Path: csiph.com!v102.xanadu-bbs.net!xanadu-bbs.net!news.albasani.net!news.stack.nl!newsfeed.xs4all.nl!newsfeed2a.news.xs4all.nl!xs4all!newsgate.cistron.nl!newsgate.news.xs4all.nl!post.news.xs4all.nl!not-for-mail
To: python-list@python.org
From: Lele Gaifax <lele@metapensiero.it>
Subject: Adapt bash readline operate-and-get-next
Date: Mon, 18 Aug 2014 20:49:13 +0200
Organization: Nautilus Entertainments
References: <232acf45-096d-466a-aa75-06d8c378b128@googlegroups.com> <53cc376e$0$2898$e4fe514c@news.xs4all.nl> <53926733-5e65-482f-96bc-0171c6a93d59@googlegroups.com> <mailman.12102.1405904534.18130.python-list@python.org> <4882fd4d-b772-4ebb-8aaa-0c20be6051b6@googlegroups.com> <mailman.12108.1405910327.18130.python-list@python.org> <lqj806$52h$1@reader1.panix.com> <CAPTjJmr8q-nQvgiwY7eWp8zMMZDi-OdvmrOKs-xCs=M4O2jR5Q@mail.gmail.com> <mailman.12130.1405958264.18130.python-list@python.org> <53cd47fc$0$6574$c3e8da3$5496439d@news.astraweb.com>
Mime-Version: 1.0
Content-Type: multipart/mixed; boundary="=-=-="
User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.3.93 (gnu/linux)
Cancel-Lock: sha1:zsON0z132Ldro4k/gFdBvreMcPI=
Precedence: list
Newsgroups: comp.lang.python
Message-ID: <mailman.13110.1408387774.18130.python-list@python.org>
Lines: 136
NNTP-Posting-Host: 2001:888:2000:d::a6
Xref: csiph.com comp.lang.python:76502

--=-=-=
Content-Type: text/plain

Steven D'Aprano <steve+comp.lang.python@pearwood.info> writes:

> On Mon, 21 Jul 2014 17:57:22 +0200, Lele Gaifax wrote:
>> Granted, the readline library exposes a "operate-and-get-next" function,
>> by default bound to \C-o...
>
> Have you actually got that working in Python with the readline module? 
> I've tried and tried and cannot get it to work. Any hints gratefully 
> appreciated.

This is just a first attempt to adapt the Bash code to the Python
readline.c module: I'm very surprised that the half-an-hour I spent on
it, mostly to locate related code, actually full filled the goal :-)

The patch isn't complete, in particular, it does not work on Apple's
libedit, because I have no way to try it on that system. Also, I'm not
fluent with Mercurial, so this is just a "hg diff".

Even if I know this is not the right forum and I should (and I
eventually do, assuming a positive feedback) instead open a ticket and
attach the patch there, I'd like to hear opinions on whether this should
be enabled by default, and possibly get in touch with some Apple
owner...

ciao, lele.

--=-=-=
Content-Type: text/x-diff
Content-Disposition: attachment; filename=readline.patch

diff -r e5f78085499e Modules/readline.c
--- a/Modules/readline.c	Mon Aug 18 17:48:15 2014 +0300
+++ b/Modules/readline.c	Mon Aug 18 20:46:43 2014 +0200
@@ -73,6 +73,13 @@
                                    int num_matches, int max_length);
 #endif
 
+#if !defined(__APPLE__)
+static rl_hook_func_t *old_rl_startup_hook = (rl_hook_func_t *)NULL;
+static int hist_last_line_added;
+static int set_saved_history(void);
+static int operate_and_get_next(int count, int c);
+#endif
+
 /* Memory allocated for rl_completer_word_break_characters
    (see issue #17289 for the motivation). */
 static char *completer_word_break_characters;
@@ -1032,6 +1039,10 @@
            With libedit, this call makes readline() crash. */
         rl_variable_bind ("enable-meta-key", "off");
     }
+    
+    /* XXX: determine whether the following works on libedit */
+    rl_add_defun("operate-and-get-next", operate_and_get_next, -1);
+    rl_bind_key_if_unbound_in_map(CTRL('O'), operate_and_get_next, emacs_standard_keymap);
 #endif
 
     /* Initialize (allows .inputrc to override)
@@ -1287,3 +1298,61 @@
     setup_readline(mod_state);
     return m;
 }
+
+#ifndef __APPLE__
+
+/* XXX: determine whether the following works on libedit */
+
+/* Following code taken from bash' bashline.c */
+
+/* The equivalent of the Korn shell C-o operate-and-get-next-history-line
+   editing command. */
+static int saved_history_line_to_use = -1;
+static int last_saved_history_line = -1;
+
+#define HISTORY_FULL() (history_is_stifled() && history_length >= history_max_entries)
+
+static int
+set_saved_history()
+{
+    /* XXX - compensate for assumption that history was `shuffled' if it was
+       actually not. */
+    if (HISTORY_FULL() &&
+	hist_last_line_added == 0 &&
+	saved_history_line_to_use < history_length - 1)
+	saved_history_line_to_use++;
+
+    if (saved_history_line_to_use >= 0)	{
+	rl_get_previous_history(history_length - saved_history_line_to_use, 0);
+	last_saved_history_line = saved_history_line_to_use;
+    }
+    
+    saved_history_line_to_use = -1;
+    rl_startup_hook = old_rl_startup_hook;
+    
+    return 0;
+}
+
+static int
+operate_and_get_next (int count, int c)
+{
+    int where;
+
+    /* Accept the current line. */
+    rl_newline(1, c);
+    
+    /* Find the current line, and find the next line to use. */
+    where = where_history();
+    
+    if (HISTORY_FULL() || (where >= history_length - 1))
+	saved_history_line_to_use = where;
+    else
+	saved_history_line_to_use = where + 1;
+    
+    old_rl_startup_hook = rl_startup_hook;
+    rl_startup_hook = set_saved_history;
+    
+    return 0;
+}
+
+#endif

--=-=-=
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 8bit


-- 
nickname: Lele Gaifax | Quando vivrò di quello che ho pensato ieri
real: Emanuele Gaifas | comincerò ad aver paura di chi mi copia.
lele@metapensiero.it  |                 -- Fortunato Depero, 1929.

--=-=-=--