From: Junio C Hamano <gitster@pobox.com>
Date: Fri, 19 Jul 2013 19:59:43 GMT
Subject: Re: [PATCH v6 2/4] config: improve support for http.<url>.* settings
Message-ID: <7vehauuxqo.fsf@alter.siamese.dyndns.org>
In-Reply-To: <2cca0770a1e8495ac1418834c57f23d@f74d39fa044aa309eaea14b9f57fe79>

"Kyle J. McKay" <mackyle@gmail.com> writes:

> +#define URL_ALPHA "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
> +#define URL_DIGIT "0123456789"
> +#define URL_HEXDIGIT URL_DIGIT "ABCDEFabcdef"
> +#define URL_ALPHADIGIT URL_ALPHA URL_DIGIT
> +#define URL_SCHEME_CHARS URL_ALPHADIGIT "+.-"
> +#define URL_HOST_CHARS URL_ALPHADIGIT ".-[:]" /* IPv6 literals need [:] */
> +#define URL_UNSAFE_CHARS " <>\"%{}|\\^`" /* plus 0x00-0x1F,0x7F-0xFF */
> +#define URL_GEN_RESERVED ":/?#[]@"
> +#define URL_SUB_RESERVED "!$&'()*+,;="
> +#define URL_RESERVED URL_GEN_RESERVED URL_SUB_RESERVED /* only allowed delims */
> + ...
> +	while (from_len) {
> +		int ch = *from++;
> +		int was_esc = 0;
> +
> +		from_len--;
> +		if (ch == '%') {
> +			if (from_len < 2 ||
> +			    !strchr(URL_HEXDIGIT, from[0]) ||
> +			    !strchr(URL_HEXDIGIT, from[1]))

I actually do like the readability of the approach in this patch,
but these repeated strchrs() in a loop may want to be optimized,
using a trick similar to what is used in ctype.c::sane_ctype[].

A small build-time-only program or script gen-http-ctype.perl that
defines and uses these URL_* cpp macros and generates a C source
file http-ctype-gen.c that can be #included from http.c, with
something like this in the Makefile:

	http-ctype-gen.c: gen-http-ctype.perl
		rm -f $@ $@+
                $(PERL_PATH) gen-http-ctype.perl >$@+
                mv $@+ $@
	http.o: http.c http-ctype-gen.c

would give us both readability and efficiency, perhaps?