sunet/scheme/httpd/surflets/bindings.scm

90 lines
3.3 KiB
Scheme

;; 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)))
(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))
(form-data (read-string content-length input-port)))
(let ((form-bindings (form-query-list form-data)))
(obtain-lock *cache-lock*)
(set! *POST-bindings-cache* (cons (cons (make-weak-pointer surflet-request)
form-bindings)
*POST-bindings-cache*))
(release-lock *cache-lock*)
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 ((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)
(cdar cache) ; request is cached
(loop (cdr cache))) ; request isn't cached
(begin
;; request object is gone ==> remove it from list
(set! cache (cdr cache))
(loop cache))))))))
(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))))