lib/Format/UnwrappedLineParser.h

//===--- UnwrappedLineParser.h - Format C++ code ----------------*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
///
/// \file
/// \brief This file contains the declaration of the UnwrappedLineParser,
/// which turns a stream of tokens into UnwrappedLines.
///
/// This is EXPERIMENTAL code under heavy development. It is not in a state yet,
/// where it can be used to format real code.
///
//===----------------------------------------------------------------------===//

#ifndef LLVM_CLANG_FORMAT_UNWRAPPED_LINE_PARSER_H
#define LLVM_CLANG_FORMAT_UNWRAPPED_LINE_PARSER_H

#include "clang/Basic/IdentifierTable.h"
#include "clang/Basic/SourceManager.h"
#include "clang/Format/Format.h"
#include "clang/Lex/Lexer.h"

#include <vector>

namespace clang {
namespace format {

/// \brief A wrapper around a \c Token storing information about the
/// whitespace characters preceeding it.
struct FormatToken {
  FormatToken()
      : NewlinesBefore(0), HasUnescapedNewline(false), WhiteSpaceLength(0),
        TokenLength(0), IsFirst(false), MustBreakBefore(false) {
  }

  /// \brief The \c Token.
  Token Tok;

  /// \brief The number of newlines immediately before the \c Token.
  ///
  /// This can be used to determine what the user wrote in the original code
  /// and thereby e.g. leave an empty line between two function definitions.
  unsigned NewlinesBefore;

  /// \brief Whether there is at least one unescaped newline before the \c
  /// Token.
  bool HasUnescapedNewline;

  /// \brief The location of the start of the whitespace immediately preceeding
  /// the \c Token.
  ///
  /// Used together with \c WhiteSpaceLength to create a \c Replacement.
  SourceLocation WhiteSpaceStart;

  /// \brief The length in characters of the whitespace immediately preceeding
  /// the \c Token.
  unsigned WhiteSpaceLength;

  /// \brief The length of the non-whitespace parts of the token. This is
  /// necessary because we need to handle escaped newlines that are stored
  /// with the token.
  unsigned TokenLength;

  /// \brief Indicates that this is the first token.
  bool IsFirst;

  /// \brief Whether there must be a line break before this token.
  ///
  /// This happens for example when a preprocessor directive ended directly
  /// before the token.
  bool MustBreakBefore;

  // FIXME: We currently assume that there is exactly one token in this vector
  // except for the very last token that does not have any children.
  /// \brief All tokens that logically follow this token.
  std::vector<FormatToken> Children;
};

/// \brief An unwrapped line is a sequence of \c Token, that we would like to
/// put on a single line if there was no column limit.
///
/// This is used as a main interface between the \c UnwrappedLineParser and the
/// \c UnwrappedLineFormatter. The key property is that changing the formatting
/// within an unwrapped line does not affect any other unwrapped lines.
struct UnwrappedLine {
  UnwrappedLine() : Level(0), InPPDirective(false) {
  }

  /// \brief The \c Token comprising this \c UnwrappedLine.
  FormatToken RootToken;

  /// \brief The indent level of the \c UnwrappedLine.
  unsigned Level;

  /// \brief Whether this \c UnwrappedLine is part of a preprocessor directive.
  bool InPPDirective;
};

class UnwrappedLineConsumer {
public:
  virtual ~UnwrappedLineConsumer() {
  }
  virtual void consumeUnwrappedLine(const UnwrappedLine &Line) = 0;
};

class FormatTokenSource {
public:
  virtual ~FormatTokenSource() {
  }
  virtual FormatToken getNextToken() = 0;
};

class UnwrappedLineParser {
public:
  UnwrappedLineParser(const FormatStyle &Style, FormatTokenSource &Tokens,
                      UnwrappedLineConsumer &Callback);

  /// Returns true in case of a structural error.
  bool parse();

private:
  bool parseFile();
  bool parseLevel(bool HasOpeningBrace);
  bool parseBlock(unsigned AddLevels = 1);
  void parsePPDirective();
  void parsePPDefine();
  void parsePPUnknown();
  void parseComments();
  void parseStructuralElement();
  void parseParens();
  void parseIfThenElse();
  void parseForOrWhileLoop();
  void parseDoWhile();
  void parseLabel();
  void parseCaseLabel();
  void parseSwitch();
  void parseNamespace();
  void parseAccessSpecifier();
  void parseEnum();
  void parseStructOrClass();
  void addUnwrappedLine();
  bool eof() const;
  void nextToken();
  void readToken();

  // FIXME: We are constantly running into bugs where Line.Level is incorrectly
  // subtracted from beyond 0. Introduce a method to subtract from Line.Level
  // and use that everywhere in the Parser.
  llvm::OwningPtr<UnwrappedLine> Line;
  bool RootTokenInitialized;
  FormatToken *LastInCurrentLine;
  FormatToken FormatTok;
  bool MustBreakBeforeNextToken;

  const FormatStyle &Style;
  FormatTokenSource *Tokens;
  UnwrappedLineConsumer &Callback;
};

} // end namespace format
} // end namespace clang

#endif // LLVM_CLANG_FORMAT_UNWRAPPED_LINE_PARSER_H