1 /*

     2  * Copyright 2001-2004 Unicode, Inc.

     3  *

     4  * Disclaimer

     5  *

     6  * This source code is provided as is by Unicode, Inc. No claims are

     7  * made as to fitness for any particular purpose. No warranties of any

     8  * kind are expressed or implied. The recipient agrees to determine

     9  * applicability of information provided. If this file has been

    10  * purchased on magnetic or optical media from Unicode, Inc., the

    11  * sole remedy for any claim will be exchange of defective media

    12  * within 90 days of receipt.

    13  *

    14  * Limitations on Rights to Redistribute This Code

    15  *

    16  * Unicode, Inc. hereby grants the right to freely use the information

    17  * supplied in this file in the creation of products supporting the

    18  * Unicode Standard, and to make copies of this file in any form

    19  * for internal or external distribution as long as this notice

    20  * remains attached.

    21  */

    22 

    23 /* ---------------------------------------------------------------------

    24 

    25     Conversions between UTF32, UTF-16, and UTF-8. Source code file.

    26     Author: Mark E. Davis, 1994.

    27     Rev History: Rick McGowan, fixes & updates May 2001.

    28     Sept 2001: fixed const & error conditions per

    29     mods suggested by S. Parent & A. Lillich.

    30     June 2002: Tim Dodd added detection and handling of incomplete

    31     source sequences, enhanced error detection, added casts

    32     to eliminate compiler warnings.

    33     July 2003: slight mods to back out aggressive FFFE detection.

    34     Jan 2004: updated switches in from-UTF8 conversions.

    35     Oct 2004: updated to use UNI_MAX_LEGAL_UTF32 in UTF-32 conversions.

    36 

    37     See the header file "ConvertUTF.h" for complete documentation.

    38 

    39 ------------------------------------------------------------------------ */

    40 

    41 

    42 #include "convertutf.h"

    43 #ifdef CVTUTF_DEBUG

    44 #include <stdio.h>

    45 #endif

    46 

    47 static const int halfShift  = 10; /* used for shifting by 10 bits */

    48 

    49 static const UTF32 halfBase = 0x0010000UL;

    50 static const UTF32 halfMask = 0x3FFUL;

    51 

    52 #define UNI_SUR_HIGH_START  (UTF32)0xD800

    53 #define UNI_SUR_HIGH_END    (UTF32)0xDBFF

    54 #define UNI_SUR_LOW_START   (UTF32)0xDC00

    55 #define UNI_SUR_LOW_END     (UTF32)0xDFFF

    56 #define false      0

    57 #define true        1

    58 

    59 /* --------------------------------------------------------------------- */

    60 

    61 ConversionResult ConvertUTF32toUTF16(

    62     const UTF32** sourceStart, const UTF32* sourceEnd,

    63     UTF16** targetStart, UTF16* targetEnd, ConversionFlags flags)

    64 {

    65     ConversionResult result = conversionOK;

    66     const UTF32* source = *sourceStart;

    67     UTF16* target = *targetStart;

    68     while (source < sourceEnd)

    69     {

    70         UTF32 ch;

    71         if (target >= targetEnd)

    72         {

    73             result = targetExhausted;

    74             break;

    75         }

    76         ch = *source++;

    77         if (ch <= UNI_MAX_BMP)   /* Target is a character <= 0xFFFF */

    78         {

    79             /* UTF-16 surrogate values are illegal in UTF-32; 0xffff or 0xfffe are both reserved values */

    80             if (ch >= UNI_SUR_HIGH_START && ch <= UNI_SUR_LOW_END)

    81             {

    82                 if (flags == strictConversion)

    83                 {

    84                     --source; /* return to the illegal value itself */

    85                     result = sourceIllegal;

    86                     break;

    87                 }

    88                 else

    89                 {

    90                     *target++ = UNI_REPLACEMENT_CHAR;

    91                 }

    92             }

    93             else

    94             {

    95                 *target++ = (UTF16)ch; /* normal case */

    96             }

    97         }

    98         else if (ch > UNI_MAX_LEGAL_UTF32)

    99         {

   100             if (flags == strictConversion)

   101             {

   102                 result = sourceIllegal;

   103             }

   104             else

   105             {

   106                 *target++ = UNI_REPLACEMENT_CHAR;

   107             }

   108         }

   109         else

   110         {

   111             /* target is a character in range 0xFFFF - 0x10FFFF. */

   112             if (target + 1 >= targetEnd)

