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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 #ifndef TOOLS_GN_PARSER_H_
      6 #define TOOLS_GN_PARSER_H_
      7 
      8 #include <vector>
      9 
     10 #include "base/basictypes.h"
     11 #include "base/gtest_prod_util.h"
     12 #include "base/memory/scoped_ptr.h"
     13 #include "tools/gn/err.h"
     14 #include "tools/gn/parse_tree.h"
     15 
     16 // Parses a series of tokens. The resulting AST will refer to the tokens passed
     17 // to the input, so the tokens an the file data they refer to must outlive your
     18 // use of the ParseNode.
     19 class Parser {
     20  public:
     21   // Will return a null pointer and set the err on error.
     22   static scoped_ptr<ParseNode> Parse(const std::vector<Token>& tokens,
     23                                      Err* err);
     24 
     25   // Alternative to parsing that assumes the input is an expression.
     26   static scoped_ptr<ParseNode> ParseExpression(const std::vector<Token>& tokens,
     27                                                Err* err);
     28 
     29  private:
     30   // Vector must be valid for lifetime of call.
     31   Parser(const std::vector<Token>& tokens, Err* err);
     32   ~Parser();
     33 
     34   scoped_ptr<AccessorNode> ParseAccessor();
     35   scoped_ptr<BlockNode> ParseBlock(bool need_braces);
     36   scoped_ptr<ConditionNode> ParseCondition();
     37   scoped_ptr<ParseNode> ParseExpression();
     38   scoped_ptr<ParseNode> ParseExpressionExceptBinaryOperators();
     39   scoped_ptr<FunctionCallNode> ParseFunctionCall();
     40   scoped_ptr<ListNode> ParseList(const Token& expected_begin,
     41                                  const Token& expected_end);
     42   scoped_ptr<ParseNode> ParseParenExpression();
     43   scoped_ptr<UnaryOpNode> ParseUnaryOp();
     44 
     45   bool IsToken(Token::Type type, char* str) const;
     46 
     47   // Gets an error corresponding to the last token. When we hit an EOF
     48   // usually we've already gone beyond the end (or maybe there are no tokens)
     49   // so there is some tricky logic to report this.
     50   Err MakeEOFError(const std::string& message,
     51                    const std::string& help = std::string()) const;
     52 
     53   const Token& cur_token() const { return tokens_[cur_]; }
     54 
     55   bool done() const { return at_end() || has_error(); }
     56   bool at_end() const { return cur_ >= tokens_.size(); }
     57   bool has_error() const { return err_->has_error(); }
     58 
     59   const Token& next_token() const { return tokens_[cur_ + 1]; }
     60   bool has_next_token() const { return cur_ + 1 < tokens_.size(); }
     61 
     62   const std::vector<Token>& tokens_;
     63 
     64   Err* err_;
     65 
     66   // Current index into the tokens.
     67   size_t cur_;
     68 
     69   FRIEND_TEST_ALL_PREFIXES(Parser, BinaryOp);
     70   FRIEND_TEST_ALL_PREFIXES(Parser, Block);
     71   FRIEND_TEST_ALL_PREFIXES(Parser, Condition);
     72   FRIEND_TEST_ALL_PREFIXES(Parser, Expression);
     73   FRIEND_TEST_ALL_PREFIXES(Parser, FunctionCall);
     74   FRIEND_TEST_ALL_PREFIXES(Parser, List);
     75   FRIEND_TEST_ALL_PREFIXES(Parser, ParenExpression);
     76   FRIEND_TEST_ALL_PREFIXES(Parser, UnaryOp);
     77 
     78   DISALLOW_COPY_AND_ASSIGN(Parser);
     79 };
     80 
     81 #endif  // TOOLS_GN_PARSER_H_
     82