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      1 //  2016 and later: Unicode, Inc. and others.
      2 // License & terms of use: http://www.unicode.org/copyright.html
      3 /*
      4 ******************************************************************************
      5 *
      6 *   Copyright (C) 2003-2016, International Business Machines
      7 *   Corporation and others.  All Rights Reserved.
      8 *
      9 ******************************************************************************
     10 *   file name:  ucnv_ext.cpp
     11 *   encoding:   UTF-8
     12 *   tab size:   8 (not used)
     13 *   indentation:4
     14 *
     15 *   created on: 2003jun13
     16 *   created by: Markus W. Scherer
     17 *
     18 *   Conversion extensions
     19 */
     20 
     21 #include "unicode/utypes.h"
     22 
     23 #if !UCONFIG_NO_CONVERSION && !UCONFIG_NO_LEGACY_CONVERSION
     24 
     25 #include "unicode/uset.h"
     26 #include "unicode/ustring.h"
     27 #include "ucnv_bld.h"
     28 #include "ucnv_cnv.h"
     29 #include "ucnv_ext.h"
     30 #include "cmemory.h"
     31 #include "uassert.h"
     32 
     33 /* to Unicode --------------------------------------------------------------- */
     34 
     35 /*
     36  * @return lookup value for the byte, if found; else 0
     37  */
     38 static inline uint32_t
     39 ucnv_extFindToU(const uint32_t *toUSection, int32_t length, uint8_t byte) {
     40     uint32_t word0, word;
     41     int32_t i, start, limit;
     42 
     43     /* check the input byte against the lowest and highest section bytes */
     44     start=(int32_t)UCNV_EXT_TO_U_GET_BYTE(toUSection[0]);
     45     limit=(int32_t)UCNV_EXT_TO_U_GET_BYTE(toUSection[length-1]);
     46     if(byte<start || limit<byte) {
     47         return 0; /* the byte is out of range */
     48     }
     49 
     50     if(length==((limit-start)+1)) {
     51         /* direct access on a linear array */
     52         return UCNV_EXT_TO_U_GET_VALUE(toUSection[byte-start]); /* could be 0 */
     53     }
     54 
     55     /* word0 is suitable for <=toUSection[] comparison, word for <toUSection[] */
     56     word0=UCNV_EXT_TO_U_MAKE_WORD(byte, 0);
     57 
     58     /*
     59      * Shift byte once instead of each section word and add 0xffffff.
     60      * We will compare the shifted/added byte (bbffffff) against
     61      * section words which have byte values in the same bit position.
     62      * If and only if byte bb < section byte ss then bbffffff<ssvvvvvv
     63      * for all v=0..f
     64      * so we need not mask off the lower 24 bits of each section word.
     65      */
     66     word=word0|UCNV_EXT_TO_U_VALUE_MASK;
     67 
     68     /* binary search */
     69     start=0;
     70     limit=length;
     71     for(;;) {
     72         i=limit-start;
     73         if(i<=1) {
     74             break; /* done */
     75         }
     76         /* start<limit-1 */
     77 
     78         if(i<=4) {
     79             /* linear search for the last part */
     80             if(word0<=toUSection[start]) {
     81                 break;
     82             }
     83             if(++start<limit && word0<=toUSection[start]) {
     84                 break;
     85             }
     86             if(++start<limit && word0<=toUSection[start]) {
     87                 break;
     88             }
     89             /* always break at start==limit-1 */
     90             ++start;
     91             break;
     92         }
     93 
     94         i=(start+limit)/2;
     95         if(word<toUSection[i]) {
     96             limit=i;
     97         } else {
     98             start=i;
     99         }
    100     }
    101 
    102     /* did we really find it? */
    103     if(start<limit && byte==UCNV_EXT_TO_U_GET_BYTE(word=toUSection[start])) {
    104         return UCNV_EXT_TO_U_GET_VALUE(word); /* never 0 */
    105     } else {
    106         return 0; /* not found */
    107     }
    108 }
    109 
    110 /*
    111  * TRUE if not an SI/SO stateful converter,
    112  * or if the match length fits with the current converter state
    113  */
    114 #define UCNV_EXT_TO_U_VERIFY_SISO_MATCH(sisoState, match) \
    115     ((sisoState)<0 || ((sisoState)==0) == (match==1))
    116 
    117 /*
    118  * this works like ucnv_extMatchFromU() except
    119  * - the first character is in pre
    120  * - no trie is used
    121  * - the returned matchLength is not offset by 2
    122  */
    123 static int32_t
    124 ucnv_extMatchToU(const int32_t *cx, int8_t sisoState,
    125                  const char *pre, int32_t preLength,
    126                  const char *src, int32_t srcLength,
    127                  uint32_t *pMatchValue,
    128                  UBool /*useFallback*/, UBool flush) {
    129     const uint32_t *toUTable, *toUSection;
    130 
    131     uint32_t value, matchValue;
    132     int32_t i, j, idx, length, matchLength;
    133     uint8_t b;
    134 
    135     if(cx==NULL || cx[UCNV_EXT_TO_U_LENGTH]<=0) {
    136         return 0; /* no extension data, no match */
    137     }
    138 
    139     /* initialize */
    140     toUTable=UCNV_EXT_ARRAY(cx, UCNV_EXT_TO_U_INDEX, uint32_t);
