tor-browser

ubidiln.cpp (48717B)

---

// © 2016 and later: Unicode, Inc. and others.
// License & terms of use: http://www.unicode.org/copyright.html
/*
******************************************************************************
*
*   Copyright (C) 1999-2015, International Business Machines
*   Corporation and others.  All Rights Reserved.
*
******************************************************************************
*   file name:  ubidiln.c
*   encoding:   UTF-8
*   tab size:   8 (not used)
*   indentation:4
*
*   created on: 1999aug06
*   created by: Markus W. Scherer, updated by Matitiahu Allouche
*/

#include "cmemory.h"
#include "unicode/utypes.h"
#include "unicode/ustring.h"
#include "unicode/uchar.h"
#include "unicode/ubidi.h"
#include "ubidiimp.h"
#include "uassert.h"

/*
* General remarks about the functions in this file:
*
* These functions deal with the aspects of potentially mixed-directional
* text in a single paragraph or in a line of a single paragraph
* which has already been processed according to
* the Unicode 6.3 BiDi algorithm as defined in
* https://www.unicode.org/reports/tr9/ , version 28,
* also described in The Unicode Standard, Version 6.3.0 .
*
* This means that there is a UBiDi object with a levels
* and a dirProps array.
* paraLevel and direction are also set.
* Only if the length of the text is zero, then levels==dirProps==nullptr.
*
* The overall directionality of the paragraph
* or line is used to bypass the reordering steps if possible.
* Even purely RTL text does not need reordering there because
* the ubidi_getLogical/VisualIndex() functions can compute the
* index on the fly in such a case.
*
* The implementation of the access to same-level-runs and of the reordering
* do attempt to provide better performance and less memory usage compared to
* a direct implementation of especially rule (L2) with an array of
* one (32-bit) integer per text character.
*
* Here, the levels array is scanned as soon as necessary, and a vector of
* same-level-runs is created. Reordering then is done on this vector.
* For each run of text positions that were resolved to the same level,
* only 8 bytes are stored: the first text position of the run and the visual
* position behind the run after reordering.
* One sign bit is used to hold the directionality of the run.
* This is inefficient if there are many very short runs. If the average run
* length is <2, then this uses more memory.
*
* In a further attempt to save memory, the levels array is never changed
* after all the resolution rules (Xn, Wn, Nn, In).
* Many functions have to consider the field trailingWSStart:
* if it is less than length, then there is an implicit trailing run
* at the paraLevel,
* which is not reflected in the levels array.
* This allows a line UBiDi object to use the same levels array as
* its paragraph parent object.
*
* When a UBiDi object is created for a line of a paragraph, then the
* paragraph's levels and dirProps arrays are reused by way of setting
* a pointer into them, not by copying. This again saves memory and forbids to
* change the now shared levels for (L1).
*/

/* handle trailing WS (L1) -------------------------------------------------- */

/*
* setTrailingWSStart() sets the start index for a trailing
* run of WS in the line. This is necessary because we do not modify
* the paragraph's levels array that we just point into.
* Using trailingWSStart is another form of performing (L1).
*
* To make subsequent operations easier, we also include the run
* before the WS if it is at the paraLevel - we merge the two here.
*
* This function is called only from ubidi_setLine(), so pBiDi->paraLevel is
* set correctly for the line even when contextual multiple paragraphs.
*/
static void
setTrailingWSStart(UBiDi *pBiDi) {
   /* pBiDi->direction!=UBIDI_MIXED */

   const DirProp *dirProps=pBiDi->dirProps;
   UBiDiLevel *levels=pBiDi->levels;
   int32_t start=pBiDi->length;
   UBiDiLevel paraLevel=pBiDi->paraLevel;

   /* If the line is terminated by a block separator, all preceding WS etc...
      are already set to paragraph level.
      Setting trailingWSStart to pBidi->length will avoid changing the
      level of B chars from 0 to paraLevel in ubidi_getLevels when
      orderParagraphsLTR==true.
    */
   if(dirProps[start-1]==B) {
       pBiDi->trailingWSStart=start;   /* currently == pBiDi->length */
       return;
   }
   /* go backwards across all WS, BN, explicit codes */
   while(start>0 && DIRPROP_FLAG(dirProps[start-1])&MASK_WS) {
       --start;
   }

   /* if the WS run can be merged with the previous run then do so here */
   while(start>0 && levels[start-1]==paraLevel) {
       --start;
   }

   pBiDi->trailingWSStart=start;
}

/* ubidi_setLine ------------------------------------------------------------ */

U_CAPI void U_EXPORT2
ubidi_setLine(const UBiDi *pParaBiDi,
             int32_t start, int32_t limit,
             UBiDi *pLineBiDi,
             UErrorCode *pErrorCode) {
   int32_t length;

   /* check the argument values */
   RETURN_VOID_IF_NULL_OR_FAILING_ERRCODE(pErrorCode);
   RETURN_VOID_IF_NOT_VALID_PARA(pParaBiDi, *pErrorCode);
   RETURN_VOID_IF_BAD_RANGE(start, 0, limit, *pErrorCode);
   RETURN_VOID_IF_BAD_RANGE(limit, 0, pParaBiDi->length+1, *pErrorCode);
   if(pLineBiDi==nullptr) {
       *pErrorCode=U_ILLEGAL_ARGUMENT_ERROR;
       return;
   }
   if(ubidi_getParagraph(pParaBiDi, start, nullptr, nullptr, nullptr, pErrorCode) !=
      ubidi_getParagraph(pParaBiDi, limit-1, nullptr, nullptr, nullptr, pErrorCode)) {
       /* the line crosses a paragraph boundary */
       *pErrorCode=U_ILLEGAL_ARGUMENT_ERROR;
       return;
   }

