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      1 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #include "tools/gn/tokenizer.h"
      6 
      7 #include "base/logging.h"
      8 #include "tools/gn/input_file.h"
      9 
     10 namespace {
     11 
     12 bool CouldBeTwoCharOperatorBegin(char c) {
     13   return c == '<' || c == '>' || c == '!' || c == '=' || c == '-' ||
     14          c == '+' || c == '|' || c == '&';
     15 }
     16 
     17 bool CouldBeTwoCharOperatorEnd(char c) {
     18   return c == '=' || c == '|' || c == '&';
     19 }
     20 
     21 bool CouldBeOneCharOperator(char c) {
     22   return c == '=' || c == '<' || c == '>' || c == '+' || c == '!' ||
     23          c == ':' || c == '|' || c == '&' || c == '-';
     24 }
     25 
     26 bool CouldBeOperator(char c) {
     27   return CouldBeOneCharOperator(c) || CouldBeTwoCharOperatorBegin(c);
     28 }
     29 
     30 bool IsScoperChar(char c) {
     31   return c == '(' || c == ')' || c == '[' || c == ']' || c == '{' || c == '}';
     32 }
     33 
     34 Token::Type GetSpecificOperatorType(base::StringPiece value) {
     35   if (value == "=")
     36     return Token::EQUAL;
     37   if (value == "+")
     38     return Token::PLUS;
     39   if (value == "-")
     40     return Token::MINUS;
     41   if (value == "+=")
     42     return Token::PLUS_EQUALS;
     43   if (value == "-=")
     44     return Token::MINUS_EQUALS;
     45   if (value == "==")
     46     return Token::EQUAL_EQUAL;
     47   if (value == "!=")
     48     return Token::NOT_EQUAL;
     49   if (value == "<=")
     50     return Token::LESS_EQUAL;
     51   if (value == ">=")
     52     return Token::GREATER_EQUAL;
     53   if (value == "<")
     54     return Token::LESS_THAN;
     55   if (value == ">")
     56     return Token::GREATER_THAN;
     57   if (value == "&&")
     58     return Token::BOOLEAN_AND;
     59   if (value == "||")
     60     return Token::BOOLEAN_OR;
     61   if (value == "!")
     62     return Token::BANG;
     63   if (value == ".")
     64     return Token::DOT;
     65   return Token::INVALID;
     66 }
     67 
     68 }  // namespace
     69 
     70 Tokenizer::Tokenizer(const InputFile* input_file, Err* err)
     71     : input_file_(input_file),
     72       input_(input_file->contents()),
     73       err_(err),
     74       cur_(0),
     75       line_number_(1),
     76       char_in_line_(1) {
     77 }
     78 
     79 Tokenizer::~Tokenizer() {
     80 }
     81 
     82 // static
     83 std::vector<Token> Tokenizer::Tokenize(const InputFile* input_file, Err* err) {
     84   Tokenizer t(input_file, err);
     85   return t.Run();
     86 }
     87 
     88 std::vector<Token> Tokenizer::Run() {
     89   DCHECK(tokens_.empty());
     90   while (!done()) {
     91     AdvanceToNextToken();
     92     if (done())
     93       break;
     94     Location location = GetCurrentLocation();
     95 
     96     Token::Type type = ClassifyCurrent();
     97     if (type == Token::INVALID) {
     98       *err_ = GetErrorForInvalidToken(location);
     99       break;
    100     }
    101     size_t token_begin = cur_;
    102     AdvanceToEndOfToken(location, type);
    103     if (has_error())
    104       break;
    105     size_t token_end = cur_;
    106 
    107     base::StringPiece token_value(&input_.data()[token_begin],
    108                                   token_end - token_begin);
    109 
    110     if (type == Token::UNCLASSIFIED_OPERATOR)
    111       type = GetSpecificOperatorType(token_value);
    112     if (type == Token::IDENTIFIER) {
    113       if (token_value == "if")
    114         type = Token::IF;
    115       else if (token_value == "else")
    116         type = Token::ELSE;
    117       else if (token_value == "true")
    118         type = Token::TRUE_TOKEN;
    119       else if (token_value == "false")
    120         type = Token::FALSE_TOKEN;
    121     }
    122 
    123     // TODO(brettw) This just strips comments from the token stream. This
    124     // is probably wrong, they should be removed at a later stage so we can
    125     // do things like rewrite the file. But this makes the parser simpler and
    126     // is OK for now.
