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;; This file is part of scheme-GNUnet, a partial Scheme port of GNUnet.
;; Copyright (C) 2021 Maxime Devos
;;
;; scheme-GNUnet is free software: you can redistribute it and/or modify it
;; under the terms of the GNU Affero General Public License as published
;; by the Free Software Foundation, either version 3 of the License,
;; or (at your option) any later version.
;;
;; scheme-GNUnet is distributed in the hope that it will be useful, but
;; WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
;; Affero General Public License for more details.
;;
;; You should have received a copy of the GNU Affero General Public License
;; along with this program. If not, see <http://www.gnu.org/licenses/>.
;;
;; SPDX-License-Identifier: AGPL3.0-or-later
;; Brief: Interface to the network size estimation service.
;; C author: Nathan Evans
;; Scheme author: Maxime Devos
;;
;; The Scheme implementation is _not_ based on the C implementation,
;; though the Scheme API is structured after the C API and slightly
;; extended.
(define-library (gnu gnunet nse client)
(export estimate?
estimate:logarithmic-number-peers
estimate:number-peers
estimate:standard-deviation
estimate:timestamp
server?
connect
disconnect!
estimate)
(import (only (rnrs base)
begin define quote lambda case values expt = else apply
and >=)
(only (rnrs control)
when unless)
(only (rnrs records syntactic)
define-record-type)
(only (ice-9 atomic)
make-atomic-box atomic-box-ref atomic-box-set!)
(only (fibers)
spawn-fiber)
(only (fibers conditions)
make-condition wait wait-operation signal-condition!)
(only (fibers operations)
choice-operation perform-operation)
(only (gnu extractor enum)
symbol-value value->index)
(only (guile)
define* const)
(only (gnu gnunet util struct)
/:message-header)
(only (gnu gnunet utils bv-slice)
make-slice/read-write slice-length)
(only (gnu gnunet netstruct syntactic)
read% set%! sizeof)
(only (gnu gnunet mq handler)
message-handler
message-handlers)
(only (gnu gnunet mq)
send-message! close-queue!)
(only (gnu gnunet mq-impl stream)
connect/fibers)
(only (gnu gnunet mq error-reporting)
report-error)
(gnu gnunet message protocols)
(only (gnu gnunet nse struct)
/:msg:nse:estimate))
(begin
(define-record-type (<estimate> %make-estimate estimate?)
(fields (immutable logarithmic-number-peers
%estimate:logarithmic-number-peers)
(immutable standard-deviation %estimate:standard-deviation)
(immutable timestamp %estimate:timestamp))
(sealed #t)
(opaque #t))
(define-record-type (<server> %make-server server?)
;; Atomic box of <estimate>
(fields (immutable estimate/box server-estimate/box)
;; Atomic box of boolean. Initially #f. Set this
;; to #t before signalling request-close-condition.
(immutable request-close?/box
server-request-close?/box)
(immutable request-close-condition
server-request-close-condition)))
(define (estimate server)
"Return the current estimate of the number of peers on the network,
in some unspecified format. Alternatively, if no estimate is available
yet, return @code{#false}."
(atomic-box-ref (server-estimate/box server)))
(define (estimate:logarithmic-number-peers estimate)
"Return the logarithm (base 2) of the number of peers on the network
in @var{estimate} as a positive flonum (possibly zero or infinite)."
(%estimate:logarithmic-number-peers estimate))
(define (estimate:standard-deviation estimate)
"Return the standard deviation of the logarithmic estimate
of the number of peers of the last 64 rounds as a positive flonum
(possibly zero or infinite)."
(%estimate:standard-deviation estimate))
(define (estimate:number-peers estimate)
"Return the estimate of the number of peers on the network in
@var{estimate} as a strictly-positive flonum, at least @code{1.0}
and possibly infinite."
(expt 2.0 (estimate:logarithmic-number-peers estimate)))
(define (estimate:timestamp estimate)
"Return when the estimate @var{estimate} was made, as a standard GNUnet
timestamp."
(%estimate:timestamp estimate))
(define (disconnect! server)
"Asynchronuously disconnect from the NSE server and stop reconnecting,
even if not connected. This is an idempotent operation."