   113             {

   114                 --source; /* Back up source pointer! */

   115                 result = targetExhausted;

   116                 break;

   117             }

   118             ch -= halfBase;

   119             *target++ = (UTF16)((ch >> halfShift) + UNI_SUR_HIGH_START);

   120             *target++ = (UTF16)((ch & halfMask) + UNI_SUR_LOW_START);

   121         }

   122     }

   123     *sourceStart = source;

   124     *targetStart = target;

   125     return result;

   126 }

   127 

   128 /* --------------------------------------------------------------------- */

   129 

   130 ConversionResult ConvertUTF16toUTF32(

   131     const UTF16** sourceStart, const UTF16* sourceEnd,

   132     UTF32** targetStart, UTF32* targetEnd, ConversionFlags flags)

   133 {

   134     ConversionResult result = conversionOK;

   135     const UTF16* source = *sourceStart;

   136     UTF32* target = *targetStart;

   137     UTF32 ch, ch2;

   138     while (source < sourceEnd)

   139     {

   140         const UTF16* oldSource = source; /*  In case we have to back up because of target overflow. */

   141         ch = *source++;

   142         /* If we have a surrogate pair, convert to UTF32 first. */

   143         if (ch >= UNI_SUR_HIGH_START && ch <= UNI_SUR_HIGH_END)

   144         {

   145             /* If the 16 bits following the high surrogate are in the source buffer... */

   146             if (source < sourceEnd)

   147             {

   148                 ch2 = *source;

   149                 /* If it's a low surrogate, convert to UTF32. */

   150                 if (ch2 >= UNI_SUR_LOW_START && ch2 <= UNI_SUR_LOW_END)

   151                 {

   152                     ch = ((ch - UNI_SUR_HIGH_START) << halfShift)

   153                          + (ch2 - UNI_SUR_LOW_START) + halfBase;

   154                     ++source;

   155                 }

   156                 else if (flags == strictConversion)   /* it's an unpaired high surrogate */

   157                 {

   158                     --source; /* return to the illegal value itself */

   159                     result = sourceIllegal;

   160                     break;

   161                 }

   162             }

   163             else   /* We don't have the 16 bits following the high surrogate. */

   164             {

   165                 --source; /* return to the high surrogate */

   166                 result = sourceExhausted;

   167                 break;

   168             }

   169         }

   170         else if (flags == strictConversion)

   171         {

   172             /* UTF-16 surrogate values are illegal in UTF-32 */

   173             if (ch >= UNI_SUR_LOW_START && ch <= UNI_SUR_LOW_END)

   174             {

   175                 --source; /* return to the illegal value itself */

   176                 result = sourceIllegal;

   177                 break;

   178             }

   179         }

   180         if (target >= targetEnd)

   181         {

   182             source = oldSource; /* Back up source pointer! */

   183             result = targetExhausted;

   184             break;

   185         }

   186         *target++ = ch;

   187     }

   188     *sourceStart = source;

   189     *targetStart = target;

   190 #ifdef CVTUTF_DEBUG

   191     if (result == sourceIllegal)

   192     {

   193         fprintf(stderr, "ConvertUTF16toUTF32 illegal seq 0x%04x,%04x\n", ch, ch2);

   194         fflush(stderr);

   195     }

   196 #endif

   197     return result;

   198 }

   199 

   200 /* --------------------------------------------------------------------- */

   201 

   202 /*

   203  * Index into the table below with the first byte of a UTF-8 sequence to

   204  * get the number of trailing bytes that are supposed to follow it.

   205  * Note that *legal* UTF-8 values can't have 4 or 5-bytes. The table is

   206  * left as-is for anyone who may want to do such conversion, which was

   207  * allowed in earlier algorithms.

   208  */

   209 static const char trailingBytesForUTF8[256] =

   210 {

   211     0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,

   212     0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,

   213     0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,

   214     0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,

   215     0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,

   216     0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,

   217     1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,

   218     2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2, 3,3,3,3,3,3,3,3,4,4,4,4,5,5,5,5

   219 };

   220 

   221 /*

   222  * Magic values subtracted from a buffer value during UTF8 conversion.

   223  * This table contains as many values as there might be trailing bytes

   224  * in a UTF-8 sequence.

