Aren
/
NetBSD
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

The libedit implementation of history_get() also differs from the GNU 

implementation:  libedit goes to the entry with the given number
stored in the HistEvent structure, while GNU subtracts history_base,
then advances that many entries from the oldest one.  If entries were
removed in between, GNU advances further than libedit.

The call sequence H_CURR, H_DELDATA, H_CURR, H_NEXT_EVDATA looks
weird, as if part of that must somehow be redundant.  But actually,
the user interface is so counter-intuitive that every single step
is really required.

 - The first H_CURR is needed to be able to go back after an error.
 - The H_DELDATA is needed to move the cursor.  Even though it takes
   a pointer to ev, that structure is not filled in when the call
   succeeds.  H_DELDATA only moves the cursor, it doesn't tell us
   the new event number.
 - Consequently, the second H_CURR is required to get ev.num filled
   in.  But it doesn't return the data because ev has no field for
   that.
 - So even though the cursor is already positioned correctly,
   H_NEXT_EVDATA is needed as the final step merely to get the data.

(Ingo Schwarze)
This commit is contained in:
christos 2016-05-09 21:25:11 +00:00
parent 8a99e51de9
commit 05b61ce72a
1 changed files with 21 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

30
lib/libedit/readline.c
View File

@ -1,4 +1,4 @@
/* $NetBSD: readline.c,v 1.130 2016/05/08 20:15:00 christos Exp $ */
/* $NetBSD: readline.c,v 1.131 2016/05/09 21:25:11 christos Exp $ */
/*-
* Copyright (c) 1997 The NetBSD Foundation, Inc.
@ -31,7 +31,7 @@
#include "config.h"
#if !defined(lint) && !defined(SCCSID)
__RCSID("$NetBSD: readline.c,v 1.130 2016/05/08 20:15:00 christos Exp $");
__RCSID("$NetBSD: readline.c,v 1.131 2016/05/09 21:25:11 christos Exp $");
#endif /* not lint && not SCCSID */
#include <sys/types.h>
@ -1400,25 +1400,37 @@ history_get(int num)
if (h == NULL || e == NULL)
rl_initialize();
if (num < history_base)
return NULL;
/* save current position */
if (history(h, &ev, H_CURR) != 0)
return NULL;
curr_num = ev.num;
/* start from the oldest */
if (history(h, &ev, H_LAST) != 0)
return NULL; /* error */
/* look forwards for event matching specified offset */
if (history(h, &ev, H_NEXT_EVDATA, num, &she.data))
return NULL;
/*
* use H_DELDATA to set to nth history (without delete) by passing
* (void **)-1 -- as in history_set_pos
*/
if (history(h, &ev, H_DELDATA, num - history_base, (void **)-1) != 0)
goto out;
/* get current entry */
if (history(h, &ev, H_CURR) != 0)
goto out;
if (history(h, &ev, H_NEXT_EVDATA, ev.num, &she.data) != 0)
goto out;
she.line = ev.str;
/* restore pointer to where it was */
(void)history(h, &ev, H_SET, curr_num);
return &she;
out:
/* restore pointer to where it was */
(void)history(h, &ev, H_SET, curr_num);
return NULL;
}