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      1 #include "clang/AST/CommentLexer.h"
      2 #include "clang/AST/CommentCommandTraits.h"
      3 #include "clang/AST/CommentDiagnostic.h"
      4 #include "clang/Basic/CharInfo.h"
      5 #include "llvm/ADT/StringExtras.h"
      6 #include "llvm/ADT/StringSwitch.h"
      7 #include "llvm/Support/ConvertUTF.h"
      8 #include "llvm/Support/ErrorHandling.h"
      9 
     10 namespace clang {
     11 namespace comments {
     12 
     13 void Token::dump(const Lexer &L, const SourceManager &SM) const {
     14   llvm::errs() << "comments::Token Kind=" << Kind << " ";
     15   Loc.dump(SM);
     16   llvm::errs() << " " << Length << " \"" << L.getSpelling(*this, SM) << "\"\n";
     17 }
     18 
     19 static inline bool isHTMLNamedCharacterReferenceCharacter(char C) {
     20   return isLetter(C);
     21 }
     22 
     23 static inline bool isHTMLDecimalCharacterReferenceCharacter(char C) {
     24   return isDigit(C);
     25 }
     26 
     27 static inline bool isHTMLHexCharacterReferenceCharacter(char C) {
     28   return isHexDigit(C);
     29 }
     30 
     31 static inline StringRef convertCodePointToUTF8(
     32                                       llvm::BumpPtrAllocator &Allocator,
     33                                       unsigned CodePoint) {
     34   char *Resolved = Allocator.Allocate<char>(UNI_MAX_UTF8_BYTES_PER_CODE_POINT);
     35   char *ResolvedPtr = Resolved;
     36   if (llvm::ConvertCodePointToUTF8(CodePoint, ResolvedPtr))
     37     return StringRef(Resolved, ResolvedPtr - Resolved);
     38   else
     39     return StringRef();
     40 }
     41 
     42 namespace {
     43 
     44 #include "clang/AST/CommentHTMLTags.inc"
     45 #include "clang/AST/CommentHTMLNamedCharacterReferences.inc"
     46 
     47 } // unnamed namespace
     48 
     49 StringRef Lexer::resolveHTMLNamedCharacterReference(StringRef Name) const {
     50   // Fast path, first check a few most widely used named character references.
     51   return llvm::StringSwitch<StringRef>(Name)
     52       .Case("amp", "&")
     53       .Case("lt", "<")
     54       .Case("gt", ">")
     55       .Case("quot", "\"")
     56       .Case("apos", "\'")
     57       // Slow path.
     58       .Default(translateHTMLNamedCharacterReferenceToUTF8(Name));
     59 }
     60 
     61 StringRef Lexer::resolveHTMLDecimalCharacterReference(StringRef Name) const {
     62   unsigned CodePoint = 0;
     63   for (unsigned i = 0, e = Name.size(); i != e; ++i) {
     64     assert(isHTMLDecimalCharacterReferenceCharacter(Name[i]));
     65     CodePoint *= 10;
     66     CodePoint += Name[i] - '0';
     67   }
     68   return convertCodePointToUTF8(Allocator, CodePoint);
     69 }
     70 
     71 StringRef Lexer::resolveHTMLHexCharacterReference(StringRef Name) const {
     72   unsigned CodePoint = 0;
     73   for (unsigned i = 0, e = Name.size(); i != e; ++i) {
     74     CodePoint *= 16;
     75     const char C = Name[i];
     76     assert(isHTMLHexCharacterReferenceCharacter(C));
     77     CodePoint += llvm::hexDigitValue(C);
     78   }
     79   return convertCodePointToUTF8(Allocator, CodePoint);
     80 }
     81 
     82 void Lexer::skipLineStartingDecorations() {
     83   // This function should be called only for C comments
     84   assert(CommentState == LCS_InsideCComment);
     85 
     86   if (BufferPtr == CommentEnd)
     87     return;
     88 
     89   switch (*BufferPtr) {
     90   case ' ':
     91   case '\t':
     92   case '\f':
     93   case '\v': {
     94     const char *NewBufferPtr = BufferPtr;
     95     NewBufferPtr++;
     96     if (NewBufferPtr == CommentEnd)
     97       return;
     98 
     99     char C = *NewBufferPtr;
    100     while (isHorizontalWhitespace(C)) {
    101       NewBufferPtr++;
    102       if (NewBufferPtr == CommentEnd)
    103         return;
    104       C = *NewBufferPtr;
    105     }
    106     if (C == '*')
    107       BufferPtr = NewBufferPtr + 1;
    108     break;
    109   }
    110   case '*':
    111     BufferPtr++;
    112     break;
    113   }
    114 }
    115 
    116 namespace {
    117 /// Returns pointer to the first newline character in the string.