   225  */

   226 static const UTF32 offsetsFromUTF8[6] = { 0x00000000UL, 0x00003080UL, 0x000E2080UL,

   227                                         0x03C82080UL, 0xFA082080UL, 0x82082080UL

   228                                         };

   229 

   230 /*

   231  * Once the bits are split out into bytes of UTF-8, this is a mask OR-ed

   232  * into the first byte, depending on how many bytes follow.  There are

   233  * as many entries in this table as there are UTF-8 sequence types.

   234  * (I.e., one byte sequence, two byte... etc.). Remember that sequencs

   235  * for *legal* UTF-8 will be 4 or fewer bytes total.

   236  */

   237 static const UTF8 firstByteMark[7] = { 0x00, 0x00, 0xC0, 0xE0, 0xF0, 0xF8, 0xFC };

   238 

   239 /* --------------------------------------------------------------------- */

   240 

   241 /* The interface converts a whole buffer to avoid function-call overhead.

   242  * Constants have been gathered. Loops & conditionals have been removed as

   243  * much as possible for efficiency, in favor of drop-through switches.

   244  * (See "Note A" at the bottom of the file for equivalent code.)

   245  * If your compiler supports it, the "isLegalUTF8" call can be turned

   246  * into an inline function.

   247  */

   248 

   249 /* --------------------------------------------------------------------- */

   250 

   251 ConversionResult ConvertUTF16toUTF8(

   252     const UTF16** sourceStart, const UTF16* sourceEnd,

   253     UTF8** targetStart, UTF8* targetEnd, ConversionFlags flags)

   254 {

   255     ConversionResult result = conversionOK;

   256     const UTF16* source = *sourceStart;

   257     UTF8* target = *targetStart;

   258     while (source < sourceEnd)

   259     {

   260         UTF32 ch;

   261         unsigned short bytesToWrite = 0;

   262         const UTF32 byteMask = 0xBF;

   263         const UTF32 byteMark = 0x80;

   264         const UTF16* oldSource = source; /* In case we have to back up because of target overflow. */

   265         ch = *source++;

   266         /* If we have a surrogate pair, convert to UTF32 first. */

   267         if (ch >= UNI_SUR_HIGH_START && ch <= UNI_SUR_HIGH_END)

   268         {

   269             /* If the 16 bits following the high surrogate are in the source buffer... */

   270             if (source < sourceEnd)

   271             {

   272                 UTF32 ch2 = *source;

   273                 /* If it's a low surrogate, convert to UTF32. */

   274                 if (ch2 >= UNI_SUR_LOW_START && ch2 <= UNI_SUR_LOW_END)

   275                 {

   276                     ch = ((ch - UNI_SUR_HIGH_START) << halfShift)

   277                          + (ch2 - UNI_SUR_LOW_START) + halfBase;

   278                     ++source;

   279                 }

   280                 else if (flags == strictConversion)   /* it's an unpaired high surrogate */

   281                 {

   282                     --source; /* return to the illegal value itself */

   283                     result = sourceIllegal;

   284                     break;

   285                 }

   286             }

   287             else   /* We don't have the 16 bits following the high surrogate. */

   288             {

   289                 --source; /* return to the high surrogate */

   290                 result = sourceExhausted;

   291                 break;

   292             }

   293         }

   294         else if (flags == strictConversion)

   295         {

   296             /* UTF-16 surrogate values are illegal in UTF-32 */

   297             if (ch >= UNI_SUR_LOW_START && ch <= UNI_SUR_LOW_END)

   298             {

   299                 --source; /* return to the illegal value itself */

   300                 result = sourceIllegal;

   301                 break;

   302             }

   303         }

   304         /* Figure out how many bytes the result will require */

   305         if (ch < (UTF32)0x80)

   306         {

   307             bytesToWrite = 1;

   308         }

   309         else if (ch < (UTF32)0x800)

   310         {

   311             bytesToWrite = 2;

   312         }

   313         else if (ch < (UTF32)0x10000)

   314         {

   315             bytesToWrite = 3;

   316         }

   317         else if (ch < (UTF32)0x110000)

   318         {

   319             bytesToWrite = 4;

   320         }

   321         else

   322         {

   323             bytesToWrite = 3;

   324             ch = UNI_REPLACEMENT_CHAR;

   325         }

   326 

   327         target += bytesToWrite;

   328         if (target > targetEnd)

   329         {

   330             source = oldSource; /* Back up source pointer! */

   331             target -= bytesToWrite;

   332             result = targetExhausted;

   333             break;

