chiark - git - mdw - sod/blob - src/lexer-proto.lisp

   1 ;;; -*-lisp-*-
   2 ;;;
   3 ;;; Protocol for lexical analysis
   4 ;;;
   5 ;;; (c) 2009 Straylight/Edgeware
   6 ;;;
   7
   8 ;;;----- Licensing notice ---------------------------------------------------
   9 ;;;
  10 ;;; This file is part of the Sensible Object Design, an object system for C.
  11 ;;;
  12 ;;; SOD is free software; you can redistribute it and/or modify
  13 ;;; it under the terms of the GNU General Public License as published by
  14 ;;; the Free Software Foundation; either version 2 of the License, or
  15 ;;; (at your option) any later version.
  16 ;;;
  17 ;;; SOD is distributed in the hope that it will be useful,
  18 ;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  19 ;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20 ;;; GNU General Public License for more details.
  21 ;;;
  22 ;;; You should have received a copy of the GNU General Public License
  23 ;;; along with SOD; if not, write to the Free Software Foundation,
  24 ;;; Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  25
  26 (cl:in-package #:sod)
  27
  28 ;;;--------------------------------------------------------------------------
  29 ;;; Class definition.
  30
  31 (export 'sod-token-scanner)
  32 (defclass sod-token-scanner (token-scanner)
  33   ((char-scanner :initarg :char-scanner :reader token-scanner-char-scanner))
  34   (:documentation
  35    "A token scanner for SOD input files.
  36
  37    Not a lot here, apart from a character scanner to read from and the
  38    standard token scanner infrastructure."))
  39
  40 ;;;--------------------------------------------------------------------------
  41 ;;; Indicators and error messages.
  42
  43 (defvar *indicator-map* (make-hash-table)
  44   "Hash table mapping indicator objects to human-readable descriptions.")
  45
  46 (export 'define-indicator)
  47 (defun define-indicator (indicator description)
  48   "Associate an INDICATOR with its textual DESCRIPTION.
  49
  50    Updates the the `*indicator-map*'."
  51   (setf (gethash indicator *indicator-map*) description)
  52   indicator)
  53
  54 (export 'syntax-error)
  55 (defun syntax-error (scanner expected &key (continuep t) location)
  56   "Signal a (maybe) continuable syntax error."
  57   (labels ((show-token (type value)
  58              (if (characterp type)
  59                  (format nil "~/sod::show-char/" type)
  60                  (case type
  61                    (:id (format nil "<identifier~@[ `~A'~]>" value))
  62                    (:int "<integer-literal>")
  63                    (:string "<string-literal>")
  64                    (:char "<character-literal>")
  65                    (:eof "<end-of-file>")
  66                    (:ellipsis "`...'")
  67                    (t (format nil "<? ~S~@[ ~S~]>" type value)))))
  68            (show-expected (thing)
  69              (acond ((gethash thing *indicator-map*) it)
  70                     ((atom thing) (show-token thing nil))
  71                     ((eq (car thing) :id)
  72                      (format nil "`~A'" (cadr thing)))
  73                     (t (format nil "<? ~S>" thing)))))
  74     (funcall (if continuep #'cerror*-with-location #'error-with-location)
  75              (or location scanner)
  76              "Syntax error: ~
  77               expected ~{~#[<bug>~;~A~;~A or ~A~:;~A, ~]~} ~
  78               but found ~A"
  79              (mapcar #'show-expected expected)
  80              (show-token (token-type scanner) (token-value scanner)))))
  81
  82 (export 'lexer-error)
  83 (defun lexer-error (char-scanner expected &key location)
  84   "Signal a continuable lexical error."