    118 const char *findNewline(const char *BufferPtr, const char *BufferEnd) {
    119   for ( ; BufferPtr != BufferEnd; ++BufferPtr) {
    120     if (isVerticalWhitespace(*BufferPtr))
    121       return BufferPtr;
    122   }
    123   return BufferEnd;
    124 }
    125 
    126 const char *skipNewline(const char *BufferPtr, const char *BufferEnd) {
    127   if (BufferPtr == BufferEnd)
    128     return BufferPtr;
    129 
    130   if (*BufferPtr == '\n')
    131     BufferPtr++;
    132   else {
    133     assert(*BufferPtr == '\r');
    134     BufferPtr++;
    135     if (BufferPtr != BufferEnd && *BufferPtr == '\n')
    136       BufferPtr++;
    137   }
    138   return BufferPtr;
    139 }
    140 
    141 const char *skipNamedCharacterReference(const char *BufferPtr,
    142                                         const char *BufferEnd) {
    143   for ( ; BufferPtr != BufferEnd; ++BufferPtr) {
    144     if (!isHTMLNamedCharacterReferenceCharacter(*BufferPtr))
    145       return BufferPtr;
    146   }
    147   return BufferEnd;
    148 }
    149 
    150 const char *skipDecimalCharacterReference(const char *BufferPtr,
    151                                           const char *BufferEnd) {
    152   for ( ; BufferPtr != BufferEnd; ++BufferPtr) {
    153     if (!isHTMLDecimalCharacterReferenceCharacter(*BufferPtr))
    154       return BufferPtr;
    155   }
    156   return BufferEnd;
    157 }
    158 
    159 const char *skipHexCharacterReference(const char *BufferPtr,
    160                                       const char *BufferEnd) {
    161   for ( ; BufferPtr != BufferEnd; ++BufferPtr) {
    162     if (!isHTMLHexCharacterReferenceCharacter(*BufferPtr))
    163       return BufferPtr;
    164   }
    165   return BufferEnd;
    166 }
    167 
    168 bool isHTMLIdentifierStartingCharacter(char C) {
    169   return isLetter(C);
    170 }
    171 
    172 bool isHTMLIdentifierCharacter(char C) {
    173   return isAlphanumeric(C);
    174 }
    175 
    176 const char *skipHTMLIdentifier(const char *BufferPtr, const char *BufferEnd) {
    177   for ( ; BufferPtr != BufferEnd; ++BufferPtr) {
    178     if (!isHTMLIdentifierCharacter(*BufferPtr))
    179       return BufferPtr;
    180   }
    181   return BufferEnd;
    182 }
    183 
    184 /// Skip HTML string quoted in single or double quotes.  Escaping quotes inside
    185 /// string allowed.
    186 ///
    187 /// Returns pointer to closing quote.
    188 const char *skipHTMLQuotedString(const char *BufferPtr, const char *BufferEnd)
    189 {
    190   const char Quote = *BufferPtr;
    191   assert(Quote == '\"' || Quote == '\'');
    192 
    193   BufferPtr++;
    194   for ( ; BufferPtr != BufferEnd; ++BufferPtr) {
    195     const char C = *BufferPtr;
    196     if (C == Quote && BufferPtr[-1] != '\\')
    197       return BufferPtr;
    198   }
    199   return BufferEnd;
    200 }
    201 
    202 const char *skipWhitespace(const char *BufferPtr, const char *BufferEnd) {
    203   for ( ; BufferPtr != BufferEnd; ++BufferPtr) {
    204     if (!isWhitespace(*BufferPtr))
    205       return BufferPtr;
    206   }
    207   return BufferEnd;
    208 }
    209 
    210 bool isWhitespace(const char *BufferPtr, const char *BufferEnd) {
    211   return skipWhitespace(BufferPtr, BufferEnd) == BufferEnd;
    212 }
    213 
    214 bool isCommandNameStartCharacter(char C) {
    215   return isLetter(C);
    216 }
    217 
    218 bool isCommandNameCharacter(char C) {
    219   return isAlphanumeric(C);
    220 }
    221 
    222 const char *skipCommandName(const char *BufferPtr, const char *BufferEnd) {
    223   for ( ; BufferPtr != BufferEnd; ++BufferPtr) {
    224     if (!isCommandNameCharacter(*BufferPtr))
    225       return BufferPtr;
    226   }
    227   return BufferEnd;
    228 }
    229 
    230 /// Return the one past end pointer for BCPL comments.
