Home | History | Annotate | Download | only in Support 
      1 //===--- YAMLParser.cpp - Simple YAML parser ------------------------------===//
      2 //
      3 //                     The LLVM Compiler Infrastructure
      4 //
      5 // This file is distributed under the University of Illinois Open Source
      6 // License. See LICENSE.TXT for details.
      7 //
      8 //===----------------------------------------------------------------------===//
      9 //
     10 //  This file implements a YAML parser.
     11 //
     12 //===----------------------------------------------------------------------===//
     13 
     14 #include "llvm/Support/YAMLParser.h"
     15 #include "llvm/ADT/SmallVector.h"
     16 #include "llvm/ADT/StringExtras.h"
     17 #include "llvm/ADT/Twine.h"
     18 #include "llvm/ADT/ilist.h"
     19 #include "llvm/ADT/ilist_node.h"
     20 #include "llvm/Support/ErrorHandling.h"
     21 #include "llvm/Support/MemoryBuffer.h"
     22 #include "llvm/Support/SourceMgr.h"
     23 #include "llvm/Support/raw_ostream.h"
     24 
     25 using namespace llvm;
     26 using namespace yaml;
     27 
     28 enum UnicodeEncodingForm {
     29   UEF_UTF32_LE, ///< UTF-32 Little Endian
     30   UEF_UTF32_BE, ///< UTF-32 Big Endian
     31   UEF_UTF16_LE, ///< UTF-16 Little Endian
     32   UEF_UTF16_BE, ///< UTF-16 Big Endian
     33   UEF_UTF8,     ///< UTF-8 or ascii.
     34   UEF_Unknown   ///< Not a valid Unicode encoding.
     35 };
     36 
     37 /// EncodingInfo - Holds the encoding type and length of the byte order mark if
     38 ///                it exists. Length is in {0, 2, 3, 4}.
     39 typedef std::pair<UnicodeEncodingForm, unsigned> EncodingInfo;
     40 
     41 /// getUnicodeEncoding - Reads up to the first 4 bytes to determine the Unicode
     42 ///                      encoding form of \a Input.
     43 ///
     44 /// @param Input A string of length 0 or more.
     45 /// @returns An EncodingInfo indicating the Unicode encoding form of the input
     46 ///          and how long the byte order mark is if one exists.
     47 static EncodingInfo getUnicodeEncoding(StringRef Input) {
     48   if (Input.size() == 0)
     49     return std::make_pair(UEF_Unknown, 0);
     50 
     51   switch (uint8_t(Input[0])) {
     52   case 0x00:
     53     if (Input.size() >= 4) {
     54       if (  Input[1] == 0
     55          && uint8_t(Input[2]) == 0xFE
     56          && uint8_t(Input[3]) == 0xFF)
     57         return std::make_pair(UEF_UTF32_BE, 4);
     58       if (Input[1] == 0 && Input[2] == 0 && Input[3] != 0)
     59         return std::make_pair(UEF_UTF32_BE, 0);
     60     }
     61 
     62     if (Input.size() >= 2 && Input[1] != 0)
     63       return std::make_pair(UEF_UTF16_BE, 0);
     64     return std::make_pair(UEF_Unknown, 0);
     65   case 0xFF:
     66     if (  Input.size() >= 4
     67        && uint8_t(Input[1]) == 0xFE
     68        && Input[2] == 0
     69        && Input[3] == 0)
     70       return std::make_pair(UEF_UTF32_LE, 4);
     71 
     72     if (Input.size() >= 2 && uint8_t(Input[1]) == 0xFE)
     73       return std::make_pair(UEF_UTF16_LE, 2);
     74     return std::make_pair(UEF_Unknown, 0);
     75   case 0xFE:
     76     if (Input.size() >= 2 && uint8_t(Input[1]) == 0xFF)
     77       return std::make_pair(UEF_UTF16_BE, 2);
     78     return std::make_pair(UEF_Unknown, 0);
     79   case 0xEF:
     80     if (  Input.size() >= 3
     81        && uint8_t(Input[1]) == 0xBB
     82        && uint8_t(Input[2]) == 0xBF)
     83       return std::make_pair(UEF_UTF8, 3);
     84     return std::make_pair(UEF_Unknown, 0);
     85   }
     86 
     87   // It could still be utf-32 or utf-16.
     88   if (Input.size() >= 4 && Input[1] == 0 && Input[2] == 0 && Input[3] == 0)
     89     return std::make_pair(UEF_UTF32_LE, 0);
     90 
     91   if (Input.size() >= 2 && Input[1] == 0)
     92     return std::make_pair(UEF_UTF16_LE, 0);
     93 
     94   return std::make_pair(UEF_UTF8, 0);
     95 }
     96 
     97 namespace llvm {
     98 namespace yaml {
     99 /// Token - A single YAML token.
    100 struct Token : ilist_node<Token> {
    101   enum TokenKind {
    102     TK_Error, // Uninitialized token.
    103     TK_StreamStart,
    104     TK_StreamEnd,
    105     TK_VersionDirective,
    106     TK_TagDirective,
    107     TK_DocumentStart,
    108     TK_DocumentEnd,
    109     TK_BlockEntry,
    110     TK_BlockEnd,
    111     TK_BlockSequenceStart,
    112     TK_BlockMappingStart,
    113     TK_FlowEntry,
    114     TK_FlowSequenceStart,
    115     TK_FlowSequenceEnd,
    116     TK_FlowMappingStart,
    117     TK_FlowMappingEnd,
    118     TK_Key,
    119     TK_Value,
    120     TK_Scalar,
    121     TK_Alias,
    122     TK_Anchor,
    123     TK_Tag
    124   } Kind;
    125 
    126   /// A string of length 0 or more whose begin() points to the logical location
    127   /// of the token in the input.
    128   StringRef Range;
    129 
    130   Token() : Kind(TK_Error) {}
    131 };
    132 }
    133 }
    134 
    135 namespace llvm {
    136 template<>
    137 struct ilist_sentinel_traits<Token> {
    138   Token *createSentinel() const {
    139     return &Sentinel;
    140   }
    141   static void destroySentinel(Token*) {}
    142 
    143   Token *provideInitialHead() const { return createSentinel(); }
    144   Token *ensureHead(Token*) const { return createSentinel(); }
    145   static void noteHead(Token*, Token*) {}
    146 
    147 private:
    148   mutable Token Sentinel;
    149 };
    150 
    151 template<>
    152 struct ilist_node_traits<Token> {
    153   Token *createNode(const Token &V) {
    154     return new (Alloc.Allocate<Token>()) Token(V);
    155   }
    156   static void deleteNode(Token *V) {}
    157 
    158   void addNodeToList(Token *) {}
    159   void removeNodeFromList(Token *) {}
    160   void transferNodesFromList(ilist_node_traits &    /*SrcTraits*/,
    161                              ilist_iterator<Token> /*first*/,
    162                              ilist_iterator<Token> /*last*/) {}
    163 
    164   BumpPtrAllocator Alloc;
    165 };
    166 }
    167 
    168 typedef ilist<Token> TokenQueueT;
    169 
    170 namespace {
    171 /// @brief This struct is used to track simple keys.
    172 ///
    173 /// Simple keys are handled by creating an entry in SimpleKeys for each Token
    174 /// which could legally be the start of a simple key. When peekNext is called,
    175 /// if the Token To be returned is referenced by a SimpleKey, we continue
    176 /// tokenizing until that potential simple key has either been found to not be
    177 /// a simple key (we moved on to the next line or went further than 1024 chars).
    178 /// Or when we run into a Value, and then insert a Key token (and possibly
    179 /// others) before the SimpleKey's Tok.
    180 struct SimpleKey {
    181   TokenQueueT::iterator Tok;
    182   unsigned Column;
    183   unsigned Line;
    184   unsigned FlowLevel;
    185   bool IsRequired;
    186 
    187   bool operator ==(const SimpleKey &Other) {
    188     return Tok == Other.Tok;
    189   }
    190 };
    191 }
    192 
    193 /// @brief The Unicode scalar value of a UTF-8 minimal well-formed code unit
    194 ///        subsequence and the subsequence's length in code units (uint8_t).
    195 ///        A length of 0 represents an error.
    196 typedef std::pair<uint32_t, unsigned> UTF8Decoded;
    197 
    198 static UTF8Decoded decodeUTF8(StringRef Range) {
    199   StringRef::iterator Position= Range.begin();
    200   StringRef::iterator End = Range.end();
    201   // 1 byte: [0x00, 0x7f]
    202   // Bit pattern: 0xxxxxxx
    203   if ((*Position & 0x80) == 0) {
    204      return std::make_pair(*Position, 1);
    205   }
    206   // 2 bytes: [0x80, 0x7ff]
    207   // Bit pattern: 110xxxxx 10xxxxxx
    208   if (Position + 1 != End &&
    209       ((*Position & 0xE0) == 0xC0) &&
    210       ((*(Position + 1) & 0xC0) == 0x80)) {
    211     uint32_t codepoint = ((*Position & 0x1F) << 6) |
    212                           (*(Position + 1) & 0x3F);
    213     if (codepoint >= 0x80)
    214       return std::make_pair(codepoint, 2);
    215   }
    216   // 3 bytes: [0x8000, 0xffff]
    217   // Bit pattern: 1110xxxx 10xxxxxx 10xxxxxx
    218   if (Position + 2 != End &&
    219       ((*Position & 0xF0) == 0xE0) &&
    220       ((*(Position + 1) & 0xC0) == 0x80) &&
    221       ((*(Position + 2) & 0xC0) == 0x80)) {
    222     uint32_t codepoint = ((*Position & 0x0F) << 12) |
    223                          ((*(Position + 1) & 0x3F) << 6) |
    224                           (*(Position + 2) & 0x3F);
    225     // Codepoints between 0xD800 and 0xDFFF are invalid, as
    226     // they are high / low surrogate halves used by UTF-16.
