Check in the pristine copy of ICU 4.6...

icu46/source/common/uiter.cpp

+/*
+*******************************************************************************
+*
+*   Copyright (C) 2002-2006, International Business Machines
+*   Corporation and others.  All Rights Reserved.
+*
+*******************************************************************************
+*   file name:  uiter.cpp
+*   encoding:   US-ASCII
+*   tab size:   8 (not used)
+*   indentation:4
+*
+*   created on: 2002jan18
+*   created by: Markus W. Scherer
+*/
+
+#include "unicode/utypes.h"
+#include "unicode/ustring.h"
+#include "unicode/chariter.h"
+#include "unicode/rep.h"
+#include "unicode/uiter.h"
+#include "cstring.h"
+
+U_NAMESPACE_USE
+
+#define IS_EVEN(n) (((n)&1)==0)
+#define IS_POINTER_EVEN(p) IS_EVEN((size_t)p)
+
+U_CDECL_BEGIN
+
+/* No-Op UCharIterator implementation for illegal input --------------------- */
+
+static int32_t U_CALLCONV
+noopGetIndex(UCharIterator * /*iter*/, UCharIteratorOrigin /*origin*/) {
+    return 0;
+}
+
+static int32_t U_CALLCONV
+noopMove(UCharIterator * /*iter*/, int32_t /*delta*/, UCharIteratorOrigin /*origin*/) {
+    return 0;
+}
+
+static UBool U_CALLCONV
+noopHasNext(UCharIterator * /*iter*/) {
+    return FALSE;
+}
+
+static UChar32 U_CALLCONV
+noopCurrent(UCharIterator * /*iter*/) {
+    return U_SENTINEL;
+}
+
+static uint32_t U_CALLCONV
+noopGetState(const UCharIterator * /*iter*/) {
+    return UITER_NO_STATE;
+}
+
+static void U_CALLCONV
+noopSetState(UCharIterator * /*iter*/, uint32_t /*state*/, UErrorCode *pErrorCode) {
+    *pErrorCode=U_UNSUPPORTED_ERROR;
+}
+
+static const UCharIterator noopIterator={
+    0, 0, 0, 0, 0, 0,
+    noopGetIndex,
+    noopMove,
+    noopHasNext,
+    noopHasNext,
+    noopCurrent,
+    noopCurrent,
+    noopCurrent,
+    NULL,
+    noopGetState,
+    noopSetState
+};
+
+/* UCharIterator implementation for simple strings -------------------------- */
+
+/*
+ * This is an implementation of a code unit (UChar) iterator
+ * for UChar * strings.
+ *
+ * The UCharIterator.context field holds a pointer to the string.
+ */
+
+static int32_t U_CALLCONV
+stringIteratorGetIndex(UCharIterator *iter, UCharIteratorOrigin origin) {
+    switch(origin) {
+    case UITER_ZERO:
+        return 0;
+    case UITER_START:
+        return iter->start;
+    case UITER_CURRENT:
+        return iter->index;
+    case UITER_LIMIT:
+        return iter->limit;
+    case UITER_LENGTH:
+        return iter->length;
+    default:
+        /* not a valid origin */
+        /* Should never get here! */
+        return -1;
+    }
+}
+
+static int32_t U_CALLCONV
+stringIteratorMove(UCharIterator *iter, int32_t delta, UCharIteratorOrigin origin) {
+    int32_t pos;
+
+    switch(origin) {
+    case UITER_ZERO:
+        pos=delta;
+        break;
+    case UITER_START:
+        pos=iter->start+delta;
+        break;
+    case UITER_CURRENT:
+        pos=iter->index+delta;
+        break;
+    case UITER_LIMIT:
+        pos=iter->limit+delta;
+        break;
+    case UITER_LENGTH:
+        pos=iter->length+delta;
+        break;
+    default:
+        return -1;  /* Error */
+    }
+
+    if(pos<iter->start) {
+        pos=iter->start;
+    } else if(pos>iter->limit) {
+        pos=iter->limit;
+    }
+
+    return iter->index=pos;
+}
+
+static UBool U_CALLCONV
+stringIteratorHasNext(UCharIterator *iter) {
+    return iter->index<iter->limit;
+}
+
+static UBool U_CALLCONV
+stringIteratorHasPrevious(UCharIterator *iter) {
+    return iter->index>iter->start;
+}
+
+static UChar32 U_CALLCONV
+stringIteratorCurrent(UCharIterator *iter) {
+    if(iter->index<iter->limit) {
+        return ((const UChar *)(iter->context))[iter->index];
+    } else {
+        return U_SENTINEL;
+    }
+}
+
+static UChar32 U_CALLCONV
