url.scm

#|
Copyright (c) 2011, Marc Feeley
All rights reserved.

Redistribution and use in source and binary forms, with or
without modification, are permitted provided that the
following conditions are met:

* Redistributions of source code must retain the above
copyright notice, this list of conditions and the following
disclaimer.

* Redistributions in binary form must reproduce the above
copyright notice, this list of conditions and the following
disclaimer in the documentation and/or other materials
provided with the distribution.

* The name of the author may not be used to endorse or promote
products derived from this software without specific prior
written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
|#

(##namespace ("url#"))

(##include "~~lib/gambit#.scm")

(##include "url#.scm")

(declare
  (standard-bindings)
  (extended-bindings)
  (block)
  (fixnum)
  (not safe)
)

;;;============================================================================

;; Encoding and decoding of x-www-form-urlencoded data.

(define (url-encode str #!optional (start 0) (end (string-length str)) (space-to-plus? #f))

  (define chunk-length 1024)

  (define (hex n)
    (string-ref "0123456789ABCDEF" (bitwise-and n 15)))

  (define (encode-chunk len i end)
    (if (< i end)
        (let ((c (string-ref str i)))
          (if (or (and (char>=? c #\a) (char<=? c #\z))
                  (and (char>=? c #\A) (char<=? c #\Z))
                  (and (char>=? c #\0) (char<=? c #\9))
                  (char=? c #\-)
                  (char=? c #\_)
                  (char=? c #\.)
                  (char=? c #\!)
                  (char=? c #\~)
                  (char=? c #\*)
                  (char=? c #\')
                  (char=? c #\()
                  (char=? c #\))
                  (and (char=? c #\space) space-to-plus?))
              (let ((result (encode-chunk (+ len 1) (+ i 1) end)))
                (string-set!
                 result
                 len
                 (if (and (char=? c #\space) space-to-plus?) #\+ c))
                result)
              (let ((result (encode-chunk (+ len 3) (+ i 1) end)))
                (let ((n (char->integer c)))
                  (string-set! result (+ len 0) #\%)
                  (string-set! result (+ len 1) (hex (arithmetic-shift n -4)))
                  (string-set! result (+ len 2) (hex n))
                  result))))
        (make-string len)))

  (let loop ((i start) (chunks '()))
    (let ((span (min (- end i) chunk-length)))
      (if (= span 0)
          (##append-strings ;; apply string-append
           (reverse chunks))
          (let* ((next-i (+ i span))
                 (chunk (encode-chunk 0 i next-i)))
            (loop next-i (cons chunk chunks)))))))

(define (url-decode str #!optional (start 0) (end (string-length str)) (plus-to-space? #f))

  (define chunk-length 1024)

  (define (hex? c)
    (cond ((and (char>=? c #\0) (char<=? c #\9))
           (- (char->integer c) (char->integer #\0)))
          ((and (char>=? c #\a) (char<=? c #\f))
           (+ 10 (- (char->integer c) (char->integer #\a))))
          ((and (char>=? c #\A) (char<=? c #\F))
           (+ 10 (- (char->integer c) (char->integer #\A))))
          (else
           #f)))

  (define (decode len i end)
    (if (and (< i end)
             (< len chunk-length))
        (let ((c (string-ref str i)))
          (cond ((or (and (char>=? c #\a) (char<=? c #\z))
                     (and (char>=? c #\A) (char<=? c #\Z))
                     (and (char>=? c #\0) (char<=? c #\9))
                     (char=? c #\-)
                     (char=? c #\_)
                     (char=? c #\.)
                     (char=? c #\!)
                     (char=? c #\~)
                     (char=? c #\*)
                     (char=? c #\')
                     (char=? c #\()
                     (char=? c #\))
                     (and (char=? c #\+) plus-to-space?))
                 (let ((result (decode (+ len 1) (+ i 1) end)))
                   (and result
                        (begin
                          (string-set!
                           (cdr result)
                           len
                           (if (and (char=? c #\+) plus-to-space?) #\space c))
                          result))))
                ((char=? c #\%)
                 (if (< (+ i 2) end)
                     (let* ((a (hex? (string-ref str (+ i 1))))
                            (b (hex? (string-ref str (+ i 2)))))
                       (and a
                            b
                            (let ((result (decode (+ len 1) (+ i 3) end)))
                              (and result
                                   (begin
                                     (string-set! (cdr result)
                                                  len
                                                  (integer->char
                                                   (+ (arithmetic-shift a 4) b)))
                                     result)))))
                     #f))
                (else
                 #f)))
        (cons i (make-string len))))

  (let loop ((i start) (chunks '()))
    (if (< i end)
        (let ((x (decode 0 i end)))
          (and x
               (loop (car x) (cons (cdr x) chunks))))
        (##append-strings ;; apply string-append
         (reverse chunks)))))

;;;============================================================================