    227     if (codepoint >= 0x800 &&
    228         (codepoint < 0xD800 || codepoint > 0xDFFF))
    229       return std::make_pair(codepoint, 3);
    230   }
    231   // 4 bytes: [0x10000, 0x10FFFF]
    232   // Bit pattern: 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
    233   if (Position + 3 != End &&
    234       ((*Position & 0xF8) == 0xF0) &&
    235       ((*(Position + 1) & 0xC0) == 0x80) &&
    236       ((*(Position + 2) & 0xC0) == 0x80) &&
    237       ((*(Position + 3) & 0xC0) == 0x80)) {
    238     uint32_t codepoint = ((*Position & 0x07) << 18) |
    239                          ((*(Position + 1) & 0x3F) << 12) |
    240                          ((*(Position + 2) & 0x3F) << 6) |
    241                           (*(Position + 3) & 0x3F);
    242     if (codepoint >= 0x10000 && codepoint <= 0x10FFFF)
    243       return std::make_pair(codepoint, 4);
    244   }
    245   return std::make_pair(0, 0);
    246 }
    247 
    248 namespace llvm {
    249 namespace yaml {
    250 /// @brief Scans YAML tokens from a MemoryBuffer.
    251 class Scanner {
    252 public:
    253   Scanner(const StringRef Input, SourceMgr &SM);
    254   Scanner(MemoryBuffer *Buffer, SourceMgr &SM_);
    255 
    256   /// @brief Parse the next token and return it without popping it.
    257   Token &peekNext();
    258 
    259   /// @brief Parse the next token and pop it from the queue.
    260   Token getNext();
    261 
    262   void printError(SMLoc Loc, SourceMgr::DiagKind Kind, const Twine &Message,
    263                   ArrayRef<SMRange> Ranges = None) {
    264     SM.PrintMessage(Loc, Kind, Message, Ranges);
    265   }
    266 
    267   void setError(const Twine &Message, StringRef::iterator Position) {
    268     if (Current >= End)
    269       Current = End - 1;
    270 
    271     // Don't print out more errors after the first one we encounter. The rest
    272     // are just the result of the first, and have no meaning.
    273     if (!Failed)
    274       printError(SMLoc::getFromPointer(Current), SourceMgr::DK_Error, Message);
    275     Failed = true;
    276   }
    277 
    278   void setError(const Twine &Message) {
    279     setError(Message, Current);
    280   }
    281 
    282   /// @brief Returns true if an error occurred while parsing.
    283   bool failed() {
    284     return Failed;
    285   }
    286 
    287 private:
    288   StringRef currentInput() {
    289     return StringRef(Current, End - Current);
    290   }
    291 
    292   /// @brief Decode a UTF-8 minimal well-formed code unit subsequence starting
    293   ///        at \a Position.
    294   ///
    295   /// If the UTF-8 code units starting at Position do not form a well-formed
    296   /// code unit subsequence, then the Unicode scalar value is 0, and the length
    297   /// is 0.
    298   UTF8Decoded decodeUTF8(StringRef::iterator Position) {
    299     return ::decodeUTF8(StringRef(Position, End - Position));
    300   }
    301 
    302   // The following functions are based on the gramar rules in the YAML spec. The
    303   // style of the function names it meant to closely match how they are written
    304   // in the spec. The number within the [] is the number of the grammar rule in
    305   // the spec.
    306   //
    307   // See 4.2 [Production Naming Conventions] for the meaning of the prefixes.
    308   //
    309   // c-
    310   //   A production starting and ending with a special character.
    311   // b-
    312   //   A production matching a single line break.
    313   // nb-
    314   //   A production starting and ending with a non-break character.
    315   // s-
    316   //   A production starting and ending with a white space character.
    317   // ns-
    318   //   A production starting and ending with a non-space character.
    319   // l-
    320   //   A production matching complete line(s).
    321 
    322   /// @brief Skip a single nb-char[27] starting at Position.
    323   ///
    324   /// A nb-char is 0x9 | [0x20-0x7E] | 0x85 | [0xA0-0xD7FF] | [0xE000-0xFEFE]
    325   ///                  | [0xFF00-0xFFFD] | [0x10000-0x10FFFF]
    326   ///
    327   /// @returns The code unit after the nb-char, or Position if it's not an
    328   ///          nb-char.
    329   StringRef::iterator skip_nb_char(StringRef::iterator Position);
    330 
    331   /// @brief Skip a single b-break[28] starting at Position.
    332   ///
    333   /// A b-break is 0xD 0xA | 0xD | 0xA
    334   ///
    335   /// @returns The code unit after the b-break, or Position if it's not a
    336   ///          b-break.
    337   StringRef::iterator skip_b_break(StringRef::iterator Position);
    338 
    339   /// @brief Skip a single s-white[33] starting at Position.
    340   ///
    341   /// A s-white is 0x20 | 0x9
    342   ///
    343   /// @returns The code unit after the s-white, or Position if it's not a
    344   ///          s-white.
    345   StringRef::iterator skip_s_white(StringRef::iterator Position);
    346 
    347   /// @brief Skip a single ns-char[34] starting at Position.
    348   ///
    349   /// A ns-char is nb-char - s-white
    350   ///
    351   /// @returns The code unit after the ns-char, or Position if it's not a
    352   ///          ns-char.
    353   StringRef::iterator skip_ns_char(StringRef::iterator Position);
    354 
    355   typedef StringRef::iterator (Scanner::*SkipWhileFunc)(StringRef::iterator);
    356   /// @brief Skip minimal well-formed code unit subsequences until Func
    357   ///        returns its input.
    358   ///
    359   /// @returns The code unit after the last minimal well-formed code unit
    360   ///          subsequence that Func accepted.
    361   StringRef::iterator skip_while( SkipWhileFunc Func
    362                                 , StringRef::iterator Position);
    363 
    364   /// @brief Scan ns-uri-char[39]s starting at Cur.
    365   ///
    366   /// This updates Cur and Column while scanning.
    367   ///
    368   /// @returns A StringRef starting at Cur which covers the longest contiguous
    369   ///          sequence of ns-uri-char.
    370   StringRef scan_ns_uri_char();
    371 
    372   /// @brief Scan ns-plain-one-line[133] starting at \a Cur.
    373   StringRef scan_ns_plain_one_line();
    374 
    375   /// @brief Consume a minimal well-formed code unit subsequence starting at
    376   ///        \a Cur. Return false if it is not the same Unicode scalar value as
    377   ///        \a Expected. This updates \a Column.
    378   bool consume(uint32_t Expected);
    379 
    380   /// @brief Skip \a Distance UTF-8 code units. Updates \a Cur and \a Column.
    381   void skip(uint32_t Distance);
    382 
    383   /// @brief Return true if the minimal well-formed code unit subsequence at
    384   ///        Pos is whitespace or a new line
    385   bool isBlankOrBreak(StringRef::iterator Position);
    386 
    387   /// @brief If IsSimpleKeyAllowed, create and push_back a new SimpleKey.
    388   void saveSimpleKeyCandidate( TokenQueueT::iterator Tok
    389                              , unsigned AtColumn
    390                              , bool IsRequired);
    391 
    392   /// @brief Remove simple keys that can no longer be valid simple keys.
    393   ///
    394   /// Invalid simple keys are not on the current line or are further than 1024
    395   /// columns back.
    396   void removeStaleSimpleKeyCandidates();
    397 
    398   /// @brief Remove all simple keys on FlowLevel \a Level.
    399   void removeSimpleKeyCandidatesOnFlowLevel(unsigned Level);
    400 
    401   /// @brief Unroll indentation in \a Indents back to \a Col. Creates BlockEnd
    402   ///        tokens if needed.
    403   bool unrollIndent(int ToColumn);
    404 
    405   /// @brief Increase indent to \a Col. Creates \a Kind token at \a InsertPoint
    406   ///        if needed.
    407   bool rollIndent( int ToColumn
    408                  , Token::TokenKind Kind
    409                  , TokenQueueT::iterator InsertPoint);
    410 
    411   /// @brief Skip whitespace and comments until the start of the next token.
    412   void scanToNextToken();
    413 
    414   /// @brief Must be the first token generated.
    415   bool scanStreamStart();
    416 
    417   /// @brief Generate tokens needed to close out the stream.
    418   bool scanStreamEnd();
    419 
    420   /// @brief Scan a %BLAH directive.
    421   bool scanDirective();
    422 
    423   /// @brief Scan a ... or ---.
    424   bool scanDocumentIndicator(bool IsStart);
    425 
    426   /// @brief Scan a [ or { and generate the proper flow collection start token.
    427   bool scanFlowCollectionStart(bool IsSequence);
    428 
    429   /// @brief Scan a ] or } and generate the proper flow collection end token.
    430   bool scanFlowCollectionEnd(bool IsSequence);
    431 
    432   /// @brief Scan the , that separates entries in a flow collection.
    433   bool scanFlowEntry();
    434 
    435   /// @brief Scan the - that starts block sequence entries.
    436   bool scanBlockEntry();
    437 
    438   /// @brief Scan an explicit ? indicating a key.
    439   bool scanKey();
    440 
    441   /// @brief Scan an explicit : indicating a value.
    442   bool scanValue();
    443 
    444   /// @brief Scan a quoted scalar.
    445   bool scanFlowScalar(bool IsDoubleQuoted);
    446 
    447   /// @brief Scan an unquoted scalar.
    448   bool scanPlainScalar();
    449 
    450   /// @brief Scan an Alias or Anchor starting with * or &.
    451   bool scanAliasOrAnchor(bool IsAlias);
    452 
    453   /// @brief Scan a block scalar starting with | or >.
    454   bool scanBlockScalar(bool IsLiteral);
    455 
    456   /// @brief Scan a tag of the form !stuff.
    457   bool scanTag();
    458 
    459   /// @brief Dispatch to the next scanning function based on \a *Cur.
    460   bool fetchMoreTokens();
    461 
    462   /// @brief The SourceMgr used for diagnostics and buffer management.
    463   SourceMgr &SM;
    464 
    465   /// @brief The original input.
    466   MemoryBuffer *InputBuffer;
    467 
    468   /// @brief The current position of the scanner.
    469   StringRef::iterator Current;
    470 
    471   /// @brief The end of the input (one past the last character).
    472   StringRef::iterator End;
    473 
    474   /// @brief Current YAML indentation level in spaces.
    475   int Indent;
    476 
    477   /// @brief Current column number in Unicode code points.
    478   unsigned Column;
    479 
    480   /// @brief Current line number.
    481   unsigned Line;
    482 
    483   /// @brief How deep we are in flow style containers. 0 Means at block level.
    484   unsigned FlowLevel;
    485 
    486   /// @brief Are we at the start of the stream?
    487   bool IsStartOfStream;
    488 
    489   /// @brief Can the next token be the start of a simple key?
    490   bool IsSimpleKeyAllowed;
    491 
    492   /// @brief True if an error has occurred.
