gnu: guile-fibers: Add (fibers io-wakeup).

This patch is required by gnunet-scheme.  It has been submitted upstream at
<https://github.com/wingo/fibers/pull/50>, but there has not been any response
so far.

* gnu/packages/patches/guile-fibers-wait-for-io-readiness.patch: New file.
* gnu/packages/guile-xyz.scm (guile-fibers-1.1)[source]{patches}: Add it.
* gnu/local.mk (dist_patch_DATA): Add it.

Signed-off-by: Ludovic Courtès <ludo@gnu.org>

1 files changed, 346 insertions, 0 deletions

diff --git a/gnu/packages/patches/guile-fibers-wait-for-io-readiness.patch b/gnu/packages/patches/guile-fibers-wait-for-io-readiness.patch
new file mode 100644
index 0000000000..d5d5cf44e6
--- /dev/null
+++ b/gnu/packages/patches/guile-fibers-wait-for-io-readiness.patch
@@ -0,0 +1,346 @@
+Scheme-GNUnet requires the new operations 'wait-until-port-readable-operation'
+and 'wait-until-port-readable-operation' for communicating with services.
+This patch has been previously submitted at <https://github.com/wingo/fibers/pull/50>,
+on Sep 16, 2021.  As of Feb 3, 2022, upstream has not responded yet.
+
+diff --git a/Makefile.am b/Makefile.am
+index e2db57e..0134255 100644
+--- a/Makefile.am
++++ b/Makefile.am
+@@ -33,6 +33,7 @@ SOURCES = \
+ 	fibers/deque.scm \
+ 	fibers/epoll.scm \
+ 	fibers/interrupts.scm \
++	fibers/io-wakeup.scm \
+ 	fibers/nameset.scm \
+ 	fibers/operations.scm \
+ 	fibers/posix-clocks.scm \
+@@ -67,6 +68,7 @@ TESTS = \
+ 	tests/conditions.scm \
+ 	tests/channels.scm \
+ 	tests/foreign.scm \
++	tests/io-wakeup.scm \
+ 	tests/parameters.scm \
+ 	tests/preemption.scm \
+ 	tests/speedup.scm
+diff --git a/fibers.texi b/fibers.texi
+index 52f7177..0990c8f 100644
+--- a/fibers.texi
++++ b/fibers.texi
+@@ -12,6 +12,7 @@ This manual is for Fibers (version @value{VERSION}, updated
+ @value{UPDATED})
+ 
+ Copyright 2016-2022 Andy Wingo
++Copyright 2021 Maxime Devos
+ 
+ @quotation
+ @c For more information, see COPYING.docs in the fibers
+@@ -453,6 +454,7 @@ of operations for channels and timers, and an internals interface.
+ * Channels::             Share memory by communicating.
+ * Timers::               Operations on time.
+ * Conditions::           Waiting for simple state changes.
++* Port Readiness::       Waiting until a port is ready for I/O.
+ * REPL Commands::        Experimenting with Fibers at the console.
+ * Schedulers and Tasks:: Fibers are built from lower-level primitives.
+ @end menu
+@@ -722,6 +724,28 @@ signalled.  Equivalent to @code{(perform-operation (wait-operation
+ cvar))}.
+ @end defun
+ 
++@node Port Readiness
++@section Port Readiness
++
++These two operations can be used on file ports to wait until
++they are readable or writable.  Spurious wake-ups are possible.
++This is complementary to Guile's suspendable ports.
++
++@example
++(use-modules (fibers io-wakeup))
++@end example
++
++@defun wait-until-port-readable-operation port
++Make an operation that will succeed with no values when the input
++port @var{port} becomes readable.  For passive sockets, this operation
++succeeds when a connection becomes available.
++@end defun
++
++@defun wait-until-port-writable-operation
++Make an operation that will succeed with no values when the output
++port @var{port} becomes writable.
++@end defun
++
+ @node REPL Commands
+ @section REPL Commands
+ 
+diff --git a/fibers/io-wakeup.scm b/fibers/io-wakeup.scm
+new file mode 100644
+index 0000000..5df03f1
+--- /dev/null
++++ b/fibers/io-wakeup.scm
+@@ -0,0 +1,93 @@
++;; Fibers: cooperative, event-driven user-space threads.
++
++;;;; Copyright (C) 2016,2021 Free Software Foundation, Inc.
++;;;; Copyright (C) 2021 Maxime Devos
++;;;;
++;;;; This library is free software; you can redistribute it and/or
++;;;; modify it under the terms of the GNU Lesser General Public
++;;;; License as published by the Free Software Foundation; either
++;;;; version 3 of the License, or (at your option) any later version.
++;;;;
++;;;; This library 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
++;;;; Lesser General Public License for more details.
++;;;;
++;;;; You should have received a copy of the GNU Lesser General Public
++;;;; License along with this library; if not, write to the Free Software
++;;;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
++;;;;
++
++(define-module (fibers io-wakeup)
++  #:use-module (fibers scheduler)
