linux-kernel - Re: 2.6.19: slight performance optimization for lib/string.c's strstrip()

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Date:	Sun, 10 Dec 2006 16:02:54 -0800 (PST)
From:	Amit Choudhary <amit2030@...oo.com>
To:	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: 2.6.19: slight performance optimization for lib/string.c's strstrip()

> Suggested replacement:
> 
> char *strstrip(char *s)
> {
> size_t size;
> char *end;
> 
> while (*s && isspace(*s))
> s++;
> if (!*s)
> return s;
> size = strlen(s);
> 
> end = s + size - 1;
> while (end > s && isspace(*end))
> end--;
> *(end + 1) = '\0';
> 
> return s;
> }
> EXPORT_SYMBOL(strstrip);

How about this:

char *strstrip(char *s)
{
        size_t less = 0;
        char c = 0;
        char *e = NULL;

        while ((c=*s) && isspace(c))
                s++;
        if (!c)
                return s;

        e = s;

        while (c=*e) {
                 less = isspace(c) ? (less + 1) : 0;
                 e++;
        }

        *(e-less) = 0;

        return s;
}

1. no need to scan trailing spaces twice (once in strlen and then again).
2. pointer dereference only once per loop rather than multiple times.

Regards,
Amit

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