   /* set the values in pLineBiDi from its pParaBiDi parent */
   pLineBiDi->pParaBiDi=nullptr;          /* mark unfinished setLine */
   pLineBiDi->text=pParaBiDi->text+start;
   length=pLineBiDi->length=limit-start;
   pLineBiDi->resultLength=pLineBiDi->originalLength=length;
   pLineBiDi->paraLevel=GET_PARALEVEL(pParaBiDi, start);
   pLineBiDi->paraCount=pParaBiDi->paraCount;
   pLineBiDi->runs=nullptr;
   pLineBiDi->flags=0;
   pLineBiDi->reorderingMode=pParaBiDi->reorderingMode;
   pLineBiDi->reorderingOptions=pParaBiDi->reorderingOptions;
   pLineBiDi->controlCount=0;
   if(pParaBiDi->controlCount>0) {
       int32_t j;
       for(j=start; j<limit; j++) {
           if(IS_BIDI_CONTROL_CHAR(pParaBiDi->text[j])) {
               pLineBiDi->controlCount++;
           }
       }
       pLineBiDi->resultLength-=pLineBiDi->controlCount;
   }

   pLineBiDi->dirProps=pParaBiDi->dirProps+start;
   pLineBiDi->levels=pParaBiDi->levels+start;
   pLineBiDi->runCount=-1;

   if(pParaBiDi->direction!=UBIDI_MIXED) {
       /* the parent is already trivial */
       pLineBiDi->direction=pParaBiDi->direction;

       /*
        * The parent's levels are all either
        * implicitly or explicitly ==paraLevel;
        * do the same here.
        */
       if(pParaBiDi->trailingWSStart<=start) {
           pLineBiDi->trailingWSStart=0;
       } else if(pParaBiDi->trailingWSStart<limit) {
           pLineBiDi->trailingWSStart=pParaBiDi->trailingWSStart-start;
       } else {
           pLineBiDi->trailingWSStart=length;
       }
   } else {
       const UBiDiLevel *levels=pLineBiDi->levels;
       int32_t i, trailingWSStart;
       UBiDiLevel level;

       setTrailingWSStart(pLineBiDi);
       trailingWSStart=pLineBiDi->trailingWSStart;

       /* recalculate pLineBiDi->direction */
       if(trailingWSStart==0) {
           /* all levels are at paraLevel */
           pLineBiDi->direction=(UBiDiDirection)(pLineBiDi->paraLevel&1);
       } else {
           /* get the level of the first character */
           level=(UBiDiLevel)(levels[0]&1);

           /* if there is anything of a different level, then the line is mixed */
           if(trailingWSStart<length && (pLineBiDi->paraLevel&1)!=level) {
               /* the trailing WS is at paraLevel, which differs from levels[0] */
               pLineBiDi->direction=UBIDI_MIXED;
           } else {
               /* see if levels[1..trailingWSStart-1] have the same direction as levels[0] and paraLevel */
               i=1;
               for(;;) {
                   if(i==trailingWSStart) {
                       /* the direction values match those in level */
                       pLineBiDi->direction=(UBiDiDirection)level;
                       break;
                   } else if((levels[i]&1)!=level) {
                       pLineBiDi->direction=UBIDI_MIXED;
                       break;
                   }
                   ++i;
               }
           }
       }

       switch(pLineBiDi->direction) {
       case UBIDI_LTR:
           /* make sure paraLevel is even */
           pLineBiDi->paraLevel=(UBiDiLevel)((pLineBiDi->paraLevel+1)&~1);

           /* all levels are implicitly at paraLevel (important for ubidi_getLevels()) */
           pLineBiDi->trailingWSStart=0;
           break;
       case UBIDI_RTL:
           /* make sure paraLevel is odd */
           pLineBiDi->paraLevel|=1;

           /* all levels are implicitly at paraLevel (important for ubidi_getLevels()) */
           pLineBiDi->trailingWSStart=0;
           break;
       default:
           break;
       }
   }
   pLineBiDi->pParaBiDi=pParaBiDi;     /* mark successful setLine */
}

U_CAPI UBiDiLevel U_EXPORT2
ubidi_getLevelAt(const UBiDi *pBiDi, int32_t charIndex) {
   /* return paraLevel if in the trailing WS run, otherwise the real level */
   if(!IS_VALID_PARA_OR_LINE(pBiDi) || charIndex<0 || pBiDi->length<=charIndex) {
       return 0;
   } else if(pBiDi->direction!=UBIDI_MIXED || charIndex>=pBiDi->trailingWSStart) {
       return GET_PARALEVEL(pBiDi, charIndex);
   } else {
       return pBiDi->levels[charIndex];
   }
}

U_CAPI const UBiDiLevel * U_EXPORT2
ubidi_getLevels(UBiDi *pBiDi, UErrorCode *pErrorCode) {
   int32_t start, length;

   RETURN_IF_NULL_OR_FAILING_ERRCODE(pErrorCode, nullptr);
   RETURN_IF_NOT_VALID_PARA_OR_LINE(pBiDi, *pErrorCode, nullptr);
   if((length=pBiDi->length)<=0) {
       *pErrorCode=U_ILLEGAL_ARGUMENT_ERROR;
       return nullptr;
   }
   if((start=pBiDi->trailingWSStart)==length) {
       /* the current levels array reflects the WS run */
       return pBiDi->levels;
   }

   /*
    * After the previous if(), we know that the levels array
    * has an implicit trailing WS run and therefore does not fully
    * reflect itself all the levels.
    * This must be a UBiDi object for a line, and
    * we need to create a new levels array.
    */
   if(getLevelsMemory(pBiDi, length)) {
       UBiDiLevel *levels=pBiDi->levelsMemory;

       if(start>0 && levels!=pBiDi->levels) {
           uprv_memcpy(levels, pBiDi->levels, start);
       }
       /* pBiDi->paraLevel is ok even if contextual multiple paragraphs,
          since pBidi is a line object                                     */
       uprv_memset(levels+start, pBiDi->paraLevel, length-start);

       /* this new levels array is set for the line and reflects the WS run */
       pBiDi->trailingWSStart=length;
       return pBiDi->levels=levels;
   } else {
       /* out of memory */
       *pErrorCode=U_MEMORY_ALLOCATION_ERROR;
       return nullptr;
   }
}

