;;;; This software is part of the SBCL system. See the README file for
;;;; more information.
;;;;
;;;; This software is derived from the CMU CL system, which was
;;;; written at Carnegie Mellon University and released into the
;;;; public domain. The software is in the public domain and is
;;;; provided with absolutely no warranty. See the COPYING and CREDITS
;;;; files for more information.

(in-package "SB-ALIEN")

;;;; C string support.

(define-alien-type-class (c-string :include pointer :include-args (to))
  (external-format :default :type keyword)
  (element-type 'character :type (member character base-char))
  (not-null nil :type boolean))

(define-alien-type-translator c-string
    (&key (external-format :default)
          (element-type 'character)
          (not-null nil))
  (make-alien-c-string-type
   :to (parse-alien-type 'char (sb-kernel:make-null-lexenv))
   :element-type element-type
   :external-format external-format
   :not-null not-null))

(defun c-string-external-format (type)
  (let ((external-format (alien-c-string-type-external-format type)))
    (if (eq external-format :default)
        #+sb-xc-host (bug "No default c-string-external-format")
        #-sb-xc-host (default-c-string-external-format)
        external-format)))

(define-alien-type-method (c-string :unparse) (type)
  (let* ((external-format (alien-c-string-type-external-format type))
         (element-type (alien-c-string-type-element-type type))
         (not-null (alien-c-string-type-not-null type))
         (tail
          (append (unless (eq :default external-format)
                    (list :external-format external-format))
                  (unless (eq 'character element-type)
                    (list :element-type element-type))
                  (when not-null
                    (list :not-null t)))))
    (if tail
        (cons 'c-string tail)
        'c-string)))

(define-alien-type-method (c-string :lisp-rep) (type)
  (let ((possibilities '(simple-string (alien (* char)) (simple-array (unsigned-byte 8)))))
    (if (alien-c-string-type-not-null type)
        `(or ,@possibilities)
        `(or null ,@possibilities))))

(define-alien-type-method (c-string :deport-pin-p) (type)
  (declare (ignore type))
  t)

(defun c-string-needs-conversion-p (type)
  #+sb-xc-host
  (declare (ignore type))
  #+sb-xc-host
  t
  #-sb-xc-host
  (let ((external-format (sb-impl::get-external-format
                          ;; Can't use C-STRING-EXTERNAL-FORMAT here,
                          ;; since the meaning of :DEFAULT can change
                          ;; when *DEFAULT-C-STRING-EXTERNAL-FORMAT*
                          ;; changes.
                          (alien-c-string-type-external-format type))))
    (not (and external-format
              (or (eq (first (sb-impl::ef-names external-format)) :ascii)
                  ;; On non-SB-UNICODE all latin-1 codepoints will fit
                  ;; into a base-char, on SB-UNICODE they won't.
                  #-sb-unicode
                  (eq (first (sb-impl::ef-names external-format)) :latin-1))))))

(declaim (ftype (sfunction (t) nil) null-error))
(defun null-error (type)
  #-sb-xc-host(declare (optimize sb-kernel:allow-non-returning-tail-call))
  (aver (alien-c-string-type-not-null type))
  (error 'type-error
         :expected-type `(alien ,(unparse-alien-type type))
         :datum nil))

(define-alien-type-method (c-string :naturalize-gen) (type alien)
  `(if (zerop (sap-int ,alien))
       ,(if (alien-c-string-type-not-null type)
            `(null-error ',type)
            nil)
       ;; Check whether we need to do a full external-format
       ;; conversion, or whether we can just do a cheap byte-by-byte
       ;; copy of the c-string data.
       ;;
       ;; On SB-UNICODE we can never do the cheap copy, even if the
       ;; external format and element-type are suitable, since
       ;; simple-base-strings may not contain ISO-8859-1 characters.
       ;; If we need to check for non-ascii data in the input, we
       ;; might as well go through the usual external-format machinery
       ;; instead of rewriting another version of it.
       ,(if #+sb-unicode t
            #-sb-unicode (c-string-needs-conversion-p type)
            `(c-string-to-string ,alien
                                 (c-string-external-format ,type)
                                 (alien-c-string-type-element-type
                                  ,type))
            `(%naturalize-c-string ,alien))))

(define-alien-type-method (c-string :deport-gen) (type value)
  ;; This SAP taking is safe as DEPORT callers pin the VALUE when
  ;; necessary.
  `(etypecase ,value
     (null
      ,(if (alien-c-string-type-not-null type)
           `(null-error ',type)
           `(int-sap 0)))
     ((alien (* char)) (alien-sap ,value))
     (vector (vector-sap ,value))))

(define-alien-type-method (c-string :deport-alloc-gen) (type value)
  `(etypecase ,value
     (null
      ,(if (alien-c-string-type-not-null type)
           `(null-error ',type)
           nil))
     ((alien (* char)) ,value)
     ;; If the alien type is not ascii-compatible (+SB-UNICODE)
     ;; or latin-1-compatible (-SB-UNICODE), we need to do
     ;; external format conversion.
     ,@(if (c-string-needs-conversion-p type)
           `((t
              (string-to-c-string ,value
                                  (c-string-external-format ,type))))
           `((simple-base-string
              ,value)
             (simple-string
              (string-to-c-string ,value
                                  (c-string-external-format ,type)))))))