    493   bool Failed;
    494 
    495   /// @brief Queue of tokens. This is required to queue up tokens while looking
    496   ///        for the end of a simple key. And for cases where a single character
    497   ///        can produce multiple tokens (e.g. BlockEnd).
    498   TokenQueueT TokenQueue;
    499 
    500   /// @brief Indentation levels.
    501   SmallVector<int, 4> Indents;
    502 
    503   /// @brief Potential simple keys.
    504   SmallVector<SimpleKey, 4> SimpleKeys;
    505 };
    506 
    507 } // end namespace yaml
    508 } // end namespace llvm
    509 
    510 /// encodeUTF8 - Encode \a UnicodeScalarValue in UTF-8 and append it to result.
    511 static void encodeUTF8( uint32_t UnicodeScalarValue
    512                       , SmallVectorImpl<char> &Result) {
    513   if (UnicodeScalarValue <= 0x7F) {
    514     Result.push_back(UnicodeScalarValue & 0x7F);
    515   } else if (UnicodeScalarValue <= 0x7FF) {
    516     uint8_t FirstByte = 0xC0 | ((UnicodeScalarValue & 0x7C0) >> 6);
    517     uint8_t SecondByte = 0x80 | (UnicodeScalarValue & 0x3F);
    518     Result.push_back(FirstByte);
    519     Result.push_back(SecondByte);
    520   } else if (UnicodeScalarValue <= 0xFFFF) {
    521     uint8_t FirstByte = 0xE0 | ((UnicodeScalarValue & 0xF000) >> 12);
    522     uint8_t SecondByte = 0x80 | ((UnicodeScalarValue & 0xFC0) >> 6);
    523     uint8_t ThirdByte = 0x80 | (UnicodeScalarValue & 0x3F);
    524     Result.push_back(FirstByte);
    525     Result.push_back(SecondByte);
    526     Result.push_back(ThirdByte);
    527   } else if (UnicodeScalarValue <= 0x10FFFF) {
    528     uint8_t FirstByte = 0xF0 | ((UnicodeScalarValue & 0x1F0000) >> 18);
    529     uint8_t SecondByte = 0x80 | ((UnicodeScalarValue & 0x3F000) >> 12);
    530     uint8_t ThirdByte = 0x80 | ((UnicodeScalarValue & 0xFC0) >> 6);
    531     uint8_t FourthByte = 0x80 | (UnicodeScalarValue & 0x3F);
    532     Result.push_back(FirstByte);
    533     Result.push_back(SecondByte);
    534     Result.push_back(ThirdByte);
    535     Result.push_back(FourthByte);
    536   }
    537 }
    538 
    539 bool yaml::dumpTokens(StringRef Input, raw_ostream &OS) {
    540   SourceMgr SM;
    541   Scanner scanner(Input, SM);
    542   while (true) {
    543     Token T = scanner.getNext();
    544     switch (T.Kind) {
    545     case Token::TK_StreamStart:
    546       OS << "Stream-Start: ";
    547       break;
    548     case Token::TK_StreamEnd:
    549       OS << "Stream-End: ";
    550       break;
    551     case Token::TK_VersionDirective:
    552       OS << "Version-Directive: ";
    553       break;
    554     case Token::TK_TagDirective:
    555       OS << "Tag-Directive: ";
    556       break;
    557     case Token::TK_DocumentStart:
    558       OS << "Document-Start: ";
    559       break;
    560     case Token::TK_DocumentEnd:
    561       OS << "Document-End: ";
    562       break;
    563     case Token::TK_BlockEntry:
    564       OS << "Block-Entry: ";
    565       break;
    566     case Token::TK_BlockEnd:
    567       OS << "Block-End: ";
    568       break;
    569     case Token::TK_BlockSequenceStart:
    570       OS << "Block-Sequence-Start: ";
    571       break;
    572     case Token::TK_BlockMappingStart:
    573       OS << "Block-Mapping-Start: ";
    574       break;
    575     case Token::TK_FlowEntry:
    576       OS << "Flow-Entry: ";
    577       break;
    578     case Token::TK_FlowSequenceStart:
    579       OS << "Flow-Sequence-Start: ";
    580       break;
    581     case Token::TK_FlowSequenceEnd:
    582       OS << "Flow-Sequence-End: ";
    583       break;
    584     case Token::TK_FlowMappingStart:
    585       OS << "Flow-Mapping-Start: ";
    586       break;
    587     case Token::TK_FlowMappingEnd:
    588       OS << "Flow-Mapping-End: ";
    589       break;
    590     case Token::TK_Key:
    591       OS << "Key: ";
    592       break;
    593     case Token::TK_Value:
    594       OS << "Value: ";
    595       break;
    596     case Token::TK_Scalar:
    597       OS << "Scalar: ";
    598       break;
    599     case Token::TK_Alias:
    600       OS << "Alias: ";
    601       break;
    602     case Token::TK_Anchor:
    603       OS << "Anchor: ";
    604       break;
    605     case Token::TK_Tag:
    606       OS << "Tag: ";
    607       break;
    608     case Token::TK_Error:
    609       break;
    610     }
    611     OS << T.Range << "\n";
    612     if (T.Kind == Token::TK_StreamEnd)
    613       break;
    614     else if (T.Kind == Token::TK_Error)
    615       return false;
    616   }
    617   return true;
    618 }
    619 
    620 bool yaml::scanTokens(StringRef Input) {
    621   llvm::SourceMgr SM;
    622   llvm::yaml::Scanner scanner(Input, SM);
    623   for (;;) {
    624     llvm::yaml::Token T = scanner.getNext();
    625     if (T.Kind == Token::TK_StreamEnd)
    626       break;
    627     else if (T.Kind == Token::TK_Error)
    628       return false;
    629   }
    630   return true;
    631 }
    632 
    633 std::string yaml::escape(StringRef Input) {
    634   std::string EscapedInput;
    635   for (StringRef::iterator i = Input.begin(), e = Input.end(); i != e; ++i) {
    636     if (*i == '\\')
    637       EscapedInput += "\\\\";
    638     else if (*i == '"')
    639       EscapedInput += "\\\"";
    640     else if (*i == 0)
    641       EscapedInput += "\\0";
    642     else if (*i == 0x07)
    643       EscapedInput += "\\a";
    644     else if (*i == 0x08)
    645       EscapedInput += "\\b";
    646     else if (*i == 0x09)
    647       EscapedInput += "\\t";
    648     else if (*i == 0x0A)
    649       EscapedInput += "\\n";
    650     else if (*i == 0x0B)
    651       EscapedInput += "\\v";
    652     else if (*i == 0x0C)
    653       EscapedInput += "\\f";
    654     else if (*i == 0x0D)
    655       EscapedInput += "\\r";
    656     else if (*i == 0x1B)
    657       EscapedInput += "\\e";
    658     else if ((unsigned char)*i < 0x20) { // Control characters not handled above.
    659       std::string HexStr = utohexstr(*i);
    660       EscapedInput += "\\x" + std::string(2 - HexStr.size(), '0') + HexStr;
    661     } else if (*i & 0x80) { // UTF-8 multiple code unit subsequence.
    662       UTF8Decoded UnicodeScalarValue
    663         = decodeUTF8(StringRef(i, Input.end() - i));
    664       if (UnicodeScalarValue.second == 0) {
    665         // Found invalid char.
    666         SmallString<4> Val;
    667         encodeUTF8(0xFFFD, Val);
    668         EscapedInput.insert(EscapedInput.end(), Val.begin(), Val.end());
    669         // FIXME: Error reporting.
    670         return EscapedInput;
    671       }
    672       if (UnicodeScalarValue.first == 0x85)
    673         EscapedInput += "\\N";
    674       else if (UnicodeScalarValue.first == 0xA0)
    675         EscapedInput += "\\_";
    676       else if (UnicodeScalarValue.first == 0x2028)
    677         EscapedInput += "\\L";
    678       else if (UnicodeScalarValue.first == 0x2029)
    679         EscapedInput += "\\P";
    680       else {
    681         std::string HexStr = utohexstr(UnicodeScalarValue.first);
    682         if (HexStr.size() <= 2)
    683           EscapedInput += "\\x" + std::string(2 - HexStr.size(), '0') + HexStr;
    684         else if (HexStr.size() <= 4)
    685           EscapedInput += "\\u" + std::string(4 - HexStr.size(), '0') + HexStr;
    686         else if (HexStr.size() <= 8)
    687           EscapedInput += "\\U" + std::string(8 - HexStr.size(), '0') + HexStr;
    688       }
    689       i += UnicodeScalarValue.second - 1;
    690     } else
    691       EscapedInput.push_back(*i);
    692   }
    693   return EscapedInput;
    694 }
    695 
    696 Scanner::Scanner(StringRef Input, SourceMgr &sm)
    697   : SM(sm)
    698   , Indent(-1)
    699   , Column(0)
    700   , Line(0)
    701   , FlowLevel(0)
    702   , IsStartOfStream(true)
    703   , IsSimpleKeyAllowed(true)
    704   , Failed(false) {
    705   InputBuffer = MemoryBuffer::getMemBuffer(Input, "YAML");
    706   SM.AddNewSourceBuffer(InputBuffer, SMLoc());
    707   Current = InputBuffer->getBufferStart();
    708   End = InputBuffer->getBufferEnd();
    709 }
    710 
    711 Scanner::Scanner(MemoryBuffer *Buffer, SourceMgr &SM_)
    712   : SM(SM_)
    713   , InputBuffer(Buffer)
    714   , Current(InputBuffer->getBufferStart())
    715   , End(InputBuffer->getBufferEnd())
    716   , Indent(-1)
    717   , Column(0)
    718   , Line(0)
    719   , FlowLevel(0)
    720   , IsStartOfStream(true)
    721   , IsSimpleKeyAllowed(true)
    722   , Failed(false) {
    723     SM.AddNewSourceBuffer(InputBuffer, SMLoc());
    724 }
    725 
    726 Token &Scanner::peekNext() {
    727   // If the current token is a possible simple key, keep parsing until we
    728   // can confirm.
    729   bool NeedMore = false;
    730   while (true) {
    731     if (TokenQueue.empty() || NeedMore) {
    732       if (!fetchMoreTokens()) {
    733         TokenQueue.clear();
    734         TokenQueue.push_back(Token());
    735         return TokenQueue.front();
    736       }
    737     }
    738     assert(!TokenQueue.empty() &&
    739             "fetchMoreTokens lied about getting tokens!");
    740 
    741     removeStaleSimpleKeyCandidates();
    742     SimpleKey SK;
    743     SK.Tok = TokenQueue.front();
    744     if (std::find(SimpleKeys.begin(), SimpleKeys.end(), SK)
    745         == SimpleKeys.end())
    746       break;
    747     else
    748       NeedMore = true;
    749   }
    750   return TokenQueue.front();
    751 }
    752 
    753 Token Scanner::getNext() {
    754   Token Ret = peekNext();
    755   // TokenQueue can be empty if there was an error getting the next token.
