569 lines
19 KiB
Scheme
569 lines
19 KiB
Scheme
;; Request-handlers for scheme web server
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;; general request-handler-combinator:
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;; predicate: path x request --> boolean
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;; if #t, handler is called
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;; if #f, default-handler is called
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(define (make-request-handler predicate handler default-handler)
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(lambda (path req)
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(if (predicate path req)
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(handler path req)
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(default-handler path req))))
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;; same as make-request-handler except that the predicate is only
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;; called with the path:
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;; predicate: path --> boolean
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(define (make-path-handler predicate handler default-handler)
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(make-request-handler
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(lambda (path req) (predicate path)) handler default-handler))
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;; selects handler according to host-field of http-request
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(define (make-hostname-handler hostname handler default-handler)
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(make-request-handler
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(lambda (path req)
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;; we expect only one host-header-field
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(string=? hostname (string-trim (get-header (request:headers req) 'host))))
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handler default-handler))
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;; selects handler according to path-prefix
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;; if path-prefix matches, handler is called without the path-prefix
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(define (make-path-prefix-handler path-prefix handler default-handler)
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(lambda (path req)
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(if (string=? path-prefix (car path))
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(handler (cdr path) req)
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(default-handler path req))))
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(define server/buffer-size 8192) ; WTF
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;;; (alist-path-dispatcher handler-alist default-handler) -> handler
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;;; This function creates a table-driven path-handler that dispatches off
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;;; of the car of the request path. The handler uses the car to index into
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;;; a path-handler alist. If it finds a hit, it recurses using the table's
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;;; path-handler. If no hits, it handles the path with a default handler.
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;;; An alist handler is passed the tail of the original path; the
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;;; default handler gets the entire original path.
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;;;
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;;; This procedure is how you say: "If the first element of the URL's
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;;; path is 'foo', do X; if it's 'bar', do Y; otherwise, do Z."
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(define (alist-path-dispatcher handler-alist default-handler)
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(fold-right
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(lambda (handler-pair default-handler)
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(make-path-prefix-handler
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(car handler-pair)
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(cdr handler-pair)
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default-handler))
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default-handler
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handler-alist))
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;;; (home-dir-handler user-public-dir) -> handler
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;;; Return a path handler that looks things up in a specific directory
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;;; in the user's home directory. If ph = (home-dir-handler "public_html")
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;;; then ph is a path-handler that serves files out of peoples' public_html
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;;; subdirectory. So
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;;; (ph '("shivers" "hk.html") req)
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;;; will serve the file
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;;; ~shivers/public_html/hk.html
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;;; The path handler treats the URL path as (<user> . <file-path>),
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;;; serving
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;;; ~<user>/<user-public-dir>/<file-path>
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(define (home-dir-handler user-public-dir)
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(lambda (path req)
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(if (pair? path)
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(serve-rooted-file-path (string-append (http-homedir (car path) req)
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"/"
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user-public-dir)
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(cdr path)
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file-serve
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req)
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(http-error http-reply/bad-request req
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"Path contains no home directory."))))
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;;; (tilde-home-dir-handler-predicate path)
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;;; (tilde-home-dir-handler user-public-dir)
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;;; If the car of the path is a tilde-marked home directory (e.g., "~kgk"),
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;;; do home-directory service as in HOME-DIR-HANDLER, otherwise punt to the
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;;; default handler.
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(define (tilde-home-dir-handler-predicate path)
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(lambda (path)
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(and (pair? path) ; Is it a ~foo/...
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(let ((head (car path))) ; home-directory path?
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(and (> (string-length head) 0)
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(char=? (string-ref head 0) #\~))))))
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(define (tilde-home-dir-handler user-public-dir)
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(lambda (path req)
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(let* ((tilde-home (car path)) ; Yes.
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(slen (string-length tilde-home))
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(subdir (string-append
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(http-homedir (substring tilde-home 1 slen) req)
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"/"
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user-public-dir)))
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(serve-rooted-file-path subdir (cdr path) file-serve req))))
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;;; Make a handler that serves files relative to a particular root
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;;; in the file system. You may follow symlinks, but you can't back up
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;;; past ROOT with ..'s.
