330 lines
11 KiB
Scheme
330 lines
11 KiB
Scheme
;; the servlet handler
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;; Copyright Andreas Bernauer, 2002
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;;; instance-table: entry for every new request on a servlet page
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(define-record-type instance :instance
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(make-instance servlet-name continuation-table continuation-table-lock
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continuation-counter)
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instance?
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(servlet-name instance-servlet-name)
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(continuation-table instance-continuation-table)
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(continuation-table-lock instance-continuation-table-lock)
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(continuation-counter instance-continuation-counter))
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(define-record-type session :session
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(make-session instance-id return-continuation)
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session?
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(instance-id really-session-instance-id
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set-session-instance-id!)
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(return-continuation really-session-return-continuation
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set-session-return-continuation!))
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(define *instance-table* (make-integer-table)) ; instance-id is index
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(define *instance-table-lock* (make-lock))
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(define random
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(let* ((source (make-random-source))
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(random-integer (begin
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(random-source-randomize! source)
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(random-source-make-integers source))))
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(lambda ()
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(random-integer 1073741824)))) ; I hope, 1+ billion is enough....
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(define (servlet-handler servlet-path)
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(lambda (path req)
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(if (pair? path) ; need at least one element
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(let ((request-method (request:method req))
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(full-path (uri-path-list->path path)))
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(cond
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((string=? full-path "profile") ; triggers profiling
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(http-syslog (syslog-level debug)
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"profiling: triggered in servlet-handler [~a]"
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(profile-space)) ; PROFILE
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(make-http-error-response http-status/accepted req "profiled"))
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((string=? full-path "reset") ; triggers cache clearing
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(http-syslog (syslog-level debug)
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"servlet-handler: clearing plugin cache")
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(reset-plugin-cache!)
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(http-syslog (syslog-level debug)
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"servlet-handler: clearing instance table")
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(reset-instance-table!))
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(make-http-error-response http-status/accepted req "plugin cache cleared"))
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((or (string=? request-method "GET")
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; (string=? request-method "POST")) ; do this at later time
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)
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(with-cwd
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servlet-path
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(if (resume-url? full-path)
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(resume-url full-path req)
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(launch-new-instance full-path req))))
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(else
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(make-http-error-response http-status/method-not-allowed req
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request-method))))
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(make-http-error-response http-status/bad-request req
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(format #f "Bad path: ~s" path)))))
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(define (launch-new-instance full-path req)
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(if (file-not-exists? full-path)
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(make-http-error-response http-status/not-found req full-path)
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(begin
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(obtain-lock *instance-table-lock*)
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;; no access to instance table until new instance-id is saved
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(let ((instance-id (generate-new-table-id *instance-table*)))
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(table-set! *instance-table* instance-id
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(make-instance full-path ; used to make
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; redirections to origin
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(make-integer-table) ; continuation table
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(make-lock) ; continuation table lock
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(make-thread-safe-counter))) ; continuation counter
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(release-lock *instance-table-lock*)
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(let ((plugin (with-fatal-error-handler*
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(lambda (condition decline)
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(instance-delete! instance-id)
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(decline))
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(lambda ()
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(get-plugin-rt-structure full-path)))))
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(reset
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(begin
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(register-session! instance-id 'no-return)
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(with-names-from-rt-structure
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plugin plugin-interface
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(main req)))))))))
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;; try to get continuation-table and then the continuation
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(define resume-url
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(let ((bad-request
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(lambda (full-path req)
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(make-http-error-response
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http-status/bad-request req
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(format #f "The servlet does not accept any requests any more or your URL is illformed.<BR>
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You can try starting at the <A HREF=~a>beginning</a>."
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(resume-url-servlet-name full-path)))))
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(lookup-continuation-table
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(lambda (instance continuation-table continuation-id)
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(let ((continuation-table-lock (instance-continuation-table-lock instance)))
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(obtain-lock continuation-table-lock)
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(let ((result (table-ref continuation-table continuation-id)))
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(release-lock continuation-table-lock)
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result)))))
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(lambda (full-path req)
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(receive (instance-id continuation-id)
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(resume-url-ids full-path)
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(let ((instance (instance-lookup instance-id)))
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(if instance
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(let* ((continuation-table (instance-continuation-table instance))
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(resume (lookup-continuation-table instance continuation-table
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continuation-id)))
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(if resume
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(reset
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(begin
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(register-session! instance-id 'no-return)
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; (error "This may never return." ; for debugging
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(resume req)))
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(bad-request full-path req)))
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(bad-request full-path req)))
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))))
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(define (send/suspend response-maker)
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(shift return
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(let* ((instance-id (session-instance-id))
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(instance (instance-lookup instance-id))
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(continuations-table (instance-continuation-table instance))
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(continuation-table-lock (instance-continuation-table-lock instance))
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(continuation-counter (instance-next-continuation-counter instance)))
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(obtain-lock continuation-table-lock)
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(let ((continuation-id (generate-new-table-id continuations-table)))
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(table-set! continuations-table continuation-id return)
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(release-lock continuation-table-lock)
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(let ((new-url (make-resume-url (instance-servlet-name instance)
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instance-id
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continuation-counter
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continuation-id)))
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(response-maker new-url))))))
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(define (send/finish response)
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(instance-delete! (session-instance-id))
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response)
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;; access to instance-table
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(define (instance-lookup instance-id)
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(obtain-lock *instance-table-lock*)
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(let ((result (table-ref *instance-table* instance-id)))
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(release-lock *instance-table-lock*)
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result))
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(define (instance-next-continuation-counter instance)
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(thread-safe-counter-next!