    231 /// Handles newlines escaped with backslash or trigraph for backslahs.
    232 const char *findBCPLCommentEnd(const char *BufferPtr, const char *BufferEnd) {
    233   const char *CurPtr = BufferPtr;
    234   while (CurPtr != BufferEnd) {
    235     while (!isVerticalWhitespace(*CurPtr)) {
    236       CurPtr++;
    237       if (CurPtr == BufferEnd)
    238         return BufferEnd;
    239     }
    240     // We found a newline, check if it is escaped.
    241     const char *EscapePtr = CurPtr - 1;
    242     while(isHorizontalWhitespace(*EscapePtr))
    243       EscapePtr--;
    244 
    245     if (*EscapePtr == '\\' ||
    246         (EscapePtr - 2 >= BufferPtr && EscapePtr[0] == '/' &&
    247          EscapePtr[-1] == '?' && EscapePtr[-2] == '?')) {
    248       // We found an escaped newline.
    249       CurPtr = skipNewline(CurPtr, BufferEnd);
    250     } else
    251       return CurPtr; // Not an escaped newline.
    252   }
    253   return BufferEnd;
    254 }
    255 
    256 /// Return the one past end pointer for C comments.
    257 /// Very dumb, does not handle escaped newlines or trigraphs.
    258 const char *findCCommentEnd(const char *BufferPtr, const char *BufferEnd) {
    259   for ( ; BufferPtr != BufferEnd; ++BufferPtr) {
    260     if (*BufferPtr == '*') {
    261       assert(BufferPtr + 1 != BufferEnd);
    262       if (*(BufferPtr + 1) == '/')
    263         return BufferPtr;
    264     }
    265   }
    266   llvm_unreachable("buffer end hit before '*/' was seen");
    267 }
    268 
    269 } // unnamed namespace
    270 
    271 void Lexer::formTokenWithChars(Token &Result, const char *TokEnd,
    272                                tok::TokenKind Kind) {
    273   const unsigned TokLen = TokEnd - BufferPtr;
    274   Result.setLocation(getSourceLocation(BufferPtr));
    275   Result.setKind(Kind);
    276   Result.setLength(TokLen);
    277 #ifndef NDEBUG
    278   Result.TextPtr = "<UNSET>";
    279   Result.IntVal = 7;
    280 #endif
    281   BufferPtr = TokEnd;
    282 }
    283 
    284 void Lexer::lexCommentText(Token &T) {
    285   assert(CommentState == LCS_InsideBCPLComment ||
    286          CommentState == LCS_InsideCComment);
    287 
    288   switch (State) {
    289   case LS_Normal:
    290     break;
    291   case LS_VerbatimBlockFirstLine:
    292     lexVerbatimBlockFirstLine(T);
    293     return;
    294   case LS_VerbatimBlockBody:
    295     lexVerbatimBlockBody(T);
    296     return;
    297   case LS_VerbatimLineText:
    298     lexVerbatimLineText(T);
    299     return;
    300   case LS_HTMLStartTag:
    301     lexHTMLStartTag(T);
    302     return;
    303   case LS_HTMLEndTag:
    304     lexHTMLEndTag(T);
    305     return;
    306   }
    307 
    308   assert(State == LS_Normal);
    309 
    310   const char *TokenPtr = BufferPtr;
    311   assert(TokenPtr < CommentEnd);
    312   while (TokenPtr != CommentEnd) {
    313     switch(*TokenPtr) {
    314       case '\\':
    315       case '@': {
    316         // Commands that start with a backslash and commands that start with
    317         // 'at' have equivalent semantics.  But we keep information about the
    318         // exact syntax in AST for comments.