+stringIteratorNext(UCharIterator *iter) {
+    if(iter->index<iter->limit) {
+        return ((const UChar *)(iter->context))[iter->index++];
+    } else {
+        return U_SENTINEL;
+    }
+}
+
+static UChar32 U_CALLCONV
+stringIteratorPrevious(UCharIterator *iter) {
+    if(iter->index>iter->start) {
+        return ((const UChar *)(iter->context))[--iter->index];
+    } else {
+        return U_SENTINEL;
+    }
+}
+
+static uint32_t U_CALLCONV
+stringIteratorGetState(const UCharIterator *iter) {
+    return (uint32_t)iter->index;
+}
+
+static void U_CALLCONV
+stringIteratorSetState(UCharIterator *iter, uint32_t state, UErrorCode *pErrorCode) {
+    if(pErrorCode==NULL || U_FAILURE(*pErrorCode)) {
+        /* do nothing */
+    } else if(iter==NULL) {
+        *pErrorCode=U_ILLEGAL_ARGUMENT_ERROR;
+    } else if((int32_t)state<iter->start || iter->limit<(int32_t)state) {
+        *pErrorCode=U_INDEX_OUTOFBOUNDS_ERROR;
+    } else {
+        iter->index=(int32_t)state;
+    }
+}
+
+static const UCharIterator stringIterator={
+    0, 0, 0, 0, 0, 0,
+    stringIteratorGetIndex,
+    stringIteratorMove,
+    stringIteratorHasNext,
+    stringIteratorHasPrevious,
+    stringIteratorCurrent,
+    stringIteratorNext,
+    stringIteratorPrevious,
+    NULL,
+    stringIteratorGetState,
+    stringIteratorSetState
+};
+
+U_CAPI void U_EXPORT2
+uiter_setString(UCharIterator *iter, const UChar *s, int32_t length) {
+    if(iter!=0) {
+        if(s!=0 && length>=-1) {
+            *iter=stringIterator;
+            iter->context=s;
+            if(length>=0) {
+                iter->length=length;
+            } else {
+                iter->length=u_strlen(s);
+            }
+            iter->limit=iter->length;
+        } else {
+            *iter=noopIterator;
+        }
+    }
+}
+
+/* UCharIterator implementation for UTF-16BE strings ------------------------ */
+
+/*
+ * This is an implementation of a code unit (UChar) iterator
+ * for UTF-16BE strings, i.e., strings in byte-vectors where
+ * each UChar is stored as a big-endian pair of bytes.
+ *
+ * The UCharIterator.context field holds a pointer to the string.
+ * Everything works just like with a normal UChar iterator (uiter_setString),
+ * except that UChars are assembled from byte pairs.
+ */
+
+/* internal helper function */
+static inline UChar32
+utf16BEIteratorGet(UCharIterator *iter, int32_t index) {
+    const uint8_t *p=(const uint8_t *)iter->context;
+    return ((UChar)p[2*index]<<8)|(UChar)p[2*index+1];
+}
+
+static UChar32 U_CALLCONV
+utf16BEIteratorCurrent(UCharIterator *iter) {
+    int32_t index;
+
+    if((index=iter->index)<iter->limit) {
+        return utf16BEIteratorGet(iter, index);
+    } else {
+        return U_SENTINEL;
+    }
+}
+
+static UChar32 U_CALLCONV
+utf16BEIteratorNext(UCharIterator *iter) {
+    int32_t index;
+
+    if((index=iter->index)<iter->limit) {
+        iter->index=index+1;
+        return utf16BEIteratorGet(iter, index);
+    } else {
+        return U_SENTINEL;
+    }
+}
+
+static UChar32 U_CALLCONV
+utf16BEIteratorPrevious(UCharIterator *iter) {
+    int32_t index;
+
+    if((index=iter->index)>iter->start) {
+        iter->index=--index;
+        return utf16BEIteratorGet(iter, index);
+    } else {
+        return U_SENTINEL;
+    }
+}
+
+static const UCharIterator utf16BEIterator={
+    0, 0, 0, 0, 0, 0,
+    stringIteratorGetIndex,
+    stringIteratorMove,
+    stringIteratorHasNext,
+    stringIteratorHasPrevious,
+    utf16BEIteratorCurrent,
+    utf16BEIteratorNext,
+    utf16BEIteratorPrevious,
+    NULL,
+    stringIteratorGetState,
+    stringIteratorSetState
+};
+
+/*
+ * Count the number of UChars in a UTF-16BE string before a terminating UChar NUL,
+ * i.e., before a pair of 0 bytes where the first 0 byte is at an even
+ * offset from s.