U_CAPI void U_EXPORT2
ubidi_getLogicalRun(const UBiDi *pBiDi, int32_t logicalPosition,
                   int32_t *pLogicalLimit, UBiDiLevel *pLevel) {
   UErrorCode errorCode;
   int32_t runCount, visualStart, logicalLimit, logicalFirst, i;
   Run iRun;

   errorCode=U_ZERO_ERROR;
   RETURN_VOID_IF_BAD_RANGE(logicalPosition, 0, pBiDi->length, errorCode);
   /* ubidi_countRuns will check VALID_PARA_OR_LINE */
   runCount=ubidi_countRuns((UBiDi *)pBiDi, &errorCode);
   if(U_FAILURE(errorCode)) {
       return;
   }
   /* this is done based on runs rather than on levels since levels have
      a special interpretation when UBIDI_REORDER_RUNS_ONLY
    */
   visualStart=logicalLimit=0;
   iRun=pBiDi->runs[0];

   for(i=0; i<runCount; i++) {
       iRun = pBiDi->runs[i];
       logicalFirst=GET_INDEX(iRun.logicalStart);
       logicalLimit=logicalFirst+iRun.visualLimit-visualStart;
       if((logicalPosition>=logicalFirst) &&
          (logicalPosition<logicalLimit)) {
           break;
       }
       visualStart = iRun.visualLimit;
   }
   if(pLogicalLimit) {
       *pLogicalLimit=logicalLimit;
   }
   if(pLevel) {
       if(pBiDi->reorderingMode==UBIDI_REORDER_RUNS_ONLY) {
           *pLevel=(UBiDiLevel)GET_ODD_BIT(iRun.logicalStart);
       }
       else if(pBiDi->direction!=UBIDI_MIXED || logicalPosition>=pBiDi->trailingWSStart) {
           *pLevel=GET_PARALEVEL(pBiDi, logicalPosition);
       } else {
       *pLevel=pBiDi->levels[logicalPosition];
       }
   }
}

/* runs API functions ------------------------------------------------------- */

U_CAPI int32_t U_EXPORT2
ubidi_countRuns(UBiDi *pBiDi, UErrorCode *pErrorCode) {
   RETURN_IF_NULL_OR_FAILING_ERRCODE(pErrorCode, -1);
   RETURN_IF_NOT_VALID_PARA_OR_LINE(pBiDi, *pErrorCode, -1);
   ubidi_getRuns(pBiDi, pErrorCode);
   if(U_FAILURE(*pErrorCode)) {
       return -1;
   }
   return pBiDi->runCount;
}

U_CAPI UBiDiDirection U_EXPORT2
ubidi_getVisualRun(UBiDi *pBiDi, int32_t runIndex,
                  int32_t *pLogicalStart, int32_t *pLength)
{
   int32_t start;
   UErrorCode errorCode = U_ZERO_ERROR;
   RETURN_IF_NOT_VALID_PARA_OR_LINE(pBiDi, errorCode, UBIDI_LTR);
   ubidi_getRuns(pBiDi, &errorCode);
   if(U_FAILURE(errorCode)) {
       return UBIDI_LTR;
   }
   RETURN_IF_BAD_RANGE(runIndex, 0, pBiDi->runCount, errorCode, UBIDI_LTR);

   start=pBiDi->runs[runIndex].logicalStart;
   if(pLogicalStart!=nullptr) {
       *pLogicalStart=GET_INDEX(start);
   }
   if(pLength!=nullptr) {
       if(runIndex>0) {
           *pLength=pBiDi->runs[runIndex].visualLimit-
                    pBiDi->runs[runIndex-1].visualLimit;
       } else {
           *pLength=pBiDi->runs[0].visualLimit;
       }
   }
   return (UBiDiDirection)GET_ODD_BIT(start);
}

/* in trivial cases there is only one trivial run; called by ubidi_getRuns() */
static void
getSingleRun(UBiDi *pBiDi, UBiDiLevel level) {
   /* simple, single-run case */
   pBiDi->runs=pBiDi->simpleRuns;
   pBiDi->runCount=1;

   /* fill and reorder the single run */
   pBiDi->runs[0].logicalStart=MAKE_INDEX_ODD_PAIR(0, level);
   pBiDi->runs[0].visualLimit=pBiDi->length;
   pBiDi->runs[0].insertRemove=0;
}

/* reorder the runs array (L2) ---------------------------------------------- */

/*
* Reorder the same-level runs in the runs array.
* Here, runCount>1 and maxLevel>=minLevel>=paraLevel.
* All the visualStart fields=logical start before reordering.
* The "odd" bits are not set yet.
*
* Reordering with this data structure lends itself to some handy shortcuts:
*
* Since each run is moved but not modified, and since at the initial maxLevel
* each sequence of same-level runs consists of only one run each, we
* don't need to do anything there and can predecrement maxLevel.
* In many simple cases, the reordering is thus done entirely in the
* index mapping.
* Also, reordering occurs only down to the lowest odd level that occurs,
* which is minLevel|1. However, if the lowest level itself is odd, then
* in the last reordering the sequence of the runs at this level or higher
* will be all runs, and we don't need the elaborate loop to search for them.
* This is covered by ++minLevel instead of minLevel|=1 followed
* by an extra reorder-all after the reorder-some loop.
* About a trailing WS run:
* Such a run would need special treatment because its level is not
* reflected in levels[] if this is not a paragraph object.
* Instead, all characters from trailingWSStart on are implicitly at
* paraLevel.
* However, for all maxLevel>paraLevel, this run will never be reordered
* and does not need to be taken into account. maxLevel==paraLevel is only reordered
* if minLevel==paraLevel is odd, which is done in the extra segment.
* This means that for the main reordering loop we don't need to consider
* this run and can --runCount. If it is later part of the all-runs
* reordering, then runCount is adjusted accordingly.
*/
static void
reorderLine(UBiDi *pBiDi, UBiDiLevel minLevel, UBiDiLevel maxLevel) {
   Run *runs, tempRun;
   UBiDiLevel *levels;
   int32_t firstRun, endRun, limitRun, runCount;

   /* nothing to do? */
   if(maxLevel<=(minLevel|1)) {
       return;
   }

   /*
    * Reorder only down to the lowest odd level
    * and reorder at an odd minLevel in a separate, simpler loop.
    * See comments above for why minLevel is always incremented.
    */
   ++minLevel;

   runs=pBiDi->runs;
   levels=pBiDi->levels;
   runCount=pBiDi->runCount;

   /* do not include the WS run at paraLevel<=old minLevel except in the simple loop */
   if(pBiDi->trailingWSStart<pBiDi->length) {
       --runCount;
   }

   while(--maxLevel>=minLevel) {
       firstRun=0;

