;;; tq.el --- utility to maintain a transaction queue
+;; Copyright (C) 1985, 1986, 1987, 1992, 2002, 2003, 2004,
+;; 2005, 2006 Free Software Foundation, Inc.
+
;; Author: Scott Draves <spot@cs.cmu.edu>
+;; Maintainer: FSF
;; Adapted-By: ESR
;; Keywords: extensions
-;; Commentary:
-
-;;; manages receiving a stream asynchronously,
-;;; parsing it into transactions, and then calling
-;;; handler functions
+;; This file is part of GNU Emacs.
+
+;; GNU Emacs 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 2, or (at your option)
+;; any later version.
+
+;; GNU Emacs 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 GNU Emacs; see the file COPYING. If not, write to the
+;; Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+;; Boston, MA 02110-1301, USA.
+
+;;; Commentary:
+
+;; This file manages receiving a stream asynchronously, parsing it
+;; into transactions, and then calling the associated handler function
+;; upon the completion of each transaction.
-;;; Our basic structure is the queue/process/buffer triple. Each entry
-;;; of the queue is a regexp/closure/function triple. We buffer
-;;; bytes from the process until we see the regexp at the head of the
-;;; queue. Then we call the function with the closure and the
-;;; collected bytes.
+;; Our basic structure is the queue/process/buffer triple. Each entry
+;; of the queue part is a list of question, regexp, closure, and
+;; function that is consed to the last element.
+
+;; A transaction queue may be created by calling `tq-create'.
+
+;; A request may be added to the queue by calling `tq-enqueue'. If
+;; the `delay-question' argument is non-nil, we will wait to send the
+;; question to the process until it has finished sending other input.
+;; Otherwise, once a request is enqueued, we send the given question
+;; immediately to the process.
+
+;; We then buffer bytes from the process until we see the regexp that
+;; was provided in the call to `tq-enqueue'. Then we call the
+;; provided function with the closure and the collected bytes. If we
+;; have indicated that the question from the next transaction was not
+;; sent immediately, send it at this point, awaiting the response.
;;; Code:
-(provide 'tq)
+;;; Accessors
+
+;; This part looks like (queue . (process . buffer))
+(defun tq-queue (tq) (car tq))
+(defun tq-process (tq) (car (cdr tq)))
+(defun tq-buffer (tq) (cdr (cdr tq)))
+;; The structure of `queue' is as follows
+;; ((question regexp closure . fn)
+;; <other queue entries>)
+;; question: string to send to the process
+(defun tq-queue-head-question (tq) (car (car (tq-queue tq))))
+;; regexp: regular expression that matches the end of a response from
+;; the process
+(defun tq-queue-head-regexp (tq) (car (cdr (car (tq-queue tq)))))
+;; closure: additional data to pass to function
+(defun tq-queue-head-closure (tq) (car (cdr (cdr (car (tq-queue tq))))))
+;; fn: function to call upon receiving a complete response from the
+;; process
+(defun tq-queue-head-fn (tq) (cdr (cdr (cdr (car (tq-queue tq))))))
+
+;; Determine whether queue is empty
+(defun tq-queue-empty (tq) (not (tq-queue tq)))
+
+;;; Core functionality
+
+;;;###autoload
(defun tq-create (process)
- "Create and return a transaction queue. PROCESS should be capable
-of sending and receiving streams of bytes. It may be a local process,
-or it may be connected to a tcp server on another machine."
+ "Create and return a transaction queue communicating with PROCESS.
+PROCESS should be a subprocess capable of sending and receiving
+streams of bytes. It may be a local process, or it may be connected
+to a tcp server on another machine."
(let ((tq (cons nil (cons process
(generate-new-buffer
(concat " tq-temp-"
(process-name process)))))))
(set-process-filter process
- (`(lambda (proc string)
- (tq-filter '(, tq) string))))
+ `(lambda (proc string)
+ (tq-filter ',tq string)))
tq))
-;;; accessors
-(defun tq-queue (tq) (car tq))
-(defun tq-process (tq) (car (cdr tq)))
-(defun tq-buffer (tq) (cdr (cdr tq)))
-
-(defun tq-queue-add (tq re closure fn)
+(defun tq-queue-add (tq question re closure fn)
(setcar tq (nconc (tq-queue tq)
- (cons (cons re (cons closure fn)) nil)))
+ (cons (cons question (cons re (cons closure fn))) nil)))
'ok)
-(defun tq-queue-head-regexp (tq) (car (car (tq-queue tq))))
-(defun tq-queue-head-fn (tq) (cdr (cdr (car (tq-queue tq)))))
-(defun tq-queue-head-closure (tq) (car (cdr (car (tq-queue tq)))))
-(defun tq-queue-empty (tq) (not (tq-queue tq)))
-(defun tq-queue-pop (tq) (setcar tq (cdr (car tq))) (null (car tq)))
-
-
-;;; must add to queue before sending!
-(defun tq-enqueue (tq question regexp closure fn)
- "Add a transaction to TQ. Send question to the process, and call FN
-with CLOSURE and and the answer, when it appears. The end of the
-answer is identified by REGEXP."
- (tq-queue-add tq regexp closure fn)
- (process-send-string (tq-process tq) question))
+(defun tq-queue-pop (tq)
+ (setcar tq (cdr (car tq)))
+ (let ((question (tq-queue-head-question tq)))
+ (when question
+ (process-send-string (tq-process tq) question)))
+ (null (car tq)))
+
+(defun tq-enqueue (tq question regexp closure fn &optional delay-question)
+ "Add a transaction to transaction queue TQ.
+This sends the string QUESTION to the process that TQ communicates with.
+
+When the corresponding answer comes back, we call FN with two
+arguments: CLOSURE, which may contain additional data that FN
+needs, and the answer to the question.
+
+REGEXP is a regular expression to match the entire answer;
+that's how we tell where the answer ends.
+
+If DELAY-QUESTION is non-nil, delay sending this question until
+the process has finished replying to any previous questions.
+This produces more reliable results with some processes."
+ (let ((sendp (or (not delay-question)
+ (not (tq-queue-head-question tq)))))
+ (tq-queue-add tq (unless sendp question) regexp closure fn)
+ (when sendp
+ (process-send-string (tq-process tq) question))))
(defun tq-close (tq)
- "Shut down the process, and destroy the evidence."
+ "Shut down transaction queue TQ, terminating the process."
(delete-process (tq-process tq))
(kill-buffer (tq-buffer tq)))
(defun tq-filter (tq string)
"Append STRING to the TQ's buffer; then process the new data."
- (set-buffer (tq-buffer tq))
- (goto-char (point-max))
- (insert string)
- (tq-process-buffer tq))
+ (with-current-buffer (tq-buffer tq)
+ (goto-char (point-max))
+ (insert string)
+ (tq-process-buffer tq)))
(defun tq-process-buffer (tq)
"Check TQ's buffer for the regexp at the head of the queue."
(copy-to-buffer buf (point-min) (point-max))
(delete-region (point-min) (point))
(pop-to-buffer buf nil)
- (error (concat "Spurious communication from process "
- (process-name (tq-process tq))
- ", see buffer *spurious*.")))
+ (error "Spurious communication from process %s, see buffer %s"
+ (process-name (tq-process tq))
+ (buffer-name buf)))
(goto-char (point-min))
(if (re-search-forward (tq-queue-head-regexp tq) nil t)
(let ((answer (buffer-substring (point-min) (point))))
(delete-region (point-min) (point))
- (funcall (tq-queue-head-fn tq)
- (tq-queue-head-closure tq)
- answer)
- (tq-queue-pop tq)
+ (unwind-protect
+ (condition-case nil
+ (funcall (tq-queue-head-fn tq)
+ (tq-queue-head-closure tq)
+ answer)
+ (error nil))
+ (tq-queue-pop tq))
(tq-process-buffer tq))))))
+(provide 'tq)
+
+;;; arch-tag: 65dea08c-4edd-4cde-83a5-e8a15b993b79
;;; tq.el ends here