    319         tok::TokenKind CommandKind =
    320             (*TokenPtr == '@') ? tok::at_command : tok::backslash_command;
    321         TokenPtr++;
    322         if (TokenPtr == CommentEnd) {
    323           formTextToken(T, TokenPtr);
    324           return;
    325         }
    326         char C = *TokenPtr;
    327         switch (C) {
    328         default:
    329           break;
    330 
    331         case '\\': case '@': case '&': case '$':
    332         case '#':  case '<': case '>': case '%':
    333         case '\"': case '.': case ':':
    334           // This is one of \\ \@ \& \$ etc escape sequences.
    335           TokenPtr++;
    336           if (C == ':' && TokenPtr != CommentEnd && *TokenPtr == ':') {
    337             // This is the \:: escape sequence.
    338             TokenPtr++;
    339           }
    340           StringRef UnescapedText(BufferPtr + 1, TokenPtr - (BufferPtr + 1));
    341           formTokenWithChars(T, TokenPtr, tok::text);
    342           T.setText(UnescapedText);
    343           return;
    344         }
    345 
    346         // Don't make zero-length commands.
    347         if (!isCommandNameStartCharacter(*TokenPtr)) {
    348           formTextToken(T, TokenPtr);
    349           return;
    350         }
    351 
    352         TokenPtr = skipCommandName(TokenPtr, CommentEnd);
    353         unsigned Length = TokenPtr - (BufferPtr + 1);
    354 
    355         // Hardcoded support for lexing LaTeX formula commands
    356         // \f$ \f[ \f] \f{ \f} as a single command.
    357         if (Length == 1 && TokenPtr[-1] == 'f' && TokenPtr != CommentEnd) {
    358           C = *TokenPtr;
    359           if (C == '$' || C == '[' || C == ']' || C == '{' || C == '}') {
    360             TokenPtr++;
    361             Length++;
    362           }
    363         }
    364 
    365         const StringRef CommandName(BufferPtr + 1, Length);
    366 
    367         const CommandInfo *Info = Traits.getCommandInfoOrNULL(CommandName);
    368         if (!Info) {
    369           if ((Info = Traits.getTypoCorrectCommandInfo(CommandName))) {
    370             StringRef CorrectedName = Info->Name;
    371             SourceLocation Loc = getSourceLocation(BufferPtr);
    372             SourceRange CommandRange(Loc.getLocWithOffset(1),
    373                                      getSourceLocation(TokenPtr));
    374             Diag(Loc, diag::warn_correct_comment_command_name)
    375               << CommandName << CorrectedName
    376               << FixItHint::CreateReplacement(CommandRange, CorrectedName);
    377           } else {
    378             formTokenWithChars(T, TokenPtr, tok::unknown_command);
    379             T.setUnknownCommandName(CommandName);
    380             Diag(T.getLocation(), diag::warn_unknown_comment_command_name);
    381             return;
    382           }
    383         }
    384         if (Info->IsVerbatimBlockCommand) {
    385           setupAndLexVerbatimBlock(T, TokenPtr, *BufferPtr, Info);
    386           return;
    387         }
    388         if (Info->IsVerbatimLineCommand) {
    389           setupAndLexVerbatimLine(T, TokenPtr, Info);
    390           return;
    391         }
    392         formTokenWithChars(T, TokenPtr, CommandKind);
    393         T.setCommandID(Info->getID());
    394         return;
    395       }
    396 
    397       case '&':
    398         lexHTMLCharacterReference(T);
    399         return;
    400 
    401       case '<': {
    402         TokenPtr++;
    403         if (TokenPtr == CommentEnd) {
    404           formTextToken(T, TokenPtr);
    405           return;
    406         }
    407         const char C = *TokenPtr;
    408         if (isHTMLIdentifierStartingCharacter(C))
    409           setupAndLexHTMLStartTag(T);
    410         else if (C == '/')
    411           setupAndLexHTMLEndTag(T);
    412         else
    413           formTextToken(T, TokenPtr);
    414 
    415         return;
    416       }
    417 
    418       case '\n':
    419       case '\r':
    420         TokenPtr = skipNewline(TokenPtr, CommentEnd);
    421         formTokenWithChars(T, TokenPtr, tok::newline);
    422 
    423         if (CommentState == LCS_InsideCComment)
    424           skipLineStartingDecorations();
    425         return;
    426 
    427       default: {
    428         size_t End = StringRef(TokenPtr, CommentEnd - TokenPtr).