    141     idx=0;
    142 
    143     matchValue=0;
    144     i=j=matchLength=0;
    145 
    146     if(sisoState==0) {
    147         /* SBCS state of an SI/SO stateful converter, look at only exactly 1 byte */
    148         if(preLength>1) {
    149             return 0; /* no match of a DBCS sequence in SBCS mode */
    150         } else if(preLength==1) {
    151             srcLength=0;
    152         } else /* preLength==0 */ {
    153             if(srcLength>1) {
    154                 srcLength=1;
    155             }
    156         }
    157         flush=TRUE;
    158     }
    159 
    160     /* we must not remember fallback matches when not using fallbacks */
    161 
    162     /* match input units until there is a full match or the input is consumed */
    163     for(;;) {
    164         /* go to the next section */
    165         toUSection=toUTable+idx;
    166 
    167         /* read first pair of the section */
    168         value=*toUSection++;
    169         length=UCNV_EXT_TO_U_GET_BYTE(value);
    170         value=UCNV_EXT_TO_U_GET_VALUE(value);
    171         if( value!=0 &&
    172             (UCNV_EXT_TO_U_IS_ROUNDTRIP(value) ||
    173              TO_U_USE_FALLBACK(useFallback)) &&
    174             UCNV_EXT_TO_U_VERIFY_SISO_MATCH(sisoState, i+j)
    175         ) {
    176             /* remember longest match so far */
    177             matchValue=value;
    178             matchLength=i+j;
    179         }
    180 
    181         /* match pre[] then src[] */
    182         if(i<preLength) {
    183             b=(uint8_t)pre[i++];
    184         } else if(j<srcLength) {
    185             b=(uint8_t)src[j++];
    186         } else {
    187             /* all input consumed, partial match */
    188             if(flush || (length=(i+j))>UCNV_EXT_MAX_BYTES) {
    189                 /*
    190                  * end of the entire input stream, stop with the longest match so far
    191                  * or: partial match must not be longer than UCNV_EXT_MAX_BYTES
    192                  * because it must fit into state buffers
    193                  */
    194                 break;
    195             } else {
    196                 /* continue with more input next time */
    197                 return -length;
    198             }
    199         }
    200 
    201         /* search for the current UChar */
    202         value=ucnv_extFindToU(toUSection, length, b);
    203         if(value==0) {
    204             /* no match here, stop with the longest match so far */
    205             break;
    206         } else {
    207             if(UCNV_EXT_TO_U_IS_PARTIAL(value)) {
    208                 /* partial match, continue */
    209                 idx=(int32_t)UCNV_EXT_TO_U_GET_PARTIAL_INDEX(value);
    210             } else {
    211                 if( (UCNV_EXT_TO_U_IS_ROUNDTRIP(value) ||
    212                      TO_U_USE_FALLBACK(useFallback)) &&
    213                     UCNV_EXT_TO_U_VERIFY_SISO_MATCH(sisoState, i+j)
    214                 ) {
    215                     /* full match, stop with result */
    216                     matchValue=value;
    217                     matchLength=i+j;
    218                 } else {
    219                     /* full match on fallback not taken, stop with the longest match so far */
    220                 }
    221                 break;
    222             }
    223         }
    224     }
    225 
    226     if(matchLength==0) {
    227         /* no match at all */
    228         return 0;
    229     }
    230 
    231     /* return result */
    232     *pMatchValue=UCNV_EXT_TO_U_MASK_ROUNDTRIP(matchValue);
    233     return matchLength;
    234 }
    235 
    236 static inline void
    237 ucnv_extWriteToU(UConverter *cnv, const int32_t *cx,
    238                  uint32_t value,
    239                  UChar **target, const UChar *targetLimit,
    240                  int32_t **offsets, int32_t srcIndex,
    241                  UErrorCode *pErrorCode) {
    242     /* output the result */
    243     if(UCNV_EXT_TO_U_IS_CODE_POINT(value)) {
    244         /* output a single code point */
    245         ucnv_toUWriteCodePoint(
    246             cnv, UCNV_EXT_TO_U_GET_CODE_POINT(value),
    247             target, targetLimit,
    248             offsets, srcIndex,
    249             pErrorCode);
    250     } else {
    251         /* output a string - with correct data we have resultLength>0 */
    252         ucnv_toUWriteUChars(
    253             cnv,
    254             UCNV_EXT_ARRAY(cx, UCNV_EXT_TO_U_UCHARS_INDEX, UChar)+
    255                 UCNV_EXT_TO_U_GET_INDEX(value),
    256             UCNV_EXT_TO_U_GET_LENGTH(value),
    257             target, targetLimit,
    258             offsets, srcIndex,
    259             pErrorCode);
    260     }
    261 }
    262 
    263 /*
    264  * get the SI/SO toU state (state 0 is for SBCS, 1 for DBCS),
    265  * or 1 for DBCS-only,
    266  * or -1 if the converter is not SI/SO stateful
    267  *
    268  * Note: For SI/SO stateful converters getting here,
    269  * cnv->mode==0 is equivalent to firstLength==1.