    127     if (type != Token::COMMENT)
    128       tokens_.push_back(Token(location, type, token_value));
    129   }
    130   if (err_->has_error())
    131     tokens_.clear();
    132   return tokens_;
    133 }
    134 
    135 // static
    136 size_t Tokenizer::ByteOffsetOfNthLine(const base::StringPiece& buf, int n) {
    137   int cur_line = 1;
    138   size_t cur_byte = 0;
    139 
    140   DCHECK(n > 0);
    141 
    142   if (n == 1)
    143     return 0;
    144 
    145   while (cur_byte < buf.size()) {
    146     if (IsNewline(buf, cur_byte)) {
    147       cur_line++;
    148       if (cur_line == n)
    149         return cur_byte + 1;
    150     }
    151     cur_byte++;
    152   }
    153   return -1;
    154 }
    155 
    156 // static
    157 bool Tokenizer::IsNewline(const base::StringPiece& buffer, size_t offset) {
    158   DCHECK(offset < buffer.size());
    159   // We may need more logic here to handle different line ending styles.
    160   return buffer[offset] == '\n';
    161 }
    162 
    163 
    164 void Tokenizer::AdvanceToNextToken() {
    165   while (!at_end() && IsCurrentWhitespace())
    166     Advance();
    167 }
    168 
    169 Token::Type Tokenizer::ClassifyCurrent() const {
    170   DCHECK(!at_end());
    171   char next_char = cur_char();
    172   if (IsAsciiDigit(next_char))
    173     return Token::INTEGER;
    174   if (next_char == '"')
    175     return Token::STRING;
    176 
    177   // Note: '-' handled specially below.
    178   if (next_char != '-' && CouldBeOperator(next_char))
    179     return Token::UNCLASSIFIED_OPERATOR;
    180 
    181   if (IsIdentifierFirstChar(next_char))
    182     return Token::IDENTIFIER;
    183 
    184   if (next_char == '[')
    185     return Token::LEFT_BRACKET;
    186   if (next_char == ']')
    187     return Token::RIGHT_BRACKET;
    188   if (next_char == '(')
    189     return Token::LEFT_PAREN;
    190   if (next_char == ')')
    191     return Token::RIGHT_PAREN;
    192   if (next_char == '{')
    193     return Token::LEFT_BRACE;
    194   if (next_char == '}')
    195     return Token::RIGHT_BRACE;
    196 
    197   if (next_char == '.')
    198     return Token::DOT;
    199   if (next_char == ',')
    200     return Token::COMMA;
    201 
    202   if (next_char == '#')
    203     return Token::COMMENT;
    204 
    205   // For the case of '-' differentiate between a negative number and anything
    206   // else.
    207   if (next_char == '-') {
    208     if (!CanIncrement())
    209       return Token::UNCLASSIFIED_OPERATOR;  // Just the minus before end of
    210                                             // file.
    211     char following_char = input_[cur_ + 1];
    212     if (IsAsciiDigit(following_char))
    213       return Token::INTEGER;
    214     return Token::UNCLASSIFIED_OPERATOR;
    215   }
    216 
    217   return Token::INVALID;
    218 }
    219 
    220 void Tokenizer::AdvanceToEndOfToken(const Location& location,
    221                                     Token::Type type) {
    222   switch (type) {
    223     case Token::INTEGER:
    224       do {
    225         Advance();
    226       } while (!at_end() && IsAsciiDigit(cur_char()));
    227       if (!at_end()) {
    228         // Require the char after a number to be some kind of space, scope,
    229         // or operator.
    230         char c = cur_char();
    231         if (!IsCurrentWhitespace() && !CouldBeOperator(c) &&
    232             !IsScoperChar(c) && c != ',') {
    233           *err_ = Err(GetCurrentLocation(),
    234                       "This is not a valid number.",
    235                       "Learn to count.");
    236           // Highlight the number.