    756   if (!TokenQueue.empty())
    757     TokenQueue.pop_front();
    758 
    759   // There cannot be any referenced Token's if the TokenQueue is empty. So do a
    760   // quick deallocation of them all.
    761   if (TokenQueue.empty()) {
    762     TokenQueue.Alloc.Reset();
    763   }
    764 
    765   return Ret;
    766 }
    767 
    768 StringRef::iterator Scanner::skip_nb_char(StringRef::iterator Position) {
    769   if (Position == End)
    770     return Position;
    771   // Check 7 bit c-printable - b-char.
    772   if (   *Position == 0x09
    773       || (*Position >= 0x20 && *Position <= 0x7E))
    774     return Position + 1;
    775 
    776   // Check for valid UTF-8.
    777   if (uint8_t(*Position) & 0x80) {
    778     UTF8Decoded u8d = decodeUTF8(Position);
    779     if (   u8d.second != 0
    780         && u8d.first != 0xFEFF
    781         && ( u8d.first == 0x85
    782           || ( u8d.first >= 0xA0
    783             && u8d.first <= 0xD7FF)
    784           || ( u8d.first >= 0xE000
    785             && u8d.first <= 0xFFFD)
    786           || ( u8d.first >= 0x10000
    787             && u8d.first <= 0x10FFFF)))
    788       return Position + u8d.second;
    789   }
    790   return Position;
    791 }
    792 
    793 StringRef::iterator Scanner::skip_b_break(StringRef::iterator Position) {
    794   if (Position == End)
    795     return Position;
    796   if (*Position == 0x0D) {
    797     if (Position + 1 != End && *(Position + 1) == 0x0A)
    798       return Position + 2;
    799     return Position + 1;
    800   }
    801 
    802   if (*Position == 0x0A)
    803     return Position + 1;
    804   return Position;
    805 }
    806 
    807 
    808 StringRef::iterator Scanner::skip_s_white(StringRef::iterator Position) {
    809   if (Position == End)
    810     return Position;
    811   if (*Position == ' ' || *Position == '\t')
    812     return Position + 1;
    813   return Position;
    814 }
    815 
    816 StringRef::iterator Scanner::skip_ns_char(StringRef::iterator Position) {
    817   if (Position == End)
    818     return Position;
    819   if (*Position == ' ' || *Position == '\t')
    820     return Position;
    821   return skip_nb_char(Position);
    822 }
    823 
    824 StringRef::iterator Scanner::skip_while( SkipWhileFunc Func
    825                                        , StringRef::iterator Position) {
    826   while (true) {
    827     StringRef::iterator i = (this->*Func)(Position);
    828     if (i == Position)
    829       break;
    830     Position = i;
    831   }
    832   return Position;
    833 }
    834 
    835 static bool is_ns_hex_digit(const char C) {
    836   return    (C >= '0' && C <= '9')
    837          || (C >= 'a' && C <= 'z')
    838          || (C >= 'A' && C <= 'Z');
    839 }
    840 
    841 static bool is_ns_word_char(const char C) {
    842   return    C == '-'
    843          || (C >= 'a' && C <= 'z')
    844          || (C >= 'A' && C <= 'Z');
    845 }
    846 
    847 StringRef Scanner::scan_ns_uri_char() {
    848   StringRef::iterator Start = Current;
    849   while (true) {
    850     if (Current == End)
    851       break;
    852     if ((   *Current == '%'
    853           && Current + 2 < End
    854           && is_ns_hex_digit(*(Current + 1))
    855           && is_ns_hex_digit(*(Current + 2)))
    856         || is_ns_word_char(*Current)
    857         || StringRef(Current, 1).find_first_of("#;/?:@&=+$,_.!~*'()[]")
    858           != StringRef::npos) {
    859       ++Current;
    860       ++Column;
    861     } else
    862       break;
    863   }
    864   return StringRef(Start, Current - Start);
    865 }
    866 
    867 StringRef Scanner::scan_ns_plain_one_line() {
    868   StringRef::iterator start = Current;
    869   // The first character must already be verified.
    870   ++Current;
    871   while (true) {
    872     if (Current == End) {
    873       break;
    874     } else if (*Current == ':') {
    875       // Check if the next character is a ns-char.
    876       if (Current + 1 == End)
    877         break;
    878       StringRef::iterator i = skip_ns_char(Current + 1);
    879       if (Current + 1 != i) {
    880         Current = i;
    881         Column += 2; // Consume both the ':' and ns-char.
    882       } else
    883         break;
    884     } else if (*Current == '#') {
    885       // Check if the previous character was a ns-char.
    886       // The & 0x80 check is to check for the trailing byte of a utf-8
    887       if (*(Current - 1) & 0x80 || skip_ns_char(Current - 1) == Current) {
    888         ++Current;
    889         ++Column;
    890       } else
    891         break;
    892     } else {
    893       StringRef::iterator i = skip_nb_char(Current);
    894       if (i == Current)
    895         break;
    896       Current = i;
    897       ++Column;
    898     }
    899   }
    900   return StringRef(start, Current - start);
    901 }
    902 
    903 bool Scanner::consume(uint32_t Expected) {
    904   if (Expected >= 0x80)
    905     report_fatal_error("Not dealing with this yet");
    906   if (Current == End)
    907     return false;
    908   if (uint8_t(*Current) >= 0x80)
    909     report_fatal_error("Not dealing with this yet");
    910   if (uint8_t(*Current) == Expected) {
    911     ++Current;
    912     ++Column;
    913     return true;
    914   }
    915   return false;
    916 }
    917 
    918 void Scanner::skip(uint32_t Distance) {
    919   Current += Distance;
    920   Column += Distance;
    921   assert(Current <= End && "Skipped past the end");
    922 }
    923 
    924 bool Scanner::isBlankOrBreak(StringRef::iterator Position) {
    925   if (Position == End)
    926     return false;
    927   if (   *Position == ' ' || *Position == '\t'
    928       || *Position == '\r' || *Position == '\n')
    929     return true;
    930   return false;
    931 }
    932 
    933 void Scanner::saveSimpleKeyCandidate( TokenQueueT::iterator Tok
    934                                     , unsigned AtColumn
    935                                     , bool IsRequired) {
    936   if (IsSimpleKeyAllowed) {
    937     SimpleKey SK;
    938     SK.Tok = Tok;
    939     SK.Line = Line;
    940     SK.Column = AtColumn;
    941     SK.IsRequired = IsRequired;
    942     SK.FlowLevel = FlowLevel;
    943     SimpleKeys.push_back(SK);
    944   }
    945 }
    946 
    947 void Scanner::removeStaleSimpleKeyCandidates() {
    948   for (SmallVectorImpl<SimpleKey>::iterator i = SimpleKeys.begin();
    949                                             i != SimpleKeys.end();) {
    950     if (i->Line != Line || i->Column + 1024 < Column) {
    951       if (i->IsRequired)
    952         setError( "Could not find expected : for simple key"
    953                 , i->Tok->Range.begin());
    954       i = SimpleKeys.erase(i);
    955     } else
    956       ++i;
    957   }
    958 }
    959 
    960 void Scanner::removeSimpleKeyCandidatesOnFlowLevel(unsigned Level) {
    961   if (!SimpleKeys.empty() && (SimpleKeys.end() - 1)->FlowLevel == Level)
    962     SimpleKeys.pop_back();
    963 }
    964 
    965 bool Scanner::unrollIndent(int ToColumn) {
    966   Token T;
    967   // Indentation is ignored in flow.
    968   if (FlowLevel != 0)
    969     return true;
    970 
    971   while (Indent > ToColumn) {
    972     T.Kind = Token::TK_BlockEnd;
    973     T.Range = StringRef(Current, 1);
    974     TokenQueue.push_back(T);
    975     Indent = Indents.pop_back_val();
    976   }
    977 
    978   return true;
    979 }
    980 
    981 bool Scanner::rollIndent( int ToColumn
    982                         , Token::TokenKind Kind
    983                         , TokenQueueT::iterator InsertPoint) {
    984   if (FlowLevel)
    985     return true;
    986   if (Indent < ToColumn) {
    987     Indents.push_back(Indent);
    988     Indent = ToColumn;
    989 
    990     Token T;
    991     T.Kind = Kind;
    992     T.Range = StringRef(Current, 0);
    993     TokenQueue.insert(InsertPoint, T);
    994   }
    995   return true;
    996 }
    997 
    998 void Scanner::scanToNextToken() {
    999   while (true) {
   1000     while (*Current == ' ' || *Current == '\t') {
   1001       skip(1);
   1002     }
   1003 
   1004     // Skip comment.
   1005     if (*Current == '#') {
   1006       while (true) {
   1007         // This may skip more than one byte, thus Column is only incremented
   1008         // for code points.
   1009         StringRef::iterator i = skip_nb_char(Current);
   1010         if (i == Current)
   1011           break;
   1012         Current = i;
   1013         ++Column;
   1014       }
   1015     }
   1016 
   1017     // Skip EOL.
   1018     StringRef::iterator i = skip_b_break(Current);
   1019     if (i == Current)
   1020       break;
   1021     Current = i;
   1022     ++Line;
   1023     Column = 0;
   1024     // New lines may start a simple key.
   1025     if (!FlowLevel)
   1026       IsSimpleKeyAllowed = true;
   1027   }
   1028 }
   1029 
   1030 bool Scanner::scanStreamStart() {
   1031   IsStartOfStream = false;
   1032 
   1033   EncodingInfo EI = getUnicodeEncoding(currentInput());
   1034 
   1035   Token T;
   1036   T.Kind = Token::TK_StreamStart;
   1037   T.Range = StringRef(Current, EI.second);
   1038   TokenQueue.push_back(T);
   1039   Current += EI.second;
   1040   return true;
   1041 }
   1042 
   1043 bool Scanner::scanStreamEnd() {
   1044   // Force an ending new line if one isn't present.
