Negative length limit?

Discussion:

Cejka Rudolf

2015-04-10 17:00:03 UTC

Hello,
would it be possible to allow negative length limit in format
specification? For example, #{=10:pane_title} include first 10
characters, while #{=-10:pane_title} would include last 10 characters?

Maybe something like this? (tmux-1.9a)

--- format.c.orig 2015-04-10 17:42:31.000000000 +0200
+++ format.c 2015-04-10 18:34:26.000000000 +0200
@@ -197,7 +197,7 @@
char *copy, *copy0, *endptr, *ptr, *saved;
const char *value;
size_t valuelen;
- u_long limit = ULONG_MAX;
+ long limit = LONG_MAX;

/* Make a copy of the key. */
copy0 = copy = xmalloc(keylen + 1);
@@ -210,8 +210,8 @@
switch (*copy) {
case '=':
errno = 0;
- limit = strtoul(copy + 1, &endptr, 10);
- if (errno == ERANGE && limit == ULONG_MAX)
+ limit = strtol(copy + 1, &endptr, 10);
+ if (errno == ERANGE && (limit == LONG_MAX || limit == LONG_MIN))
goto fail;
copy = endptr;
break;
@@ -259,7 +259,11 @@
valuelen = strlen(value);

/* Truncate the value if needed. */
- if (valuelen > limit)
+ if (limit < 0 && valuelen > -limit) {
+ value += valuelen + limit;
+ valuelen = -limit;
+ }
+ if (limit >= 0 && valuelen > limit)
valuelen = limit;

/* Expand the buffer and copy in the value. */

--
Rudolf Cejka <cejkar at fit.vutbr.cz> http://www.fit.vutbr.cz/~cejkar
Brno University of Technology, Faculty of Information Technology
Bozetechova 2, 612 66 Brno, Czech Republic

Nicholas Marriott

2015-04-14 11:24:08 UTC

Permalink

Don't see a problem with this, can you add a line to the manpage too?

Post by Cejka Rudolf
Hello,
would it be possible to allow negative length limit in format
specification? For example, #{=10:pane_title} include first 10
characters, while #{=-10:pane_title} would include last 10 characters?
Maybe something like this? (tmux-1.9a)
--- format.c.orig 2015-04-10 17:42:31.000000000 +0200
+++ format.c 2015-04-10 18:34:26.000000000 +0200
@@ -197,7 +197,7 @@
char *copy, *copy0, *endptr, *ptr, *saved;
const char *value;
size_t valuelen;
- u_long limit = ULONG_MAX;
+ long limit = LONG_MAX;
/* Make a copy of the key. */
copy0 = copy = xmalloc(keylen + 1);
@@ -210,8 +210,8 @@
switch (*copy) {
errno = 0;
- limit = strtoul(copy + 1, &endptr, 10);
- if (errno == ERANGE && limit == ULONG_MAX)
+ limit = strtol(copy + 1, &endptr, 10);
+ if (errno == ERANGE && (limit == LONG_MAX || limit == LONG_MIN))
goto fail;
copy = endptr;
break;
@@ -259,7 +259,11 @@
valuelen = strlen(value);
/* Truncate the value if needed. */
- if (valuelen > limit)
+ if (limit < 0 && valuelen > -limit) {
+ value += valuelen + limit;
+ valuelen = -limit;
+ }
+ if (limit >= 0 && valuelen > limit)
valuelen = limit;
/* Expand the buffer and copy in the value. */
--
Rudolf Cejka <cejkar at fit.vutbr.cz> http://www.fit.vutbr.cz/~cejkar
Brno University of Technology, Faculty of Information Technology
Bozetechova 2, 612 66 Brno, Czech Republic
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Nicholas Marriott

2015-04-15 16:01:30 UTC

Permalink

Actually I spoke too soon, should have tried to apply the diff
first. Sorry.

Your diff doesn't apply because it is against an older version and we
changed it so that the length limits work with UTF-8. You'll need to
take a look at the code in Git and probably add a function to do this in
a safe way with UTF-8 (like utf8_trimcstr does for start of string).

The short form #24T is no longer supported.

Post by Nicholas Marriott
Don't see a problem with this, can you add a line to the manpage too?

--- tmux.1.orig 2015-04-15 17:19:32.000000000 +0200
+++ tmux.1 2015-04-15 17:24:56.000000000 +0200
@@ -3080,7 +3080,8 @@
A limit may be placed on the length of the resultant string by prefixing it
by an
.Ql = ,
-a number and a colon, so
+a number and a colon, where positive number means left part of the string
+and negative number right part. For example,
.Ql #{=10:pane_title}
will include at most the first 10 characters of the pane title.
.Pp
However, I have found a problem in manpage and sources: On another place
in manpage, there is in status-left section: "Where appropriate, special
character sequences may be prefixed with a number to specify the maximum
length, for example `#24T'.". But I think that this short form is broken.
In status.c in status_replace(), there is a loop with status_replace1(),
which does something that I could not understand: "#24T" is replaced to
"#T" and "#1T" to "#"? Why? And only then format_expand() is called, so
string length limit in short form seems to be effectively removed?

Post by Nicholas Marriott

--
Rudolf Cejka <cejkar at fit.vutbr.cz> http://www.fit.vutbr.cz/~cejkar
Brno University of Technology, Faculty of Information Technology
Bozetechova 2, 612 66 Brno, Czech Republic