safer-read.lisp

(defpackage :overlord/safer-read
  (:use :cl :serapeum)
  (:export :safer-read-from-string :safer-read)
  (:documentation "Safer variants of read and read-from-string."))

(in-package :overlord/safer-read)

;;; Adapted from LoL.

(defparameter *safer-read-blacklist*
  '(#\# #+(or) #\: #\|))

(def rt (copy-readtable nil))

(defun safer-reader-error (stream closech)
  (declare (ignore stream closech))
  (error "safer-read failure"))

(dolist (c *safer-read-blacklist*)
  (set-macro-character
   c #'safer-reader-error nil rt))

(defun safer-read-from-string (s &key fail)
  (if (stringp s)
      (with-input-from-string (s s)
        (safer-read s :fail fail))
      fail))

(defun safer-read (s &key fail recursive)
  (let ((*readtable* rt) *read-eval*)
    (handler-bind
        ((error (lambda (condition)
                  (declare (ignore condition))
                  (return-from
                   safer-read fail))))
      (read s t nil recursive))))