+ */
+static int32_t
+utf16BE_strlen(const char *s) {
+    if(IS_POINTER_EVEN(s)) {
+        /*
+         * even-aligned, call u_strlen(s)
+         * we are probably on a little-endian machine, but searching for UChar NUL
+         * does not care about endianness
+         */
+        return u_strlen((const UChar *)s);
+    } else {
+        /* odd-aligned, search for pair of 0 bytes */
+        const char *p=s;
+
+        while(!(*p==0 && p[1]==0)) {
+            p+=2;
+        }
+        return (int32_t)((p-s)/2);
+    }
+}
+
+U_CAPI void U_EXPORT2
+uiter_setUTF16BE(UCharIterator *iter, const char *s, int32_t length) {
+    if(iter!=NULL) {
+        /* allow only even-length strings (the input length counts bytes) */
+        if(s!=NULL && (length==-1 || (length>=0 && IS_EVEN(length)))) {
+            /* length/=2, except that >>=1 also works for -1 (-1/2==0, -1>>1==-1) */
+            length>>=1;
+
+            if(U_IS_BIG_ENDIAN && IS_POINTER_EVEN(s)) {
+                /* big-endian machine and 2-aligned UTF-16BE string: use normal UChar iterator */
+                uiter_setString(iter, (const UChar *)s, length);
+                return;
+            }
+
+            *iter=utf16BEIterator;
+            iter->context=s;
+            if(length>=0) {
+                iter->length=length;
+            } else {
+                iter->length=utf16BE_strlen(s);
+            }
+            iter->limit=iter->length;
+        } else {
+            *iter=noopIterator;
+        }
+    }
+}
+
+/* UCharIterator wrapper around CharacterIterator --------------------------- */
+
+/*
+ * This is wrapper code around a C++ CharacterIterator to
+ * look like a C UCharIterator.
+ *
+ * The UCharIterator.context field holds a pointer to the CharacterIterator.
+ */
+
+static int32_t U_CALLCONV
+characterIteratorGetIndex(UCharIterator *iter, UCharIteratorOrigin origin) {
+    switch(origin) {
+    case UITER_ZERO:
+        return 0;
+    case UITER_START:
+        return ((CharacterIterator *)(iter->context))->startIndex();
+    case UITER_CURRENT:
+        return ((CharacterIterator *)(iter->context))->getIndex();
+    case UITER_LIMIT:
+        return ((CharacterIterator *)(iter->context))->endIndex();
+    case UITER_LENGTH:
+        return ((CharacterIterator *)(iter->context))->getLength();
+    default:
+        /* not a valid origin */
+        /* Should never get here! */
+        return -1;
+    }
+}
+
+static int32_t U_CALLCONV
+characterIteratorMove(UCharIterator *iter, int32_t delta, UCharIteratorOrigin origin) {
+    switch(origin) {
+    case UITER_ZERO:
+        ((CharacterIterator *)(iter->context))->setIndex(delta);
+        return ((CharacterIterator *)(iter->context))->getIndex();
+    case UITER_START:
+    case UITER_CURRENT:
+    case UITER_LIMIT:
+        return ((CharacterIterator *)(iter->context))->move(delta, (CharacterIterator::EOrigin)origin);
+    case UITER_LENGTH:
+        ((CharacterIterator *)(iter->context))->setIndex(((CharacterIterator *)(iter->context))->getLength()+delta);
+        return ((CharacterIterator *)(iter->context))->getIndex();
+    default:
+        /* not a valid origin */
+        /* Should never get here! */
+        return -1;
+    }
+}
+
+static UBool U_CALLCONV
+characterIteratorHasNext(UCharIterator *iter) {
+    return ((CharacterIterator *)(iter->context))->hasNext();
+}
+
+static UBool U_CALLCONV
+characterIteratorHasPrevious(UCharIterator *iter) {
+    return ((CharacterIterator *)(iter->context))->hasPrevious();
+}
+
+static UChar32 U_CALLCONV
+characterIteratorCurrent(UCharIterator *iter) {
+    UChar32 c;
+
+    c=((CharacterIterator *)(iter->context))->current();
+    if(c!=0xffff || ((CharacterIterator *)(iter->context))->hasNext()) {
+        return c;
+    } else {
+        return U_SENTINEL;
+    }
+}
+
+static UChar32 U_CALLCONV
+characterIteratorNext(UCharIterator *iter) {
+    if(((CharacterIterator *)(iter->context))->hasNext()) {
+        return ((CharacterIterator *)(iter->context))->nextPostInc();
+    } else {
+        return U_SENTINEL;