++  #:use-module (fibers operations)
++  #:use-module (ice-9 atomic)
++  #:use-module (ice-9 match)
++  #:use-module (ice-9 threads)
++  #:use-module (ice-9 ports internal)
++  #:export (wait-until-port-readable-operation
++	    wait-until-port-writable-operation))
++
++(define *poll-sched* (make-atomic-box #f))
++
++(define (poll-sched)
++  (or (atomic-box-ref *poll-sched*)
++      (let ((sched (make-scheduler)))
++        (cond
++         ((atomic-box-compare-and-swap! *poll-sched* #f sched))
++         (else
++          ;; FIXME: Would be nice to clean up this thread at some point.
++          (call-with-new-thread
++           (lambda ()
++             (define (finished?) #f)
++             (run-scheduler sched finished?)))
++          sched)))))
++
++;; These procedure are subject to spurious wakeups.
++
++(define (readable? port)
++  "Test if PORT is writable."
++  (match (select (vector port) #() #() 0)
++    ((#() #() #()) #f)
++    ((#(_) #() #()) #t)))
++
++(define (writable? port)
++  "Test if PORT is writable."
++  (match (select #() (vector port) #() 0)
++    ((#() #() #()) #f)
++    ((#() #(_) #()) #t)))
++
++(define (make-wait-operation ready? schedule-when-ready port port-ready-fd this-procedure)
++  (make-base-operation #f
++                       (lambda _
++                         (and (ready? port) values))
++                       (lambda (flag sched resume)
++                         (define (commit)
++                           (match (atomic-box-compare-and-swap! flag 'W 'S)
++                             ('W (resume values))
++                             ('C (commit))
++                             ('S #f)))
++                         (if sched
++                             (schedule-when-ready
++                              sched (port-ready-fd port) commit)
++                             (schedule-task
++                              (poll-sched)
++                              (lambda ()
++                                (perform-operation (this-procedure port))
++                                (commit)))))))
++
++(define (wait-until-port-readable-operation port)
++  "Make an operation that will succeed when PORT is readable."
++  (unless (input-port? port)
++    (error "refusing to wait forever for input on non-input port"))
++  (make-wait-operation readable? schedule-task-when-fd-readable port
++                       port-read-wait-fd
++                       wait-until-port-readable-operation))
++
++(define (wait-until-port-writable-operation port)
++  "Make an operation that will succeed when PORT is writable."
++  (unless (output-port? port)
++    (error "refusing to wait forever for output on non-output port"))
++  (make-wait-operation writable? schedule-task-when-fd-writable port
++                       port-write-wait-fd
++                       wait-until-port-writable-operation))
+diff --git a/tests/io-wakeup.scm b/tests/io-wakeup.scm
+new file mode 100644
+index 0000000..c14fa81
+--- /dev/null
++++ b/tests/io-wakeup.scm
+@@ -0,0 +1,167 @@
++;; Fibers: cooperative, event-driven user-space threads.
++
++;;;; Copyright (C) 2016 Free Software Foundation, Inc.
++;;;; Copyright (C) 2021 Maxime Devos
++;;;;
++;;;; This library is free software; you can redistribute it and/or
++;;;; modify it under the terms of the GNU Lesser General Public
++;;;; License as published by the Free Software Foundation; either
++;;;; version 3 of the License, or (at your option) any later version.
++;;;;
++;;;; This library 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
++;;;; Lesser General Public License for more details.
++;;;;
++;;;; You should have received a copy of the GNU Lesser General Public
++;;;; License along with this library; if not, write to the Free Software
++;;;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
++;;;;
++
++(define-module (tests io-wakeup)
++  #:use-module (rnrs bytevectors)
++  #:use-module (ice-9 control)
++  #:use-module (ice-9 suspendable-ports)
++  #:use-module (ice-9 binary-ports)
++  #:use-module (fibers)
++  #:use-module (fibers io-wakeup)
++  #:use-module (fibers operations)
++  #:use-module (fibers timers))
++
++(define failed? #f)
++
++(define-syntax-rule (assert-equal expected actual)
++  (let ((x expected))
++    (format #t "assert ~s equal to ~s: " 'actual x)
++    (force-output)
++    (let ((y actual))
++      (cond
