;;;
;;; Code freely lifted from various places with compatible license
;;; terms.  Most of this code is copyright Gilbert Baumann
;;; <unk6@rz.uni-karlsruhe.de>.  The bugs are copyright Walter
;;; C. Pelissero <walter@pelissero.de>.
;;;

;;; This library is free software; you can redistribute it and/or
;;; modify it under the terms of the GNU Library General Public
;;; License as published by the Free Software Foundation; either
;;; version 2 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
;;; Library General Public License for more details.
;;;
;;; You should have received a copy of the GNU Library General Public
;;; License along with this library; if not, write to the 
;;; Free Software Foundation, Inc., 59 Temple Place - Suite 330, 
;;; Boston, MA  02111-1307  USA.

(in-package :sclf)

(defun make-lock (&optional name)
  (mp:make-lock name))

(defun make-recursive-lock (&optional name)
  (mp:make-lock name :kind :recursive))

(defmacro with-lock-held ((lock &key whostate (wait t) timeout) &body forms)
  `(mp:with-lock-held (,lock ,(or whostate "Lock Wait")
                             :wait wait
                             ,@(when timeout (list :timeout timeout)))
     ,@forms))

(defmacro with-recursive-lock-held ((lock &key wait timeout) &body forms)
  `(mp:with-lock-held (,lock
                       ,@(when wait (list :wait wait))
                       ,@(when timeout (list :timeout timeout)))
     ,@forms))

(defstruct condition-variable
  (lock (make-lock "condition variable"))
  (value nil)
  (process-queue nil))

(defun %release-lock (lock) ; copied from with-lock-held in multiproc.lisp
  #+i486 (kernel:%instance-set-conditional
          lock 2 mp:*current-process* nil)
  #-i486 (when (eq (lock-process lock) mp:*current-process*)
           (setf (lock-process lock) nil)))

(defun condition-wait (cv lock &optional timeout)
  (declare (ignore timeout))		;For now
  (loop
     (let ((cv-lock (condition-variable-lock cv)))
       (with-lock-held (cv-lock)
         (when (condition-variable-value cv)
           (setf (condition-variable-value cv) nil)
           (return-from condition-wait t))
         (setf (condition-variable-process-queue cv)
               (nconc (condition-variable-process-queue cv)
                      (list mp:*current-process*)))
         (%release-lock lock))
       (mp:process-add-arrest-reason mp:*current-process* cv)
       (let ((cv-val nil))
         (with-lock-held (cv-lock)
           (setq cv-val (condition-variable-value cv))
           (when cv-val
             (setf (condition-variable-value cv) nil)))
         (when cv-val
           (mp::lock-wait lock "waiting for condition variable lock")
           (return-from condition-wait t))))))

(defun condition-notify (cv)
  (with-lock-held ((condition-variable-lock cv))
    (let ((proc (pop (condition-variable-process-queue cv))))
      ;; The waiting process may have released the CV lock but not
      ;; suspended itself yet
      (when proc
        (loop
         for activep = (mp:process-active-p proc)
         while activep
         do (mp:process-yield))
        (setf (condition-variable-value cv) t)
        (mp:process-revoke-arrest-reason proc cv))))
  ;; Give the other process a chance
  (mp:process-yield))

(defun process-execute (process function)
  (mp:process-preset process function)
  ;; For some obscure reason process-preset doesn't make the process
  ;; runnable.  I'm sure it's me who didn't understand how
  ;; multiprocessing works under CMUCL, despite the vast documentation
  ;; available.
  (mp:enable-process process)
  (mp:process-add-run-reason process :enable))

(defun destroy-process (process)
  ;; silnetly ignore a process that is trying to destroy itself
  (unless (eq (mp:current-process)
              process)
    (mp:destroy-process process)))

(defun restart-process (process)
  (mp:restart-process process)
  (mp:enable-process process)
  (mp:process-add-run-reason process :enable))

(defun process-alive-p (process)
  (mp:process-alive-p process))

(defun process-join (process)
  (error "PROCESS-JOIN not support under CMUCL."))