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(define (rooted-file-handler root)
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(lambda (path req)
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(serve-rooted-file-path root path file-serve req)))
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;;; Dito, but also serve directory indices for directories without
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;;; index.html. ICON-NAME specifies how to generate the links to
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;;; various decorative icons for the listings. It can either be a
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;;; procedure which gets passed one of the icon tags in TAG->ICON and
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;;; is expected to return a link pointing to the icon. If it is a
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;;; string, that is taken as prefix to which the names from TAG->ICON
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;;; are appended.
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(define (rooted-file-or-directory-handler root icon-name)
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(let ((file-serve-and-dir (file-server-and-dir icon-name)))
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(lambda (path req)
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(serve-rooted-file-path root path file-serve-and-dir req))))
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;;; The null path handler -- handles nothing, sends back an error reply.
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;;; Can be useful as the default in table-driven path handlers.
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(define (null-path-handler path req)
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(http-error http-reply/not-found req))
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;;;; Support procs for the path handlers
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;;; (SERVE-ROOTED-FILE-PATH root file-path req)
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;;; Do a request for a file. The file-name is determined by appending the
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;;; the FILE-PATH list the string ROOT. E.g., if
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;;; ROOT = "/usr/shivers" FILE-PATH = ("a" "b" "c" "foo.html")
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;;; then we serve file
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;;; /usr/shivers/a/b/c/foo.html
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;;; Elements of FILE-PATH are *not allowed* to contain .. elements.
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;;; (N.B.: Although the ..'s can appear in relative URI's, /foo/../ path
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;;; sequences are processed away by the browser when the URI is converted
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;;; to an absolute URI before it is sent off to the server.)
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;;; It is possible to sneak a .. past this kind of front-end resolving by
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;;; encoding it (e.g., "foo%2F%2E%2E" for "foo/.."). If the client tries
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;;; this, SERVE-ROOTED-FILE-PATH will catch it, and abort the transaction.
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;;; So you cannot make the reference back up past ROOT. E.g., this is
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;;; not allowed:
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;;; FILE-PATH = ("a" "../.." "c" "foo.html")
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;;;
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;;; Only GET and HEAD ops are provided.
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;;; The URL's <search> component must be #f.
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;;; The file is served if the server has read or stat(2) access to it,
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;;; respectively. If the server is run as root, this might be a problem.
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;;;
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;;; FILE-SERVE is a procedure which gets passed the file name, the
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;;; path, and the HTTP request to serve the file propert after the
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;;; security checks. Look in ROOTED-FILE-HANDLER and
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;;; ROOTED-FILE-OR-DIRECTORY-HANDLER for examples on how to feed this.
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(define (serve-rooted-file-path root file-path file-serve req)
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(if (http-url:search (request:url req))
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(http-error http-reply/bad-request req
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"Indexed search not provided for this URL.")
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(cond ((dotdot-check root file-path) =>
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(lambda (fname) (file-serve fname file-path req)))
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(else
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(http-error http-reply/bad-request req
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"URL contains unresolvable ..'s.")))))
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;; Just (file-info fname) with error handling.
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(define (stat-carefully fname req)
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(with-errno-handler
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((errno packet)
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((errno/noent)
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(http-error http-reply/not-found req))
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((errno/acces)
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(http-error http-reply/forbidden req)))
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(file-info fname #t)))
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;;; A basic file request handler -- ship the dude the file. No fancy path
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;;; checking. That has presumably been taken care of. This handler only
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;;; takes care of GET and HEAD methods.
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(define (file-serve-or-dir fname file-path req directory-serve)
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(if (file-name-directory? fname) ; Simple index generation.
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(directory-serve fname file-path req)
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(let ((request-method (request:method req)))
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(cond
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((or (string=? request-method "GET")
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(string=? request-method "HEAD")) ; Absolutely.