    270  */
    271 #define UCNV_SISO_STATE(cnv) \
    272     ((cnv)->sharedData->mbcs.outputType==MBCS_OUTPUT_2_SISO ? (int8_t)(cnv)->mode : \
    273      (cnv)->sharedData->mbcs.outputType==MBCS_OUTPUT_DBCS_ONLY ? 1 : -1)
    274 
    275 /*
    276  * target<targetLimit; set error code for overflow
    277  */
    278 U_CFUNC UBool
    279 ucnv_extInitialMatchToU(UConverter *cnv, const int32_t *cx,
    280                         int32_t firstLength,
    281                         const char **src, const char *srcLimit,
    282                         UChar **target, const UChar *targetLimit,
    283                         int32_t **offsets, int32_t srcIndex,
    284                         UBool flush,
    285                         UErrorCode *pErrorCode) {
    286     uint32_t value = 0;  /* initialize output-only param to 0 to silence gcc */
    287     int32_t match;
    288 
    289     /* try to match */
    290     match=ucnv_extMatchToU(cx, (int8_t)UCNV_SISO_STATE(cnv),
    291                            (const char *)cnv->toUBytes, firstLength,
    292                            *src, (int32_t)(srcLimit-*src),
    293                            &value,
    294                            cnv->useFallback, flush);
    295     if(match>0) {
    296         /* advance src pointer for the consumed input */
    297         *src+=match-firstLength;
    298 
    299         /* write result to target */
    300         ucnv_extWriteToU(cnv, cx,
    301                          value,
    302                          target, targetLimit,
    303                          offsets, srcIndex,
    304                          pErrorCode);
    305         return TRUE;
    306     } else if(match<0) {
    307         /* save state for partial match */
    308         const char *s;
    309         int32_t j;
    310 
    311         /* copy the first code point */
    312         s=(const char *)cnv->toUBytes;
    313         cnv->preToUFirstLength=(int8_t)firstLength;
    314         for(j=0; j<firstLength; ++j) {
    315             cnv->preToU[j]=*s++;
    316         }
    317 
    318         /* now copy the newly consumed input */
    319         s=*src;
    320         match=-match;
    321         for(; j<match; ++j) {
    322             cnv->preToU[j]=*s++;
    323         }
    324         *src=s; /* same as *src=srcLimit; because we reached the end of input */
    325         cnv->preToULength=(int8_t)match;
    326         return TRUE;
    327     } else /* match==0 no match */ {
    328         return FALSE;
    329     }
    330 }
    331 
    332 U_CFUNC UChar32
    333 ucnv_extSimpleMatchToU(const int32_t *cx,
    334                        const char *source, int32_t length,
    335                        UBool useFallback) {
    336     uint32_t value = 0;  /* initialize output-only param to 0 to silence gcc */
    337     int32_t match;
    338 
    339     if(length<=0) {
    340         return 0xffff;
    341     }
    342 
    343     /* try to match */
    344     match=ucnv_extMatchToU(cx, -1,
    345                            source, length,
    346                            NULL, 0,
    347                            &value,
    348                            useFallback, TRUE);
    349     if(match==length) {
    350         /* write result for simple, single-character conversion */
    351         if(UCNV_EXT_TO_U_IS_CODE_POINT(value)) {
    352             return UCNV_EXT_TO_U_GET_CODE_POINT(value);
    353         }
    354     }
    355 
    356     /*
    357      * return no match because
    358      * - match>0 && value points to string: simple conversion cannot handle multiple code points
    359      * - match>0 && match!=length: not all input consumed, forbidden for this function
    360      * - match==0: no match found in the first place
    361      * - match<0: partial match, not supported for simple conversion (and flush==TRUE)
    362      */
    363     return 0xfffe;
    364 }
    365 
    366 /*
    367  * continue partial match with new input
    368  * never called for simple, single-character conversion
    369  */
    370 U_CFUNC void
    371 ucnv_extContinueMatchToU(UConverter *cnv,
    372                          UConverterToUnicodeArgs *pArgs, int32_t srcIndex,
    373                          UErrorCode *pErrorCode) {
    374     uint32_t value = 0;  /* initialize output-only param to 0 to silence gcc */
    375     int32_t match, length;
    376 
    377     match=ucnv_extMatchToU(cnv->sharedData->mbcs.extIndexes, (int8_t)UCNV_SISO_STATE(cnv),
    378                            cnv->preToU, cnv->preToULength,
    379                            pArgs->source, (int32_t)(pArgs->sourceLimit-pArgs->source),
    380                            &value,
    381                            cnv->useFallback, pArgs->flush);
    382     if(match>0) {
    383         if(match>=cnv->preToULength) {
    384             /* advance src pointer for the consumed input */
    385             pArgs->source+=match-cnv->preToULength;
    386             cnv->preToULength=0;
    387         } else {
    388             /* the match did not use all of preToU[] - keep the rest for replay */
    389             length=cnv->preToULength-match;
    390             uprv_memmove(cnv->preToU, cnv->preToU+match, length);
    391             cnv->preToULength=(int8_t)-length;
    392         }
    393 
    394         /* write result */
    395         ucnv_extWriteToU(cnv, cnv->sharedData->mbcs.extIndexes,
    396                          value,
    397                          &pArgs->target, pArgs->targetLimit,
    398                          &pArgs->offsets, srcIndex,
    399                          pErrorCode);
    400     } else if(match<0) {
    401         /* save state for partial match */
    402         const char *s;
    403         int32_t j;
    404 
    405         /* just _append_ the newly consumed input to preToU[] */
    406         s=pArgs->source;
    407         match=-match;
    408         for(j=cnv->preToULength; j<match; ++j) {
    409             cnv->preToU[j]=*s++;
    410         }
    411         pArgs->source=s; /* same as *src=srcLimit; because we reached the end of input */
    412         cnv->preToULength=(int8_t)match;
    413     } else /* match==0 */ {
    414         /*
    415          * no match
    416          *
    417          * We need to split the previous input into two parts:
    418          *
    419          * 1. The first codepage character is unmappable - that's how we got into
    420          *    trying the extension data in the first place.
    421          *    We need to move it from the preToU buffer
    422          *    to the error buffer, set an error code,
    423          *    and prepare the rest of the previous input for 2.
    424          *
    425          * 2. The rest of the previous input must be converted once we
    426          *    come back from the callback for the first character.
    427          *    At that time, we have to try again from scratch to convert
    428          *    these input characters.
    429          *    The replay will be handled by the ucnv.c conversion code.
    430          */
    431 
    432         /* move the first codepage character to the error field */
    433         uprv_memcpy(cnv->toUBytes, cnv->preToU, cnv->preToUFirstLength);
    434         cnv->toULength=cnv->preToUFirstLength;
    435 
    436         /* move the rest up inside the buffer */
    437         length=cnv->preToULength-cnv->preToUFirstLength;
    438         if(length>0) {
    439             uprv_memmove(cnv->preToU, cnv->preToU+cnv->preToUFirstLength, length);
    440         }
    441 
    442         /* mark preToU for replay */
    443         cnv->preToULength=(int8_t)-length;
    444 
    445         /* set the error code for unassigned */
    446         *pErrorCode=U_INVALID_CHAR_FOUND;
    447     }
    448 }
    449 
    450 /* from Unicode ------------------------------------------------------------- */
    451 
    452 // Use roundtrips, "good one-way" mappings, and some normal fallbacks.