   334         }

   335         switch (bytesToWrite)   /* note: everything falls through. */

   336         {

   337         case 4:

   338             *--target = (UTF8)((ch | byteMark) & byteMask);

   339             ch >>= 6;

   340         case 3:

   341             *--target = (UTF8)((ch | byteMark) & byteMask);

   342             ch >>= 6;

   343         case 2:

   344             *--target = (UTF8)((ch | byteMark) & byteMask);

   345             ch >>= 6;

   346         case 1:

   347             *--target = (UTF8)(ch | firstByteMark[bytesToWrite]);

   348         }

   349         target += bytesToWrite;

   350     }

   351     *sourceStart = source;

   352     *targetStart = target;

   353     return result;

   354 }

   355 

   356 /* --------------------------------------------------------------------- */

   357 

   358 /*

   359  * Utility routine to tell whether a sequence of bytes is legal UTF-8.

   360  * This must be called with the length pre-determined by the first byte.

   361  * If not calling this from ConvertUTF8to*, then the length can be set by:

   362  *  length = trailingBytesForUTF8[*source]+1;

   363  * and the sequence is illegal right away if there aren't that many bytes

   364  * available.

   365  * If presented with a length > 4, this returns false.  The Unicode

   366  * definition of UTF-8 goes up to 4-byte sequences.

   367  */

   368 

   369 static Boolean isLegalUTF8(const UTF8 *source, int length)

   370 {

   371     UTF8 a;

   372     const UTF8 *srcptr = source+length;

   373     switch (length)

   374     {

   375     default:

   376         return false;

   377         /* Everything else falls through when "true"... */

   378     case 4:

   379         if ((a = (*--srcptr)) < 0x80 || a > 0xBF) return false;

   380     case 3:

   381         if ((a = (*--srcptr)) < 0x80 || a > 0xBF) return false;

   382     case 2:

   383         if ((a = (*--srcptr)) > 0xBF) return false;

   384 

   385         switch (*source)

   386         {

   387             /* no fall-through in this inner switch */

   388         case 0xE0:

   389             if (a < 0xA0) return false;

   390             break;

   391         case 0xED:

   392             if (a > 0x9F) return false;

   393             break;

   394         case 0xF0:

   395             if (a < 0x90) return false;

   396             break;

   397         case 0xF4:

   398             if (a > 0x8F) return false;

   399             break;

   400         default:

   401             if (a < 0x80) return false;

   402         }

   403 

   404     case 1:

   405         if (*source >= 0x80 && *source < 0xC2) return false;

   406     }

   407     if (*source > 0xF4) return false;

   408     return true;

   409 }

   410 

   411 /* --------------------------------------------------------------------- */

   412 

   413 /*

   414  * Exported function to return whether a UTF-8 sequence is legal or not.

   415  * This is not used here; it's just exported.

   416  */

   417 Boolean isLegalUTF8Sequence(const UTF8 *source, const UTF8 *sourceEnd)

   418 {

   419     int length = trailingBytesForUTF8[*source]+1;

   420     if (source+length > sourceEnd)

   421     {

   422         return false;

   423     }

   424     return isLegalUTF8(source, length);

   425 }

   426 

   427 /* --------------------------------------------------------------------- */

   428 

   429 ConversionResult ConvertUTF8toUTF16(

   430     const UTF8** sourceStart, const UTF8* sourceEnd,

   431     UTF16** targetStart, UTF16* targetEnd, ConversionFlags flags)

   432 {

   433     ConversionResult result = conversionOK;

   434     const UTF8* source = *sourceStart;

   435     UTF16* target = *targetStart;

   436     while (source < sourceEnd)

   437     {

   438         UTF32 ch = 0;

   439         unsigned short extraBytesToRead = trailingBytesForUTF8[*source];

   440         if (source + extraBytesToRead >= sourceEnd)

   441         {

   442             result = sourceExhausted;

   443             break;

   444         }

   445         /* Do this check whether lenient or strict */

   446         if (! isLegalUTF8(source, extraBytesToRead+1))

   447         {

   448             result = sourceIllegal;

   449             break;

   450         }

   451         /*

   452          * The cases all fall through. See "Note A" below.

