[PATCH] Optimise trim_string() front-trimming

[Ralph Boehme]

On Sun, Jun 19, 2016 at 08:20:03PM +1000, Martin Schwenke wrote:
> On Fri, 26 Jun 2015 16:13:51 -0700, Herb Lewis <hlewis at panasas.com>
> wrote:
> 
> > We really should fix trim_string as well. The front trimming calls
> > memmove for each character/string found instead of finding
> > the first non-match and then calling memmove once.
> 
> Like this?  Sometimes it is worth saving easy suggestions and
> attacking them when fighting a cold...  :-)

:) Get well soon!

> Attached patches:
> 
> 1. Add some tests for trim_string()

rb: me.

> 2. Optimise trim_string()'s front trimming to call memmove(3) just once

I think the len check can be removed in the while loop as it never
changes and maybe move the strlen() call right after the check that
ensures len will be > 0.

@@ -804,16 +804,15 @@ _PUBLIC_ bool trim_string(char *s, const char
*front, const char *back)
        /* Ignore null or empty strings. */
        if (!s || (s[0] == '\0'))
                return false;
+       len = strlen(s);
 
        front_len       = front? strlen(front) : 0;
        back_len        = back? strlen(back) : 0;
 
-       len = strlen(s);
-
        if (front_len) {
                size_t front_trim = 0;
 
-               while (len && strncmp(s+front_trim, front, front_len)==0) {
+               while (strncmp(s+front_trim, front, front_len)==0) {
                        front_trim += front_len;
                }
                if (front_trim > 0) {

If you agree, feel free to push with this change.

Cheerio!
-slow