    429                          find_first_of("\n\r\\@&<");
    430         if (End != StringRef::npos)
    431           TokenPtr += End;
    432         else
    433           TokenPtr = CommentEnd;
    434         formTextToken(T, TokenPtr);
    435         return;
    436       }
    437     }
    438   }
    439 }
    440 
    441 void Lexer::setupAndLexVerbatimBlock(Token &T,
    442                                      const char *TextBegin,
    443                                      char Marker, const CommandInfo *Info) {
    444   assert(Info->IsVerbatimBlockCommand);
    445 
    446   VerbatimBlockEndCommandName.clear();
    447   VerbatimBlockEndCommandName.append(Marker == '\\' ? "\\" : "@");
    448   VerbatimBlockEndCommandName.append(Info->EndCommandName);
    449 
    450   formTokenWithChars(T, TextBegin, tok::verbatim_block_begin);
    451   T.setVerbatimBlockID(Info->getID());
    452 
    453   // If there is a newline following the verbatim opening command, skip the
    454   // newline so that we don't create an tok::verbatim_block_line with empty
    455   // text content.
    456   if (BufferPtr != CommentEnd &&
    457       isVerticalWhitespace(*BufferPtr)) {
    458     BufferPtr = skipNewline(BufferPtr, CommentEnd);
    459     State = LS_VerbatimBlockBody;
    460     return;
    461   }
    462 
    463   State = LS_VerbatimBlockFirstLine;
    464 }
    465 
    466 void Lexer::lexVerbatimBlockFirstLine(Token &T) {
    467 again:
    468   assert(BufferPtr < CommentEnd);
    469 
    470   // FIXME: It would be better to scan the text once, finding either the block
    471   // end command or newline.
    472   //
    473   // Extract current line.
    474   const char *Newline = findNewline(BufferPtr, CommentEnd);
    475   StringRef Line(BufferPtr, Newline - BufferPtr);
    476 
    477   // Look for end command in current line.
    478   size_t Pos = Line.find(VerbatimBlockEndCommandName);
    479   const char *TextEnd;
    480   const char *NextLine;
    481   if (Pos == StringRef::npos) {
    482     // Current line is completely verbatim.
    483     TextEnd = Newline;
    484     NextLine = skipNewline(Newline, CommentEnd);
    485   } else if (Pos == 0) {
    486     // Current line contains just an end command.
    487     const char *End = BufferPtr + VerbatimBlockEndCommandName.size();
    488     StringRef Name(BufferPtr + 1, End - (BufferPtr + 1));
    489     formTokenWithChars(T, End, tok::verbatim_block_end);
    490     T.setVerbatimBlockID(Traits.getCommandInfo(Name)->getID());
    491     State = LS_Normal;
    492     return;
    493   } else {
    494     // There is some text, followed by end command.  Extract text first.
    495     TextEnd = BufferPtr + Pos;
    496     NextLine = TextEnd;
    497     // If there is only whitespace before end command, skip whitespace.
    498     if (isWhitespace(BufferPtr, TextEnd)) {
    499       BufferPtr = TextEnd;
    500       goto again;
    501     }
    502   }
    503 
    504   StringRef Text(BufferPtr, TextEnd - BufferPtr);
    505   formTokenWithChars(T, NextLine, tok::verbatim_block_line);
    506   T.setVerbatimBlockText(Text);
    507 
    508   State = LS_VerbatimBlockBody;
    509 }
    510 
    511 void Lexer::lexVerbatimBlockBody(Token &T) {
    512   assert(State == LS_VerbatimBlockBody);
    513 
    514   if (CommentState == LCS_InsideCComment)
    515     skipLineStartingDecorations();
    516 
    517   lexVerbatimBlockFirstLine(T);
    518 }
    519 
    520 void Lexer::setupAndLexVerbatimLine(Token &T, const char *TextBegin,
    521                                     const CommandInfo *Info) {
    522   assert(Info->IsVerbatimLineCommand);
    523   formTokenWithChars(T, TextBegin, tok::verbatim_line_name);
    524   T.setVerbatimLineID(Info->getID());
    525 
    526   State = LS_VerbatimLineText;
    527 }
    528 
    529 void Lexer::lexVerbatimLineText(Token &T) {
    530   assert(State == LS_VerbatimLineText);
    531 
    532   // Extract current line.