   1045   if (Column != 0) {
   1046     Column = 0;
   1047     ++Line;
   1048   }
   1049 
   1050   unrollIndent(-1);
   1051   SimpleKeys.clear();
   1052   IsSimpleKeyAllowed = false;
   1053 
   1054   Token T;
   1055   T.Kind = Token::TK_StreamEnd;
   1056   T.Range = StringRef(Current, 0);
   1057   TokenQueue.push_back(T);
   1058   return true;
   1059 }
   1060 
   1061 bool Scanner::scanDirective() {
   1062   // Reset the indentation level.
   1063   unrollIndent(-1);
   1064   SimpleKeys.clear();
   1065   IsSimpleKeyAllowed = false;
   1066 
   1067   StringRef::iterator Start = Current;
   1068   consume('%');
   1069   StringRef::iterator NameStart = Current;
   1070   Current = skip_while(&Scanner::skip_ns_char, Current);
   1071   StringRef Name(NameStart, Current - NameStart);
   1072   Current = skip_while(&Scanner::skip_s_white, Current);
   1073 
   1074   if (Name == "YAML") {
   1075     Current = skip_while(&Scanner::skip_ns_char, Current);
   1076     Token T;
   1077     T.Kind = Token::TK_VersionDirective;
   1078     T.Range = StringRef(Start, Current - Start);
   1079     TokenQueue.push_back(T);
   1080     return true;
   1081   }
   1082   return false;
   1083 }
   1084 
   1085 bool Scanner::scanDocumentIndicator(bool IsStart) {
   1086   unrollIndent(-1);
   1087   SimpleKeys.clear();
   1088   IsSimpleKeyAllowed = false;
   1089 
   1090   Token T;
   1091   T.Kind = IsStart ? Token::TK_DocumentStart : Token::TK_DocumentEnd;
   1092   T.Range = StringRef(Current, 3);
   1093   skip(3);
   1094   TokenQueue.push_back(T);
   1095   return true;
   1096 }
   1097 
   1098 bool Scanner::scanFlowCollectionStart(bool IsSequence) {
   1099   Token T;
   1100   T.Kind = IsSequence ? Token::TK_FlowSequenceStart
   1101                       : Token::TK_FlowMappingStart;
   1102   T.Range = StringRef(Current, 1);
   1103   skip(1);
   1104   TokenQueue.push_back(T);
   1105 
   1106   // [ and { may begin a simple key.
   1107   saveSimpleKeyCandidate(TokenQueue.back(), Column - 1, false);
   1108 
   1109   // And may also be followed by a simple key.
   1110   IsSimpleKeyAllowed = true;
   1111   ++FlowLevel;
   1112   return true;
   1113 }
   1114 
   1115 bool Scanner::scanFlowCollectionEnd(bool IsSequence) {
   1116   removeSimpleKeyCandidatesOnFlowLevel(FlowLevel);
   1117   IsSimpleKeyAllowed = false;
   1118   Token T;
   1119   T.Kind = IsSequence ? Token::TK_FlowSequenceEnd
   1120                       : Token::TK_FlowMappingEnd;
   1121   T.Range = StringRef(Current, 1);
   1122   skip(1);
   1123   TokenQueue.push_back(T);
   1124   if (FlowLevel)
   1125     --FlowLevel;
   1126   return true;
   1127 }
   1128 
   1129 bool Scanner::scanFlowEntry() {
   1130   removeSimpleKeyCandidatesOnFlowLevel(FlowLevel);
   1131   IsSimpleKeyAllowed = true;
   1132   Token T;
   1133   T.Kind = Token::TK_FlowEntry;
   1134   T.Range = StringRef(Current, 1);
   1135   skip(1);
   1136   TokenQueue.push_back(T);
   1137   return true;
   1138 }
   1139 
   1140 bool Scanner::scanBlockEntry() {
   1141   rollIndent(Column, Token::TK_BlockSequenceStart, TokenQueue.end());
   1142   removeSimpleKeyCandidatesOnFlowLevel(FlowLevel);
   1143   IsSimpleKeyAllowed = true;
   1144   Token T;
   1145   T.Kind = Token::TK_BlockEntry;
   1146   T.Range = StringRef(Current, 1);
   1147   skip(1);
   1148   TokenQueue.push_back(T);
   1149   return true;
   1150 }
   1151 
   1152 bool Scanner::scanKey() {
   1153   if (!FlowLevel)
   1154     rollIndent(Column, Token::TK_BlockMappingStart, TokenQueue.end());
   1155 
   1156   removeSimpleKeyCandidatesOnFlowLevel(FlowLevel);
   1157   IsSimpleKeyAllowed = !FlowLevel;
   1158 
   1159   Token T;
   1160   T.Kind = Token::TK_Key;
   1161   T.Range = StringRef(Current, 1);
   1162   skip(1);
   1163   TokenQueue.push_back(T);
   1164   return true;
   1165 }
   1166 
   1167 bool Scanner::scanValue() {
   1168   // If the previous token could have been a simple key, insert the key token
   1169   // into the token queue.
   1170   if (!SimpleKeys.empty()) {
   1171     SimpleKey SK = SimpleKeys.pop_back_val();
   1172     Token T;
   1173     T.Kind = Token::TK_Key;
   1174     T.Range = SK.Tok->Range;
   1175     TokenQueueT::iterator i, e;
   1176     for (i = TokenQueue.begin(), e = TokenQueue.end(); i != e; ++i) {
   1177       if (i == SK.Tok)
   1178         break;
   1179     }
   1180     assert(i != e && "SimpleKey not in token queue!");
   1181     i = TokenQueue.insert(i, T);
   1182 
   1183     // We may also need to add a Block-Mapping-Start token.
   1184     rollIndent(SK.Column, Token::TK_BlockMappingStart, i);
   1185 
   1186     IsSimpleKeyAllowed = false;
   1187   } else {
   1188     if (!FlowLevel)
   1189       rollIndent(Column, Token::TK_BlockMappingStart, TokenQueue.end());
   1190     IsSimpleKeyAllowed = !FlowLevel;
   1191   }
   1192 
   1193   Token T;
   1194   T.Kind = Token::TK_Value;
   1195   T.Range = StringRef(Current, 1);
   1196   skip(1);
   1197   TokenQueue.push_back(T);
   1198   return true;
   1199 }
   1200 
   1201 // Forbidding inlining improves performance by roughly 20%.
   1202 // FIXME: Remove once llvm optimizes this to the faster version without hints.
   1203 LLVM_ATTRIBUTE_NOINLINE static bool
   1204 wasEscaped(StringRef::iterator First, StringRef::iterator Position);
   1205 
   1206 // Returns whether a character at 'Position' was escaped with a leading '\'.
   1207 // 'First' specifies the position of the first character in the string.
   1208 static bool wasEscaped(StringRef::iterator First,
   1209                        StringRef::iterator Position) {
   1210   assert(Position - 1 >= First);
   1211   StringRef::iterator I = Position - 1;
   1212   // We calculate the number of consecutive '\'s before the current position
   1213   // by iterating backwards through our string.
   1214   while (I >= First && *I == '\\') --I;
   1215   // (Position - 1 - I) now contains the number of '\'s before the current
   1216   // position. If it is odd, the character at 'Position' was escaped.
   1217   return (Position - 1 - I) % 2 == 1;
   1218 }
   1219 
   1220 bool Scanner::scanFlowScalar(bool IsDoubleQuoted) {
   1221   StringRef::iterator Start = Current;
   1222   unsigned ColStart = Column;
   1223   if (IsDoubleQuoted) {
   1224     do {
   1225       ++Current;
   1226       while (Current != End && *Current != '"')
   1227         ++Current;
   1228       // Repeat until the previous character was not a '\' or was an escaped
   1229       // backslash.
   1230     } while (   Current != End
   1231              && *(Current - 1) == '\\'
   1232              && wasEscaped(Start + 1, Current));
   1233   } else {
   1234     skip(1);
   1235     while (true) {
   1236       // Skip a ' followed by another '.
   1237       if (Current + 1 < End && *Current == '\'' && *(Current + 1) == '\'') {
   1238         skip(2);
   1239         continue;
   1240       } else if (*Current == '\'')
   1241         break;
   1242       StringRef::iterator i = skip_nb_char(Current);
   1243       if (i == Current) {
   1244         i = skip_b_break(Current);
   1245         if (i == Current)
   1246           break;
   1247         Current = i;
   1248         Column = 0;
   1249         ++Line;
   1250       } else {
   1251         if (i == End)
   1252           break;
   1253         Current = i;
   1254         ++Column;
   1255       }
   1256     }
   1257   }
   1258 
   1259   if (Current == End) {
   1260     setError("Expected quote at end of scalar", Current);
   1261     return false;
   1262   }
   1263 
   1264   skip(1); // Skip ending quote.
   1265   Token T;
   1266   T.Kind = Token::TK_Scalar;
   1267   T.Range = StringRef(Start, Current - Start);
   1268   TokenQueue.push_back(T);
   1269 
   1270   saveSimpleKeyCandidate(TokenQueue.back(), ColStart, false);
   1271 
   1272   IsSimpleKeyAllowed = false;
   1273 
   1274   return true;
   1275 }
   1276 
   1277 bool Scanner::scanPlainScalar() {
   1278   StringRef::iterator Start = Current;
   1279   unsigned ColStart = Column;
   1280   unsigned LeadingBlanks = 0;
   1281   assert(Indent >= -1 && "Indent must be >= -1 !");
   1282   unsigned indent = static_cast<unsigned>(Indent + 1);
   1283   while (true) {
   1284     if (*Current == '#')
   1285       break;
   1286 
   1287     while (!isBlankOrBreak(Current)) {
   1288       if (  FlowLevel && *Current == ':'
   1289           && !(isBlankOrBreak(Current + 1) || *(Current + 1) == ',')) {
   1290         setError("Found unexpected ':' while scanning a plain scalar", Current);
   1291         return false;
   1292       }
   1293 
   1294       // Check for the end of the plain scalar.
   1295       if (  (*Current == ':' && isBlankOrBreak(Current + 1))
   1296           || (  FlowLevel
   1297           && (StringRef(Current, 1).find_first_of(",:?[]{}")
   1298               != StringRef::npos)))
   1299         break;
   1300 
   1301       StringRef::iterator i = skip_nb_char(Current);
   1302       if (i == Current)
   1303         break;
   1304       Current = i;
   1305       ++Column;
   1306     }
   1307 
   1308     // Are we at the end?
   1309     if (!isBlankOrBreak(Current))
   1310       break;
   1311 
   1312     // Eat blanks.