    453 static inline UBool
    454 extFromUUseMapping(UBool useFallback, uint32_t value, UChar32 firstCP) {
    455     return
    456         ((value&UCNV_EXT_FROM_U_STATUS_MASK)!=0 ||
    457             FROM_U_USE_FALLBACK(useFallback, firstCP)) &&
    458         (value&UCNV_EXT_FROM_U_RESERVED_MASK)==0;
    459 }
    460 
    461 /*
    462  * @return index of the UChar, if found; else <0
    463  */
    464 static inline int32_t
    465 ucnv_extFindFromU(const UChar *fromUSection, int32_t length, UChar u) {
    466     int32_t i, start, limit;
    467 
    468     /* binary search */
    469     start=0;
    470     limit=length;
    471     for(;;) {
    472         i=limit-start;
    473         if(i<=1) {
    474             break; /* done */
    475         }
    476         /* start<limit-1 */
    477 
    478         if(i<=4) {
    479             /* linear search for the last part */
    480             if(u<=fromUSection[start]) {
    481                 break;
    482             }
    483             if(++start<limit && u<=fromUSection[start]) {
    484                 break;
    485             }
    486             if(++start<limit && u<=fromUSection[start]) {
    487                 break;
    488             }
    489             /* always break at start==limit-1 */
    490             ++start;
    491             break;
    492         }
    493 
    494         i=(start+limit)/2;
    495         if(u<fromUSection[i]) {
    496             limit=i;
    497         } else {
    498             start=i;
    499         }
    500     }
    501 
    502     /* did we really find it? */
    503     if(start<limit && u==fromUSection[start]) {
    504         return start;
    505     } else {
    506         return -1; /* not found */
    507     }
    508 }
    509 
    510 /*
    511  * @param cx pointer to extension data; if NULL, returns 0
    512  * @param firstCP the first code point before all the other UChars
    513  * @param pre UChars that must match; !initialMatch: partial match with them
    514  * @param preLength length of pre, >=0
    515  * @param src UChars that can be used to complete a match
    516  * @param srcLength length of src, >=0
    517  * @param pMatchValue [out] output result value for the match from the data structure
    518  * @param useFallback "use fallback" flag, usually from cnv->useFallback
    519  * @param flush TRUE if the end of the input stream is reached
    520  * @return >1: matched, return value=total match length (number of input units matched)
    521  *          1: matched, no mapping but request for <subchar1>
    522  *             (only for the first code point)
    523  *          0: no match
    524  *         <0: partial match, return value=negative total match length
    525  *             (partial matches are never returned for flush==TRUE)
    526  *             (partial matches are never returned as being longer than UCNV_EXT_MAX_UCHARS)
    527  *         the matchLength is 2 if only firstCP matched, and >2 if firstCP and
    528  *         further code units matched
    529  */
    530 static int32_t
    531 ucnv_extMatchFromU(const int32_t *cx,
    532                    UChar32 firstCP,
    533                    const UChar *pre, int32_t preLength,
    534                    const UChar *src, int32_t srcLength,
    535                    uint32_t *pMatchValue,
    536                    UBool useFallback, UBool flush) {
    537     const uint16_t *stage12, *stage3;
    538     const uint32_t *stage3b;
    539 
    540     const UChar *fromUTableUChars, *fromUSectionUChars;
    541     const uint32_t *fromUTableValues, *fromUSectionValues;
    542 
    543     uint32_t value, matchValue;
    544     int32_t i, j, idx, length, matchLength;
    545     UChar c;
    546 
    547     if(cx==NULL) {
    548         return 0; /* no extension data, no match */
    549     }
    550 
    551     /* trie lookup of firstCP */
    552     idx=firstCP>>10; /* stage 1 index */
    553     if(idx>=cx[UCNV_EXT_FROM_U_STAGE_1_LENGTH]) {
    554         return 0; /* the first code point is outside the trie */
    555     }
    556 
    557     stage12=UCNV_EXT_ARRAY(cx, UCNV_EXT_FROM_U_STAGE_12_INDEX, uint16_t);
    558     stage3=UCNV_EXT_ARRAY(cx, UCNV_EXT_FROM_U_STAGE_3_INDEX, uint16_t);
    559     idx=UCNV_EXT_FROM_U(stage12, stage3, idx, firstCP);
    560 
    561     stage3b=UCNV_EXT_ARRAY(cx, UCNV_EXT_FROM_U_STAGE_3B_INDEX, uint32_t);
    562     value=stage3b[idx];
    563     if(value==0) {
    564         return 0;
    565     }
    566 
    567     /*
    568      * Tests for (value&UCNV_EXT_FROM_U_RESERVED_MASK)==0:
    569      * Do not interpret values with reserved bits used, for forward compatibility,
    570      * and do not even remember intermediate results with reserved bits used.