+    }
+}
+
+static UChar32 U_CALLCONV
+characterIteratorPrevious(UCharIterator *iter) {
+    if(((CharacterIterator *)(iter->context))->hasPrevious()) {
+        return ((CharacterIterator *)(iter->context))->previous();
+    } else {
+        return U_SENTINEL;
+    }
+}
+
+static uint32_t U_CALLCONV
+characterIteratorGetState(const UCharIterator *iter) {
+    return ((CharacterIterator *)(iter->context))->getIndex();
+}
+
+static void U_CALLCONV
+characterIteratorSetState(UCharIterator *iter, uint32_t state, UErrorCode *pErrorCode) {
+    if(pErrorCode==NULL || U_FAILURE(*pErrorCode)) {
+        /* do nothing */
+    } else if(iter==NULL || iter->context==NULL) {
+        *pErrorCode=U_ILLEGAL_ARGUMENT_ERROR;
+    } else if((int32_t)state<((CharacterIterator *)(iter->context))->startIndex() || ((CharacterIterator *)(iter->context))->endIndex()<(int32_t)state) {
+        *pErrorCode=U_INDEX_OUTOFBOUNDS_ERROR;
+    } else {
+        ((CharacterIterator *)(iter->context))->setIndex((int32_t)state);
+    }
+}
+
+static const UCharIterator characterIteratorWrapper={
+    0, 0, 0, 0, 0, 0,
+    characterIteratorGetIndex,
+    characterIteratorMove,
+    characterIteratorHasNext,
+    characterIteratorHasPrevious,
+    characterIteratorCurrent,
+    characterIteratorNext,
+    characterIteratorPrevious,
+    NULL,
+    characterIteratorGetState,
+    characterIteratorSetState
+};
+
+U_CAPI void U_EXPORT2
+uiter_setCharacterIterator(UCharIterator *iter, CharacterIterator *charIter) {
+    if(iter!=0) {
+        if(charIter!=0) {
+            *iter=characterIteratorWrapper;
+            iter->context=charIter;
+        } else {
+            *iter=noopIterator;
+        }
+    }
+}
+
+/* UCharIterator wrapper around Replaceable --------------------------------- */
+
+/*
+ * This is an implementation of a code unit (UChar) iterator
+ * based on a Replaceable object.
+ *
+ * The UCharIterator.context field holds a pointer to the Replaceable.
+ * UCharIterator.length and UCharIterator.index hold Replaceable.length()
+ * and the iteration index.
+ */
+
+static UChar32 U_CALLCONV
+replaceableIteratorCurrent(UCharIterator *iter) {
+    if(iter->index<iter->limit) {
+        return ((Replaceable *)(iter->context))->charAt(iter->index);
+    } else {
+        return U_SENTINEL;
+    }
+}
+
+static UChar32 U_CALLCONV
+replaceableIteratorNext(UCharIterator *iter) {
+    if(iter->index<iter->limit) {
+        return ((Replaceable *)(iter->context))->charAt(iter->index++);
+    } else {
+        return U_SENTINEL;
+    }
+}
+
+static UChar32 U_CALLCONV
+replaceableIteratorPrevious(UCharIterator *iter) {
+    if(iter->index>iter->start) {
+        return ((Replaceable *)(iter->context))->charAt(--iter->index);
+    } else {
+        return U_SENTINEL;
+    }
+}
+
+static const UCharIterator replaceableIterator={
+    0, 0, 0, 0, 0, 0,
+    stringIteratorGetIndex,
+    stringIteratorMove,
+    stringIteratorHasNext,
+    stringIteratorHasPrevious,
+    replaceableIteratorCurrent,
+    replaceableIteratorNext,
+    replaceableIteratorPrevious,
+    NULL,
+    stringIteratorGetState,
+    stringIteratorSetState
+};
+
+U_CAPI void U_EXPORT2
+uiter_setReplaceable(UCharIterator *iter, const Replaceable *rep) {
+    if(iter!=0) {
+        if(rep!=0) {
+            *iter=replaceableIterator;
+            iter->context=rep;
+            iter->limit=iter->length=rep->length();
+        } else {
+            *iter=noopIterator;
+        }
+    }
+}
+
+/* UCharIterator implementation for UTF-8 strings --------------------------- */
+
+/*
+ * Possible, probably necessary only for an implementation for arbitrary
+ * converters:
+ * Maintain a buffer (ring buffer?) for a piece of converted 16-bit text.
+ * This would require to turn reservedFn into a close function and
+ * to introduce a uiter_close(iter).
+ */
+
+#define UITER_CNV_CAPACITY 16
+
+/*
+ * Minimal implementation:
+ * Maintain a single-UChar buffer for an additional surrogate.
+ * The caller must not modify start and limit because they are used internally.
