lock.sls

;;; -*- mode:scheme; coding:utf-8; -*-
;;;
;;; springkussen/misc/lock.sls - Mutex
;;;  
;;;   Copyright (c) 2022  Takashi Kato  <ktakashi@ymail.com>
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;; Vanilla implementation of lock, using SRFI-18 or dummy
#!r6rs
(library (springkussen misc lock)
    (export (rename (make-mutex make-lock))
	    with-lock)
    (import (rnrs)
	    (springkussen misc eval-binding))

(define make-mutex (binding (srfi :18) make-mutex (lambda () (list 'dummy))))
(define mutex-lock!  (binding (srfi :18) mutex-lock! (lambda (m) m)))
(define mutex-unlock!  (binding (srfi :18) mutex-unlock! (lambda (m) m)))
  
(define-syntax with-lock
  (syntax-rules ()
    ((_ lock body0 body* ...)
     (let ((m lock))
       (define (thunk) body0 body* ...)
       (guard (e (else (mutex-unlock! m) (raise e)))
	 (mutex-lock! m)
	 (let ((r (thunk)))
	   (mutex-unlock! m)
	   r))))))

)