       /* loop for all sequences of runs */
       for(;;) {
           /* look for a sequence of runs that are all at >=maxLevel */
           /* look for the first run of such a sequence */
           while(firstRun<runCount && levels[runs[firstRun].logicalStart]<maxLevel) {
               ++firstRun;
           }
           if(firstRun>=runCount) {
               break;  /* no more such runs */
           }

           /* look for the limit run of such a sequence (the run behind it) */
           for(limitRun=firstRun; ++limitRun<runCount && levels[runs[limitRun].logicalStart]>=maxLevel;) {}

           /* Swap the entire sequence of runs from firstRun to limitRun-1. */
           endRun=limitRun-1;
           while(firstRun<endRun) {
               tempRun = runs[firstRun];
               runs[firstRun]=runs[endRun];
               runs[endRun]=tempRun;
               ++firstRun;
               --endRun;
           }

           if(limitRun==runCount) {
               break;  /* no more such runs */
           } else {
               firstRun=limitRun+1;
           }
       }
   }

   /* now do maxLevel==old minLevel (==odd!), see above */
   if(!(minLevel&1)) {
       firstRun=0;

       /* include the trailing WS run in this complete reordering */
       if(pBiDi->trailingWSStart==pBiDi->length) {
           --runCount;
       }

       /* Swap the entire sequence of all runs. (endRun==runCount) */
       while(firstRun<runCount) {
           tempRun=runs[firstRun];
           runs[firstRun]=runs[runCount];
           runs[runCount]=tempRun;
           ++firstRun;
           --runCount;
       }
   }
}

/* compute the runs array --------------------------------------------------- */

static int32_t getRunFromLogicalIndex(UBiDi *pBiDi, int32_t logicalIndex) {
   Run *runs=pBiDi->runs;
   int32_t runCount=pBiDi->runCount, visualStart=0, i, length, logicalStart;

   for(i=0; i<runCount; i++) {
       length=runs[i].visualLimit-visualStart;
       logicalStart=GET_INDEX(runs[i].logicalStart);
       if((logicalIndex>=logicalStart) && (logicalIndex<(logicalStart+length))) {
           return i;
       }
       visualStart+=length;
   }
   /* we should never get here */
   UPRV_UNREACHABLE_EXIT;
}

/*
* Compute the runs array from the levels array.
* After ubidi_getRuns() returns true, runCount is guaranteed to be >0
* and the runs are reordered.
* Odd-level runs have visualStart on their visual right edge and
* they progress visually to the left.
* If option UBIDI_OPTION_INSERT_MARKS is set, insertRemove will contain the
* sum of appropriate LRM/RLM_BEFORE/AFTER flags.
* If option UBIDI_OPTION_REMOVE_CONTROLS is set, insertRemove will contain the
* negative number of BiDi control characters within this run.
*/
U_CFUNC UBool
ubidi_getRuns(UBiDi *pBiDi, UErrorCode*) {
   /*
    * This method returns immediately if the runs are already set. This
    * includes the case of length==0 (handled in setPara)..
    */
   if (pBiDi->runCount>=0) {
       return true;
   }

   if(pBiDi->direction!=UBIDI_MIXED) {
       /* simple, single-run case - this covers length==0 */
       /* pBiDi->paraLevel is ok even for contextual multiple paragraphs */
       getSingleRun(pBiDi, pBiDi->paraLevel);
   } else /* UBIDI_MIXED, length>0 */ {
       /* mixed directionality */
       int32_t length=pBiDi->length, limit;
       UBiDiLevel *levels=pBiDi->levels;
       int32_t i, runCount;
       UBiDiLevel level=UBIDI_DEFAULT_LTR;   /* initialize with no valid level */
       /*
        * If there are WS characters at the end of the line
        * and the run preceding them has a level different from
        * paraLevel, then they will form their own run at paraLevel (L1).
        * Count them separately.
        * We need some special treatment for this in order to not
        * modify the levels array which a line UBiDi object shares
        * with its paragraph parent and its other line siblings.
        * In other words, for the trailing WS, it may be
        * levels[]!=paraLevel but we have to treat it like it were so.
        */
       limit=pBiDi->trailingWSStart;
       /* count the runs, there is at least one non-WS run, and limit>0 */
       runCount=0;
       for(i=0; i<limit; ++i) {
           /* increment runCount at the start of each run */
           if(levels[i]!=level) {
               ++runCount;
               level=levels[i];
           }
       }

       /*
        * We don't need to see if the last run can be merged with a trailing
        * WS run because setTrailingWSStart() would have done that.
        */
       if(runCount==1 && limit==length) {
           /* There is only one non-WS run and no trailing WS-run. */
           getSingleRun(pBiDi, levels[0]);
       } else /* runCount>1 || limit<length */ {
           /* allocate and set the runs */
           Run *runs;
           int32_t runIndex, start;
           UBiDiLevel minLevel=UBIDI_MAX_EXPLICIT_LEVEL+1, maxLevel=0;

           /* now, count a (non-mergeable) WS run */
           if(limit<length) {
               ++runCount;
           }

           /* runCount>1 */
           if(getRunsMemory(pBiDi, runCount)) {
               runs=pBiDi->runsMemory;
           } else {
               return false;
           }

           /* set the runs */
           /* FOOD FOR THOUGHT: this could be optimized, e.g.:
            * 464->444, 484->444, 575->555, 595->555
            * However, that would take longer. Check also how it would
            * interact with BiDi control removal and inserting Marks.
            */
           runIndex=0;

           /* search for the run limits and initialize visualLimit values with the run lengths */
           i=0;
           do {
               /* prepare this run */
               start=i;
               level=levels[i];
               if(level<minLevel) {
                   minLevel=level;
               }
               if(level>maxLevel) {
                   maxLevel=level;
               }

               /* look for the run limit */
               while(++i<limit && levels[i]==level) {}

               /* i is another run limit */
               runs[runIndex].logicalStart=start;
               runs[runIndex].visualLimit=i-start;
               runs[runIndex].insertRemove=0;
               ++runIndex;
           } while(i<limit);

           if(limit<length) {
               /* there is a separate WS run */
               runs[runIndex].logicalStart=limit;
               runs[runIndex].visualLimit=length-limit;
               /* For the trailing WS run, pBiDi->paraLevel is ok even
                  if contextual multiple paragraphs.                   */
               if(pBiDi->paraLevel<minLevel) {
                   minLevel=pBiDi->paraLevel;
               }
           }

