share/txr/stdlib/with-resources.tl


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;; Copyright 2015-2017
;; Kaz Kylheku <kaz@kylheku.com>
;; Vancouver, Canada
;; All rights reserved.
;;
;; Redistribution and use in source and binary forms, with or without
;; modification, are permitted provided that the following conditions are met:
;;
;; 1. Redistributions of source code must retain the above copyright notice, this
;;    list of conditions and the following disclaimer.
;;
;; 2. Redistributions in binary form must reproduce the above copyright notice,
;;    this list of conditions and the following disclaimer in the documentation
;;    and/or other materials provided with the distribution.
;;
;; THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
;; ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
;; WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
;; DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
;; FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
;; DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
;; SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
;; CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
;; OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
;; OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

(defmacro with-resources (res-bindings . body)
  (tree-case res-bindings
    (((var init cleanup) . rest)
     ^(let ((,var ,init))
        (when ,var
          (unwind-protect
            (with-resources ,rest ,*body)
            ,cleanup))))
    (((var init) . rest)
     ^(let ((,var ,init))
        (with-resources ,rest ,*body)))
    ((var . rest)
     ^(let (,var)
        (with-resources ,rest ,*body)))
    (nil
      ^(progn ,*body))
    (other (error "with-resources: bad syntax"))))

(defmacro with-objects (var-init-forms . body)
  (let ((gens (mapcar (ret (gensym)) var-init-forms)))
    ^(let ,gens
       (unwind-protect
         (let* ,(mapcar (aret ^(,@2 (set ,@1 ,@3))) gens var-init-forms)
           ,*body)
         ,*(reverse (mapcar (ret ^(call-finalizers ,@1)) gens))))))