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ICU-5243 improve algorithm for RTL inverse bidi, add some comments

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X-SVN-Rev: 19930
This commit is contained in:
Matitiahu Allouche 2006-07-31 15:05:42 +00:00
parent 7c4d4cbda7
commit 0dd06e16fb
1 changed files with 94 additions and 13 deletions
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107
icu4c/source/common/ubidi.c
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@ -215,6 +215,9 @@ ubidi_getMemory(void **pMemory, int32_t *pSize, UBool mayAllocate, int32_t sizeN
/* not enough memory, and we must not allocate */
return FALSE;
} else if(sizeNeeded!=*pSize && mayAllocate) {
/* FOOD FOR THOUGHT: in hope to improve performance, we should
* try never shrinking memory, only growing it when required.
*/
/* we may try to grow or shrink */
void *memory;
@ -336,6 +339,7 @@ getDirProps(UBiDi *pBiDi) {
UBool isDefaultLevelInverse=isDefaultLevel &&
(pBiDi->reorderingMode==UBIDI_REORDER_INVERSE_LIKE_DIRECT ||
pBiDi->reorderingMode==UBIDI_REORDER_INVERSE_FOR_NUMBERS_SPECIAL);
int32_t lastArabicPos=-1;
int32_t controlCount=0;
UBool removeBiDiControls = pBiDi->reorderingOptions &
UBIDI_OPTION_REMOVE_CONTROLS;
@ -410,12 +414,16 @@ getDirProps(UBiDi *pBiDi) {
lastStrongDir=0;
lastStrongLTR=i; /* i is index to next character */
}
else if(dirProp==R || dirProp==AL) {
else if(dirProp==R) {
lastStrongDir=CONTEXT_RTL;
}
else if(dirProp==AL) {
lastStrongDir=CONTEXT_RTL;
lastArabicPos=i-1;
}
else if(dirProp==B) {
if(pBiDi->reorderingOptions & UBIDI_OPTION_STREAMING) {
pBiDi->length = i; /* i is index to next character */
pBiDi->length=i; /* i is index to next character */
}
if(isDefaultLevelInverse && (lastStrongDir==CONTEXT_RTL) &&(paraDir!=lastStrongDir)) {
for( ; paraStart<i; paraStart++) {
@ -465,6 +473,7 @@ getDirProps(UBiDi *pBiDi) {
pBiDi->controlCount = controlCount;
pBiDi->flags=flags;
pBiDi->lastArabicPos=lastArabicPos;
}
/* perform (X1)..(X9) ------------------------------------------------------- */
@ -1026,17 +1035,18 @@ static const ImpTab impTabR_INVERSE_LIKE_DIRECT = /* Odd paragraph level */
{
/* L , R , EN , AN , ON , S , B , Res */
/* 0 : init */ { 1 , 0 , 2 , 2 , 0 , 0 , 0 , 0 },
/* 1 : L */ { 1 , 0 , 1 , 3 , _(1,4), _(1,4), 0 , 1 },
/* 1 : L */ { 1 , 0 , 1 , 2 , _(1,3), _(1,3), 0 , 1 },
/* 2 : EN/AN */ { 1 , 0 , 2 , 2 , 0 , 0 , 0 , 1 },
/* 3 : L+AN */ { 1 , 0 , 1 , 3 , 5 , 5 , 0 , 1 },
/* 4 : L+ON */ { _(2,1), 0 , 6 , 3 , 4 , 4 , 0 , 0 },
/* 5 : L+AN+ON */ { 1 , 0 , 1 , 3 , 5 , 5 , 0 , 0 },
/* 6 : L+ON+EN */ { _(2,1), 0 , 6 , 3 , 4 , 4 , 0 , 1 }
/* 3 : L+ON */ { _(2,1), _(3,0), 6 , 4 , 3 , 3 , _(3,0), 0 },
/* 4 : L+ON+AN */ { _(2,1), _(3,0), 6 , 4 , 5 , 5 , _(3,0), 3 },
/* 5 : L+AN+ON */ { _(2,1), _(3,0), 6 , 4 , 5 , 5 , _(3,0), 2 },
/* 6 : L+ON+EN */ { _(2,1), _(3,0), 6 , 4 , 3 , 3 , _(3,0), 1 }
};
static const ImpAct impAct1 = {0,1,11,12};
static const ImpTabPair impTab_INVERSE_LIKE_DIRECT = {
{(ImpTab*)&impTabL_DEFAULT,
(ImpTab*)&impTabR_INVERSE_LIKE_DIRECT},
{(ImpAct*)&impAct0, (ImpAct*)&impAct0}};
{(ImpAct*)&impAct0, (ImpAct*)&impAct1}};
static const ImpTab impTabL_INVERSE_LIKE_DIRECT_WITH_MARKS =
/* The case handled in this table is (visually): R EN L