           /* set the object fields */
           pBiDi->runs=runs;
           pBiDi->runCount=runCount;

           reorderLine(pBiDi, minLevel, maxLevel);

           /* now add the direction flags and adjust the visualLimit's to be just that */
           /* this loop will also handle the trailing WS run */
           limit=0;
           for(i=0; i<runCount; ++i) {
               ADD_ODD_BIT_FROM_LEVEL(runs[i].logicalStart, levels[runs[i].logicalStart]);
               limit+=runs[i].visualLimit;
               runs[i].visualLimit=limit;
           }

           /* Set the "odd" bit for the trailing WS run. */
           /* For a RTL paragraph, it will be the *first* run in visual order. */
           /* For the trailing WS run, pBiDi->paraLevel is ok even if
              contextual multiple paragraphs.                          */
           if(runIndex<runCount) {
               int32_t trailingRun = ((pBiDi->paraLevel & 1) != 0)? 0 : runIndex;

               ADD_ODD_BIT_FROM_LEVEL(runs[trailingRun].logicalStart, pBiDi->paraLevel);
           }
       }
   }

   /* handle insert LRM/RLM BEFORE/AFTER run */
   if(pBiDi->insertPoints.size>0) {
       Point *point, *start=pBiDi->insertPoints.points,
                     *limit=start+pBiDi->insertPoints.size;
       int32_t runIndex;
       for(point=start; point<limit; point++) {
           runIndex=getRunFromLogicalIndex(pBiDi, point->pos);
           pBiDi->runs[runIndex].insertRemove|=point->flag;
       }
   }

   /* handle remove BiDi control characters */
   if(pBiDi->controlCount>0) {
       int32_t runIndex;
       const char16_t *start=pBiDi->text, *limit=start+pBiDi->length, *pu;
       for(pu=start; pu<limit; pu++) {
           if(IS_BIDI_CONTROL_CHAR(*pu)) {
               runIndex=getRunFromLogicalIndex(pBiDi, (int32_t)(pu-start));
               pBiDi->runs[runIndex].insertRemove--;
           }
       }
   }

   return true;
}

static UBool
prepareReorder(const UBiDiLevel *levels, int32_t length,
              int32_t *indexMap,
              UBiDiLevel *pMinLevel, UBiDiLevel *pMaxLevel) {
   int32_t start;
   UBiDiLevel level, minLevel, maxLevel;

   if(levels==nullptr || length<=0) {
       return false;
   }

   /* determine minLevel and maxLevel */
   minLevel=UBIDI_MAX_EXPLICIT_LEVEL+1;
   maxLevel=0;
   for(start=length; start>0;) {
       level=levels[--start];
       if(level>UBIDI_MAX_EXPLICIT_LEVEL+1) {
           return false;
       }
       if(level<minLevel) {
           minLevel=level;
       }
       if(level>maxLevel) {
           maxLevel=level;
       }
   }
   *pMinLevel=minLevel;
   *pMaxLevel=maxLevel;

   /* initialize the index map */
   for(start=length; start>0;) {
       --start;
       indexMap[start]=start;
   }

   return true;
}

/* reorder a line based on a levels array (L2) ------------------------------ */

U_CAPI void U_EXPORT2
ubidi_reorderLogical(const UBiDiLevel *levels, int32_t length, int32_t *indexMap) {
   int32_t start, limit, sumOfSosEos;
   UBiDiLevel minLevel = 0, maxLevel = 0;

   if(indexMap==nullptr || !prepareReorder(levels, length, indexMap, &minLevel, &maxLevel)) {
       return;
   }

   /* nothing to do? */
   if(minLevel==maxLevel && (minLevel&1)==0) {
       return;
   }

   /* reorder only down to the lowest odd level */
   minLevel|=1;

   /* loop maxLevel..minLevel */
   do {
       start=0;

       /* loop for all sequences of levels to reorder at the current maxLevel */
       for(;;) {
           /* look for a sequence of levels that are all at >=maxLevel */
           /* look for the first index of such a sequence */
           while(start<length && levels[start]<maxLevel) {
               ++start;
           }
           if(start>=length) {
               break;  /* no more such sequences */
           }

           /* look for the limit of such a sequence (the index behind it) */
           for(limit=start; ++limit<length && levels[limit]>=maxLevel;) {}

           /*
            * sos=start of sequence, eos=end of sequence
            *
            * The closed (inclusive) interval from sos to eos includes all the logical
            * and visual indexes within this sequence. They are logically and
            * visually contiguous and in the same range.
            *
            * For each run, the new visual index=sos+eos-old visual index;
            * we pre-add sos+eos into sumOfSosEos ->
            * new visual index=sumOfSosEos-old visual index;
            */
           sumOfSosEos=start+limit-1;

           /* reorder each index in the sequence */
           do {
               indexMap[start]=sumOfSosEos-indexMap[start];
           } while(++start<limit);

           /* start==limit */
           if(limit==length) {
               break;  /* no more such sequences */
           } else {
               start=limit+1;
           }
       }
   } while(--maxLevel>=minLevel);
}

U_CAPI void U_EXPORT2
ubidi_reorderVisual(const UBiDiLevel *levels, int32_t length, int32_t *indexMap) {
   int32_t start, end, limit, temp;
   UBiDiLevel minLevel = 0, maxLevel = 0;

   if(indexMap==nullptr || !prepareReorder(levels, length, indexMap, &minLevel, &maxLevel)) {
       return;
   }

   /* nothing to do? */
   if(minLevel==maxLevel && (minLevel&1)==0) {
       return;
   }

   /* reorder only down to the lowest odd level */
   minLevel|=1;

   /* loop maxLevel..minLevel */
   do {
       start=0;

       /* loop for all sequences of levels to reorder at the current maxLevel */
       for(;;) {
           /* look for a sequence of levels that are all at >=maxLevel */
           /* look for the first index of such a sequence */
           while(start<length && levels[start]<maxLevel) {
               ++start;
           }
           if(start>=length) {
               break;  /* no more such runs */
           }