    533   const char *Newline = findNewline(BufferPtr, CommentEnd);
    534   const StringRef Text(BufferPtr, Newline - BufferPtr);
    535   formTokenWithChars(T, Newline, tok::verbatim_line_text);
    536   T.setVerbatimLineText(Text);
    537 
    538   State = LS_Normal;
    539 }
    540 
    541 void Lexer::lexHTMLCharacterReference(Token &T) {
    542   const char *TokenPtr = BufferPtr;
    543   assert(*TokenPtr == '&');
    544   TokenPtr++;
    545   if (TokenPtr == CommentEnd) {
    546     formTextToken(T, TokenPtr);
    547     return;
    548   }
    549   const char *NamePtr;
    550   bool isNamed = false;
    551   bool isDecimal = false;
    552   char C = *TokenPtr;
    553   if (isHTMLNamedCharacterReferenceCharacter(C)) {
    554     NamePtr = TokenPtr;
    555     TokenPtr = skipNamedCharacterReference(TokenPtr, CommentEnd);
    556     isNamed = true;
    557   } else if (C == '#') {
    558     TokenPtr++;
    559     if (TokenPtr == CommentEnd) {
    560       formTextToken(T, TokenPtr);
    561       return;
    562     }
    563     C = *TokenPtr;
    564     if (isHTMLDecimalCharacterReferenceCharacter(C)) {
    565       NamePtr = TokenPtr;
    566       TokenPtr = skipDecimalCharacterReference(TokenPtr, CommentEnd);
    567       isDecimal = true;
    568     } else if (C == 'x' || C == 'X') {
    569       TokenPtr++;
    570       NamePtr = TokenPtr;
    571       TokenPtr = skipHexCharacterReference(TokenPtr, CommentEnd);
    572     } else {
    573       formTextToken(T, TokenPtr);
    574       return;
    575     }
    576   } else {
    577     formTextToken(T, TokenPtr);
    578     return;
    579   }
    580   if (NamePtr == TokenPtr || TokenPtr == CommentEnd ||
    581       *TokenPtr != ';') {
    582     formTextToken(T, TokenPtr);
    583     return;
    584   }
    585   StringRef Name(NamePtr, TokenPtr - NamePtr);
    586   TokenPtr++; // Skip semicolon.
    587   StringRef Resolved;
    588   if (isNamed)
    589     Resolved = resolveHTMLNamedCharacterReference(Name);
    590   else if (isDecimal)
    591     Resolved = resolveHTMLDecimalCharacterReference(Name);
    592   else
    593     Resolved = resolveHTMLHexCharacterReference(Name);
    594 
    595   if (Resolved.empty()) {
    596     formTextToken(T, TokenPtr);
    597     return;
    598   }
    599   formTokenWithChars(T, TokenPtr, tok::text);
    600   T.setText(Resolved);
    601   return;
    602 }
    603 
    604 void Lexer::setupAndLexHTMLStartTag(Token &T) {
    605   assert(BufferPtr[0] == '<' &&
    606          isHTMLIdentifierStartingCharacter(BufferPtr[1]));
    607   const char *TagNameEnd = skipHTMLIdentifier(BufferPtr + 2, CommentEnd);
    608   StringRef Name(BufferPtr + 1, TagNameEnd - (BufferPtr + 1));
    609   if (!isHTMLTagName(Name)) {
    610     formTextToken(T, TagNameEnd);
    611     return;
    612   }
    613 
    614   formTokenWithChars(T, TagNameEnd, tok::html_start_tag);
    615   T.setHTMLTagStartName(Name);
    616 
    617   BufferPtr = skipWhitespace(BufferPtr, CommentEnd);
    618 
    619   const char C = *BufferPtr;
    620   if (BufferPtr != CommentEnd &&
    621       (C == '>' || C == '/' || isHTMLIdentifierStartingCharacter(C)))
    622     State = LS_HTMLStartTag;
    623 }
    624 
    625 void Lexer::lexHTMLStartTag(Token &T) {
    626   assert(State == LS_HTMLStartTag);
    627 
    628   const char *TokenPtr = BufferPtr;
    629   char C = *TokenPtr;
    630   if (isHTMLIdentifierCharacter(C)) {
    631     TokenPtr = skipHTMLIdentifier(TokenPtr, CommentEnd);
    632     StringRef Ident(BufferPtr, TokenPtr - BufferPtr);
    633     formTokenWithChars(T, TokenPtr, tok::html_ident);
    634     T.setHTMLIdent(Ident);
    635   } else {
    636     switch (C) {
    637     case '=':
    638       TokenPtr++;
    639       formTokenWithChars(T, TokenPtr, tok::html_equals);
    640       break;
    641     case '\"':
    642     case '\'': {
    643       const char *OpenQuote = TokenPtr;
    644       TokenPtr = skipHTMLQuotedString(TokenPtr, CommentEnd);
    645       const char *ClosingQuote = TokenPtr;
    646       if (TokenPtr != CommentEnd) // Skip closing quote.