+ *
+ * Use UCharIterator fields as follows:
+ *   context        pointer to UTF-8 string
+ *   length         UTF-16 length of the string; -1 until lazy evaluation
+ *   start          current UTF-8 index
+ *   index          current UTF-16 index; may be -1="unknown" after setState()
+ *   limit          UTF-8 length of the string
+ *   reservedField  supplementary code point
+ *
+ * Since UCharIterator delivers 16-bit code units, the iteration can be
+ * currently in the middle of the byte sequence for a supplementary code point.
+ * In this case, reservedField will contain that code point and start will
+ * point to after the corresponding byte sequence. The UTF-16 index will be
+ * one less than what it would otherwise be corresponding to the UTF-8 index.
+ * Otherwise, reservedField will be 0.
+ */
+
+/*
+ * Possible optimization for NUL-terminated UTF-8 and UTF-16 strings:
+ * Add implementations that do not call strlen() for iteration but check for NUL.
+ */
+
+static int32_t U_CALLCONV
+utf8IteratorGetIndex(UCharIterator *iter, UCharIteratorOrigin origin) {
+    switch(origin) {
+    case UITER_ZERO:
+    case UITER_START:
+        return 0;
+    case UITER_CURRENT:
+        if(iter->index<0) {
+            /* the current UTF-16 index is unknown after setState(), count from the beginning */
+            const uint8_t *s;
+            UChar32 c;
+            int32_t i, limit, index;
+
+            s=(const uint8_t *)iter->context;
+            i=index=0;
+            limit=iter->start; /* count up to the UTF-8 index */
+            while(i<limit) {
+                U8_NEXT(s, i, limit, c);
+                if(c<=0xffff) {
+                    ++index;
+                } else {
+                    index+=2;
+                }
+            }
+
+            iter->start=i; /* just in case setState() did not get us to a code point boundary */
+            if(i==iter->limit) {
+                iter->length=index; /* in case it was <0 or wrong */
+            }
+            if(iter->reservedField!=0) {
+                --index; /* we are in the middle of a supplementary code point */
+            }
+            iter->index=index;
+        }
+        return iter->index;
+    case UITER_LIMIT:
+    case UITER_LENGTH:
+        if(iter->length<0) {
+            const uint8_t *s;
+            UChar32 c;
+            int32_t i, limit, length;
+
+            s=(const uint8_t *)iter->context;
+            if(iter->index<0) {
+                /*
+                 * the current UTF-16 index is unknown after setState(),
+                 * we must first count from the beginning to here
+                 */
+                i=length=0;
+                limit=iter->start;
+
+                /* count from the beginning to the current index */
+                while(i<limit) {
+                    U8_NEXT(s, i, limit, c);
+                    if(c<=0xffff) {
+                        ++length;
+                    } else {
+                        length+=2;
+                    }
+                }
+
+                /* assume i==limit==iter->start, set the UTF-16 index */
+                iter->start=i; /* just in case setState() did not get us to a code point boundary */
+                iter->index= iter->reservedField!=0 ? length-1 : length;
+            } else {
+                i=iter->start;
+                length=iter->index;
+                if(iter->reservedField!=0) {
+                    ++length;
+                }
+            }
+
+            /* count from the current index to the end */
+            limit=iter->limit;
+            while(i<limit) {
+                U8_NEXT(s, i, limit, c);
+                if(c<=0xffff) {
+                    ++length;
+                } else {
+                    length+=2;
+                }
+            }
+            iter->length=length;
+        }
+        return iter->length;
+    default:
+        /* not a valid origin */
+        /* Should never get here! */
+        return -1;
+    }
+}
+
+static int32_t U_CALLCONV
+utf8IteratorMove(UCharIterator *iter, int32_t delta, UCharIteratorOrigin origin) {
+    const uint8_t *s;
+    UChar32 c;
+    int32_t pos; /* requested UTF-16 index */
+    int32_t i; /* UTF-8 index */
+    UBool havePos;
+
+    /* calculate the requested UTF-16 index */
+    switch(origin) {
+    case UITER_ZERO:
+    case UITER_START:
+        pos=delta;
+        havePos=TRUE;
+        /* iter->index<0 (unknown) is possible */
