tools/gn/parser.h

   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 <map>
   9 #include <vector>
  10
  11 #include "base/basictypes.h"
  12 #include "base/gtest_prod_util.h"
  13 #include "base/memory/scoped_ptr.h"
  14 #include "tools/gn/err.h"
  15 #include "tools/gn/parse_tree.h"
  16
  17 class Parser;
  18 typedef scoped_ptr<ParseNode> (Parser::*PrefixFunc)(Token token);
  19 typedef scoped_ptr<ParseNode> (Parser::*InfixFunc)(scoped_ptr<ParseNode> left,
  20                                                    Token token);
  21
  22 extern const char kGrammar_Help[];
  23
  24 struct ParserHelper {
  25   PrefixFunc prefix;
  26   InfixFunc infix;
  27   int precedence;
  28 };
  29
  30 // Parses a series of tokens. The resulting AST will refer to the tokens passed
  31 // to the input, so the tokens an the file data they refer to must outlive your
  32 // use of the ParseNode.
  33 class Parser {
  34  public:
  35   // Will return a null pointer and set the err on error.
  36   static scoped_ptr<ParseNode> Parse(const std::vector<Token>& tokens,
  37                                      Err* err);
  38
  39   // Alternative to parsing that assumes the input is an expression.
  40   static scoped_ptr<ParseNode> ParseExpression(const std::vector<Token>& tokens,
  41                                                Err* err);
  42
  43   // Alternative to parsing that assumes the input is a literal value.
  44   static scoped_ptr<ParseNode> ParseValue(const std::vector<Token>& tokens,
  45                                           Err* err);
  46
  47  private:
  48   // Vector must be valid for lifetime of call.
  49   Parser(const std::vector<Token>& tokens, Err* err);
  50   ~Parser();
  51
  52   scoped_ptr<ParseNode> ParseExpression();
  53
  54   // Parses an expression with the given precedence or higher.
  55   scoped_ptr<ParseNode> ParseExpression(int precedence);
  56
  57   // |PrefixFunc|s used in parsing expressions.
  58   scoped_ptr<ParseNode> Literal(Token token);
  59   scoped_ptr<ParseNode> Name(Token token);
  60   scoped_ptr<ParseNode> Group(Token token);
  61   scoped_ptr<ParseNode> Not(Token token);
  62   scoped_ptr<ParseNode> List(Token token);
  63   scoped_ptr<ParseNode> BlockComment(Token token);
  64
  65   // |InfixFunc|s used in parsing expressions.
  66   scoped_ptr<ParseNode> BinaryOperator(scoped_ptr<ParseNode> left, Token token);
  67   scoped_ptr<ParseNode> IdentifierOrCall(scoped_ptr<ParseNode> left,
  68                                          Token token);
  69   scoped_ptr<ParseNode> Assignment(scoped_ptr<ParseNode> left, Token token);
  70   scoped_ptr<ParseNode> Subscript(scoped_ptr<ParseNode> left, Token token);
  71   scoped_ptr<ParseNode> DotOperator(scoped_ptr<ParseNode> left, Token token);
  72
  73   // Helper to parse a comma separated list, optionally allowing trailing
  74   // commas (allowed in [] lists, not in function calls).
  75   scoped_ptr<ListNode> ParseList(Token start_token,
  76                                  Token::Type stop_before,
  77                                  bool allow_trailing_comma);
  78
  79   scoped_ptr<ParseNode> ParseFile();
  80   scoped_ptr<ParseNode> ParseStatement();
  81   scoped_ptr<BlockNode> ParseBlock();
  82   scoped_ptr<ParseNode> ParseCondition();
  83
  84   // Generates a pre- and post-order traversal of the tree.
  85   void TraverseOrder(const ParseNode* root,
  86                      std::vector<const ParseNode*>* pre,
  87                      std::vector<const ParseNode*>* post);
  88
  89   // Attach comments to nearby syntax.
  90   void AssignComments(ParseNode* file);
  91
  92   bool IsAssignment(const ParseNode* node) const;
  93   bool IsStatementBreak(Token::Type token_type) const;
  94
  95   bool LookAhead(Token::Type type);
  96   bool Match(Token::Type type);
  97   Token Consume(Token::Type type, const char* error_message);
  98   Token Consume(Token::Type* types,
  99                 size_t num_types,
 100                 const char* error_message);
 101   Token Consume();
 102
 103   const Token& cur_token() const { return tokens_[cur_]; }
 104
 105   bool done() const { return at_end() || has_error(); }
 106   bool at_end() const { return cur_ >= tokens_.size(); }
 107   bool has_error() const { return err_->has_error(); }
 108
 109   std::vector<Token> tokens_;
 110   std::vector<Token> line_comment_tokens_;
 111   std::vector<Token> suffix_comment_tokens_;
 112
 113   static ParserHelper expressions_[Token::NUM_TYPES];
 114
 115   Err* err_;
 116
 117   // Current index into the tokens.
 118   size_t cur_;
 119
 120   FRIEND_TEST_ALL_PREFIXES(Parser, BinaryOp);
 121   FRIEND_TEST_ALL_PREFIXES(Parser, Block);
 122   FRIEND_TEST_ALL_PREFIXES(Parser, Condition);
 123   FRIEND_TEST_ALL_PREFIXES(Parser, Expression);
 124   FRIEND_TEST_ALL_PREFIXES(Parser, FunctionCall);
 125   FRIEND_TEST_ALL_PREFIXES(Parser, List);
 126   FRIEND_TEST_ALL_PREFIXES(Parser, ParenExpression);
 127   FRIEND_TEST_ALL_PREFIXES(Parser, UnaryOp);
 128
 129   DISALLOW_COPY_AND_ASSIGN(Parser);
 130 };
 131
 132 #endif  // TOOLS_GN_PARSER_H_