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// go-linemap.h -- interface to location tracking   -*- C++ -*-

// Copyright 2011 The Go 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 GO_LINEMAP_H

#define GO_LINEMAP_H

#include "go-system.h"

// The backend must define a type named Location which holds

// information about a location in a source file.  The only thing the

// frontend does with instances of Location is pass them back to the

// backend interface.  The Location type must be assignable, and it

// must be comparable: i.e., it must support operator= and operator<.

// The type is normally passed by value rather than by reference, and

// it should support that efficiently.  The type should be defined in

// "go-location.h".

#include "go-location.h"

// The Linemap class is a pure abstract interface, plus some static

// convenience functions.  The backend must implement the interface.

class Linemap

{

 public:

  Linemap()

  {

    // Only one instance of Linemap is allowed to exist.

    go_assert(Linemap::instance_ == NULL);

    Linemap::instance_ = this;

  }

  virtual

  ~Linemap() { Linemap::instance_ = NULL; }

  // Subsequent Location values will come from the file named

  // FILE_NAME, starting at LINE_BEGIN.  Normally LINE_BEGIN will be

  // 0, but it will be non-zero if the Go source has a //line comment.

  virtual void

  start_file(const char* file_name, unsigned int line_begin) = 0;

  // Subsequent Location values will come from the line LINE_NUMBER,

  // in the current file.  LINE_SIZE is the size of the line in bytes.

  // This will normally be called for every line in a source file.

  virtual void

  start_line(unsigned int line_number, unsigned int line_size) = 0;

  // Get a Location representing column position COLUMN on the current

  // line in the current file.

  virtual Location

  get_location(unsigned int column) = 0;

  // Stop generating Location values.  This will be called after all

  // input files have been read, in case any cleanup is required.

  virtual void

  stop() = 0;

 protected:

  // Return a special Location used for predeclared identifiers.  This

  // Location should be different from that for any actual source

  // file.  This location will be used for various different types,

  // functions, and objects created by the frontend.

  virtual Location

  get_predeclared_location() = 0;

  // Return a special Location which indicates that no actual location

  // is known.  This is used for undefined objects and for errors.

  virtual Location

  get_unknown_location() = 0;

  // Return whether the argument is the Location returned by

  // get_predeclared_location.

  virtual bool

  is_predeclared(Location) = 0;

  // Return whether the argument is the Location returned by

  // get_unknown_location.

  virtual bool

  is_unknown(Location) = 0;

  // The single existing instance of Linemap.

  static Linemap *instance_;

 public:

  // Following are convenience static functions, which allow us to

  // access some virtual functions without explicitly passing around

  // an instance of Linemap.

  // Return the special Location used for predeclared identifiers.

  static Location

  predeclared_location()

  {

    go_assert(Linemap::instance_ != NULL);

    return Linemap::instance_->get_predeclared_location();

  }

  // Return the special Location used when no location is known.

  static Location

  unknown_location()

  {

    go_assert(Linemap::instance_ != NULL);

    return Linemap::instance_->get_unknown_location();

  }

  // Return whether the argument is the special location used for

  // predeclared identifiers.

  static bool

  is_predeclared_location(Location loc)

  {

    go_assert(Linemap::instance_ != NULL);

    return Linemap::instance_->is_predeclared(loc);

  }

  // Return whether the argument is the special location used when no

  // location is known.

  static bool

  is_unknown_location(Location loc)

  {

    go_assert(Linemap::instance_ != NULL);

    return Linemap::instance_->is_unknown(loc);

  }

};

// The backend interface must define this function.  It should return

// a fully implemented instance of Linemap.

extern Linemap* go_get_linemap();

#endif // !defined(GO_LINEMAP_H)