linux-kernel - Re: [RFC/PATCH 1/8] lib: string: Introduce strreplace

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Date:	Thu, 04 Jun 2015 03:56:07 -0700
From:	Joe Perches <joe@...ches.com>
To:	Rasmus Villemoes <linux@...musvillemoes.dk>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC/PATCH 1/8] lib: string: Introduce strreplace

On Thu, 2015-06-04 at 11:37 +0200, Rasmus Villemoes wrote:
> Strings are sometimes sanitized by replacing a certain character
> (often '/') by another (often '!'). In a few places, this is done the
> same way Schlemiel the Painter would do it.

:)

> Others are slightly
> smarter but still do multiple strchr() calls. Introduce strreplace()
> to do this using a single function call and a single pass over the
> string.
> 
> One would expect the return value to be one of three things: void, s,
> or the number of replacements made. I chose the fourth, returning a
> pointer to the end of the string. This is more likely to be useful
> (for example allowing the caller to avoid a strlen call).

You used in one of the follow-on patches too.

> diff --git a/lib/string.c b/lib/string.c
[]
> @@ -849,3 +849,20 @@ void *memchr_inv(const void *start, int c, size_t bytes)
>  	return check_bytes8(start, value, bytes % 8);
>  }
>  EXPORT_SYMBOL(memchr_inv);
> +
> +/**
> + * strreplace - Replace all occurences of character in string

occurrences

> + * @s: The string to operate on
> + * @bad: The character being replaced
> + * @good: The character @bad is replaced with.
> + *
> + * Returns pointer to the nul byte at the end of @s.
> + */
> +char *strreplace(char *s, char bad, char good)
> +{
> +	for (; *s; ++s)
> +		if (*s == bad)
> +			*s = good;
> +	return s;
> +}
> +EXPORT_SYMBOL(strreplace);

Seems sensible, but the name maybe could be be more
explicit as strreplace seems like it should more like
a string substitution rather than a char substitution.

Maybe strsubstchr or something like it (strtranschr?)

Because it's so tiny, perhaps this could be inline
instead of EXPORT_SYMBOL.

Maybe from and to instead of good and bad arguments.


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