   1313     StringRef::iterator Tmp = Current;
   1314     while (isBlankOrBreak(Tmp)) {
   1315       StringRef::iterator i = skip_s_white(Tmp);
   1316       if (i != Tmp) {
   1317         if (LeadingBlanks && (Column < indent) && *Tmp == '\t') {
   1318           setError("Found invalid tab character in indentation", Tmp);
   1319           return false;
   1320         }
   1321         Tmp = i;
   1322         ++Column;
   1323       } else {
   1324         i = skip_b_break(Tmp);
   1325         if (!LeadingBlanks)
   1326           LeadingBlanks = 1;
   1327         Tmp = i;
   1328         Column = 0;
   1329         ++Line;
   1330       }
   1331     }
   1332 
   1333     if (!FlowLevel && Column < indent)
   1334       break;
   1335 
   1336     Current = Tmp;
   1337   }
   1338   if (Start == Current) {
   1339     setError("Got empty plain scalar", Start);
   1340     return false;
   1341   }
   1342   Token T;
   1343   T.Kind = Token::TK_Scalar;
   1344   T.Range = StringRef(Start, Current - Start);
   1345   TokenQueue.push_back(T);
   1346 
   1347   // Plain scalars can be simple keys.
   1348   saveSimpleKeyCandidate(TokenQueue.back(), ColStart, false);
   1349 
   1350   IsSimpleKeyAllowed = false;
   1351 
   1352   return true;
   1353 }
   1354 
   1355 bool Scanner::scanAliasOrAnchor(bool IsAlias) {
   1356   StringRef::iterator Start = Current;
   1357   unsigned ColStart = Column;
   1358   skip(1);
   1359   while(true) {
   1360     if (   *Current == '[' || *Current == ']'
   1361         || *Current == '{' || *Current == '}'
   1362         || *Current == ','
   1363         || *Current == ':')
   1364       break;
   1365     StringRef::iterator i = skip_ns_char(Current);
   1366     if (i == Current)
   1367       break;
   1368     Current = i;
   1369     ++Column;
   1370   }
   1371 
   1372   if (Start == Current) {
   1373     setError("Got empty alias or anchor", Start);
   1374     return false;
   1375   }
   1376 
   1377   Token T;
   1378   T.Kind = IsAlias ? Token::TK_Alias : Token::TK_Anchor;
   1379   T.Range = StringRef(Start, Current - Start);
   1380   TokenQueue.push_back(T);
   1381 
   1382   // Alias and anchors can be simple keys.
   1383   saveSimpleKeyCandidate(TokenQueue.back(), ColStart, false);
   1384 
   1385   IsSimpleKeyAllowed = false;
   1386 
   1387   return true;
   1388 }
   1389 
   1390 bool Scanner::scanBlockScalar(bool IsLiteral) {
   1391   StringRef::iterator Start = Current;
   1392   skip(1); // Eat | or >
   1393   while(true) {
   1394     StringRef::iterator i = skip_nb_char(Current);
   1395     if (i == Current) {
   1396       if (Column == 0)
   1397         break;
   1398       i = skip_b_break(Current);
   1399       if (i != Current) {
   1400         // We got a line break.
   1401         Column = 0;
   1402         ++Line;
   1403         Current = i;
   1404         continue;
   1405       } else {
   1406         // There was an error, which should already have been printed out.
   1407         return false;
   1408       }
   1409     }
   1410     Current = i;
   1411     ++Column;
   1412   }
   1413 
   1414   if (Start == Current) {
   1415     setError("Got empty block scalar", Start);
   1416     return false;
   1417   }
   1418 
   1419   Token T;
   1420   T.Kind = Token::TK_Scalar;
   1421   T.Range = StringRef(Start, Current - Start);
   1422   TokenQueue.push_back(T);
   1423   return true;
   1424 }
   1425 
   1426 bool Scanner::scanTag() {
   1427   StringRef::iterator Start = Current;
   1428   unsigned ColStart = Column;
   1429   skip(1); // Eat !.
   1430   if (Current == End || isBlankOrBreak(Current)); // An empty tag.
   1431   else if (*Current == '<') {
   1432     skip(1);
   1433     scan_ns_uri_char();
   1434     if (!consume('>'))
   1435       return false;
   1436   } else {
   1437     // FIXME: Actually parse the c-ns-shorthand-tag rule.
   1438     Current = skip_while(&Scanner::skip_ns_char, Current);
   1439   }
   1440 
   1441   Token T;
   1442   T.Kind = Token::TK_Tag;
   1443   T.Range = StringRef(Start, Current - Start);
   1444   TokenQueue.push_back(T);
   1445 
   1446   // Tags can be simple keys.
   1447   saveSimpleKeyCandidate(TokenQueue.back(), ColStart, false);
   1448 
   1449   IsSimpleKeyAllowed = false;
   1450 
   1451   return true;
   1452 }
   1453 
   1454 bool Scanner::fetchMoreTokens() {
   1455   if (IsStartOfStream)
   1456     return scanStreamStart();
   1457 
   1458   scanToNextToken();
   1459 
   1460   if (Current == End)
   1461     return scanStreamEnd();
   1462 
   1463   removeStaleSimpleKeyCandidates();
   1464 
   1465   unrollIndent(Column);
   1466 
   1467   if (Column == 0 && *Current == '%')
   1468     return scanDirective();
   1469 
   1470   if (Column == 0 && Current + 4 <= End
   1471       && *Current == '-'
   1472       && *(Current + 1) == '-'
   1473       && *(Current + 2) == '-'
   1474       && (Current + 3 == End || isBlankOrBreak(Current + 3)))
   1475     return scanDocumentIndicator(true);
   1476 
   1477   if (Column == 0 && Current + 4 <= End
   1478       && *Current == '.'
   1479       && *(Current + 1) == '.'
   1480       && *(Current + 2) == '.'
   1481       && (Current + 3 == End || isBlankOrBreak(Current + 3)))
   1482     return scanDocumentIndicator(false);
   1483 
   1484   if (*Current == '[')
   1485     return scanFlowCollectionStart(true);
   1486 
   1487   if (*Current == '{')
   1488     return scanFlowCollectionStart(false);
   1489 
   1490   if (*Current == ']')
   1491     return scanFlowCollectionEnd(true);
   1492 
   1493   if (*Current == '}')
   1494     return scanFlowCollectionEnd(false);
   1495 
   1496   if (*Current == ',')
   1497     return scanFlowEntry();
   1498 
   1499   if (*Current == '-' && isBlankOrBreak(Current + 1))
   1500     return scanBlockEntry();
   1501 
   1502   if (*Current == '?' && (FlowLevel || isBlankOrBreak(Current + 1)))
   1503     return scanKey();
   1504 
   1505   if (*Current == ':' && (FlowLevel || isBlankOrBreak(Current + 1)))
   1506     return scanValue();
   1507 
   1508   if (*Current == '*')
   1509     return scanAliasOrAnchor(true);
   1510 
   1511   if (*Current == '&')
   1512     return scanAliasOrAnchor(false);
   1513 
   1514   if (*Current == '!')
   1515     return scanTag();
   1516 
   1517   if (*Current == '|' && !FlowLevel)
   1518     return scanBlockScalar(true);
   1519 
   1520   if (*Current == '>' && !FlowLevel)
   1521     return scanBlockScalar(false);
   1522 
   1523   if (*Current == '\'')
   1524     return scanFlowScalar(false);
   1525 
   1526   if (*Current == '"')
   1527     return scanFlowScalar(true);
   1528 
   1529   // Get a plain scalar.
   1530   StringRef FirstChar(Current, 1);
   1531   if (!(isBlankOrBreak(Current)
   1532         || FirstChar.find_first_of("-?:,[]{}#&*!|>'\"%@`") != StringRef::npos)
   1533       || (*Current == '-' && !isBlankOrBreak(Current + 1))
   1534       || (!FlowLevel && (*Current == '?' || *Current == ':')
   1535           && isBlankOrBreak(Current + 1))
   1536       || (!FlowLevel && *Current == ':'
   1537                       && Current + 2 < End
   1538                       && *(Current + 1) == ':'
   1539                       && !isBlankOrBreak(Current + 2)))
   1540     return scanPlainScalar();
   1541 
   1542   setError("Unrecognized character while tokenizing.");
   1543   return false;
   1544 }
   1545 
   1546 Stream::Stream(StringRef Input, SourceMgr &SM)
   1547   : scanner(new Scanner(Input, SM))
   1548   , CurrentDoc(0) {}
   1549 
   1550 Stream::Stream(MemoryBuffer *InputBuffer, SourceMgr &SM)
   1551   : scanner(new Scanner(InputBuffer, SM))
   1552   , CurrentDoc(0) {}
   1553 
   1554 Stream::~Stream() {}
   1555 
   1556 bool Stream::failed() { return scanner->failed(); }
   1557 
   1558 void Stream::printError(Node *N, const Twine &Msg) {
   1559   SmallVector<SMRange, 1> Ranges;
   1560   Ranges.push_back(N->getSourceRange());
   1561   scanner->printError( N->getSourceRange().Start
   1562                      , SourceMgr::DK_Error
   1563                      , Msg
   1564                      , Ranges);
   1565 }
   1566 
   1567 void Stream::handleYAMLDirective(const Token &t) {
   1568   // TODO: Ensure version is 1.x.
   1569 }
   1570 
   1571 document_iterator Stream::begin() {
   1572   if (CurrentDoc)
   1573     report_fatal_error("Can only iterate over the stream once");
   1574 
   1575   // Skip Stream-Start.
   1576   scanner->getNext();
   1577 
   1578   CurrentDoc.reset(new Document(*this));
   1579   return document_iterator(CurrentDoc);
   1580 }
   1581 
   1582 document_iterator Stream::end() {
   1583   return document_iterator();
   1584 }
   1585 
   1586 void Stream::skip() {
   1587   for (document_iterator i = begin(), e = end(); i != e; ++i)
   1588     i->skip();
   1589 }
   1590 
   1591 Node::Node(unsigned int Type, OwningPtr<Document> &D, StringRef A)
   1592   : Doc(D)
   1593   , TypeID(Type)
   1594   , Anchor(A) {
   1595   SMLoc Start = SMLoc::getFromPointer(peekNext().Range.begin());
   1596   SourceRange = SMRange(Start, Start);
   1597 }
   1598 
   1599 Token &Node::peekNext() {
   1600   return Doc->peekNext();
   1601 }
   1602 
   1603 Token Node::getNext() {
   1604   return Doc->getNext();
   1605 }
   1606 
   1607 Node *Node::parseBlockNode() {
   1608   return Doc->parseBlockNode();
   1609 }
   1610 
   1611 BumpPtrAllocator &Node::getAllocator() {
   1612   return Doc->NodeAllocator;
   1613 }
   1614 
   1615 void Node::setError(const Twine &Msg, Token &Tok) const {
   1616   Doc->setError(Msg, Tok);
   1617 }
   1618 
   1619 bool Node::failed() const {
   1620   return Doc->failed();
   1621 }
   1622 
   1623 
   1624 
   1625 StringRef ScalarNode::getValue(SmallVectorImpl<char> &Storage) const {
   1626   // TODO: Handle newlines properly. We need to remove leading whitespace.
