Add initial prototype for the GN meta-buildsystem.

tools/gn/parser.h

Index: tools/gn/parser.h
diff --git a/tools/gn/parser.h b/tools/gn/parser.h
new file mode 100644
index 0000000000000000000000000000000000000000..252b801a682f9cd27ed8763c0674526e80f55cb3
--- /dev/null
+++ b/tools/gn/parser.h
@@ -0,0 +1,81 @@
+// Copyright (c) 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef TOOLS_GN_PARSER_H_
+#define TOOLS_GN_PARSER_H_
+
+#include <vector>
+
+#include "base/basictypes.h"
+#include "base/gtest_prod_util.h"
+#include "base/memory/scoped_ptr.h"
+#include "tools/gn/err.h"
+#include "tools/gn/parse_tree.h"
+
+// Parses a series of tokens. The resulting AST will refer to the tokens passed
+// to the input, so the tokens an the file data they refer to must outlive your
+// use of the ParseNode.
+class Parser {
+ public:
+  // Will return a null pointer and set the err on error.
+  static scoped_ptr<ParseNode> Parse(const std::vector<Token>& tokens,
+                                     Err* err);
+
+  // Alternative to parsing that assumes the input is an expression.
+  static scoped_ptr<ParseNode> ParseExpression(const std::vector<Token>& tokens,
+                                               Err* err);
+
+ private:
+  // Vector must be valid for lifetime of call.
+  Parser(const std::vector<Token>& tokens, Err* err);
+  ~Parser();
+
+  scoped_ptr<AccessorNode> ParseAccessor();
+  scoped_ptr<BlockNode> ParseBlock(bool need_braces);
+  scoped_ptr<ConditionNode> ParseCondition();
+  scoped_ptr<ParseNode> ParseExpression();
+  scoped_ptr<ParseNode> ParseExpressionExceptBinaryOperators();
+  scoped_ptr<FunctionCallNode> ParseFunctionCall();
+  scoped_ptr<ListNode> ParseList(const Token& expected_begin,
+                                 const Token& expected_end);
+  scoped_ptr<ParseNode> ParseParenExpression();
+  scoped_ptr<UnaryOpNode> ParseUnaryOp();
+
+  bool IsToken(Token::Type type, char* str) const;
+
+  // Gets an error corresponding to the last token. When we hit an EOF
+  // usually we've already gone beyond the end (or maybe there are no tokens)
+  // so there is some tricky logic to report this.
+  Err MakeEOFError(const std::string& message,
+                   const std::string& help = std::string()) const;
+
+  const Token& cur_token() const { return tokens_[cur_]; }
+
+  bool done() const { return at_end() || has_error(); }
+  bool at_end() const { return cur_ >= tokens_.size(); }
+  bool has_error() const { return err_->has_error(); }
+
+  const Token& next_token() const { return tokens_[cur_ + 1]; }
+  bool has_next_token() const { return cur_ + 1 < tokens_.size(); }
+
+  const std::vector<Token>& tokens_;
+
+  Err* err_;
+
+  // Current index into the tokens.
+  size_t cur_;
+
+  FRIEND_TEST_ALL_PREFIXES(Parser, BinaryOp);
+  FRIEND_TEST_ALL_PREFIXES(Parser, Block);
+  FRIEND_TEST_ALL_PREFIXES(Parser, Condition);
+  FRIEND_TEST_ALL_PREFIXES(Parser, Expression);
+  FRIEND_TEST_ALL_PREFIXES(Parser, FunctionCall);
+  FRIEND_TEST_ALL_PREFIXES(Parser, List);
+  FRIEND_TEST_ALL_PREFIXES(Parser, ParenExpression);
+  FRIEND_TEST_ALL_PREFIXES(Parser, UnaryOp);
+
+  DISALLOW_COPY_AND_ASSIGN(Parser);
+};
+
+#endif  // TOOLS_GN_PARSER_H_