sunet/scheme/httpd/surflets/bindings.scm

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;; Copyright 2002, 2003 Andreas Bernauer
;; Bindings of POST requests can be read only once, since they are
;; read from an input port. So we have to cache them, for the case of
;; a later GET-BINDINGS call on the same POST request. The requests
;; are referenced by a weak pointer. Thread-safe as all threads use
;; the same lock.
(define *POST-bindings-cache* '())
(define *cache-lock* (make-lock))
(define (get-bindings surflet-request)
(let ((request-method (surflet-request-method surflet-request))
(content-type (assoc 'content-type
(surflet-request-headers surflet-request))))
;; Check if we the content-type is the one we support. If there's
;; no content-type, assume the default (this is the one we
;; support).
(if (and content-type
;; Have to string-trim now, because the (buggy?) rfc822
;; implementation leaves the leading whitespace of the
;; header value.
(not (string=? (string-trim (cdr content-type))
"application/x-www-form-urlencoded")))
(error "get-bindings currently only supports
'application/x-www-form-urlencoded' as content-type"))
(cond
((string=? request-method "GET")
(form-query-list (http-url-search
(surflet-request-url surflet-request))))
((string=? request-method "POST")
(or (cached-bindings surflet-request)
(let* ((content-length (get-content-length
(surflet-request-headers surflet-request)))
(input-port (surflet-request-input-port surflet-request))
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(form-data (read-string content-length input-port))
(form-bindings (form-query-list form-data)))
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(obtain-lock *cache-lock*)
(set! *POST-bindings-cache*
(cons (cons (make-weak-pointer surflet-request)
form-bindings)
*POST-bindings-cache*))
(release-lock *cache-lock*)
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form-bindings)))
(else
(error "unsupported request type")))))
;; Looking up, if we have cached this request. While going through the
;; list, we remove entries to request objects, that are no longer
;; valid. Expecting a call for an uncached request every now and then,
;; it is guaranteed, that the list is cleaned up every now and
;; then. The cache is a list of pairs
;;; (surflet-request . computed-binding)
(define (cached-bindings surflet-request)
(obtain-lock *cache-lock*)
(let ((result
(let loop ((predecessor #f)
(cache *POST-bindings-cache*))
(if (null? cache)
#f ; no such request cached
(let* ((head (car cache))
(s-req (weak-pointer-ref (car head))))
(if s-req
(if (eq? s-req surflet-request)
(cdr head) ; request is cached
(loop (if predecessor
(cdr predecessor)
cache)
(cdr cache))) ; request isn't cached
(begin ;; request object is gone ==> remove
;; it from list
(if predecessor
(set-cdr! predecessor (cdr cache))
(set! *POST-bindings-cache* (cdr cache)))
(loop predecessor
(cdr predecessor)))))))))
(release-lock *cache-lock*)
result))
;; Will be needed when we handle POST requests.
(define (get-content-length headers)
(cond ((get-header headers 'content-length) =>
;; adopted from httpd/cgi-server.scm
(lambda (content-length) ; Skip initial whitespace (& other non-digits).
(let ((first-digit (string-index content-length char-set:digit))
(content-length-len (string-length content-length)))
(if first-digit
(string->number (substring content-length first-digit
content-length-len))
;; (status-code bad-request) req
(error "Illegal `Content-length:' header.")))))
(else
(error "No Content-length specified for POST data."))))
(define (extract-bindings key bindings)
(let ((key (if (symbol? key) (symbol->string key) key)))
(map cdr
(filter (lambda (binding)
(equal? (car binding) key))
bindings))))
(define (extract-single-binding key bindings)
(let ((key-bindings (extract-bindings key bindings)))
(if (= 1 (length key-bindings))
(car key-bindings)
(error "extract-one-binding: more than one or zero bindings found"
(length key-bindings)
key bindings))))