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;;; utils.scm -- helper procedures
;;; Copyright © 2012, 2013, 2016, 2018, 2019 Ludovic Courtès <ludo@gnu.org>
;;; Copyright © 2015 David Thompson <davet@gnu.org>
;;; Copyright © 2016 Mathieu Lirzin <mthl@gnu.org>
;;; Copyright © 2018 Clément Lassieur <clement@lassieur.org>
;;;
;;; This file is part of Cuirass.
;;;
;;; Cuirass is free software: you can redistribute it and/or modify
;;; it under the terms of the GNU General Public License as published by
;;; the Free Software Foundation, either version 3 of the License, or
;;; (at your option) any later version.
;;;
;;; Cuirass 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 General Public License for more details.
;;;
;;; You should have received a copy of the GNU General Public License
;;; along with Cuirass. If not, see <http://www.gnu.org/licenses/>.
(define-module (cuirass utils)
#:use-module (cuirass logging)
#:use-module (ice-9 match)
#:use-module (ice-9 threads)
#:use-module (rnrs bytevectors)
#:use-module (system foreign)
#:use-module (srfi srfi-1)
#:use-module (json)
#:use-module (fibers)
#:use-module (fibers channels)
#:export (alist?
object->json-scm
object->json-string
define-enumeration
unwind-protect
make-worker-thread-channel
call-with-worker-thread
with-worker-thread
%non-blocking
non-blocking
essential-task
bytevector-range))
(define (alist? obj)
"Return #t if OBJ is an alist."
(and (list? obj)
(every pair? obj)))
(define (object->json-scm obj)
"Prepare OBJ for JSON usage."
(cond ((string? obj) obj)
((number? obj) obj)
((boolean? obj) obj)
((null? obj) obj)
((symbol? obj) (symbol->string obj))
((keyword? obj) (object->json-scm (keyword->symbol obj)))
((vector? obj) (list->vector
(map object->json-scm (vector->list obj))))
((alist? obj) (map object->json-scm obj))
((pair? obj) (cons (object->json-scm (car obj))
(object->json-scm (cdr obj))))
(else (object->string obj))))
(define* (object->json-string object #:key pretty)
"Return OBJECT as a JSON object."
(scm->json-string (object->json-scm object) #:pretty pretty))
(define-syntax-rule (define-enumeration name (symbol value) ...)
"Define an 'enum' type with the given SYMBOL/VALUE pairs. NAME is defined a
macro that accepts one of these symbols and expands to the corresponding
value."
(define-syntax name
(syntax-rules (symbol ...)
((_ symbol) value)
...)))
(define-syntax-rule (unwind-protect body ... conclude)
"Evaluate BODY... and return its result(s), but always evaluate CONCLUDE
before leaving, even if an exception is raised.
This is *not* implemented with 'dynamic-wind' in order to play well with
delimited continuations and fibers."
(let ((conclusion (lambda () conclude)))
(catch #t
(lambda ()
(call-with-values
(lambda ()
body ...)
(lambda results
(conclusion)
(apply values results))))
(lambda args
(conclusion)
(apply throw args)))))
(define %worker-thread-args
(make-parameter #f))
(define (make-worker-thread-channel initializer)
"Return a channel used to offload work to a dedicated thread. ARGS are the
arguments of the worker thread procedure."
(parameterize (((@@ (fibers internal) current-fiber) #f))
(let ((channel (make-channel)))
(let ((args (initializer)))
(call-with-new-thread
(lambda ()
(parameterize ((%worker-thread-args args))
(let loop ()
(match (get-message channel)
(((? channel? reply) . (? procedure? proc))
(put-message reply (apply proc args))))
(loop))))))
channel)))
(define (call-with-worker-thread channel proc)
"Send PROC to the worker thread through CHANNEL. Return the result of PROC.
If already in the worker thread, call PROC immediately."
(let ((args (%worker-thread-args)))
(if args
(apply proc args)
(let ((reply (make-channel)))
(put-message channel (cons reply proc))
(get-message reply)))))
(define-syntax-rule (with-worker-thread channel (vars ...) exp ...)
"Evaluate EXP... in the worker thread corresponding to CHANNEL.
VARS... are bound to the arguments of the worker thread."
(call-with-worker-thread channel
(lambda (vars ...) exp ...)))
(define (%non-blocking thunk)
(parameterize (((@@ (fibers internal) current-fiber) #f))
(let ((channel (make-channel)))
(call-with-new-thread
(lambda ()
(catch #t
(lambda ()
(call-with-values thunk
(lambda values
(put-message channel `(values ,@values)))))
(lambda args
(put-message channel `(exception ,@args))))))
(match (get-message channel)
(('values . results)
(apply values results))
(('exception . args)
(apply throw args))))))
(define-syntax-rule (non-blocking exp ...)
"Evalaute EXP... in a separate thread so that it doesn't block the execution
of fibers.
This is useful when passing control to non-cooperative and non-resumable code
such as a 'clone' call in Guile-Git."
(%non-blocking (lambda () exp ...)))
(define (essential-task name exit-channel thunk)
"Return a thunk that wraps THUNK, catching exceptions and writing an exit
code to EXIT-CHANNEL when an exception occurs. The idea is that the other end
of the EXIT-CHANNEL will exit altogether when that occurs.
This is often necessary because an uncaught exception in a fiber causes it to
die silently while the rest of the program keeps going."
(lambda ()
(catch #t
thunk
(lambda _
(put-message exit-channel 1)) ;to be sure...
(lambda (key . args)
;; If something goes wrong in this fiber, we have a problem, so stop
;; everything.
(log-message "fatal: uncaught exception '~a' in '~a' fiber!"
key name)
(log-message "exception arguments: ~s" args)
(false-if-exception
(let ((stack (make-stack #t)))
(display-backtrace stack (current-error-port))
(print-exception (current-error-port)
(stack-ref stack 0)
key args)))
;; Tell the other end to exit with a non-zero code.
(put-message exit-channel 1)))))
(define %weak-references
(make-weak-key-hash-table))
(define (bytevector-range bv offset count)
"Return a bytevector that aliases the COUNT bytes of BV starting at OFFSET."
(cond ((and (zero? offset) (= count (bytevector-length bv)))
bv)
((or (> (+ offset count) (bytevector-length bv))
(< offset 0))
(throw 'out-of-range "bytevector-range"
"Bytevector range is invalid: ~S ~S"
(list offset count) (list offset count)))
(else
(let* ((pointer (bytevector->pointer bv offset))
(range (pointer->bytevector pointer count)))
(hashq-set! %weak-references range bv)
range))))
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