// 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)