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(let ((info (stat-carefully fname req)))
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(case (file-info:type info)
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((regular fifo socket)
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(send-file fname info req))
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((directory) ; Send back a redirection "foo" -> "foo/"
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(http-error http-reply/moved-perm req
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(string-append (request:uri req) "/")
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(string-append (http-url->string (request:url req))
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"/")))
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(else (http-error http-reply/forbidden req)))))
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(else (http-error http-reply/method-not-allowed req))))))
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(define (directory-index-serve fname file-path req)
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(file-serve (string-append fname "index.html") file-path req))
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(define (file-serve fname file-path req)
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(file-serve-or-dir fname file-path req directory-index-serve))
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(define (tag->alt tag)
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(case tag
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((directory) "[DIR]")
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((text) "[TXT]")
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((doc) "[DOC]")
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((image) "[IMG]")
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((movie) "[MVI]")
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((audio) "[AU ]")
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((archive) "[TAR]")
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((compressed) "[ZIP]")
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((uu) "[UU ]")
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((binhex) "[HQX]")
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((binary) "[BIN]")
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(else "[ ]")))
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;; These icons can, for example, be found in the cern-httpd-3.0
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;; distribution at http://www.w3.org/pub/WWW/Daemon/
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(define (tag->icon tag)
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(case tag
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((directory) "directory.xbm")
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((text) "text.xbm")
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((doc) "doc.xbm")
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((image) "image.xbm")
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((movie) "movie.xbm")
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((audio) "sound.xbm")
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((archive) "tar.xbm")
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((compressed) "compressed.xbm")
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((uu) "uu.xbm")
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((binhex) "binhex.xbm")
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((binary) "binary.xbm")
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((blank) "blank.xbm")
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((back) "back.xbm")
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(else "unknown.xbm")))
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(define (file-extension->tag fname)
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(let ((ext (file-name-extension fname)))
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(cond
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((string-ci=? ext ".txt") 'text)
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((or (string-ci=? ext ".doc")
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(string-ci=? ext ".html")
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(string-ci=? ext ".rtf")
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(string-ci=? ext ".tex")) 'doc)
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((or (string-ci=? ext ".gif")
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(string-ci=? ext ".jpg")
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(string-ci=? ext ".jpeg")
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(string-ci=? ext ".tiff")
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(string-ci=? ext ".tif")) 'image)
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((or (string-ci=? ext ".mpeg")
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(string-ci=? ext ".mpg")) 'movie)
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((or (string-ci=? ext ".au")
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(string-ci=? ext ".snd")
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(string-ci=? ext ".wav")) 'audio)
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((or (string-ci=? ext ".tar")
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(string-ci=? ext ".zip")
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(string-ci=? ext ".zoo")) 'archive)
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((or (string-ci=? ext ".gz")
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(string-ci=? ext ".Z")
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(string-ci=? ext ".z")) 'compressed)
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((string-ci=? ext ".uu") 'uu)
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((string-ci=? ext ".hqx") 'binhex)
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(else 'binary))))
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(define (file-tag fname type)
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(case type
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((regular fifo socket) (file-extension->tag fname))
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((directory) 'directory)
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(else 'unknown)))
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(define (time->directory-index-date-string time)
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(format-date "~d-~b-~y ~H:~M:~S GMT" (date time 0)))
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(define (read-max-lines fname max)
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(call-with-input-file
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fname
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(lambda (port)
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(let loop ((r "") (i max))
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(if (zero? i)
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r
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(let ((line (read-line port)))
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(if (eof-object? line)
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r
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(loop (string-append r " " line) (- i 1)))))))))
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(define (string-cut s n)
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(if (>= (string-length s) n)
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(substring s 0 n)
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s))
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(define html-file-header
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(let ((title-tag-regexp (make-regexp "<[Tt][Ii][Tt][Ll][Ee]>"))
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(title-close-tag-regexp (make-regexp "</[Tt][Ii][Tt][Ll][Ee]>")))
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(lambda (fname n)
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(let ((stuff (read-max-lines fname 10)))
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(cond
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((regexp-exec title-tag-regexp stuff)
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=> (lambda (open-match)
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(cond
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((regexp-exec title-close-tag-regexp stuff
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(match:end open-match 0))
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=> (lambda (close-match)
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(string-cut (substring stuff
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(match:end open-match 0)
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(match:start close-match 0))
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n)))
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(else (string-cut (substring stuff
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(match:end open-match 0)
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(string-length stuff))
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n)))))
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(else ""))))))
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(define (file-documentation fname n)
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(cond
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((file-extension->content-type fname)
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=> (lambda (content-type)
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(if (and (string=? content-type "text/html" )