   453          */

   454         switch (extraBytesToRead)

   455         {

   456         case 5:

   457             ch += *source++;

   458             ch <<= 6; /* remember, illegal UTF-8 */

   459         case 4:

   460             ch += *source++;

   461             ch <<= 6; /* remember, illegal UTF-8 */

   462         case 3:

   463             ch += *source++;

   464             ch <<= 6;

   465         case 2:

   466             ch += *source++;

   467             ch <<= 6;

   468         case 1:

   469             ch += *source++;

   470             ch <<= 6;

   471         case 0:

   472             ch += *source++;

   473         }

   474         ch -= offsetsFromUTF8[extraBytesToRead];

   475 

   476         if (target >= targetEnd)

   477         {

   478             source -= (extraBytesToRead+1); /* Back up source pointer! */

   479             result = targetExhausted;

   480             break;

   481         }

   482         if (ch <= UNI_MAX_BMP)   /* Target is a character <= 0xFFFF */

   483         {

   484             /* UTF-16 surrogate values are illegal in UTF-32 */

   485             if (ch >= UNI_SUR_HIGH_START && ch <= UNI_SUR_LOW_END)

   486             {

   487                 if (flags == strictConversion)

   488                 {

   489                     source -= (extraBytesToRead+1); /* return to the illegal value itself */

   490                     result = sourceIllegal;

   491                     break;

   492                 }

   493                 else

   494                 {

   495                     *target++ = UNI_REPLACEMENT_CHAR;

   496                 }

   497             }

   498             else

   499             {

   500                 *target++ = (UTF16)ch; /* normal case */

   501             }

   502         }

   503         else if (ch > UNI_MAX_UTF16)

   504         {

   505             if (flags == strictConversion)

   506             {

   507                 result = sourceIllegal;

   508                 source -= (extraBytesToRead+1); /* return to the start */

   509                 break; /* Bail out; shouldn't continue */

   510             }

   511             else

   512             {

   513                 *target++ = UNI_REPLACEMENT_CHAR;

   514             }

   515         }

   516         else

   517         {

   518             /* target is a character in range 0xFFFF - 0x10FFFF. */

   519             if (target + 1 >= targetEnd)

   520             {

   521                 source -= (extraBytesToRead+1); /* Back up source pointer! */

   522                 result = targetExhausted;

   523                 break;

   524             }

   525             ch -= halfBase;

   526             *target++ = (UTF16)((ch >> halfShift) + UNI_SUR_HIGH_START);

   527             *target++ = (UTF16)((ch & halfMask) + UNI_SUR_LOW_START);

   528         }

   529     }

   530     *sourceStart = source;

   531     *targetStart = target;

   532     return result;

   533 }

   534 

   535 /* --------------------------------------------------------------------- */

   536 

   537 ConversionResult ConvertUTF32toUTF8(

   538     const UTF32** sourceStart, const UTF32* sourceEnd,

   539     UTF8** targetStart, UTF8* targetEnd, ConversionFlags flags)

   540 {

   541     ConversionResult result = conversionOK;

   542     const UTF32* source = *sourceStart;

   543     UTF8* target = *targetStart;

   544     while (source < sourceEnd)

   545     {

   546         UTF32 ch;

   547         unsigned short bytesToWrite = 0;

   548         const UTF32 byteMask = 0xBF;

   549         const UTF32 byteMark = 0x80;

   550         ch = *source++;

   551         if (flags == strictConversion)

   552         {

   553             /* UTF-16 surrogate values are illegal in UTF-32 */

   554             if (ch >= UNI_SUR_HIGH_START && ch <= UNI_SUR_LOW_END)

   555             {

   556                 --source; /* return to the illegal value itself */

   557                 result = sourceIllegal;

   558                 break;

   559             }

   560         }

   561         /*

   562          * Figure out how many bytes the result will require. Turn any

   563          * illegally large UTF32 things (> Plane 17) into replacement chars.

   564          */

   565         if (ch < (UTF32)0x80)

   566         {

   567             bytesToWrite = 1;

   568         }

   569         else if (ch < (UTF32)0x800)

   570         {

   571             bytesToWrite = 2;

   572         }

   573         else if (ch < (UTF32)0x10000)

   574         {

   575             bytesToWrite = 3;

   576         }

   577         else if (ch <= UNI_MAX_LEGAL_UTF32)

   578         {

   579             bytesToWrite = 4;

   580         }

   581         else

   582         {

   583             bytesToWrite = 3;

   584             ch = UNI_REPLACEMENT_CHAR;

   585             result = sourceIllegal;

   586         }

   587 

   588         target += bytesToWrite;

   589         if (target > targetEnd)

   590         {

   591             --source; /* Back up source pointer! */

   592             target -= bytesToWrite;