           /* look for the limit of such a sequence (the index behind it) */
           for(limit=start; ++limit<length && levels[limit]>=maxLevel;) {}

           /*
            * Swap the entire interval of indexes from start to limit-1.
            * We don't need to swap the levels for the purpose of this
            * algorithm: the sequence of levels that we look at does not
            * move anyway.
            */
           end=limit-1;
           while(start<end) {
               temp=indexMap[start];
               indexMap[start]=indexMap[end];
               indexMap[end]=temp;

               ++start;
               --end;
           }

           if(limit==length) {
               break;  /* no more such sequences */
           } else {
               start=limit+1;
           }
       }
   } while(--maxLevel>=minLevel);
}

/* API functions for logical<->visual mapping ------------------------------- */

U_CAPI int32_t U_EXPORT2
ubidi_getVisualIndex(UBiDi *pBiDi, int32_t logicalIndex, UErrorCode *pErrorCode) {
   int32_t visualIndex=UBIDI_MAP_NOWHERE;
   RETURN_IF_NULL_OR_FAILING_ERRCODE(pErrorCode, -1);
   RETURN_IF_NOT_VALID_PARA_OR_LINE(pBiDi, *pErrorCode, -1);
   RETURN_IF_BAD_RANGE(logicalIndex, 0, pBiDi->length, *pErrorCode, -1);

   /* we can do the trivial cases without the runs array */
   switch(pBiDi->direction) {
   case UBIDI_LTR:
       visualIndex=logicalIndex;
       break;
   case UBIDI_RTL:
       visualIndex=pBiDi->length-logicalIndex-1;
       break;
   default:
       if(!ubidi_getRuns(pBiDi, pErrorCode)) {
           *pErrorCode=U_MEMORY_ALLOCATION_ERROR;
           return -1;
       } else {
           Run *runs=pBiDi->runs;
           int32_t i, visualStart=0, offset, length;

           /* linear search for the run, search on the visual runs */
           for(i=0; i<pBiDi->runCount; ++i) {
               length=runs[i].visualLimit-visualStart;
               offset=logicalIndex-GET_INDEX(runs[i].logicalStart);
               if(offset>=0 && offset<length) {
                   if(IS_EVEN_RUN(runs[i].logicalStart)) {
                       /* LTR */
                       visualIndex=visualStart+offset;
                   } else {
                       /* RTL */
                       visualIndex=visualStart+length-offset-1;
                   }
                   break;          /* exit for loop */
               }
               visualStart+=length;
           }
           if(i>=pBiDi->runCount) {
               return UBIDI_MAP_NOWHERE;
           }
       }
   }

   if(pBiDi->insertPoints.size>0) {
       /* add the number of added marks until the calculated visual index */
       Run *runs=pBiDi->runs;
       int32_t i, length, insertRemove;
       int32_t visualStart=0, markFound=0;
       for(i=0; ; i++, visualStart+=length) {
           length=runs[i].visualLimit-visualStart;
           insertRemove=runs[i].insertRemove;
           if(insertRemove & (LRM_BEFORE|RLM_BEFORE)) {
               markFound++;
           }
           /* is it the run containing the visual index? */
           if(visualIndex<runs[i].visualLimit) {
               return visualIndex+markFound;
           }
           if(insertRemove & (LRM_AFTER|RLM_AFTER)) {
               markFound++;
           }
       }
   }
   else if(pBiDi->controlCount>0) {
       /* subtract the number of controls until the calculated visual index */
       Run *runs=pBiDi->runs;
       int32_t i, j, start, limit, length, insertRemove;
       int32_t visualStart=0, controlFound=0;
       char16_t uchar=pBiDi->text[logicalIndex];
       /* is the logical index pointing to a control ? */
       if(IS_BIDI_CONTROL_CHAR(uchar)) {
           return UBIDI_MAP_NOWHERE;
       }
       /* loop on runs */
       for(i=0; ; i++, visualStart+=length) {
           length=runs[i].visualLimit-visualStart;
           insertRemove=runs[i].insertRemove;
           /* calculated visual index is beyond this run? */
           if(visualIndex>=runs[i].visualLimit) {
               controlFound-=insertRemove;
               continue;
           }
           /* calculated visual index must be within current run */
           if(insertRemove==0) {
               return visualIndex-controlFound;
           }
           if(IS_EVEN_RUN(runs[i].logicalStart)) {
               /* LTR: check from run start to logical index */
               start=runs[i].logicalStart;
               limit=logicalIndex;
           } else {
               /* RTL: check from logical index to run end */
               start=logicalIndex+1;
               limit=GET_INDEX(runs[i].logicalStart)+length;
           }
           for(j=start; j<limit; j++) {
               uchar=pBiDi->text[j];
               if(IS_BIDI_CONTROL_CHAR(uchar)) {
                   controlFound++;
               }
           }
           return visualIndex-controlFound;
       }
   }

   return visualIndex;
}

U_CAPI int32_t U_EXPORT2
ubidi_getLogicalIndex(UBiDi *pBiDi, int32_t visualIndex, UErrorCode *pErrorCode) {
   Run *runs;
   int32_t i, runCount, start;
   RETURN_IF_NULL_OR_FAILING_ERRCODE(pErrorCode, -1);
   RETURN_IF_NOT_VALID_PARA_OR_LINE(pBiDi, *pErrorCode, -1);
   RETURN_IF_BAD_RANGE(visualIndex, 0, pBiDi->resultLength, *pErrorCode, -1);
   /* we can do the trivial cases without the runs array */
   if(pBiDi->insertPoints.size==0 && pBiDi->controlCount==0) {
       if(pBiDi->direction==UBIDI_LTR) {
           return visualIndex;
       }
       else if(pBiDi->direction==UBIDI_RTL) {
           return pBiDi->length-visualIndex-1;
       }
   }
   if(!ubidi_getRuns(pBiDi, pErrorCode)) {
       *pErrorCode=U_MEMORY_ALLOCATION_ERROR;
       return -1;
   }