    647         TokenPtr++;
    648       formTokenWithChars(T, TokenPtr, tok::html_quoted_string);
    649       T.setHTMLQuotedString(StringRef(OpenQuote + 1,
    650                                       ClosingQuote - (OpenQuote + 1)));
    651       break;
    652     }
    653     case '>':
    654       TokenPtr++;
    655       formTokenWithChars(T, TokenPtr, tok::html_greater);
    656       State = LS_Normal;
    657       return;
    658     case '/':
    659       TokenPtr++;
    660       if (TokenPtr != CommentEnd && *TokenPtr == '>') {
    661         TokenPtr++;
    662         formTokenWithChars(T, TokenPtr, tok::html_slash_greater);
    663       } else
    664         formTextToken(T, TokenPtr);
    665 
    666       State = LS_Normal;
    667       return;
    668     }
    669   }
    670 
    671   // Now look ahead and return to normal state if we don't see any HTML tokens
    672   // ahead.
    673   BufferPtr = skipWhitespace(BufferPtr, CommentEnd);
    674   if (BufferPtr == CommentEnd) {
    675     State = LS_Normal;
    676     return;
    677   }
    678 
    679   C = *BufferPtr;
    680   if (!isHTMLIdentifierStartingCharacter(C) &&
    681       C != '=' && C != '\"' && C != '\'' && C != '>') {
    682     State = LS_Normal;
    683     return;
    684   }
    685 }
    686 
    687 void Lexer::setupAndLexHTMLEndTag(Token &T) {
    688   assert(BufferPtr[0] == '<' && BufferPtr[1] == '/');
    689 
    690   const char *TagNameBegin = skipWhitespace(BufferPtr + 2, CommentEnd);
    691   const char *TagNameEnd = skipHTMLIdentifier(TagNameBegin, CommentEnd);
    692   StringRef Name(TagNameBegin, TagNameEnd - TagNameBegin);
    693   if (!isHTMLTagName(Name)) {
    694     formTextToken(T, TagNameEnd);
    695     return;
    696   }
    697 
    698   const char *End = skipWhitespace(TagNameEnd, CommentEnd);
    699 
    700   formTokenWithChars(T, End, tok::html_end_tag);
    701   T.setHTMLTagEndName(Name);
    702 
    703   if (BufferPtr != CommentEnd && *BufferPtr == '>')
    704     State = LS_HTMLEndTag;
    705 }
    706 
    707 void Lexer::lexHTMLEndTag(Token &T) {
    708   assert(BufferPtr != CommentEnd && *BufferPtr == '>');
    709 
    710   formTokenWithChars(T, BufferPtr + 1, tok::html_greater);
    711   State = LS_Normal;
    712 }
    713 
    714 Lexer::Lexer(llvm::BumpPtrAllocator &Allocator, DiagnosticsEngine &Diags,
    715              const CommandTraits &Traits,
    716              SourceLocation FileLoc,
    717              const char *BufferStart, const char *BufferEnd):
    718     Allocator(Allocator), Diags(Diags), Traits(Traits),
    719     BufferStart(BufferStart), BufferEnd(BufferEnd),
    720     FileLoc(FileLoc), BufferPtr(BufferStart),
    721     CommentState(LCS_BeforeComment), State(LS_Normal) {
    722 }
    723 
    724 void Lexer::lex(Token &T) {
    725 again:
    726   switch (CommentState) {
    727   case LCS_BeforeComment:
    728     if (BufferPtr == BufferEnd) {
    729       formTokenWithChars(T, BufferPtr, tok::eof);
    730       return;
    731     }
    732 
    733     assert(*BufferPtr == '/');
    734     BufferPtr++; // Skip first slash.
    735     switch(*BufferPtr) {
    736     case '/': { // BCPL comment.
