linux-kernel - Re: tools: usbip: detach: avoid calling strlen() at each iteration

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Message-ID: <20150915205555.GA13203@blackmetal.musicnaut.iki.fi>
Date:	Tue, 15 Sep 2015 23:55:55 +0300
From:	Aaro Koskinen <aaro.koskinen@....fi>
To:	Eric Curtin <ericcurtin17@...il.com>
Cc:	valentina.manea.m@...il.com, shuah.kh@...sung.com,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: tools: usbip: detach: avoid calling strlen() at each iteration

Hi,

On Tue, Sep 15, 2015 at 09:27:20PM +0100, Eric Curtin wrote:
> Instead of calling strlen on every iteration of the for loop, just call it
> once and cache the result in a temporary local variable which will be used
> in the for loop instead.
> 
> Signed-off-by: Eric Curtin <ericcurtin17@...il.com>
> 
> diff --git a/tools/usb/usbip/src/usbip_detach.c b/tools/usb/usbip/src/usbip_detach.c
> index 05c6d15..9db9d21 100644
> --- a/tools/usb/usbip/src/usbip_detach.c
> +++ b/tools/usb/usbip/src/usbip_detach.c
> @@ -47,7 +47,9 @@ static int detach_port(char *port)
>  	uint8_t portnum;
>  	char path[PATH_MAX+1];
>  

The above blank line should be deleted if you declare a new local
variable below...

> -	for (unsigned int i = 0; i < strlen(port); i++)
> +	unsigned int port_len = strlen(port);
> +
> +	for (unsigned int i = 0; i < port_len; i++)

port is read only in this function, so maybe just use "const" and the
compiler should know to do the same without adding a new variable?

A.
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