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(file-readable? fname))
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(html-file-header fname n)
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"")))
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(else "")))
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(define (directory-index req dir icon-name)
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(define (pad-file-name file)
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(write-string (make-string (- 21 (string-length file))
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#\space)))
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(define (emit-file-name file)
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(let ((l (string-length file)))
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(if (<= l 20)
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(emit-text file)
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(emit-text (substring file 0 20)))))
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(define (index-entry file)
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(let* ((fname (directory-as-file-name (string-append dir file)))
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(info (stat-carefully fname req))
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(type (file-info:type info))
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(size (file-info:size info))
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(tag (file-tag file type)))
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(emit-tag #t 'img
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(cons 'src (icon-name tag))
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(cons 'alt (tag->alt tag)))
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(with-tag #t a ((href file))
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(emit-file-name file))
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(pad-file-name file)
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(emit-text (time->directory-index-date-string (file-info:mtime info)))
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(if size
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(let* ((size-string
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(string-append (number->string (quotient size 1024))
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"K"))
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(size-string
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(if (<= (string-length size-string) 7)
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size-string
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(string-append (number->string (quotient size (* 1024 1024)))
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"M")))
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(size-string
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(if (<= (string-length size-string) 8)
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(string-append
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(make-string (- 8 (string-length size-string)) #\space)
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size-string)
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size-string)))
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(write-string size-string))
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(write-string (make-string 8 #\space)))
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(write-char #\space)
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(emit-text (file-documentation fname 24))
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(newline)))
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(let ((files (with-errno-handler
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((errno packet)
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((errno/acces)
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(http-error http-reply/forbidden req)))
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(directory-files dir))))
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(for-each index-entry files)
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(length files)))
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(define (directory-server icon-name)
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(let ((icon-name
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(cond
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((procedure? icon-name) icon-name)
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((string? icon-name)
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(lambda (tag)
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(string-append icon-name (tag->icon tag))))
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(else tag->icon))))
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(lambda (fname file-path req)
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(let ((request-method (request:method req)))
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(cond
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((or (string=? request-method "GET")
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(string=? request-method "HEAD"))
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(if (not (eq? 'directory
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(file-info:type (stat-carefully fname req))))
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(http-error http-reply/forbidden req))
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(if (not (v0.9-request? req))
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(begin
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(begin-http-header #t http-reply/ok)
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(write-string "Content-type: text/html\r\n")
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(write-string "\r\n")))
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(with-tag #t html ()
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(let ((title (string-append "Index of /"
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(string-join file-path "/"))))
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(with-tag #t head ()
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(emit-title #t title))
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(with-tag #t body ()
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(emit-header #t 1 title)
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(with-tag #t pre ()
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(emit-tag #t 'img
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(cons 'src (icon-name 'blank))
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(cons 'alt " "))
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(write-string "Name ")
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(write-string "Last modified ")
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(write-string "Size ")
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(write-string "Description")
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(emit-tag #t 'hr)
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(emit-tag #t 'img
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(cons 'src (icon-name 'back))
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(cons 'alt "[UP ]"))
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(if (not (null? file-path))
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(begin
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(with-tag #t a ((href ".."))
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(write-string "Parent directory"))
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(newline)))
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(let ((n-files (directory-index req fname icon-name)))
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(emit-tag #t 'hr)
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(format #t "~d files" n-files)))))))
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(else (http-error http-reply/method-not-allowed req)))))))
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(define (index-or-directory-server icon-name)
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(let ((directory-serve (directory-server icon-name)))
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(lambda (fname file-path req)
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(let ((index-fname (string-append fname "index.html")))
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(if (file-readable? index-fname)
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(file-serve index-fname file-path req)
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(directory-serve fname file-path req))))))
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(define (file-server-and-dir icon-name)
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(let ((index-or-directory-serve (index-or-directory-server icon-name)))
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(lambda (fname file-path req)
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(file-serve-or-dir fname file-path req index-or-directory-serve))))
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;;; Look up user's home directory, generating an HTTP error reply if you lose.
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(define (http-homedir username req)
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(with-fatal-error-handler (lambda (c decline)
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|
(apply http-error http-reply/bad-request req
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"Couldn't find user's home directory."