  85   (cerror*-with-location (or location char-scanner)
  86                          "Lexical error: ~
  87                           ~:[unexpected~;~
  88                              expected ~:*~{~#[~;~A~;~A or ~A~:;~
  89                                               ~@{~A, ~#[~;or ~A~]~}~]~} ~
  90                              but found~] ~
  91                           ~/sod::show-char/"
  92            (mapcar (lambda (exp)
  93                      (typecase exp
  94                        (character (format nil "~/sod::show-char/" exp))
  95                        (string (format nil "`~A'" exp))
  96                        ((cons (eql :digit) *) (format nil "<radix-~A digit>"
  97                                                       (cadr exp)))
  98                        ((eql :eof) "<end-of-file>")
  99                        ((eql :any) "<character>")
 100                        (t (format nil "<? ~S>" exp))))
 101                    expected)
 102            (and (not (scanner-at-eof-p char-scanner))
 103                 (scanner-current-char char-scanner))))
 104
 105 (export 'skip-until)
 106 (defparse skip-until (:context (context token-scanner-context)
 107                       (&key (keep-end nil keep-end-p))
 108                       &rest token-types)
 109   "Discard tokens until we find one listed in TOKEN-TYPES.
 110
 111    If KEEP-END is true then retain the found token for later; otherwise
 112    discard it.  KEEP-END defaults to true if multiple TOKEN-TYPES are given;
 113    otherwise false.  If end-of-file is encountered then the indicator list is
 114    simply the list of TOKEN-TYPES; otherwise the result is `nil'."
 115   `(skip-until ,(parser-scanner context)
 116                (list ,@token-types)
 117                :keep-end ,(if keep-end-p keep-end
 118                               (> (length token-types) 1))))
 119
 120 (export 'error)
 121 (defparse error (:context (context token-scanner-context)
 122                  (&key ignore-unconsumed force-progress)
 123                  sub &optional (recover t))
 124   "Try to parse SUB; if it fails then report an error, and parse RECOVER.
 125
 126    This is the main way to recover from errors and continue parsing.  Even
 127    then, it's not especially brilliant.
 128
 129    If the SUB parser succeeds then just propagate its result: it's like we
 130    were never here.  Otherwise, try to recover in a sensible way so we can
 131    continue parsing.  The details of this recovery are subject to change, but
 132    the final action is generally to invoke the RECOVER parser and return its
 133    result.
 134
 135    If IGNORE-UNCONSUMED evaluates non-nil, then just propagate a failure of
 136    SUB if it didn't consume input.  (This makes it suitable for use where the
 137    parser containing `error' might be optional.)"
 138   `(parse-error-recover ,(parser-scanner context)
 139                         (parser () ,sub)
 140                         (parser () ,recover)
 141                         :ignore-unconsumed ,ignore-unconsumed
 142                         :force-progress ,force-progress))
 143
 144 ;;;--------------------------------------------------------------------------
 145 ;;; Lexical analysis utilities.
 146
 147 (export 'scan-comment)
 148 (defun scan-comment (char-scanner)
 149   "Scan a comment (either `/* ... */' or `// ...') from CHAR-SCANNER.
 150
 151    The result isn't interesting."
 152   (with-parser-context (character-scanner-context :scanner char-scanner)
 153     (let ((start (file-location char-scanner)))
 154       (parse (or (and "/*"
 155                       (lisp (let ((state nil))
 156                               (loop (cond ((scanner-at-eof-p char-scanner)
 157                                            (lexer-error char-scanner
 158                                                         (list "*/"))
 159                                            (info-with-location
 160                                             start "Comment started here")
 161                                            (return (values nil t t)))
 162                                           ((char= (scanner-current-char
 163                                                    char-scanner)
 164                                                   #\*)
 165                                            (setf state '*)
 166                                            (scanner-step char-scanner))
 167                                           ((and (eq state '*)
 168                                                 (char= (scanner-current-char
 169                                                         char-scanner)
 170                                                        #\/))
 171                                            (scanner-step char-scanner)
 172                                            (return (values nil t t)))
 173                                           (t
 174                                            (setf state nil)
 175                                            (scanner-step char-scanner)))))))
 176                  (and "//"
 177                       (skip-many () (not #\newline))
 178                       (? #\newline)))))))
 179
 180 ;;;----- That's all, folks --------------------------------------------------