+        break;
+    case UITER_CURRENT:
+        if(iter->index>=0) {
+            pos=iter->index+delta;
+            havePos=TRUE;
+        } else {
+            /* the current UTF-16 index is unknown after setState(), use only delta */
+            pos=0;
+            havePos=FALSE;
+        }
+        break;
+    case UITER_LIMIT:
+    case UITER_LENGTH:
+        if(iter->length>=0) {
+            pos=iter->length+delta;
+            havePos=TRUE;
+        } else {
+            /* pin to the end, avoid counting the length */
+            iter->index=-1;
+            iter->start=iter->limit;
+            iter->reservedField=0;
+            if(delta>=0) {
+                return UITER_UNKNOWN_INDEX;
+            } else {
+                /* the current UTF-16 index is unknown, use only delta */
+                pos=0;
+                havePos=FALSE;
+            }
+        }
+        break;
+    default:
+        return -1;  /* Error */
+    }
+
+    if(havePos) {
+        /* shortcuts: pinning to the edges of the string */
+        if(pos<=0) {
+            iter->index=iter->start=iter->reservedField=0;
+            return 0;
+        } else if(iter->length>=0 && pos>=iter->length) {
+            iter->index=iter->length;
+            iter->start=iter->limit;
+            iter->reservedField=0;
+            return iter->index;
+        }
+
+        /* minimize the number of U8_NEXT/PREV operations */
+        if(iter->index<0 || pos<iter->index/2) {
+            /* go forward from the start instead of backward from the current index */
+            iter->index=iter->start=iter->reservedField=0;
+        } else if(iter->length>=0 && (iter->length-pos)<(pos-iter->index)) {
+            /*
+             * if we have the UTF-16 index and length and the new position is
+             * closer to the end than the current index,
+             * then go backward from the end instead of forward from the current index
+             */
+            iter->index=iter->length;
+            iter->start=iter->limit;
+            iter->reservedField=0;
+        }
+
+        delta=pos-iter->index;
+        if(delta==0) {
+            return iter->index; /* nothing to do */
+        }
+    } else {
+        /* move relative to unknown UTF-16 index */
+        if(delta==0) {
+            return UITER_UNKNOWN_INDEX; /* nothing to do */
+        } else if(-delta>=iter->start) {
+            /* moving backwards by more UChars than there are UTF-8 bytes, pin to 0 */
+            iter->index=iter->start=iter->reservedField=0;
+            return 0;
+        } else if(delta>=(iter->limit-iter->start)) {
+            /* moving forward by more UChars than the remaining UTF-8 bytes, pin to the end */
+            iter->index=iter->length; /* may or may not be <0 (unknown) */
+            iter->start=iter->limit;
+            iter->reservedField=0;
+            return iter->index>=0 ? iter->index : (int32_t)UITER_UNKNOWN_INDEX;
+        }
+    }
+
+    /* delta!=0 */
+
+    /* move towards the requested position, pin to the edges of the string */
+    s=(const uint8_t *)iter->context;
+    pos=iter->index; /* could be <0 (unknown) */
+    i=iter->start;
+    if(delta>0) {
+        /* go forward */
+        int32_t limit=iter->limit;
+        if(iter->reservedField!=0) {
+            iter->reservedField=0;
+            ++pos;
+            --delta;
+        }
+        while(delta>0 && i<limit) {
+            U8_NEXT(s, i, limit, c);
+            if(c<0xffff) {
+                ++pos;
+                --delta;
+            } else if(delta>=2) {
+                pos+=2;
+                delta-=2;
+            } else /* delta==1 */ {
+                /* stop in the middle of a supplementary code point */
+                iter->reservedField=c;
+                ++pos;
+                break; /* delta=0; */
+            }
+        }
+        if(i==limit) {
+            if(iter->length<0 && iter->index>=0) {
+                iter->length= iter->reservedField==0 ? pos : pos+1;
+            } else if(iter->index<0 && iter->length>=0) {
+                iter->index= iter->reservedField==0 ? iter->length : iter->length-1;
+            }
+        }
+    } else /* delta<0 */ {
+        /* go backward */
+        if(iter->reservedField!=0) {
+            iter->reservedField=0;
+            i-=4; /* we stayed behind the supplementary code point; go before it now */
+            --pos;
+            ++delta;