   1627   if (Value[0] == '"') { // Double quoted.
   1628     // Pull off the leading and trailing "s.
   1629     StringRef UnquotedValue = Value.substr(1, Value.size() - 2);
   1630     // Search for characters that would require unescaping the value.
   1631     StringRef::size_type i = UnquotedValue.find_first_of("\\\r\n");
   1632     if (i != StringRef::npos)
   1633       return unescapeDoubleQuoted(UnquotedValue, i, Storage);
   1634     return UnquotedValue;
   1635   } else if (Value[0] == '\'') { // Single quoted.
   1636     // Pull off the leading and trailing 's.
   1637     StringRef UnquotedValue = Value.substr(1, Value.size() - 2);
   1638     StringRef::size_type i = UnquotedValue.find('\'');
   1639     if (i != StringRef::npos) {
   1640       // We're going to need Storage.
   1641       Storage.clear();
   1642       Storage.reserve(UnquotedValue.size());
   1643       for (; i != StringRef::npos; i = UnquotedValue.find('\'')) {
   1644         StringRef Valid(UnquotedValue.begin(), i);
   1645         Storage.insert(Storage.end(), Valid.begin(), Valid.end());
   1646         Storage.push_back('\'');
   1647         UnquotedValue = UnquotedValue.substr(i + 2);
   1648       }
   1649       Storage.insert(Storage.end(), UnquotedValue.begin(), UnquotedValue.end());
   1650       return StringRef(Storage.begin(), Storage.size());
   1651     }
   1652     return UnquotedValue;
   1653   }
   1654   // Plain or block.
   1655   return Value.rtrim(" ");
   1656 }
   1657 
   1658 StringRef ScalarNode::unescapeDoubleQuoted( StringRef UnquotedValue
   1659                                           , StringRef::size_type i
   1660                                           , SmallVectorImpl<char> &Storage)
   1661                                           const {
   1662   // Use Storage to build proper value.
   1663   Storage.clear();
   1664   Storage.reserve(UnquotedValue.size());
   1665   for (; i != StringRef::npos; i = UnquotedValue.find_first_of("\\\r\n")) {
   1666     // Insert all previous chars into Storage.
   1667     StringRef Valid(UnquotedValue.begin(), i);
   1668     Storage.insert(Storage.end(), Valid.begin(), Valid.end());
   1669     // Chop off inserted chars.
   1670     UnquotedValue = UnquotedValue.substr(i);
   1671 
   1672     assert(!UnquotedValue.empty() && "Can't be empty!");
   1673 
   1674     // Parse escape or line break.
   1675     switch (UnquotedValue[0]) {
   1676     case '\r':
   1677     case '\n':
   1678       Storage.push_back('\n');
   1679       if (   UnquotedValue.size() > 1
   1680           && (UnquotedValue[1] == '\r' || UnquotedValue[1] == '\n'))
   1681         UnquotedValue = UnquotedValue.substr(1);
   1682       UnquotedValue = UnquotedValue.substr(1);
   1683       break;
   1684     default:
   1685       if (UnquotedValue.size() == 1)
   1686         // TODO: Report error.
   1687         break;
   1688       UnquotedValue = UnquotedValue.substr(1);
   1689       switch (UnquotedValue[0]) {
   1690       default: {
   1691           Token T;
   1692           T.Range = StringRef(UnquotedValue.begin(), 1);
   1693           setError("Unrecognized escape code!", T);
   1694           return "";
   1695         }
   1696       case '\r':
   1697       case '\n':
   1698         // Remove the new line.
   1699         if (   UnquotedValue.size() > 1
   1700             && (UnquotedValue[1] == '\r' || UnquotedValue[1] == '\n'))
   1701           UnquotedValue = UnquotedValue.substr(1);
   1702         // If this was just a single byte newline, it will get skipped
   1703         // below.
   1704         break;
   1705       case '0':
   1706         Storage.push_back(0x00);
   1707         break;
   1708       case 'a':
   1709         Storage.push_back(0x07);
   1710         break;
   1711       case 'b':
   1712         Storage.push_back(0x08);
   1713         break;
   1714       case 't':
   1715       case 0x09:
   1716         Storage.push_back(0x09);
   1717         break;
   1718       case 'n':
   1719         Storage.push_back(0x0A);
   1720         break;
   1721       case 'v':
   1722         Storage.push_back(0x0B);
   1723         break;
   1724       case 'f':
   1725         Storage.push_back(0x0C);
   1726         break;
   1727       case 'r':
   1728         Storage.push_back(0x0D);
   1729         break;
   1730       case 'e':
   1731         Storage.push_back(0x1B);
   1732         break;
   1733       case ' ':
   1734         Storage.push_back(0x20);
   1735         break;
   1736       case '"':
   1737         Storage.push_back(0x22);
   1738         break;
   1739       case '/':
   1740         Storage.push_back(0x2F);
   1741         break;
   1742       case '\\':
   1743         Storage.push_back(0x5C);
   1744         break;
   1745       case 'N':
   1746         encodeUTF8(0x85, Storage);
   1747         break;
   1748       case '_':
   1749         encodeUTF8(0xA0, Storage);
   1750         break;
   1751       case 'L':
   1752         encodeUTF8(0x2028, Storage);
   1753         break;
   1754       case 'P':
   1755         encodeUTF8(0x2029, Storage);
   1756         break;
   1757       case 'x': {
   1758           if (UnquotedValue.size() < 3)
   1759             // TODO: Report error.
   1760             break;
   1761           unsigned int UnicodeScalarValue;
   1762           if (UnquotedValue.substr(1, 2).getAsInteger(16, UnicodeScalarValue))
   1763             // TODO: Report error.
   1764             UnicodeScalarValue = 0xFFFD;
   1765           encodeUTF8(UnicodeScalarValue, Storage);
   1766           UnquotedValue = UnquotedValue.substr(2);
   1767           break;
   1768         }
   1769       case 'u': {
   1770           if (UnquotedValue.size() < 5)
   1771             // TODO: Report error.
   1772             break;
   1773           unsigned int UnicodeScalarValue;
   1774           if (UnquotedValue.substr(1, 4).getAsInteger(16, UnicodeScalarValue))
   1775             // TODO: Report error.
   1776             UnicodeScalarValue = 0xFFFD;
   1777           encodeUTF8(UnicodeScalarValue, Storage);
   1778           UnquotedValue = UnquotedValue.substr(4);
   1779           break;
   1780         }
   1781       case 'U': {
   1782           if (UnquotedValue.size() < 9)
   1783             // TODO: Report error.
   1784             break;
   1785           unsigned int UnicodeScalarValue;
   1786           if (UnquotedValue.substr(1, 8).getAsInteger(16, UnicodeScalarValue))
   1787             // TODO: Report error.
   1788             UnicodeScalarValue = 0xFFFD;
   1789           encodeUTF8(UnicodeScalarValue, Storage);
   1790           UnquotedValue = UnquotedValue.substr(8);
   1791           break;
   1792         }
   1793       }
   1794       UnquotedValue = UnquotedValue.substr(1);
   1795     }
   1796   }
   1797   Storage.insert(Storage.end(), UnquotedValue.begin(), UnquotedValue.end());
   1798   return StringRef(Storage.begin(), Storage.size());
   1799 }
   1800 
   1801 Node *KeyValueNode::getKey() {
   1802   if (Key)
   1803     return Key;
   1804   // Handle implicit null keys.
   1805   {
   1806     Token &t = peekNext();
   1807     if (   t.Kind == Token::TK_BlockEnd
   1808         || t.Kind == Token::TK_Value
   1809         || t.Kind == Token::TK_Error) {
   1810       return Key = new (getAllocator()) NullNode(Doc);
   1811     }
   1812     if (t.Kind == Token::TK_Key)
   1813       getNext(); // skip TK_Key.
   1814   }
   1815 
   1816   // Handle explicit null keys.
   1817   Token &t = peekNext();
   1818   if (t.Kind == Token::TK_BlockEnd || t.Kind == Token::TK_Value) {
   1819     return Key = new (getAllocator()) NullNode(Doc);
   1820   }
   1821 
   1822   // We've got a normal key.
   1823   return Key = parseBlockNode();
   1824 }
   1825 
   1826 Node *KeyValueNode::getValue() {
   1827   if (Value)
   1828     return Value;
   1829   getKey()->skip();
   1830   if (failed())
   1831     return Value = new (getAllocator()) NullNode(Doc);
   1832 
   1833   // Handle implicit null values.
   1834   {
   1835     Token &t = peekNext();
   1836     if (   t.Kind == Token::TK_BlockEnd
   1837         || t.Kind == Token::TK_FlowMappingEnd
   1838         || t.Kind == Token::TK_Key
   1839         || t.Kind == Token::TK_FlowEntry
   1840         || t.Kind == Token::TK_Error) {
   1841       return Value = new (getAllocator()) NullNode(Doc);
   1842     }
   1843 
   1844     if (t.Kind != Token::TK_Value) {
   1845       setError("Unexpected token in Key Value.", t);
   1846       return Value = new (getAllocator()) NullNode(Doc);
   1847     }
   1848     getNext(); // skip TK_Value.
   1849   }
   1850 
   1851   // Handle explicit null values.
   1852   Token &t = peekNext();
   1853   if (t.Kind == Token::TK_BlockEnd || t.Kind == Token::TK_Key) {
   1854     return Value = new (getAllocator()) NullNode(Doc);
   1855   }
   1856 
   1857   // We got a normal value.