    237           err_->AppendRange(LocationRange(location, GetCurrentLocation()));
    238         }
    239       }
    240       break;
    241 
    242     case Token::STRING: {
    243       char initial = cur_char();
    244       Advance();  // Advance past initial "
    245       for (;;) {
    246         if (at_end()) {
    247           *err_ = Err(LocationRange(location, GetCurrentLocation()),
    248                       "Unterminated string literal.",
    249                       "Don't leave me hanging like this!");
    250           break;
    251         }
    252         if (IsCurrentStringTerminator(initial)) {
    253           Advance();  // Skip past last "
    254           break;
    255         } else if (cur_char() == '\n') {
    256           *err_ = Err(LocationRange(location, GetCurrentLocation()),
    257                       "Newline in string constant.");
    258         }
    259         Advance();
    260       }
    261       break;
    262     }
    263 
    264     case Token::UNCLASSIFIED_OPERATOR:
    265       // Some operators are two characters, some are one.
    266       if (CouldBeTwoCharOperatorBegin(cur_char())) {
    267         if (CanIncrement() && CouldBeTwoCharOperatorEnd(input_[cur_ + 1]))
    268           Advance();
    269       }
    270       Advance();
    271       break;
    272 
    273     case Token::IDENTIFIER:
    274       while (!at_end() && IsIdentifierContinuingChar(cur_char()))
    275         Advance();
    276       break;
    277 
    278     case Token::LEFT_BRACKET:
    279     case Token::RIGHT_BRACKET:
    280     case Token::LEFT_BRACE:
    281     case Token::RIGHT_BRACE:
    282     case Token::LEFT_PAREN:
    283     case Token::RIGHT_PAREN:
    284     case Token::DOT:
    285     case Token::COMMA:
    286       Advance();  // All are one char.
    287       break;
    288 
    289     case Token::COMMENT:
    290       // Eat to EOL.
    291       while (!at_end() && !IsCurrentNewline())
    292         Advance();
    293       break;
    294 
    295     case Token::INVALID:
    296     default:
    297       *err_ = Err(location, "Everything is all messed up",
    298                   "Please insert system disk in drive A: and press any key.");
    299       NOTREACHED();
    300       return;
    301   }
    302 }
    303 
    304 bool Tokenizer::IsCurrentWhitespace() const {
    305   DCHECK(!at_end());
    306   char c = input_[cur_];
    307   // Note that tab (0x09) is illegal.
    308   return c == 0x0A || c == 0x0B || c == 0x0C || c == 0x0D || c == 0x20;
    309 }
    310 
    311 bool Tokenizer::IsCurrentStringTerminator(char quote_char) const {
    312   DCHECK(!at_end());
    313   if (cur_char() != quote_char)
    314     return false;
    315 
    316   // Check for escaping. \" is not a string terminator, but \\" is. Count
    317   // the number of preceeding backslashes.
    318   int num_backslashes = 0;
    319   for (int i = static_cast<int>(cur_) - 1; i >= 0 && input_[i] == '\\'; i--)
    320     num_backslashes++;
    321 
    322   // Even backslashes mean that they were escaping each other and don't count
    323   // as escaping this quote.
    324   return (num_backslashes % 2) == 0;
    325 }
    326 
    327 bool Tokenizer::IsCurrentNewline() const {
    328   return IsNewline(input_, cur_);
    329 }
    330 
    331 void Tokenizer::Advance() {
    332   DCHECK(cur_ < input_.size());
    333   if (IsCurrentNewline()) {
    334     line_number_++;
    335     char_in_line_ = 1;
    336   } else {
    337     char_in_line_++;
    338   }
    339   cur_++;
    340 }
    341 
    342 Location Tokenizer::GetCurrentLocation() const {
    343   return Location(input_file_, line_number_, char_in_line_);
    344 }
    345 
    346 Err Tokenizer::GetErrorForInvalidToken(const Location& location) const {
    347   std::string help;
    348   if (cur_char() == ';') {
    349     // Semicolon.
    350     help = "Semicolons are not needed, delete this one.";
    351   } else if (cur_char() == '\t') {
    352     // Tab.
    353     help = "You got a tab character in here. Tabs are evil. "
    354            "Convert to spaces.";
    355   } else if (cur_char() == '/' && cur_ + 1 < input_.size() &&
    356       (input_[cur_ + 1] == '/' || input_[cur_ + 1] == '*')) {
    357     // Different types of comments.
    358     help = "Comments should start with # instead";
    359   } else {
    360     help = "I have no idea what this is.";
    361   }
    362 
    363   return Err(location, "Invalid token.", help);
    364 }
    365