+        }
+        while(delta<0 && i>0) {
+            U8_PREV(s, 0, i, c);
+            if(c<0xffff) {
+                --pos;
+                ++delta;
+            } else if(delta<=-2) {
+                pos-=2;
+                delta+=2;
+            } else /* delta==-1 */ {
+                /* stop in the middle of a supplementary code point */
+                i+=4; /* back to behind this supplementary code point for consistent state */
+                iter->reservedField=c;
+                --pos;
+                break; /* delta=0; */
+            }
+        }
+    }
+
+    iter->start=i;
+    if(iter->index>=0) {
+        return iter->index=pos;
+    } else {
+        /* we started with index<0 (unknown) so pos is bogus */
+        if(i<=1) {
+            return iter->index=i; /* reached the beginning */
+        } else {
+            /* we still don't know the UTF-16 index */
+            return UITER_UNKNOWN_INDEX;
+        }
+    }
+}
+
+static UBool U_CALLCONV
+utf8IteratorHasNext(UCharIterator *iter) {
+    return iter->start<iter->limit || iter->reservedField!=0;
+}
+
+static UBool U_CALLCONV
+utf8IteratorHasPrevious(UCharIterator *iter) {
+    return iter->start>0;
+}
+
+static UChar32 U_CALLCONV
+utf8IteratorCurrent(UCharIterator *iter) {
+    if(iter->reservedField!=0) {
+        return U16_TRAIL(iter->reservedField);
+    } else if(iter->start<iter->limit) {
+        const uint8_t *s=(const uint8_t *)iter->context;
+        UChar32 c;
+        int32_t i=iter->start;
+
+        U8_NEXT(s, i, iter->limit, c);
+        if(c<0) {
+            return 0xfffd;
+        } else if(c<=0xffff) {
+            return c;
+        } else {
+            return U16_LEAD(c);
+        }
+    } else {
+        return U_SENTINEL;
+    }
+}
+
+static UChar32 U_CALLCONV
+utf8IteratorNext(UCharIterator *iter) {
+    int32_t index;
+
+    if(iter->reservedField!=0) {
+        UChar trail=U16_TRAIL(iter->reservedField);
+        iter->reservedField=0;
+        if((index=iter->index)>=0) {
+            iter->index=index+1;
+        }
+        return trail;
+    } else if(iter->start<iter->limit) {
+        const uint8_t *s=(const uint8_t *)iter->context;
+        UChar32 c;
+
+        U8_NEXT(s, iter->start, iter->limit, c);
+        if((index=iter->index)>=0) {
+            iter->index=++index;
+            if(iter->length<0 && iter->start==iter->limit) {
+                iter->length= c<=0xffff ? index : index+1;
+            }
+        } else if(iter->start==iter->limit && iter->length>=0) {
+            iter->index= c<=0xffff ? iter->length : iter->length-1;
+        }
+        if(c<0) {
+            return 0xfffd;
+        } else if(c<=0xffff) {
+            return c;
+        } else {
+            iter->reservedField=c;
+            return U16_LEAD(c);
+        }
+    } else {
+        return U_SENTINEL;
+    }
+}
+
+static UChar32 U_CALLCONV
+utf8IteratorPrevious(UCharIterator *iter) {
+    int32_t index;
+
+    if(iter->reservedField!=0) {
+        UChar lead=U16_LEAD(iter->reservedField);
+        iter->reservedField=0;
+        iter->start-=4; /* we stayed behind the supplementary code point; go before it now */
+        if((index=iter->index)>0) {
+            iter->index=index-1;
+        }
+        return lead;
+    } else if(iter->start>0) {
+        const uint8_t *s=(const uint8_t *)iter->context;
+        UChar32 c;
+
+        U8_PREV(s, 0, iter->start, c);
+        if((index=iter->index)>0) {
+            iter->index=index-1;
+        } else if(iter->start<=1) {
+            iter->index= c<=0xffff ? iter->start : iter->start+1;
+        }
+        if(c<0) {
+            return 0xfffd;
+        } else if(c<=0xffff) {
+            return c;
+        } else {
+            iter->start+=4; /* back to behind this supplementary code point for consistent state */
+            iter->reservedField=c;
+            return U16_TRAIL(c);
+        }
+    } else {
+        return U_SENTINEL;
+    }
+}
+
+static uint32_t U_CALLCONV
+utf8IteratorGetState(const UCharIterator *iter) {
+    uint32_t state=(uint32_t)(iter->start<<1);
+    if(iter->reservedField!=0) {
+        state|=1;
+    }
+    return state;
+}
+
+static void U_CALLCONV
+utf8IteratorSetState(UCharIterator *iter,
+                     uint32_t state,
+                     UErrorCode *pErrorCode)
+{
+    if(pErrorCode==NULL || U_FAILURE(*pErrorCode)) {
+        /* do nothing */
+    } else if(iter==NULL) {
