sunet/scheme/httpd/seval.scm

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;;; Path handler for uploading Scheme code to the SU web server -*- Scheme -*-
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;;; This file is part of the Scheme Untergrund Networking package.
;;; Copyright (c) 1995 by Olin Shivers.
;;; For copyright information, see the file COPYING which comes with
;;; the distribution.
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;;; This is really just an handler example demonstrating how to upload code
;;; into the server.
;;; (do/timeout secs thunk)
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; Run THUNK, and gun it down if it hasn't finished in SECS seconds.
;;; Returns nothing useful, and THUNK gets executed in a subprocess,
;;; so its side-effects are invisible, as well. This is a clever kludge --
;;; it uses three subprocesses -- but I don't have interrupts, so I'm hosed.
(define (do/timeout* secs thunk)
(run (begin (let ((timer (fork (lambda () (sleep secs))))
(worker (fork thunk)))
(receive (process status) (wait-any)
(ignore-errors
(lambda ()
(signal-process (proc:pid (if (eq? worker process)
timer
worker))
signal/kill))))))))
(define-syntax do/timeout
(syntax-rules ()
((do/timeout secs body ...) (do/timeout* secs (lambda () body ...)))))
;;; The request handler for seval ops.
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
(define (seval-handler path req)
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(let ((request-method (request-method req)))
(cond
((string=? request-method "POST") ; Could do others also.
(seval path req))
(else
(make-error-response (status-code method-not-allowed) req request-method)))))
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(define (seval path req)
(make-response
(status-code ok)
#f
(time)
"text/html"
'()
(make-reader-writer-body
(lambda (iport oport options)
(let ((sexp (read-request-sexp req iport)))
(http-syslog (syslog-level debug) "read sexp: ~a" sexp)
(with-tag oport HEAD ()
(newline oport)
(emit-title oport "Scheme program output"))
(newline oport)
(with-tag oport BODY ()
(newline oport)
(do/timeout
10
(receive vals
;; Do the computation.
(begin (emit-header oport 2 "Output from execution")
(newline oport)
(with-tag oport PRE ()
(newline oport)
(force-output oport); In case we're gunned down.
(with-current-output-port oport
(eval-safely sexp))))
;; Pretty-print the returned value(s).
(emit-header oport 2 "Return value(s)")
(with-tag oport PRE ()
(for-each (lambda (val) (p val oport))
vals))))))))))
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;;; Read an HTTP request entity body from stdin. The Content-length:
;;; element of request REQ's header tells how many bytes to this entity
;;; is. The entity should be a URI-encoded form body. Pull out the
;;; program=<stuff>
;;; string, extract <stuff>, uri-decode it, parse that into an s-expression,
;;; and return it.
(define (read-request-sexp req iport)
(cond
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((get-header (request-headers req) 'content-length) =>
(lambda (cl-str) ; Take the first Content-length: header,
(let* ((cl-start (string-skip cl-str char-set:whitespace)) ; skip whitespace,
(cl (if cl-start ; & convert to
(string->number (substring cl-str ; a number.
cl-start
(string-length cl-str)))
0)) ; All whitespace?? -- WTF.
(qs (read-string cl iport)) ; Read in CL chars,
(q (parse-html-form-query qs)) ; and parse them up.
(s (cond ((assoc "program" q) => cdr)
(else (error "No program in entity body.")))))
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(http-syslog (syslog-level debug)
"Seval sexp: ~s" s)
(read (make-string-input-port s)))))
(else (error "No `Content-length:' field in POST request."))))
(define (get-header headers tag)
(cond
((assq tag headers) => cdr)
(else #f)))