterator *iter, const UChar *s, int32_t length);
 
 /**
  * Set up a UCharIterator to iterate over a UTF-16BE string
  * (byte vector with a big-endian pair of bytes per UChar).
  *
  * Everything works just like with a normal UChar iterator (uiter_setString),
  * except that UChars are assembled from byte pairs,
  * and that the length argument here indicates an even number of bytes.
  *
  * getState() simply returns the current index.
  * move() will always return the final index.
  *
  * @param iter UCharIterator structure to be set for iteration
  * @param s UTF-16BE string to iterate over
  * @param length Length of s as an even number of bytes, or -1 if NUL-terminated
  *               (NUL means pair of 0 bytes at even index from s)
  *
  * @see UCharIterator
  * @see uiter_setString
  * @stable ICU 2.6
  */
 U_CAPI void U_EXPORT2
 uiter_setUTF16BE(UCharIterator *iter, const char *s, int32_t length);
 
 /**
  * Set up a UCharIterator to iterate over a UTF-8 string.
  *
  * Sets the UCharIterator function pointers for iteration over the UTF-8 string s
  * with UTF-8 iteration boundaries 0 and length.
  * The implementation counts the UTF-16 index on the fly and
  * lazily evaluates the UTF-16 length of the text.
  *
  * The start field is used as the UTF-8 offset, the limit field as the UTF-8 length.
  * When the reservedField is not 0, then it contains a supplementary code point
  * and the UTF-16 index is between the two corresponding surrogates.
  * At that point, the UTF-8 index is behind that code point.
  *
  * The UTF-8 string pointer s is set into UCharIterator.context without copying
  * or reallocating the string contents.
  *
  * getState() returns a state value consisting of
  * - the current UTF-8 source byte index (bits 31..1)
  * - a flag (bit 0) that indicates whether the UChar position is in the middle
  *   of a surrogate pair
  *   (from a 4-byte UTF-8 sequence for the corresponding supplementary code point)
  *
  * getState() cannot also encode the UTF-16 index in the state value.
  * move(relative to limit or length), or
  * move(relative to current) after setState(), may return UITER_UNKNOWN_INDEX.
  *
  * @param iter UCharIterator structure to be set for iteration
  * @param s UTF-8 string to iterate over
  * @param length Length of s in bytes, or -1 if NUL-terminated
  *
  * @see UCharIterator
  * @stable ICU 2.6
  */
 U_CAPI void U_EXPORT2
 uiter_setUTF8(UCharIterator *iter, const char *s, int32_t length);
 
 #if U_SHOW_CPLUSPLUS_API
 
 /**
  * Set up a UCharIterator to wrap around a C++ CharacterIterator.
  *
  * Sets the UCharIterator function pointers for iteration using the
  * CharacterIterator charIter.
  *
  * The CharacterIterator pointer charIter is set into UCharIterator.context
  * without copying or cloning the CharacterIterator object.
  * The other "protected" UCharIterator fields are set to 0 and will be ignored.
  * The iteration index and boundaries are controlled by the CharacterIterator.
  *
  * getState() simply returns the current index.
  * move() will always return the final index.
  *
  * @param iter UCharIterator structure to be set for iteration
  * @param charIter CharacterIterator to wrap
  *
  * @see UCharIterator
  * @stable ICU 2.1
  */
 U_CAPI void U_EXPORT2
 uiter_setCharacterIterator(UCharIterator *iter, icu::CharacterIterator *charIter);
 
 /**
  * Set up a UCharIterator to iterate over a C++ Replaceable.
  *
  * Sets the UCharIterator function pointers for iteration over the
  * Replaceable rep with iteration boundaries start=index=0 and
  * length=limit=rep->length().
  * The "provider" may set the start, index, and limit values at any time
  * within the range 0..length=rep->length().
  * The length field will be ignored.
  *
  * The Replaceable pointer rep is set into UCharIterator.context without copying
  * or cloning/reallocating the Replaceable object.
  *
  * getState() simply returns the current index.
  * move() will always return the final index.
  *
  * @param iter UCharIterator structure to be set for iteration
  * @param rep Replaceable to iterate over
  *
  * @see UCharIterator
  * @stable ICU 2.1
  */
 U_CAPI void U_EXPORT2
 uiter_setReplaceable(UCharIterator *iter, const icu::Replaceable *rep);
 
 #endif
 
 U_CDECL_END
 
 #endif

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