(atomic-box-set! (server-request-close?/box server) #t)
(signal-condition! (server-request-close-condition server)))
;; See 'connect'.
(define* (reconnect estimate/box request-close?/box request-close-condition config
#:key
updated connected disconnected spawn #:rest rest)
(define (handle-estimate! estimate-slice)
(define estimate
(%make-estimate
(read% /:msg:nse:estimate '(size-estimate) estimate-slice)
(read% /:msg:nse:estimate '(std-deviation) estimate-slice)
(read% /:msg:nse:estimate '(timestamp) estimate-slice)))
(atomic-box-set! estimate/box estimate)
(when updated
(updated estimate)))
(define handlers
(message-handlers
(message-handler
(type (symbol-value message-type msg:nse:estimate))
((interpose code) code)
((well-formed? slice)
(and (= (slice-length slice)
(sizeof /:msg:nse:estimate '()))
;; XXX: these two lines below are not tested
(>= (read% /:msg:nse:estimate '(size-estimate) slice) 0)
(>= (read% /:msg:nse:estimate '(std-deviation) slice) 0)))
((handle! slice) (handle-estimate! slice)))))
(define (send-start!)
;; The service only starts sending estimates once
;; /:msg:nse:start is sent.
(define s (make-slice/read-write (sizeof /:message-header '())))
(set%! /:message-header '(size) s (sizeof /:message-header '()))
(set%! /:message-header '(type) s
(value->index (symbol-value message-type msg:nse:start)))
(send-message! mq s))
(define mq-defined (make-condition))
(define mq-closed (make-condition))
(define (error-handler error . arguments)
(case error
((connection:connected)
;; Make sure the message queue is actually bound to the variable
;; @var{mq} before calling @code{send-start!}, as @code{send-start!}
;; uses @var{mq}.
(wait mq-defined)
(send-start!)
(when connected (connected)))
((input:regular-end-of-file input:premature-end-of-file)
;; Call 'reconnect' after 'disconnected'. Otherwise,
;; it is possible that 'connected' is called twice without
;; a call to 'disconnected' in-between, which would presumably
;; be confusing.
(signal-condition! mq-closed)
(when disconnected (disconnected))
;; Don't reconnect after 'close-queue!'. About races: it's not
;; paramount we stop reconnecting immediately, but we should stop
;; eventually after 'request-close?/box' is set and
;; 'request-close-condition' is signalled, and 'request-close-handler'
;; will take care of closing the new queue if it shouldn't have been
;; created.
(unless (atomic-box-ref request-close?/box)
(apply reconnect estimate/box request-close?/box request-close-condition
config rest)))
((connection:interrupted)
(values))
(else
;; Weirdness. Not much that can be done except report it and
;; try to reconnect. XXX untested code path, sleep a little?
(apply report-error error arguments)
(close-queue! mq))))
;; Only started after 'mq' is defined, so no need to wait for
;; 'mq-defined'.
(define (request-close-handler)
(perform-operation
(choice-operation
(wait-operation request-close-condition)
;; Make sure the fiber exits after a reconnect.
(wait-operation mq-closed)))
(close-queue! mq))
(define mq (connect/fibers config "nse" handlers error-handler
#:spawn spawn))
(signal-condition! mq-defined)
(spawn request-close-handler))
(define* (connect config #:key updated connected disconnected
(spawn spawn-fiber))
"Connect to the NSE service in the background.
When connected, the thunk @var{connected} is called and estimates
will become available (but possibly not immediately). When a new
estimate is available, the procedure @var{updated} is called. This
procedure should accept the new estimate. When disconnected, the
thunk @code{disconnected} and updates will be (temporarily) unavailable,
until connected again. It is possible for @var{updated} to be called
shortly after calling @var{disconnected}.
The procedures @var{updated}, @var{connected} and @var{disconnected} are optional."
(define estimate/box (make-atomic-box #f))
(define request-close?/box (make-atomic-box #f))
(define request-close-condition (make-condition))
(reconnect estimate/box request-close?/box request-close-condition config
#:updated updated #:connected connected #:disconnected disconnected
#:spawn spawn)
(%make-server estimate/box request-close?/box request-close-condition))))
|