   runs=pBiDi->runs;
   runCount=pBiDi->runCount;
   if(pBiDi->insertPoints.size>0) {
       /* handle inserted LRM/RLM */
       int32_t markFound=0, insertRemove;
       int32_t visualStart=0, length;
       runs=pBiDi->runs;
       /* subtract number of marks until visual index */
       for(i=0; ; i++, visualStart+=length) {
           length=runs[i].visualLimit-visualStart;
           insertRemove=runs[i].insertRemove;
           if(insertRemove&(LRM_BEFORE|RLM_BEFORE)) {
               if(visualIndex<=(visualStart+markFound)) {
                   return UBIDI_MAP_NOWHERE;
               }
               markFound++;
           }
           /* is adjusted visual index within this run? */
           if(visualIndex<(runs[i].visualLimit+markFound)) {
               visualIndex-=markFound;
               break;
           }
           if(insertRemove&(LRM_AFTER|RLM_AFTER)) {
               if(visualIndex==(visualStart+length+markFound)) {
                   return UBIDI_MAP_NOWHERE;
               }
               markFound++;
           }
       }
   }
   else if(pBiDi->controlCount>0) {
       /* handle removed BiDi control characters */
       int32_t controlFound=0, insertRemove, length;
       int32_t logicalStart, logicalEnd, visualStart=0, j, k;
       char16_t uchar;
       UBool evenRun;
       /* add number of controls until visual index */
       for(i=0; ; i++, visualStart+=length) {
           length=runs[i].visualLimit-visualStart;
           insertRemove=runs[i].insertRemove;
           /* is adjusted visual index beyond current run? */
           if(visualIndex>=(runs[i].visualLimit-controlFound+insertRemove)) {
               controlFound-=insertRemove;
               continue;
           }
           /* adjusted visual index is within current run */
           if(insertRemove==0) {
               visualIndex+=controlFound;
               break;
           }
           /* count non-control chars until visualIndex */
           logicalStart=runs[i].logicalStart;
           evenRun=IS_EVEN_RUN(logicalStart);
           REMOVE_ODD_BIT(logicalStart);
           logicalEnd=logicalStart+length-1;
           for(j=0; j<length; j++) {
               k= evenRun ? logicalStart+j : logicalEnd-j;
               uchar=pBiDi->text[k];
               if(IS_BIDI_CONTROL_CHAR(uchar)) {
                   controlFound++;
               }
               if((visualIndex+controlFound)==(visualStart+j)) {
                   break;
               }
           }
           visualIndex+=controlFound;
           break;
       }
   }
   /* handle all cases */
   if(runCount<=10) {
       /* linear search for the run */
       for(i=0; visualIndex>=runs[i].visualLimit; ++i) {}
   } else {
       /* binary search for the run */
       int32_t begin=0, limit=runCount;

       /* the middle if() is guaranteed to find the run, we don't need a loop limit */
       for(;;) {
           i=(begin+limit)/2;
           if(visualIndex>=runs[i].visualLimit) {
               begin=i+1;
           } else if(i==0 || visualIndex>=runs[i-1].visualLimit) {
               break;
           } else {
               limit=i;
           }
       }
   }

   start=runs[i].logicalStart;
   if(IS_EVEN_RUN(start)) {
       /* LTR */
       /* the offset in runs[i] is visualIndex-runs[i-1].visualLimit */
       if(i>0) {
           visualIndex-=runs[i-1].visualLimit;
       }
       return start+visualIndex;
   } else {
       /* RTL */
       return GET_INDEX(start)+runs[i].visualLimit-visualIndex-1;
   }
}

U_CAPI void U_EXPORT2
ubidi_getLogicalMap(UBiDi *pBiDi, int32_t *indexMap, UErrorCode *pErrorCode) {
   RETURN_VOID_IF_NULL_OR_FAILING_ERRCODE(pErrorCode);
   /* ubidi_countRuns() checks for VALID_PARA_OR_LINE */
   ubidi_countRuns(pBiDi, pErrorCode);
   if(U_FAILURE(*pErrorCode)) {
       /* no op */
   } else if(indexMap==nullptr) {
       *pErrorCode=U_ILLEGAL_ARGUMENT_ERROR;
   } else {
       /* fill a logical-to-visual index map using the runs[] */
       int32_t visualStart, visualLimit, i, j, k;
       int32_t logicalStart, logicalLimit;
       Run *runs=pBiDi->runs;
       if (pBiDi->length<=0) {
           return;
       }
       if (pBiDi->length>pBiDi->resultLength) {
           uprv_memset(indexMap, 0xFF, pBiDi->length*sizeof(int32_t));
       }

       visualStart=0;
       for(j=0; j<pBiDi->runCount; ++j) {
           logicalStart=GET_INDEX(runs[j].logicalStart);
           visualLimit=runs[j].visualLimit;
           if(IS_EVEN_RUN(runs[j].logicalStart)) {
               do { /* LTR */
                   indexMap[logicalStart++]=visualStart++;
               } while(visualStart<visualLimit);
           } else {
               logicalStart+=visualLimit-visualStart;  /* logicalLimit */
               do { /* RTL */
                   indexMap[--logicalStart]=visualStart++;
               } while(visualStart<visualLimit);
           }
           /* visualStart==visualLimit; */
       }

       if(pBiDi->insertPoints.size>0) {
           int32_t markFound=0, runCount=pBiDi->runCount;
           int32_t length, insertRemove;
           visualStart=0;
           /* add number of marks found until each index */
           for(i=0; i<runCount; i++, visualStart+=length) {
               length=runs[i].visualLimit-visualStart;
               insertRemove=runs[i].insertRemove;
               if(insertRemove&(LRM_BEFORE|RLM_BEFORE)) {
                   markFound++;
               }
               if(markFound>0) {
                   logicalStart=GET_INDEX(runs[i].logicalStart);
                   logicalLimit=logicalStart+length;
                   for(j=logicalStart; j<logicalLimit; j++) {
                       indexMap[j]+=markFound;
                   }
               }
               if(insertRemove&(LRM_AFTER|RLM_AFTER)) {
                   markFound++;
               }
           }
       }
       else if(pBiDi->controlCount>0) {
           int32_t controlFound=0, runCount=pBiDi->runCount;
           int32_t length, insertRemove;
           UBool evenRun;
           char16_t uchar;
           visualStart=0;
           /* subtract number of controls found until each index */
           for(i=0; i<runCount; i++, visualStart+=length) {
               length=runs[i].visualLimit-visualStart;
               insertRemove=runs[i].insertRemove;
               /* no control found within previous runs nor within this run */
               if((controlFound-insertRemove)==0) {
                   continue;
               }
               logicalStart=runs[i].logicalStart;
               evenRun=IS_EVEN_RUN(logicalStart);
               REMOVE_ODD_BIT(logicalStart);
               logicalLimit=logicalStart+length;
               /* if no control within this run */
               if(insertRemove==0) {
                   for(j=logicalStart; j<logicalLimit; j++) {
                       indexMap[j]-=controlFound;
                   }
                   continue;
               }
               for(j=0; j<length; j++) {
                   k= evenRun ? logicalStart+j : logicalLimit-j-1;
                   uchar=pBiDi->text[k];
                   if(IS_BIDI_CONTROL_CHAR(uchar)) {
                       controlFound++;
                       indexMap[k]=UBIDI_MAP_NOWHERE;
                       continue;
                   }
                   indexMap[k]-=controlFound;
               }
           }
       }
   }
}