+        *pErrorCode=U_ILLEGAL_ARGUMENT_ERROR;
+    } else if(state==utf8IteratorGetState(iter)) {
+        /* setting to the current state: no-op */
+    } else {
+        int32_t index=(int32_t)(state>>1); /* UTF-8 index */
+        state&=1; /* 1 if in surrogate pair, must be index>=4 */
+
+        if((state==0 ? index<0 : index<4) || iter->limit<index) {
+            *pErrorCode=U_INDEX_OUTOFBOUNDS_ERROR;
+        } else {
+            iter->start=index; /* restore UTF-8 byte index */
+            if(index<=1) {
+                iter->index=index;
+            } else {
+                iter->index=-1; /* unknown UTF-16 index */
+            }
+            if(state==0) {
+                iter->reservedField=0;
+            } else {
+                /* verified index>=4 above */
+                UChar32 c;
+                U8_PREV((const uint8_t *)iter->context, 0, index, c);
+                if(c<=0xffff) {
+                    *pErrorCode=U_INDEX_OUTOFBOUNDS_ERROR;
+                } else {
+                    iter->reservedField=c;
+                }
+            }
+        }
+    }
+}
+
+static const UCharIterator utf8Iterator={
+    0, 0, 0, 0, 0, 0,
+    utf8IteratorGetIndex,
+    utf8IteratorMove,
+    utf8IteratorHasNext,
+    utf8IteratorHasPrevious,
+    utf8IteratorCurrent,
+    utf8IteratorNext,
+    utf8IteratorPrevious,
+    NULL,
+    utf8IteratorGetState,
+    utf8IteratorSetState
+};
+
+U_CAPI void U_EXPORT2
+uiter_setUTF8(UCharIterator *iter, const char *s, int32_t length) {
+    if(iter!=0) {
+        if(s!=0 && length>=-1) {
+            *iter=utf8Iterator;
+            iter->context=s;
+            if(length>=0) {
+                iter->limit=length;
+            } else {
+                iter->limit=(int32_t)uprv_strlen(s);
+            }
+            iter->length= iter->limit<=1 ? iter->limit : -1;
+        } else {
+            *iter=noopIterator;
+        }
+    }
+}
+
+/* Helper functions --------------------------------------------------------- */
+
+U_CAPI UChar32 U_EXPORT2
+uiter_current32(UCharIterator *iter) {
+    UChar32 c, c2;
+
+    c=iter->current(iter);
+    if(UTF_IS_SURROGATE(c)) {
+        if(UTF_IS_SURROGATE_FIRST(c)) {
+            /*
+             * go to the next code unit
+             * we know that we are not at the limit because c!=U_SENTINEL
+             */
+            iter->move(iter, 1, UITER_CURRENT);
+            if(UTF_IS_SECOND_SURROGATE(c2=iter->current(iter))) {
+                c=UTF16_GET_PAIR_VALUE(c, c2);
+            }
+
+            /* undo index movement */
+            iter->move(iter, -1, UITER_CURRENT);
+        } else {
+            if(UTF_IS_FIRST_SURROGATE(c2=iter->previous(iter))) {
+                c=UTF16_GET_PAIR_VALUE(c2, c);
+            }
+            if(c2>=0) {
+                /* undo index movement */
+                iter->move(iter, 1, UITER_CURRENT);
+            }
+        }
+    }
+    return c;
+}
+
+U_CAPI UChar32 U_EXPORT2
+uiter_next32(UCharIterator *iter) {
+    UChar32 c, c2;
+
+    c=iter->next(iter);
+    if(UTF_IS_FIRST_SURROGATE(c)) {
+        if(UTF_IS_SECOND_SURROGATE(c2=iter->next(iter))) {
+            c=UTF16_GET_PAIR_VALUE(c, c2);
+        } else if(c2>=0) {
+            /* unmatched first surrogate, undo index movement */
+            iter->move(iter, -1, UITER_CURRENT);
+        }
+    }
+    return c;
+}
+
+U_CAPI UChar32 U_EXPORT2
+uiter_previous32(UCharIterator *iter) {
+    UChar32 c, c2;
+
+    c=iter->previous(iter);
+    if(UTF_IS_SECOND_SURROGATE(c)) {
+        if(UTF_IS_FIRST_SURROGATE(c2=iter->previous(iter))) {
+            c=UTF16_GET_PAIR_VALUE(c2, c);
+        } else if(c2>=0) {
+            /* unmatched second surrogate, undo index movement */
+            iter->move(iter, 1, UITER_CURRENT);
+        }
+    }
+    return c;
+}
+
+U_CAPI uint32_t U_EXPORT2
+uiter_getState(const UCharIterator *iter) {
+    if(iter==NULL || iter->getState==NULL) {
+        return UITER_NO_STATE;
+    } else {
+        return iter->getState(iter);
+    }
+}
+
+U_CAPI void U_EXPORT2
+uiter_setState(UCharIterator *iter, uint32_t state, UErrorCode *pErrorCode) {
+    if(pErrorCode==NULL || U_FAILURE(*pErrorCode)) {
+        /* do nothing */
+    } else if(iter==NULL) {
+        *pErrorCode=U_ILLEGAL_ARGUMENT_ERROR;
+    } else if(iter->setState==NULL) {
+        *pErrorCode=U_UNSUPPORTED_ERROR;
+    } else {
+        iter->setState(iter, state, pErrorCode);
+    }
+}
+
+U_CDECL_END