@ -1313,6 +1323,34 @@ processPropertySeq(UBiDi *pBiDi, LevState *pLevState, uint8_t _prop,
pLevState->startON=start0;
break;
case 11: /* L after L+ON+EN/AN/ON */
level=pLevState->runLevel;
for(k=start0-1; k>=pLevState->startON; k--) {
if(levels[k]==level+3) {
while(levels[k]==level+3) {
levels[k--]-=2;
}
while(levels[k]==level) {
k--;
}
}
if(levels[k]==level+2) {
levels[k]=level;
continue;
}
levels[k]=level+1;
}
break;
case 12: /* R after L+ON+EN/AN/ON */
level=pLevState->runLevel+1;
for(k=start0-1; k>=pLevState->startON; k--) {
if(levels[k]>level) {
levels[k]-=2;
}
}
break;
default: /* we should never get here */
start=start0+25;
start/=(start-start0-25); /* force program crash */
@ -1337,7 +1375,20 @@ resolveImplicitLevels(UBiDi *pBiDi,
int32_t i, start1, start2;
uint8_t oldStateImp, stateImp, actionImp;
uint8_t gprop, resProp, cell;
UBool inverseRTL;
DirProp nextStrongProp=R;
int32_t nextStrongPos=-1;
/* check for RTL inverse BiDi mode */
/* FOOD FOR THOUGHT: in case of RTL inverse BiDi, it would make sense to
* loop on the text characters from end to start.
* This would need a different properties state table (at least different
* actions) and different levels state tables (maybe very similar to the
* LTR corresponding ones.
*/
inverseRTL=((start<pBiDi->lastArabicPos) && (GET_PARALEVEL(pBiDi, start) & 1) &&
(pBiDi->reorderingMode==UBIDI_REORDER_INVERSE_LIKE_DIRECT ||
pBiDi->reorderingMode==UBIDI_REORDER_INVERSE_FOR_NUMBERS_SPECIAL));
/* initialize for levels state table */
levState.startL2EN=-1; /* used for INVERSE_LIKE_DIRECT_WITH_MARKS */
levState.lastStrongRTL=-1; /* used for INVERSE_LIKE_DIRECT_WITH_MARKS */
@ -1356,10 +1407,36 @@ resolveImplicitLevels(UBiDi *pBiDi,
start2=start;
for(i=start; i<=limit; i++) {
if(i<limit) {
gprop=groupProp[NO_CONTEXT_RTL(dirProps[i])];
} else {
if(i>=limit) {
gprop=eor;
} else {
DirProp prop, prop1;
prop=NO_CONTEXT_RTL(dirProps[i]);
if(inverseRTL) {
if(prop==AL) {
/* AL before EN does not make it AN */
prop=R;
} else if(prop==EN) {
if(nextStrongPos<=i) {
/* look for next strong char (L/R/AL) */
int32_t j;
nextStrongProp=R; /* set default */
nextStrongPos=limit;
for(j=i+1; j<limit; j++) {
prop1=NO_CONTEXT_RTL(dirProps[j]);
if(prop1==L || prop1==R || prop1==AL) {
nextStrongProp=prop1;
nextStrongPos=j;
break;
}
}
}
if(nextStrongProp==AL) {
prop=AN;
}
}
}
gprop=groupProp[prop];
}
oldStateImp=stateImp;
cell=impTabProps[oldStateImp][gprop];
@ -1486,8 +1563,12 @@ setParaRunsOnly(UBiDi *pBiDi, const UChar *text, int32_t length,
ubidi_setPara(pBiDi, text, length, paraLevel, NULL, pErrorCode);
levels=ubidi_getLevels(pBiDi, pErrorCode);
/* instead of writing the visual text, we could use the visual map and the
dirProps array to drive the second call to ubidi_setPara */
/* FOOD FOR THOUGHT: instead of writing the visual text, we could use
* the visual map and the dirProps array to drive the second call
* to ubidi_setPara (but must make provision for possible removal of
* BiDi controls. Alternatively, only use the dirProps array via
* customized classifier callback.
*/
visualLength=ubidi_writeReordered(pBiDi, visualText, length,
UBIDI_DO_MIRRORING, pErrorCode);
pBiDi->reorderingOptions=saveOptions;