    571      */
    572 
    573     if(UCNV_EXT_TO_U_IS_PARTIAL(value)) {
    574         /* partial match, enter the loop below */
    575         idx=(int32_t)UCNV_EXT_FROM_U_GET_PARTIAL_INDEX(value);
    576 
    577         /* initialize */
    578         fromUTableUChars=UCNV_EXT_ARRAY(cx, UCNV_EXT_FROM_U_UCHARS_INDEX, UChar);
    579         fromUTableValues=UCNV_EXT_ARRAY(cx, UCNV_EXT_FROM_U_VALUES_INDEX, uint32_t);
    580 
    581         matchValue=0;
    582         i=j=matchLength=0;
    583 
    584         /* we must not remember fallback matches when not using fallbacks */
    585 
    586         /* match input units until there is a full match or the input is consumed */
    587         for(;;) {
    588             /* go to the next section */
    589             fromUSectionUChars=fromUTableUChars+idx;
    590             fromUSectionValues=fromUTableValues+idx;
    591 
    592             /* read first pair of the section */
    593             length=*fromUSectionUChars++;
    594             value=*fromUSectionValues++;
    595             if(value!=0 && extFromUUseMapping(useFallback, value, firstCP)) {
    596                 /* remember longest match so far */
    597                 matchValue=value;
    598                 matchLength=2+i+j;
    599             }
    600 
    601             /* match pre[] then src[] */
    602             if(i<preLength) {
    603                 c=pre[i++];
    604             } else if(j<srcLength) {
    605                 c=src[j++];
    606             } else {
    607                 /* all input consumed, partial match */
    608                 if(flush || (length=(i+j))>UCNV_EXT_MAX_UCHARS) {
    609                     /*
    610                      * end of the entire input stream, stop with the longest match so far
    611                      * or: partial match must not be longer than UCNV_EXT_MAX_UCHARS
    612                      * because it must fit into state buffers
    613                      */
    614                     break;
    615                 } else {
    616                     /* continue with more input next time */
    617                     return -(2+length);
    618                 }
    619             }
    620 
    621             /* search for the current UChar */
    622             idx=ucnv_extFindFromU(fromUSectionUChars, length, c);
    623             if(idx<0) {
    624                 /* no match here, stop with the longest match so far */
    625                 break;
    626             } else {
    627                 value=fromUSectionValues[idx];
    628                 if(UCNV_EXT_FROM_U_IS_PARTIAL(value)) {
    629                     /* partial match, continue */
    630                     idx=(int32_t)UCNV_EXT_FROM_U_GET_PARTIAL_INDEX(value);
    631                 } else {
    632                     if(extFromUUseMapping(useFallback, value, firstCP)) {
    633                         /* full match, stop with result */
    634                         matchValue=value;
    635                         matchLength=2+i+j;
    636                     } else {
    637                         /* full match on fallback not taken, stop with the longest match so far */
    638                     }
    639                     break;
    640                 }
    641             }
    642         }
    643 
    644         if(matchLength==0) {
    645             /* no match at all */
    646             return 0;
    647         }
    648     } else /* result from firstCP trie lookup */ {
    649         if(extFromUUseMapping(useFallback, value, firstCP)) {
    650             /* full match, stop with result */
    651             matchValue=value;
    652             matchLength=2;
    653         } else {
    654             /* fallback not taken */
    655             return 0;
    656         }
    657     }
    658 
    659     /* return result */
    660     if(matchValue==UCNV_EXT_FROM_U_SUBCHAR1) {
    661         return 1; /* assert matchLength==2 */
    662     }
    663 
    664     *pMatchValue=matchValue;
    665     return matchLength;
    666 }
    667 
    668 /*
    669  * @param value fromUnicode mapping table value; ignores roundtrip and reserved bits
    670  */
    671 static inline void
    672 ucnv_extWriteFromU(UConverter *cnv, const int32_t *cx,
    673                    uint32_t value,
    674                    char **target, const char *targetLimit,
    675                    int32_t **offsets, int32_t srcIndex,
    676                    UErrorCode *pErrorCode) {
    677     uint8_t buffer[1+UCNV_EXT_MAX_BYTES];
    678     const uint8_t *result;
    679     int32_t length, prevLength;
    680 
    681     length=UCNV_EXT_FROM_U_GET_LENGTH(value);
    682     value=(uint32_t)UCNV_EXT_FROM_U_GET_DATA(value);
    683 
    684     /* output the result */
    685     if(length<=UCNV_EXT_FROM_U_MAX_DIRECT_LENGTH) {
    686         /*
    687          * Generate a byte array and then write it below.
    688          * This is not the fastest possible way, but it should be ok for
    689          * extension mappings, and it is much simpler.
    690          * Offset and overflow handling are only done once this way.
    691          */
    692         uint8_t *p=buffer+1; /* reserve buffer[0] for shiftByte below */
    693         switch(length) {
    694         case 3:
    695             *p++=(uint8_t)(value>>16);
    696             U_FALLTHROUGH;
    697         case 2:
    698             *p++=(uint8_t)(value>>8);
    699             U_FALLTHROUGH;
    700         case 1:
    701             *p++=(uint8_t)value;
    702             U_FALLTHROUGH;
    703         default:
    704             break; /* will never occur */
    705         }
    706         result=buffer+1;
    707     } else {
    708         result=UCNV_EXT_ARRAY(cx, UCNV_EXT_FROM_U_BYTES_INDEX, uint8_t)+value;
    709     }
    710 
    711     /* with correct data we have length>0 */
    712 
    713     if((prevLength=cnv->fromUnicodeStatus)!=0) {
    714         /* handle SI/SO stateful output */
    715         uint8_t shiftByte;
    716 
    717         if(prevLength>1 && length==1) {
    718             /* change from double-byte mode to single-byte */
    719             shiftByte=(uint8_t)UCNV_SI;
    720             cnv->fromUnicodeStatus=1;
    721         } else if(prevLength==1 && length>1) {
    722             /* change from single-byte mode to double-byte */
    723             shiftByte=(uint8_t)UCNV_SO;
    724             cnv->fromUnicodeStatus=2;
    725         } else {
    726             shiftByte=0;
    727         }
    728 
    729         if(shiftByte!=0) {
    730             /* prepend the shift byte to the result bytes */
    731             buffer[0]=shiftByte;
    732             if(result!=buffer+1) {
    733                 uprv_memcpy(buffer+1, result, length);
    734             }
    735             result=buffer;
    736             ++length;
    737         }
    738     }
    739 
    740     ucnv_fromUWriteBytes(cnv, (const char *)result, length,
    741                          target, targetLimit,
    742                          offsets, srcIndex,
    743                          pErrorCode);
    744 }
    745 
    746 /*
    747  * target<targetLimit; set error code for overflow
    748  */
    749 U_CFUNC UBool
    750 ucnv_extInitialMatchFromU(UConverter *cnv, const int32_t *cx,
    751                           UChar32 cp,
    752                           const UChar **src, const UChar *srcLimit,
