;;; -*-lisp-*-
;;;
;;; Additional stream protocol.
;;;
;;; (c) 2009 Straylight/Edgeware
;;;

;;;----- Licensing notice ---------------------------------------------------
;;;
;;; This file is part of the Sensible Object Design, an object system for C.
;;;
;;; SOD is free software; you can redistribute it and/or modify
;;; it under the terms of the GNU General Public License as published by
;;; the Free Software Foundation; either version 2 of the License, or
;;; (at your option) any later version.
;;;
;;; SOD is distributed in the hope that it will be useful,
;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;;; GNU General Public License for more details.
;;;
;;; You should have received a copy of the GNU General Public License
;;; along with SOD; if not, write to the Free Software Foundation,
;;; Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.

(cl:in-package #:sod-parser)

;;;--------------------------------------------------------------------------
;;; Discovery of file names and stream positions.

(export 'stream-pathname)
(defgeneric stream-pathname (stream)
  (:documentation
   "Returns the pathname of the file that STREAM is open on.

   If STREAM is open on a file, then return the pathname of that file.
   Otherwise return nil.")

  ;; Provide some default methods.  Most streams don't have a pathname.
  ;; File-based streams provide a pathname, but it's usually been merged with
  ;; `*default-pathname-defaults*' or some such, which has made it absolute,
  ;; which isn't ideal.  We'll hack around this in more useful classes later.
  (:method ((stream stream)) nil)
  (:method ((stream file-stream)) (pathname stream)))

(export 'stream-line-and-column)
(defgeneric stream-line-and-column (stream)
  (:documentation
   "Returns the current stream position of STREAM as line/column numbers.

   Returns two values: the line and column numbers of STREAM's input
   position, or nil if the stream isn't capable of tracking these things.")
  (:method ((stream stream))
    (values nil nil)))

;;;--------------------------------------------------------------------------
;;; Enhanced stream classes.

(export '(position-aware-stream
	  position-aware-stream-file position-aware-stream-line
	  position-aware-stream-column))
(defclass position-aware-stream (proxy-stream)
  ((file :initarg :file :initform nil
	 :type (or pathname null) :accessor position-aware-stream-file)
   (line :initarg :line :initform 1
	 :type fixnum :accessor position-aware-stream-line)
   (column :initarg :column :initform 0
	   :type fixnum :accessor position-aware-stream-column))
  (:documentation
   "Character stream which keeps track of the line and column position.

   A position-aware-stream wraps an existing character stream and tracks the
   line and column position of the current stream position.  A newline
   character increases the line number by one and resets the column number to
   zero; most characters advance the column number by one, but tab advances
   to the next multiple of eight.  (This is consistent with Emacs, at least.)
   The position can be read using `stream-line-and-column'.

   This is a base class; you probably want `position-aware-input-stream' or
   `position-aware-output-stream'."))

(export 'position-aware-input-stream)
(defclass position-aware-input-stream
    (position-aware-stream proxy-character-input-stream)
  ()
  (:documentation
   "A character input stream which tracks the input position.

   This is particularly useful for parsers and suchlike, which want to
   produce accurate error-location information."))

(export 'position-aware-output-stream)
(defclass position-aware-output-stream
    (position-aware-stream proxy-character-output-stream)
  ()
  (:documentation
   "A character output stream which tracks the output position.

   This is particularly useful when generating C code: the position can be
   used to generate `#line' directives referring to the generated code after
   insertion of some user code."))

;;;----- That's all, folks --------------------------------------------------