   1858   return Value = parseBlockNode();
   1859 }
   1860 
   1861 void MappingNode::increment() {
   1862   if (failed()) {
   1863     IsAtEnd = true;
   1864     CurrentEntry = 0;
   1865     return;
   1866   }
   1867   if (CurrentEntry) {
   1868     CurrentEntry->skip();
   1869     if (Type == MT_Inline) {
   1870       IsAtEnd = true;
   1871       CurrentEntry = 0;
   1872       return;
   1873     }
   1874   }
   1875   Token T = peekNext();
   1876   if (T.Kind == Token::TK_Key || T.Kind == Token::TK_Scalar) {
   1877     // KeyValueNode eats the TK_Key. That way it can detect null keys.
   1878     CurrentEntry = new (getAllocator()) KeyValueNode(Doc);
   1879   } else if (Type == MT_Block) {
   1880     switch (T.Kind) {
   1881     case Token::TK_BlockEnd:
   1882       getNext();
   1883       IsAtEnd = true;
   1884       CurrentEntry = 0;
   1885       break;
   1886     default:
   1887       setError("Unexpected token. Expected Key or Block End", T);
   1888     case Token::TK_Error:
   1889       IsAtEnd = true;
   1890       CurrentEntry = 0;
   1891     }
   1892   } else {
   1893     switch (T.Kind) {
   1894     case Token::TK_FlowEntry:
   1895       // Eat the flow entry and recurse.
   1896       getNext();
   1897       return increment();
   1898     case Token::TK_FlowMappingEnd:
   1899       getNext();
   1900     case Token::TK_Error:
   1901       // Set this to end iterator.
   1902       IsAtEnd = true;
   1903       CurrentEntry = 0;
   1904       break;
   1905     default:
   1906       setError( "Unexpected token. Expected Key, Flow Entry, or Flow "
   1907                 "Mapping End."
   1908               , T);
   1909       IsAtEnd = true;
   1910       CurrentEntry = 0;
   1911     }
   1912   }
   1913 }
   1914 
   1915 void SequenceNode::increment() {
   1916   if (failed()) {
   1917     IsAtEnd = true;
   1918     CurrentEntry = 0;
   1919     return;
   1920   }
   1921   if (CurrentEntry)
   1922     CurrentEntry->skip();
   1923   Token T = peekNext();
   1924   if (SeqType == ST_Block) {
   1925     switch (T.Kind) {
   1926     case Token::TK_BlockEntry:
   1927       getNext();
   1928       CurrentEntry = parseBlockNode();
   1929       if (CurrentEntry == 0) { // An error occurred.
   1930         IsAtEnd = true;
   1931         CurrentEntry = 0;
   1932       }
   1933       break;
   1934     case Token::TK_BlockEnd:
   1935       getNext();
   1936       IsAtEnd = true;
   1937       CurrentEntry = 0;
   1938       break;
   1939     default:
   1940       setError( "Unexpected token. Expected Block Entry or Block End."
   1941               , T);
   1942     case Token::TK_Error:
   1943       IsAtEnd = true;
   1944       CurrentEntry = 0;
   1945     }
   1946   } else if (SeqType == ST_Indentless) {
   1947     switch (T.Kind) {
   1948     case Token::TK_BlockEntry:
   1949       getNext();
   1950       CurrentEntry = parseBlockNode();
   1951       if (CurrentEntry == 0) { // An error occurred.
   1952         IsAtEnd = true;
   1953         CurrentEntry = 0;
   1954       }
   1955       break;
   1956     default:
   1957     case Token::TK_Error:
   1958       IsAtEnd = true;
   1959       CurrentEntry = 0;
   1960     }
   1961   } else if (SeqType == ST_Flow) {
   1962     switch (T.Kind) {
   1963     case Token::TK_FlowEntry:
   1964       // Eat the flow entry and recurse.
   1965       getNext();
   1966       WasPreviousTokenFlowEntry = true;
   1967       return increment();
   1968     case Token::TK_FlowSequenceEnd:
   1969       getNext();
   1970     case Token::TK_Error:
   1971       // Set this to end iterator.
   1972       IsAtEnd = true;
   1973       CurrentEntry = 0;
   1974       break;
   1975     case Token::TK_StreamEnd:
   1976     case Token::TK_DocumentEnd:
   1977     case Token::TK_DocumentStart:
   1978       setError("Could not find closing ]!", T);
   1979       // Set this to end iterator.
   1980       IsAtEnd = true;
   1981       CurrentEntry = 0;
   1982       break;
   1983     default:
   1984       if (!WasPreviousTokenFlowEntry) {
   1985         setError("Expected , between entries!", T);
   1986         IsAtEnd = true;
   1987         CurrentEntry = 0;
   1988         break;
   1989       }
   1990       // Otherwise it must be a flow entry.
   1991       CurrentEntry = parseBlockNode();
   1992       if (!CurrentEntry) {
   1993         IsAtEnd = true;
   1994       }
   1995       WasPreviousTokenFlowEntry = false;
   1996       break;
   1997     }
   1998   }
   1999 }
   2000 
   2001 Document::Document(Stream &S) : stream(S), Root(0) {
   2002   if (parseDirectives())
   2003     expectToken(Token::TK_DocumentStart);
   2004   Token &T = peekNext();
   2005   if (T.Kind == Token::TK_DocumentStart)
   2006     getNext();
   2007 }
   2008 
   2009 bool Document::skip()  {
   2010   if (stream.scanner->failed())
   2011     return false;
   2012   if (!Root)
   2013     getRoot();
   2014   Root->skip();
   2015   Token &T = peekNext();
   2016   if (T.Kind == Token::TK_StreamEnd)
   2017     return false;
   2018   if (T.Kind == Token::TK_DocumentEnd) {
   2019     getNext();
   2020     return skip();
   2021   }
   2022   return true;
   2023 }
   2024 
   2025 Token &Document::peekNext() {
   2026   return stream.scanner->peekNext();
   2027 }
   2028 
   2029 Token Document::getNext() {
   2030   return stream.scanner->getNext();
   2031 }
   2032 
   2033 void Document::setError(const Twine &Message, Token &Location) const {
   2034   stream.scanner->setError(Message, Location.Range.begin());
   2035 }
   2036 
   2037 bool Document::failed() const {
   2038   return stream.scanner->failed();
   2039 }
   2040 
   2041 Node *Document::parseBlockNode() {
   2042   Token T = peekNext();
   2043   // Handle properties.
   2044   Token AnchorInfo;
   2045 parse_property:
   2046   switch (T.Kind) {
   2047   case Token::TK_Alias:
   2048     getNext();
   2049     return new (NodeAllocator) AliasNode(stream.CurrentDoc, T.Range.substr(1));
   2050   case Token::TK_Anchor:
   2051     if (AnchorInfo.Kind == Token::TK_Anchor) {
   2052       setError("Already encountered an anchor for this node!", T);
   2053       return 0;
   2054     }
   2055     AnchorInfo = getNext(); // Consume TK_Anchor.
   2056     T = peekNext();
   2057     goto parse_property;
   2058   case Token::TK_Tag:
   2059     getNext(); // Skip TK_Tag.
   2060     T = peekNext();
   2061     goto parse_property;
   2062   default:
   2063     break;
   2064   }
   2065 
   2066   switch (T.Kind) {
   2067   case Token::TK_BlockEntry:
   2068     // We got an unindented BlockEntry sequence. This is not terminated with
   2069     // a BlockEnd.
   2070     // Don't eat the TK_BlockEntry, SequenceNode needs it.
   2071     return new (NodeAllocator) SequenceNode( stream.CurrentDoc
   2072                                            , AnchorInfo.Range.substr(1)
   2073                                            , SequenceNode::ST_Indentless);
   2074   case Token::TK_BlockSequenceStart:
   2075     getNext();
   2076     return new (NodeAllocator)
   2077       SequenceNode( stream.CurrentDoc
   2078                   , AnchorInfo.Range.substr(1)
   2079                   , SequenceNode::ST_Block);
   2080   case Token::TK_BlockMappingStart:
   2081     getNext();
   2082     return new (NodeAllocator)
   2083       MappingNode( stream.CurrentDoc
   2084                  , AnchorInfo.Range.substr(1)
   2085                  , MappingNode::MT_Block);
   2086   case Token::TK_FlowSequenceStart:
   2087     getNext();
   2088     return new (NodeAllocator)
   2089       SequenceNode( stream.CurrentDoc
   2090                   , AnchorInfo.Range.substr(1)
   2091                   , SequenceNode::ST_Flow);
   2092   case Token::TK_FlowMappingStart:
   2093     getNext();
   2094     return new (NodeAllocator)
   2095       MappingNode( stream.CurrentDoc
   2096                  , AnchorInfo.Range.substr(1)
   2097                  , MappingNode::MT_Flow);
   2098   case Token::TK_Scalar:
   2099     getNext();
   2100     return new (NodeAllocator)
   2101       ScalarNode( stream.CurrentDoc
   2102                 , AnchorInfo.Range.substr(1)
   2103                 , T.Range);
   2104   case Token::TK_Key:
   2105     // Don't eat the TK_Key, KeyValueNode expects it.
   2106     return new (NodeAllocator)
   2107       MappingNode( stream.CurrentDoc
   2108                  , AnchorInfo.Range.substr(1)
   2109                  , MappingNode::MT_Inline);
   2110   case Token::TK_DocumentStart:
   2111   case Token::TK_DocumentEnd:
   2112   case Token::TK_StreamEnd:
   2113   default:
   2114     // TODO: Properly handle tags. "[!!str ]" should resolve to !!str "", not
   2115     //       !!null null.
   2116     return new (NodeAllocator) NullNode(stream.CurrentDoc);
   2117   case Token::TK_Error:
   2118     return 0;
   2119   }
   2120   llvm_unreachable("Control flow shouldn't reach here.");
   2121   return 0;
   2122 }
   2123 
   2124 bool Document::parseDirectives() {
   2125   bool isDirective = false;
   2126   while (true) {
   2127     Token T = peekNext();
   2128     if (T.Kind == Token::TK_TagDirective) {
   2129       handleTagDirective(getNext());
   2130       isDirective = true;
   2131     } else if (T.Kind == Token::TK_VersionDirective) {
   2132       stream.handleYAMLDirective(getNext());
   2133       isDirective = true;
   2134     } else
   2135       break;
   2136   }
   2137   return isDirective;
   2138 }
   2139 
   2140 bool Document::expectToken(int TK) {
   2141   Token T = getNext();
   2142   if (T.Kind != TK) {
   2143     setError("Unexpected token", T);
   2144     return false;
   2145   }
   2146   return true;
   2147 }
   2148