    753                           char **target, const char *targetLimit,
    754                           int32_t **offsets, int32_t srcIndex,
    755                           UBool flush,
    756                           UErrorCode *pErrorCode) {
    757     uint32_t value = 0;  /* initialize output-only param to 0 to silence gcc */
    758     int32_t match;
    759 
    760     /* try to match */
    761     match=ucnv_extMatchFromU(cx, cp,
    762                              NULL, 0,
    763                              *src, (int32_t)(srcLimit-*src),
    764                              &value,
    765                              cnv->useFallback, flush);
    766 
    767     /* reject a match if the result is a single byte for DBCS-only */
    768     if( match>=2 &&
    769         !(UCNV_EXT_FROM_U_GET_LENGTH(value)==1 &&
    770           cnv->sharedData->mbcs.outputType==MBCS_OUTPUT_DBCS_ONLY)
    771     ) {
    772         /* advance src pointer for the consumed input */
    773         *src+=match-2; /* remove 2 for the initial code point */
    774 
    775         /* write result to target */
    776         ucnv_extWriteFromU(cnv, cx,
    777                            value,
    778                            target, targetLimit,
    779                            offsets, srcIndex,
    780                            pErrorCode);
    781         return TRUE;
    782     } else if(match<0) {
    783         /* save state for partial match */
    784         const UChar *s;
    785         int32_t j;
    786 
    787         /* copy the first code point */
    788         cnv->preFromUFirstCP=cp;
    789 
    790         /* now copy the newly consumed input */
    791         s=*src;
    792         match=-match-2; /* remove 2 for the initial code point */
    793         for(j=0; j<match; ++j) {
    794             cnv->preFromU[j]=*s++;
    795         }
    796         *src=s; /* same as *src=srcLimit; because we reached the end of input */
    797         cnv->preFromULength=(int8_t)match;
    798         return TRUE;
    799     } else if(match==1) {
    800         /* matched, no mapping but request for <subchar1> */
    801         cnv->useSubChar1=TRUE;
    802         return FALSE;
    803     } else /* match==0 no match */ {
    804         return FALSE;
    805     }
    806 }
    807 
    808 /*
    809  * Used by ISO 2022 implementation.
    810  * @return number of bytes in *pValue; negative number if fallback; 0 for no mapping
    811  */
    812 U_CFUNC int32_t
    813 ucnv_extSimpleMatchFromU(const int32_t *cx,
    814                          UChar32 cp, uint32_t *pValue,
    815                          UBool useFallback) {
    816     uint32_t value;
    817     int32_t match;
    818 
    819     /* try to match */
    820     match=ucnv_extMatchFromU(cx,
    821                              cp,
    822                              NULL, 0,
    823                              NULL, 0,
    824                              &value,
    825                              useFallback, TRUE);
    826     if(match>=2) {
    827         /* write result for simple, single-character conversion */
    828         int32_t length;
    829         int isRoundtrip;
    830 
    831         isRoundtrip=UCNV_EXT_FROM_U_IS_ROUNDTRIP(value);
    832         length=UCNV_EXT_FROM_U_GET_LENGTH(value);
    833         value=(uint32_t)UCNV_EXT_FROM_U_GET_DATA(value);
    834 
    835         if(length<=UCNV_EXT_FROM_U_MAX_DIRECT_LENGTH) {
    836             *pValue=value;
    837             return isRoundtrip ? length : -length;
    838 #if 0 /* not currently used */
    839         } else if(length==4) {
    840             /* de-serialize a 4-byte result */
    841             const uint8_t *result=UCNV_EXT_ARRAY(cx, UCNV_EXT_FROM_U_BYTES_INDEX, uint8_t)+value;
    842             *pValue=
    843                 ((uint32_t)result[0]<<24)|
    844                 ((uint32_t)result[1]<<16)|
    845                 ((uint32_t)result[2]<<8)|
    846                 result[3];
    847             return isRoundtrip ? 4 : -4;
    848 #endif
    849         }
    850     }
    851 
    852     /*
    853      * return no match because
    854      * - match>1 && resultLength>4: result too long for simple conversion
    855      * - match==1: no match found, <subchar1> preferred
    856      * - match==0: no match found in the first place
    857      * - match<0: partial match, not supported for simple conversion (and flush==TRUE)
    858      */
    859     return 0;
    860 }
    861 
    862 /*
    863  * continue partial match with new input, requires cnv->preFromUFirstCP>=0
    864  * never called for simple, single-character conversion
    865  */
    866 U_CFUNC void
    867 ucnv_extContinueMatchFromU(UConverter *cnv,
    868                            UConverterFromUnicodeArgs *pArgs, int32_t srcIndex,
    869                            UErrorCode *pErrorCode) {
    870     uint32_t value = 0;  /* initialize output-only param to 0 to silence gcc */
    871     int32_t match;
    872 
    873     match=ucnv_extMatchFromU(cnv->sharedData->mbcs.extIndexes,
    874                              cnv->preFromUFirstCP,
    875                              cnv->preFromU, cnv->preFromULength,
    876                              pArgs->source, (int32_t)(pArgs->sourceLimit-pArgs->source),
    877                              &value,
    878                              cnv->useFallback, pArgs->flush);
    879     if(match>=2) {
    880         match-=2; /* remove 2 for the initial code point */
    881 
    882         if(match>=cnv->preFromULength) {
    883             /* advance src pointer for the consumed input */
    884             pArgs->source+=match-cnv->preFromULength;
    885             cnv->preFromULength=0;
    886         } else {
    887             /* the match did not use all of preFromU[] - keep the rest for replay */
    888             int32_t length=cnv->preFromULength-match;
    889             u_memmove(cnv->preFromU, cnv->preFromU+match, length);
    890             cnv->preFromULength=(int8_t)-length;
    891         }
    892 
    893         /* finish the partial match */
    894         cnv->preFromUFirstCP=U_SENTINEL;
    895 
    896         /* write result */
    897         ucnv_extWriteFromU(cnv, cnv->sharedData->mbcs.extIndexes,
    898                            value,
    899                            &pArgs->target, pArgs->targetLimit,
    900                            &pArgs->offsets, srcIndex,
    901                            pErrorCode);
    902     } else if(match<0) {
    903         /* save state for partial match */
    904         const UChar *s;
    905         int32_t j;
    906 
    907         /* just _append_ the newly consumed input to preFromU[] */
    908         s=pArgs->source;
    909         match=-match-2; /* remove 2 for the initial code point */
    910         for(j=cnv->preFromULength; j<match; ++j) {
    911             U_ASSERT(j>=0);
    912             cnv->preFromU[j]=*s++;
    913         }
    914         pArgs->source=s; /* same as *src=srcLimit; because we reached the end of input */
    915         cnv->preFromULength=(int8_t)match;
    916     } else /* match==0 or 1 */ {
    917         /*
    918          * no match
    919          *
    920          * We need to split the previous input into two parts:
    921          *
    922          * 1. The first code point is unmappable - that's how we got into
    923          *    trying the extension data in the first place.