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(instance-continuation-counter instance)))
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(define (instance-delete! instance-id)
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(obtain-lock *instance-table-lock*)
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;; why can't table entries be deleted correctly?
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(table-set! *instance-table* instance-id #f)
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(release-lock *instance-table-lock*))
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;; ID generation
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;; locking must be done by caller
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;; FIXME?: this may loop forever, if the table is full (can this happen?)
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(define (generate-new-table-id table)
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(let loop ((id (random)))
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(if (table-ref table id)
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(loop (random))
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id)))
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;; PLUGINs CACHE
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(define *plugin-table* (make-string-table)) ; full-path is index
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(define *plugin-table-lock* (make-lock))
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;; PLUGIN-NAME is like "news-dir/latest-news.scm"
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(define (get-plugin-rt-structure plugin-name)
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(let ((load-plugin
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(lambda ()
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(with-fatal-error-handler*
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(lambda (condition decline)
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(release-lock *plugin-table-lock*)
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(decline))
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(lambda ()
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;; load-config-file does not care about cwd(?)
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;; --> absolute file name needed
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(load-config-file (absolute-file-name plugin-name))
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;; plugin-structure to load must be named "plugin"
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(let ((plugin-structure (reify-structure 'plugin)))
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(load-structure plugin-structure)
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(table-set! *plugin-table* plugin-name
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(cons plugin-structure
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(file-last-mod plugin-name)))
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;; only now the lock may be released
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(release-lock *plugin-table-lock*)
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plugin-structure))))))
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(obtain-lock *plugin-table-lock*)
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(let ((plugin (table-ref *plugin-table* plugin-name)))
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(if plugin
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(if (equal? (file-last-mod plugin-name)
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(cdr plugin))
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(begin
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(release-lock *plugin-table-lock*)
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(car plugin))
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(load-plugin))
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(load-plugin)))))
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(define (reset-plugin-cache!)
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(with-fatal-error-handler*
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(lambda (condition decline)
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(release-lock *plugin-table-lock*)
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(decline))
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(lambda ()
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(obtain-lock *plugin-table-lock*)
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(set! *plugin-table* (make-string-table))
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(release-lock *plugin-table-lock*))))
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(define (reset-instance-table!)
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(with-fatal-error-handler
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(lambda (condtion decline)
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(release-lock *instance-table-lock*)
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(decline))
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(lambda ()
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(obtain-lock *instance-table-lock*)
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(set! *instance-table* (make-integer-table))
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(release-lock *instance-table*))))
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;; SESSION
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(define *session* (make-thread-cell #f))
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(define (register-session! instance-id return-continuation)
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(thread-cell-set! *session*
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(make-session instance-id return-continuation)))
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;(define (save-session-return-continuation! return-continuation)
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; (set-session-instance-id! (thread-cell-ref *session*)
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; return-continuation))
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(define (session-instance-id)
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(really-session-instance-id (thread-cell-ref *session*)))
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(define (session-return-continuation)
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(really-session-return-continuation (thread-cell-ref *session*)))
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;; RESUME-URL
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(define *resume-url-regexp* (rx (submatch (* (- printing ";")))
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";k" (submatch (* digit)) ; Instance-ID
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";c" (+ digit) "-" (submatch (* digit)))) ; Continuation-ID
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(define (make-resume-url full-path instance-id continuation-counter continuation-id)
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(string-append full-path
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";k" (number->string (session-instance-id))
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";c" (number->string continuation-counter)
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"-" (number->string continuation-id)))
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(define (resume-url-instance-id id-url)
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(receive (instance-id continuation-id)
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(resume-url-ids id-url)
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instance-id))
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(define (resume-url-continuation-id id-url)
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(receive (instance-id continuation-id)
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(resume-url-ids id-url)
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continuation-id))
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(define (resume-url-ids id-url)
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(let ((match (regexp-search *resume-url-regexp* id-url)))
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(if match
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(values (string->number (match:substring match 2))
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(string->number (match:substring match 3)))
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(error "resume-url-ids: no instance/continuation id" id-url))))
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(define (resume-url-servlet-name id-url)
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(let ((match (regexp-search *resume-url-regexp* id-url)))
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(if match
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(match:substring match 1)
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(error "resume-url-servlet-name: no servlet-name found"))))
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(define (resume-url? id-url)
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(regexp-search? *resume-url-regexp* id-url))
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;; thread-safe counter
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(define-record-type counter :counter
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(really-make-counter counter lock)
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(counter counter-counter set-counter-counter!)
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(lock counter-lock))
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(define (make-thread-safe-counter)
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(really-make-counter 0 (make-lock)))
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;;; read current value
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(define (thread-safe-counter counter)
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(obtain-lock (counter-lock counter))
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(let ((result (counter-counter counter)))
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(release-lock (counter-lock counter))
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result))
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;;; make next value and return it
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(define (thread-safe-counter-next! counter)
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(obtain-lock (counter-lock counter))
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(let ((result (+ 1 (counter-counter counter))))
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(set-counter-counter! counter result)
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(release-lock (counter-lock counter))
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result))
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; instance-table thread safe
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; continuation-table thread safe
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; generate-new-instance-id only called if thread safe
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; generate-new-continuation-id only called if thread safe
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; respect plugin timestamp |