U_CAPI void U_EXPORT2
ubidi_getVisualMap(UBiDi *pBiDi, int32_t *indexMap, UErrorCode *pErrorCode) {
   RETURN_VOID_IF_NULL_OR_FAILING_ERRCODE(pErrorCode);
   if(indexMap==nullptr) {
       *pErrorCode=U_ILLEGAL_ARGUMENT_ERROR;
       return;
   }
   /* ubidi_countRuns() checks for VALID_PARA_OR_LINE */
   ubidi_countRuns(pBiDi, pErrorCode);
   if(U_SUCCESS(*pErrorCode)) {
       /* fill a visual-to-logical index map using the runs[] */
       Run *runs=pBiDi->runs, *runsLimit=runs+pBiDi->runCount;
       int32_t logicalStart, visualStart, visualLimit, *pi=indexMap;

       if (pBiDi->resultLength<=0) {
           return;
       }
       visualStart=0;
       for(; runs<runsLimit; ++runs) {
           logicalStart=runs->logicalStart;
           visualLimit=runs->visualLimit;
           if(IS_EVEN_RUN(logicalStart)) {
               do { /* LTR */
                   *pi++ = logicalStart++;
               } while(++visualStart<visualLimit);
           } else {
               REMOVE_ODD_BIT(logicalStart);
               logicalStart+=visualLimit-visualStart;  /* logicalLimit */
               do { /* RTL */
                   *pi++ = --logicalStart;
               } while(++visualStart<visualLimit);
           }
           /* visualStart==visualLimit; */
       }

       if(pBiDi->insertPoints.size>0) {
           int32_t markFound=0, runCount=pBiDi->runCount;
           int32_t insertRemove, i, j, k;
           runs=pBiDi->runs;
           /* count all inserted marks */
           for(i=0; i<runCount; i++) {
               insertRemove=runs[i].insertRemove;
               if(insertRemove&(LRM_BEFORE|RLM_BEFORE)) {
                   markFound++;
               }
               if(insertRemove&(LRM_AFTER|RLM_AFTER)) {
                   markFound++;
               }
           }
           /* move back indexes by number of preceding marks */
           k=pBiDi->resultLength;
           for(i=runCount-1; i>=0 && markFound>0; i--) {
               insertRemove=runs[i].insertRemove;
               if(insertRemove&(LRM_AFTER|RLM_AFTER)) {
                   indexMap[--k]= UBIDI_MAP_NOWHERE;
                   markFound--;
               }
               visualStart= i>0 ? runs[i-1].visualLimit : 0;
               for(j=runs[i].visualLimit-1; j>=visualStart && markFound>0; j--) {
                   indexMap[--k]=indexMap[j];
               }
               if(insertRemove&(LRM_BEFORE|RLM_BEFORE)) {
                   indexMap[--k]= UBIDI_MAP_NOWHERE;
                   markFound--;
               }
           }
       }
       else if(pBiDi->controlCount>0) {
           int32_t runCount=pBiDi->runCount, logicalEnd;
           int32_t insertRemove, length, i, j, k, m;
           char16_t uchar;
           UBool evenRun;
           runs=pBiDi->runs;
           visualStart=0;
           /* move forward indexes by number of preceding controls */
           k=0;
           for(i=0; i<runCount; i++, visualStart+=length) {
               length=runs[i].visualLimit-visualStart;
               insertRemove=runs[i].insertRemove;
               /* if no control found yet, nothing to do in this run */
               if((insertRemove==0)&&(k==visualStart)) {
                   k+=length;
                   continue;
               }
               /* if no control in this run */
               if(insertRemove==0) {
                   visualLimit=runs[i].visualLimit;
                   for(j=visualStart; j<visualLimit; j++) {
                       indexMap[k++]=indexMap[j];
                   }
                   continue;
               }
               logicalStart=runs[i].logicalStart;
               evenRun=IS_EVEN_RUN(logicalStart);
               REMOVE_ODD_BIT(logicalStart);
               logicalEnd=logicalStart+length-1;
               for(j=0; j<length; j++) {
                   m= evenRun ? logicalStart+j : logicalEnd-j;
                   uchar=pBiDi->text[m];
                   if(!IS_BIDI_CONTROL_CHAR(uchar)) {
                       indexMap[k++]=m;
                   }
               }
           }
       }
   }
}

U_CAPI void U_EXPORT2
ubidi_invertMap(const int32_t *srcMap, int32_t *destMap, int32_t length) {
   if(srcMap!=nullptr && destMap!=nullptr && length>0) {
       const int32_t *pi;
       int32_t destLength=-1, count=0;
       /* find highest value and count positive indexes in srcMap */
       pi=srcMap+length;
       while(pi>srcMap) {
           if(*--pi>destLength) {
               destLength=*pi;
           }
           if(*pi>=0) {
               count++;
           }
       }
       destLength++;           /* add 1 for origin 0 */
       if(count<destLength) {
           /* we must fill unmatched destMap entries with -1 */
           uprv_memset(destMap, 0xFF, destLength*sizeof(int32_t));
       }
       pi=srcMap+length;
       while(length>0) {
           if(*--pi>=0) {
               destMap[*pi]=--length;
           } else {
               --length;
           }
       }
   }
}