    924          *    We need to move it from the preFromU buffer
    925          *    to the error buffer, set an error code,
    926          *    and prepare the rest of the previous input for 2.
    927          *
    928          * 2. The rest of the previous input must be converted once we
    929          *    come back from the callback for the first code point.
    930          *    At that time, we have to try again from scratch to convert
    931          *    these input characters.
    932          *    The replay will be handled by the ucnv.c conversion code.
    933          */
    934 
    935         if(match==1) {
    936             /* matched, no mapping but request for <subchar1> */
    937             cnv->useSubChar1=TRUE;
    938         }
    939 
    940         /* move the first code point to the error field */
    941         cnv->fromUChar32=cnv->preFromUFirstCP;
    942         cnv->preFromUFirstCP=U_SENTINEL;
    943 
    944         /* mark preFromU for replay */
    945         cnv->preFromULength=-cnv->preFromULength;
    946 
    947         /* set the error code for unassigned */
    948         *pErrorCode=U_INVALID_CHAR_FOUND;
    949     }
    950 }
    951 
    952 static UBool
    953 extSetUseMapping(UConverterUnicodeSet which, int32_t minLength, uint32_t value) {
    954     if(which==UCNV_ROUNDTRIP_SET) {
    955         // Add only code points for which the roundtrip flag is set.
    956         // Do not add any fallbacks, even if ucnv_fromUnicode() would use them
    957         // (fallbacks from PUA). See the API docs for ucnv_getUnicodeSet().
    958         //
    959         // By analogy, also do not add "good one-way" mappings.
    960         //
    961         // Do not add entries with reserved bits set.
    962         if(((value&(UCNV_EXT_FROM_U_ROUNDTRIP_FLAG|UCNV_EXT_FROM_U_RESERVED_MASK))!=
    963                 UCNV_EXT_FROM_U_ROUNDTRIP_FLAG)) {
    964             return FALSE;
    965         }
    966     } else /* UCNV_ROUNDTRIP_AND_FALLBACK_SET */ {
    967         // Do not add entries with reserved bits set.
    968         if((value&UCNV_EXT_FROM_U_RESERVED_MASK)!=0) {
    969             return FALSE;
    970         }
    971     }
    972     // Do not add <subchar1> entries or other (future?) pseudo-entries
    973     // with an output length of 0.
    974     return UCNV_EXT_FROM_U_GET_LENGTH(value)>=minLength;
    975 }
    976 
    977 static void
    978 ucnv_extGetUnicodeSetString(const UConverterSharedData *sharedData,
    979                             const int32_t *cx,
    980                             const USetAdder *sa,
    981                             UConverterUnicodeSet which,
    982                             int32_t minLength,
    983                             UChar32 firstCP,
    984                             UChar s[UCNV_EXT_MAX_UCHARS], int32_t length,
    985                             int32_t sectionIndex,
    986                             UErrorCode *pErrorCode) {
    987     const UChar *fromUSectionUChars;
    988     const uint32_t *fromUSectionValues;
    989 
    990     uint32_t value;
    991     int32_t i, count;
    992 
    993     fromUSectionUChars=UCNV_EXT_ARRAY(cx, UCNV_EXT_FROM_U_UCHARS_INDEX, UChar)+sectionIndex;
    994     fromUSectionValues=UCNV_EXT_ARRAY(cx, UCNV_EXT_FROM_U_VALUES_INDEX, uint32_t)+sectionIndex;
    995 
    996     /* read first pair of the section */
    997     count=*fromUSectionUChars++;
    998     value=*fromUSectionValues++;
    999 
   1000     if(extSetUseMapping(which, minLength, value)) {
   1001         if(length==U16_LENGTH(firstCP)) {
   1002             /* add the initial code point */
   1003             sa->add(sa->set, firstCP);
   1004         } else {
   1005             /* add the string so far */
   1006             sa->addString(sa->set, s, length);
   1007         }
   1008     }
   1009 
   1010     for(i=0; i<count; ++i) {
   1011         /* append this code unit and recurse or add the string */
   1012         s[length]=fromUSectionUChars[i];
   1013         value=fromUSectionValues[i];
   1014 
   1015         if(value==0) {
   1016             /* no mapping, do nothing */
   1017         } else if(UCNV_EXT_FROM_U_IS_PARTIAL(value)) {
   1018             ucnv_extGetUnicodeSetString(
   1019                 sharedData, cx, sa, which, minLength,
   1020                 firstCP, s, length+1,
   1021                 (int32_t)UCNV_EXT_FROM_U_GET_PARTIAL_INDEX(value),
   1022                 pErrorCode);
   1023         } else if(extSetUseMapping(which, minLength, value)) {
   1024             sa->addString(sa->set, s, length+1);
   1025         }
   1026     }
   1027 }
   1028 
   1029 U_CFUNC void
   1030 ucnv_extGetUnicodeSet(const UConverterSharedData *sharedData,
   1031                       const USetAdder *sa,
   1032                       UConverterUnicodeSet which,
   1033                       UConverterSetFilter filter,
   1034                       UErrorCode *pErrorCode) {
   1035     const int32_t *cx;
   1036     const uint16_t *stage12, *stage3, *ps2, *ps3;
   1037     const uint32_t *stage3b;
   1038 
   1039     uint32_t value;