++       ((equal? x y) (format #t "ok\n"))
++       (else
++        (format #t "no (got ~s)\n" y)
++        (set! failed? #t))))))
++
++(define-syntax-rule (assert-run-fibers-terminates exp)
++  (begin
++    (format #t "assert run-fibers on ~s terminates: " 'exp)
++    (force-output)
++    (let ((start (get-internal-real-time)))
++      (call-with-values (lambda () (run-fibers (lambda () exp)))
++        (lambda vals
++          (format #t "ok (~a s)\n" (/ (- (get-internal-real-time) start)
++                                      1.0 internal-time-units-per-second))
++          (apply values vals))))))
++
++(define-syntax-rule (assert-run-fibers-returns (expected ...) exp)
++  (begin
++    (call-with-values (lambda () (assert-run-fibers-terminates exp))
++      (lambda run-fiber-return-vals
++        (assert-equal '(expected ...) run-fiber-return-vals)))))
++
++
++;; Note that theoretically, on very slow systems, SECONDS might need
++;; to be increased.  However, readable/timeout? and writable/timeout?
++;; call this 5 times in a loop anyways, so the effective timeout is
++;; a fourth of a second, which should be plenty in practice.
++(define* (with-timeout op #:key (seconds 0.05) (wrap values))
++  (choice-operation op
++                    (wrap-operation (sleep-operation seconds) wrap)))
++
++(define* (readable/timeout? port #:key (allowed-spurious 5))
++  "Does waiting for readability time-out?
++Allow @var{allowed-spurious} spurious wakeups."
++  (or (perform-operation
++	(with-timeout
++	 (wrap-operation (wait-until-port-readable-operation port)
++			 (lambda () #f))
++	 #:wrap (lambda () #t)))
++      (and (> allowed-spurious 0)
++	   (readable/timeout? port #:allowed-spurious
++			      (- allowed-spurious 1)))))
++
++(define* (writable/timeout? port #:key (allowed-spurious 5))
++  "Does waiting for writability time-out?
++Allow @var{allowed-spurious} spurious wakeups."
++  (or (perform-operation
++       (with-timeout
++	(wrap-operation (wait-until-port-writable-operation port)
++			(lambda () #f))
++	#:wrap (lambda () #t)))
++      (and (> allowed-spurious 0)
++	   (writable/timeout? port #:allowed-spurious
++			      (- allowed-spurious 1)))))
++
++;; Tests:
++;;  * wait-until-port-readable-operaton / wait-until-port-writable-operation
++;;    blocks if the port isn't ready for input / output.
++;;
++;;    This is tested with a pipe (read & write)
++;;    and a listening socket (read, or accept in this case).
++;;
++;;    Due to the possibility of spurious wakeups,
++;;    a limited few spurious wakeups are tolerated.
++;;
++;;  * these operations succeed if the port is ready for input / output.
++;;
++;;    These are again tested with a pipe and a listening socket
++;;
++;; Blocking is detected with a small time-out.
++
++(define (make-listening-socket)
++  (let ((server (socket PF_INET SOCK_DGRAM 0)))
++    (bind server AF_INET INADDR_LOOPBACK 0)
++    server))
++
++(let ((s (make-listening-socket)))
++  (assert-run-fibers-returns (#t)
++			     (readable/timeout? s))
++  (assert-equal #t (readable/timeout? s))
++  (close s))
++
++(define (set-nonblocking! sock)
++  (let ((flags (fcntl sock F_GETFL)))
++    (fcntl sock F_SETFL (logior O_NONBLOCK flags))))
++
++(define-syntax-rule (with-pipes (A B) exp exp* ...)
++  (let* ((pipes (pipe))
++	 (A (car pipes))
++	 (B (cdr pipes)))
++    exp exp* ...
++    (close A)
++    (close B)))
++
++(with-pipes (A B)
++  (setvbuf A 'none)
++  (setvbuf B 'none)
++  (assert-run-fibers-returns (#t)
++			     (readable/timeout? A))
++  (assert-equal #t (readable/timeout? A))
++
++  ;; The buffer is empty, so writability is expected.
++  (assert-run-fibers-returns (#f)
++			     (writable/timeout? B))
++  (assert-equal #f (writable/timeout? B))
++
++  ;; Fill the buffer
++  (set-nonblocking! B)
++  (let ((bv (make-bytevector 1024)))
++    (let/ec k
++      (parameterize ((current-write-waiter k))
++	(let loop ()
++	  (put-bytevector B bv)
++	  (loop)))))
++
++  ;; As the buffer is full, writable/timeout? should return
++  ;; #t.
++  (assert-run-fibers-returns (#t)
++			     (writable/timeout? B))
++  ;; There's plenty to read now, so readable/timeout? should
++  ;; return #f.
++  (assert-run-fibers-returns (#f)
++			     (readable/timeout? A)))
++
++(exit (if failed? 1 0))
++
++;; Local Variables:
++;; eval: (put 'with-pipes 'scheme-indent-function 1)
++;; End: