From: Gregory Heytings <gregory@heytings.org>
To: Lars Ingebrigtsen <larsi@gnus.org>
Cc: 51523@debbugs.gnu.org, Stefan Monnier <monnier@iro.umontreal.ca>
Subject: bug#51523: 29.0.50; gnus-mime-view-part-externally very slow
Date: Mon, 01 Nov 2021 00:55:47 +0000 [thread overview]
Message-ID: <6abcac838bc0f53a0f78@heytings.org> (raw)
In-Reply-To: <87sfwgvi73.fsf@gnus.org>
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>
> This reminds me of something I've wanted more than a handful of times --
> it'd be nice to have a function/macro like
>
> (when-file-has-changed "/etc/mailcap"
> (do-the-parsing))
>
See attached patch.
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From 827f6aa9fb616d9467dcccc011a5d3eb4dbac02d Mon Sep 17 00:00:00 2001
From: Gregory Heytings <gregory@heytings.org>
Date: Mon, 1 Nov 2021 00:53:05 +0000
Subject: [PATCH] Add a macro to execute body only when a file has changed.
* lisp/subr.el (when-file-has-changed): New macro.
(when-file-has-changed--hash-table): Internal variable used by the
new macro.
---
lisp/subr.el | 16 ++++++++++++++++
1 file changed, 16 insertions(+)
diff --git a/lisp/subr.el b/lisp/subr.el
index f6dbd00532..b29c56f8c6 100644
--- a/lisp/subr.el
+++ b/lisp/subr.el
@@ -3967,6 +3967,22 @@ function-get
nil ;Re-try `get' on the same `f'.
(setq f fundef))))
val))
+
+(defvar when-file-has-changed--hash-table (make-hash-table)
+ "Internal variable used by `when-file-has-changed'.")
+
+(defmacro when-file-has-changed (file body)
+ "Execute BODY only if file has changed.
+The modification time of the FILE is compared to the modification
+time of FILE during a previous invocation of
+`when-file-has-changed'. If they differ, BODY is executed."
+ `(let* ((attr (file-attributes ,file 'integer))
+ (mtime (file-attribute-modification-time attr))
+ (saved-mtime (gethash (intern ,file)
+ when-file-has-changed--hash-table)))
+ (when (not (equal mtime saved-mtime))
+ (puthash (intern ,file) mtime when-file-has-changed--hash-table)
+ ,body)))
\f
;;;; Support for yanking and text properties.
;; Why here in subr.el rather than in simple.el? --Stef
--
2.33.0
next prev parent reply other threads:[~2021-11-01 0:55 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-31 4:11 bug#51523: 29.0.50; gnus-mime-view-part-externally very slow Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2021-10-31 15:27 ` Lars Ingebrigtsen
2021-10-31 21:47 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2021-10-31 23:41 ` Gregory Heytings
2021-11-01 0:01 ` Lars Ingebrigtsen
2021-11-01 0:11 ` Gregory Heytings
2021-11-01 0:15 ` Lars Ingebrigtsen
2021-11-01 2:26 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2021-11-01 13:38 ` Lars Ingebrigtsen
2021-11-01 0:17 ` Gregory Heytings
2021-11-01 0:21 ` Lars Ingebrigtsen
2021-11-01 0:55 ` Gregory Heytings [this message]
2021-11-01 1:24 ` Gregory Heytings
2021-11-01 1:26 ` Gregory Heytings
[not found] ` <6abcac838bb94542451d@heytings.org>
2021-11-01 9:28 ` Gregory Heytings
[not found] ` <6abcac838bb83b0904d7@heytings.org>
[not found] ` <6abcac838bad7cded4c5@heytings.org>
2021-11-01 12:26 ` Gregory Heytings
2021-11-01 13:52 ` Lars Ingebrigtsen
2021-11-01 15:00 ` Eli Zaretskii
2021-11-01 15:20 ` Gregory Heytings
2021-11-01 15:23 ` Lars Ingebrigtsen
2021-11-01 16:46 ` Eli Zaretskii
2021-11-01 16:59 ` Lars Ingebrigtsen
2021-11-01 17:03 ` Eli Zaretskii
2021-11-01 17:15 ` Eli Zaretskii
2021-11-01 17:19 ` Lars Ingebrigtsen
2021-11-01 17:21 ` Eli Zaretskii
2021-11-01 17:23 ` Lars Ingebrigtsen
2021-11-01 17:28 ` Eli Zaretskii
2021-11-01 17:34 ` Lars Ingebrigtsen
2021-11-01 18:17 ` Eli Zaretskii
2021-11-01 21:14 ` Gregory Heytings
2021-11-02 14:50 ` Lars Ingebrigtsen
2021-11-02 15:12 ` Eli Zaretskii
2021-11-03 10:45 ` Gregory Heytings
2021-11-03 12:02 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2021-11-03 12:57 ` Gregory Heytings
2021-11-03 13:17 ` Eli Zaretskii
2021-11-03 13:27 ` Gregory Heytings
2021-11-03 13:53 ` Eli Zaretskii
2021-11-03 14:25 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2021-11-03 14:26 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2021-11-03 15:20 ` Gregory Heytings
2021-11-03 18:56 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2021-11-03 13:06 ` Eli Zaretskii
2021-11-01 0:04 ` Lars Ingebrigtsen
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