   1040     int32_t st1, stage1Length, st2, st3, minLength;
   1041 
   1042     UChar s[UCNV_EXT_MAX_UCHARS];
   1043     UChar32 c;
   1044     int32_t length;
   1045 
   1046     cx=sharedData->mbcs.extIndexes;
   1047     if(cx==NULL) {
   1048         return;
   1049     }
   1050 
   1051     stage12=UCNV_EXT_ARRAY(cx, UCNV_EXT_FROM_U_STAGE_12_INDEX, uint16_t);
   1052     stage3=UCNV_EXT_ARRAY(cx, UCNV_EXT_FROM_U_STAGE_3_INDEX, uint16_t);
   1053     stage3b=UCNV_EXT_ARRAY(cx, UCNV_EXT_FROM_U_STAGE_3B_INDEX, uint32_t);
   1054 
   1055     stage1Length=cx[UCNV_EXT_FROM_U_STAGE_1_LENGTH];
   1056 
   1057     /* enumerate the from-Unicode trie table */
   1058     c=0; /* keep track of the current code point while enumerating */
   1059 
   1060     if(filter==UCNV_SET_FILTER_2022_CN) {
   1061         minLength=3;
   1062     } else if( sharedData->mbcs.outputType==MBCS_OUTPUT_DBCS_ONLY ||
   1063                filter!=UCNV_SET_FILTER_NONE
   1064     ) {
   1065         /* DBCS-only, ignore single-byte results */
   1066         minLength=2;
   1067     } else {
   1068         minLength=1;
   1069     }
   1070 
   1071     /*
   1072      * the trie enumeration is almost the same as
   1073      * in MBCSGetUnicodeSet() for MBCS_OUTPUT_1
   1074      */
   1075     for(st1=0; st1<stage1Length; ++st1) {
   1076         st2=stage12[st1];
   1077         if(st2>stage1Length) {
   1078             ps2=stage12+st2;
   1079             for(st2=0; st2<64; ++st2) {
   1080                 if((st3=(int32_t)ps2[st2]<<UCNV_EXT_STAGE_2_LEFT_SHIFT)!=0) {
   1081                     /* read the stage 3 block */
   1082                     ps3=stage3+st3;
   1083 
   1084                     do {
   1085                         value=stage3b[*ps3++];
   1086                         if(value==0) {
   1087                             /* no mapping, do nothing */
   1088                         } else if(UCNV_EXT_FROM_U_IS_PARTIAL(value)) {
   1089                             // Recurse for partial results.
   1090                             length=0;
   1091                             U16_APPEND_UNSAFE(s, length, c);
   1092                             ucnv_extGetUnicodeSetString(
   1093                                 sharedData, cx, sa, which, minLength,
   1094                                 c, s, length,
   1095                                 (int32_t)UCNV_EXT_FROM_U_GET_PARTIAL_INDEX(value),
   1096                                 pErrorCode);
   1097                         } else if(extSetUseMapping(which, minLength, value)) {
   1098                             switch(filter) {
   1099                             case UCNV_SET_FILTER_2022_CN:
   1100                                 if(!(UCNV_EXT_FROM_U_GET_LENGTH(value)==3 && UCNV_EXT_FROM_U_GET_DATA(value)<=0x82ffff)) {
   1101                                     continue;
   1102                                 }
   1103                                 break;
   1104                             case UCNV_SET_FILTER_SJIS:
   1105                                 if(!(UCNV_EXT_FROM_U_GET_LENGTH(value)==2 && (value=UCNV_EXT_FROM_U_GET_DATA(value))>=0x8140 && value<=0xeffc)) {
   1106                                     continue;
   1107                                 }
   1108                                 break;
   1109                             case UCNV_SET_FILTER_GR94DBCS:
   1110                                 if(!(UCNV_EXT_FROM_U_GET_LENGTH(value)==2 &&
   1111                                      (uint16_t)((value=UCNV_EXT_FROM_U_GET_DATA(value))-0xa1a1)<=(0xfefe - 0xa1a1) &&
   1112                                      (uint8_t)(value-0xa1)<=(0xfe - 0xa1))) {
   1113                                     continue;
   1114                                 }
   1115                                 break;
   1116                             case UCNV_SET_FILTER_HZ:
   1117                                 if(!(UCNV_EXT_FROM_U_GET_LENGTH(value)==2 &&
   1118                                      (uint16_t)((value=UCNV_EXT_FROM_U_GET_DATA(value))-0xa1a1)<=(0xfdfe - 0xa1a1) &&
   1119                                      (uint8_t)(value-0xa1)<=(0xfe - 0xa1))) {
   1120                                     continue;
   1121                                 }
   1122                                 break;
   1123                             default:
   1124                                 /*
   1125                                  * UCNV_SET_FILTER_NONE,
   1126                                  * or UCNV_SET_FILTER_DBCS_ONLY which is handled via minLength
   1127                                  */
   1128                                 break;
   1129                             }
   1130                             sa->add(sa->set, c);
   1131                         }
   1132                     } while((++c&0xf)!=0);
   1133                 } else {
   1134                     c+=16; /* empty stage 3 block */
   1135                 }
   1136             }
   1137         } else {
   1138             c+=1024; /* empty stage 2 block */
   1139         }
   1140     }
   1141 }
   1142 
   1143 #endif /* #if !UCONFIG_NO_LEGACY_CONVERSION */
   1144