    737       BufferPtr++; // Skip second slash.
    738 
    739       if (BufferPtr != BufferEnd) {
    740         // Skip Doxygen magic marker, if it is present.
    741         // It might be missing because of a typo //< or /*<, or because we
    742         // merged this non-Doxygen comment into a bunch of Doxygen comments
    743         // around it: /** ... */ /* ... */ /** ... */
    744         const char C = *BufferPtr;
    745         if (C == '/' || C == '!')
    746           BufferPtr++;
    747       }
    748 
    749       // Skip less-than symbol that marks trailing comments.
    750       // Skip it even if the comment is not a Doxygen one, because //< and /*<
    751       // are frequent typos.
    752       if (BufferPtr != BufferEnd && *BufferPtr == '<')
    753         BufferPtr++;
    754 
    755       CommentState = LCS_InsideBCPLComment;
    756       if (State != LS_VerbatimBlockBody && State != LS_VerbatimBlockFirstLine)
    757         State = LS_Normal;
    758       CommentEnd = findBCPLCommentEnd(BufferPtr, BufferEnd);
    759       goto again;
    760     }
    761     case '*': { // C comment.
    762       BufferPtr++; // Skip star.
    763 
    764       // Skip Doxygen magic marker.
    765       const char C = *BufferPtr;
    766       if ((C == '*' && *(BufferPtr + 1) != '/') || C == '!')
    767         BufferPtr++;
    768 
    769       // Skip less-than symbol that marks trailing comments.
    770       if (BufferPtr != BufferEnd && *BufferPtr == '<')
    771         BufferPtr++;
    772 
    773       CommentState = LCS_InsideCComment;
    774       State = LS_Normal;
    775       CommentEnd = findCCommentEnd(BufferPtr, BufferEnd);
    776       goto again;
    777     }
    778     default:
    779       llvm_unreachable("second character of comment should be '/' or '*'");
    780     }
    781 
    782   case LCS_BetweenComments: {
    783     // Consecutive comments are extracted only if there is only whitespace
    784     // between them.  So we can search for the start of the next comment.
    785     const char *EndWhitespace = BufferPtr;
    786     while(EndWhitespace != BufferEnd && *EndWhitespace != '/')
    787       EndWhitespace++;
    788 
    789     // Turn any whitespace between comments (and there is only whitespace
    790     // between them -- guaranteed by comment extraction) into a newline.  We
    791     // have two newlines between C comments in total (first one was synthesized
    792     // after a comment).
    793     formTokenWithChars(T, EndWhitespace, tok::newline);
    794 
    795     CommentState = LCS_BeforeComment;
    796     break;
    797   }
    798 
    799   case LCS_InsideBCPLComment:
    800   case LCS_InsideCComment:
    801     if (BufferPtr != CommentEnd) {
    802       lexCommentText(T);
    803       break;
    804     } else {
    805       // Skip C comment closing sequence.
    806       if (CommentState == LCS_InsideCComment) {
    807         assert(BufferPtr[0] == '*' && BufferPtr[1] == '/');
    808         BufferPtr += 2;
    809         assert(BufferPtr <= BufferEnd);
    810 
    811         // Synthenize newline just after the C comment, regardless if there is
    812         // actually a newline.
    813         formTokenWithChars(T, BufferPtr, tok::newline);
    814 
    815         CommentState = LCS_BetweenComments;
    816         break;
    817       } else {
    818         // Don't synthesized a newline after BCPL comment.
    819         CommentState = LCS_BetweenComments;
    820         goto again;
    821       }
    822     }
    823   }
    824 }
    825 
    826 StringRef Lexer::getSpelling(const Token &Tok,
    827                              const SourceManager &SourceMgr,
    828                              bool *Invalid) const {
    829   SourceLocation Loc = Tok.getLocation();
    830   std::pair<FileID, unsigned> LocInfo = SourceMgr.getDecomposedLoc(Loc);
    831 
    832   bool InvalidTemp = false;
    833   StringRef File = SourceMgr.getBufferData(LocInfo.first, &InvalidTemp);
    834   if (InvalidTemp) {
    835     *Invalid = true;
    836     return StringRef();
    837   }
    838 
    839   const char *Begin = File.data() + LocInfo.second;
    840   return StringRef(Begin, Tok.getLength());
    841 }
    842 
    843 } // end namespace comments
    844 } // end namespace clang
    845 
    846