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uiter.h (23299B)

---

// © 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