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|
(condition-stuff c)))
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|
|
(home-dir username)))
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|
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(define (send-file filename info req)
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|
(with-errno-handler ((errno packet)
|
|
((errno/acces)
|
|
(http-error http-reply/forbidden req))
|
|
((errno/noent)
|
|
(http-error http-reply/not-found req)))
|
|
(call-with-input-file filename
|
|
(lambda (in)
|
|
(let ((out (current-output-port)))
|
|
(if (not (v0.9-request? req))
|
|
(begin
|
|
(begin-http-header out http-reply/ok)
|
|
(receive (filename content-encoding)
|
|
(file-extension->content-encoding filename)
|
|
(if content-encoding
|
|
(format out "Content-encoding: ~A\r~%"
|
|
content-encoding))
|
|
(cond ((file-extension->content-type filename) =>
|
|
(lambda (ct)
|
|
(format out "Content-type: ~A\r~%" ct)))))
|
|
(format out "Last-modified: ~A\r~%"
|
|
(time->http-date-string (file-info:mtime info)))
|
|
(format out "Content-length: ~D\r~%" (file-info:size info))
|
|
(write-string "\r\n" out)))
|
|
(copy-inport->outport in out))))))
|
|
|
|
|
|
;;; Assemble a filename from ROOT and the elts of PATH-LIST.
|
|
;;; If the assembled filename contains a .. subdirectory, return #f,
|
|
;;; otw return the filename.
|
|
|
|
(define dotdot-check
|
|
(let ((dotdot-re (make-regexp "(^|/)\\.\\.($|/)"))) ; Matches a .. subdir.
|
|
(lambda (root path-list)
|
|
(let ((fname (if (null? path-list) root ; Bogus hack.
|
|
(string-append (file-name-as-directory root)
|
|
(string-join path-list "/")))))
|
|
(and (not (regexp-exec dotdot-re fname)) ; Check for .. subdir.
|
|
fname)))))
|
|
|
|
|
|
(define (file-extension->content-type fname)
|
|
(let ((ext (file-name-extension fname)))
|
|
(cond
|
|
((string-ci=? ext ".html") "text/html")
|
|
((string-ci=? ext ".txt") "text/plain")
|
|
((string-ci=? ext ".gif") "image/gif")
|
|
((string-ci=? ext ".png") "image/png")
|
|
((or (string-ci=? ext ".jpg")
|
|
(string-ci=? ext ".jpeg")) "image/jpeg")
|
|
((or (string-ci=? ext ".tiff")
|
|
(string-ci=? ext ".tif")) "image/tif")
|
|
((string-ci=? ext ".rtf") "text/rtf")
|
|
((or (string-ci=? ext ".mpeg")
|
|
(string-ci=? ext ".mpg")) "video/mpeg")
|
|
((or (string-ci=? ext ".au")
|
|
(string-ci=? ext ".snd")) "audio/basic")
|
|
((string-ci=? ext ".wav") "audio/x-wav")
|
|
((string-ci=? ext ".dvi") "application/x-dvi")
|
|
((or (string-ci=? ext ".tex")
|
|
(string-ci=? ext ".latex")) "application/latex")
|
|
((string-ci=? ext ".zip") "application/zip")
|
|
((string-ci=? ext ".tar") "application/tar")
|
|
((string-ci=? ext ".ps") "application/postscript")
|
|
((string-ci=? ext ".pdf") "application/pdf")
|
|
(else "application/octet-stream"))))
|
|
|
|
(define (file-extension->content-encoding fname)
|
|
(cond
|
|
((let ((ext (file-name-extension fname)))
|
|
(cond
|
|
((string-ci=? ext ".Z") "x-compress")
|
|
((string-ci=? ext ".gz") "x-gzip")
|
|
(else #f)))
|
|
=> (lambda (encoding)
|
|
(values (file-name-sans-extension fname) encoding)))
|
|
(else (values fname #f))))
|
|
|
|
;;; Timeout on network writes?
|
|
|
|
(define (copy-inport->outport in out)
|
|
(let ((buf (make-string server/buffer-size)))
|
|
(let loop ()
|
|
(cond ((read-string! buf in) => (lambda (nchars)
|
|
(write-string buf out 0 nchars)
|
|
(loop))))))
|
|
(force-output out))
|