   593             result = targetExhausted;

   594             break;

   595         }

   596         switch (bytesToWrite)   /* note: everything falls through. */

   597         {

   598         case 4:

   599             *--target = (UTF8)((ch | byteMark) & byteMask);

   600             ch >>= 6;

   601         case 3:

   602             *--target = (UTF8)((ch | byteMark) & byteMask);

   603             ch >>= 6;

   604         case 2:

   605             *--target = (UTF8)((ch | byteMark) & byteMask);

   606             ch >>= 6;

   607         case 1:

   608             *--target = (UTF8)(ch | firstByteMark[bytesToWrite]);

   609         }

   610         target += bytesToWrite;

   611     }

   612     *sourceStart = source;

   613     *targetStart = target;

   614     return result;

   615 }

   616 

   617 /* --------------------------------------------------------------------- */

   618 

   619 ConversionResult ConvertUTF8toUTF32(

   620     const UTF8** sourceStart, const UTF8* sourceEnd,

   621     UTF32** targetStart, UTF32* targetEnd, ConversionFlags flags)

   622 {

   623     ConversionResult result = conversionOK;

   624     const UTF8* source = *sourceStart;

   625     UTF32* target = *targetStart;

   626     while (source < sourceEnd)

   627     {

   628         UTF32 ch = 0;

   629         unsigned short extraBytesToRead = trailingBytesForUTF8[*source];

   630         if (source + extraBytesToRead >= sourceEnd)

   631         {

   632             result = sourceExhausted;

   633             break;

   634         }

   635         /* Do this check whether lenient or strict */

   636         if (! isLegalUTF8(source, extraBytesToRead+1))

   637         {

   638             result = sourceIllegal;

   639             break;

   640         }

   641         /*

   642          * The cases all fall through. See "Note A" below.

   643          */

   644         switch (extraBytesToRead)

   645         {

   646         case 5:

   647             ch += *source++;

   648             ch <<= 6;

   649         case 4:

   650             ch += *source++;

   651             ch <<= 6;

   652         case 3:

   653             ch += *source++;

   654             ch <<= 6;

   655         case 2:

   656             ch += *source++;

   657             ch <<= 6;

   658         case 1:

   659             ch += *source++;

   660             ch <<= 6;

   661         case 0:

   662             ch += *source++;

   663         }

   664         ch -= offsetsFromUTF8[extraBytesToRead];

   665 

   666         if (target >= targetEnd)

   667         {

   668             source -= (extraBytesToRead+1); /* Back up the source pointer! */

   669             result = targetExhausted;

   670             break;

   671         }

   672         if (ch <= UNI_MAX_LEGAL_UTF32)

   673         {

   674             /*

   675              * UTF-16 surrogate values are illegal in UTF-32, and anything

   676              * over Plane 17 (> 0x10FFFF) is illegal.

   677              */

   678             if (ch >= UNI_SUR_HIGH_START && ch <= UNI_SUR_LOW_END)

   679             {

   680                 if (flags == strictConversion)

   681                 {

   682                     source -= (extraBytesToRead+1); /* return to the illegal value itself */

   683                     result = sourceIllegal;

   684                     break;

   685                 }

   686                 else

   687                 {

   688                     *target++ = UNI_REPLACEMENT_CHAR;

   689                 }

   690             }

   691             else

   692             {

   693                 *target++ = ch;

   694             }

   695         }

   696         else   /* i.e., ch > UNI_MAX_LEGAL_UTF32 */

   697         {

   698             result = sourceIllegal;

   699             *target++ = UNI_REPLACEMENT_CHAR;

   700         }

   701     }

   702     *sourceStart = source;

   703     *targetStart = target;

   704     return result;

   705 }

   706 

   707 /* ---------------------------------------------------------------------

   708 

   709     Note A.

   710     The fall-through switches in UTF-8 reading code save a

   711     temp variable, some decrements & conditionals.  The switches

   712     are equivalent to the following loop:

   713     {

   714         int tmpBytesToRead = extraBytesToRead+1;

   715         do {

   716         ch += *source++;

   717         --tmpBytesToRead;

   718         if (tmpBytesToRead) ch <<= 6;

   719         } while (tmpBytesToRead > 0);

   720     }

   721     In UTF-8 writing code, the switches on "bytesToWrite" are

   722     similarly unrolled loops.

   723 

   724    --------------------------------------------------------------------- */