Re: [PATCH v2] macos: lazily initialize iconv

> In practice, the majority of paths do not have utf8 that needs
> the canonicalization. Lazily call iconv_open()/iconv_close() to
> avoid unnecessary overhead.
>
> Signed-off-by: Junio C Hamano <gitster@pobox.com>
> Helped-by: Ralf Thielow <ralf.thielow@gmail.com>
> Helped-by: Linus Torvalds <torvalds@linux-foundation.org>
> ---
>
>  * This is not even compile tested, so it needs testing and
>    benchmarking, as I do not even know how costly the calls to
>    open/close are when we do not have to call iconv() itself.
>
>    This reroll corrects an obvious thinko pointed out by Ralf, and
>    gets rid of an extra iconv_opened field added unnecessarily in
>    the previous round.
>
>    This was brought up by Linus in http://goo.gl/INWVc
>
>  compat/precompose_utf8.c | 19 ++++++++++++++-----
>  1 file changed, 14 insertions(+), 5 deletions(-)
>
> diff --git a/compat/precompose_utf8.c b/compat/precompose_utf8.c
> index d40d1b3..79b5528 100644
> --- a/compat/precompose_utf8.c
> +++ b/compat/precompose_utf8.c
> @@ -67,7 +67,7 @@ void probe_utf8_pathname_composition(char *path, int len)
>  
>  void precompose_argv(int argc, const char **argv)
>  {
> -	int i = 0;
> +	int i;
>  	const char *oldarg;
>  	char *newarg;
>  	iconv_t ic_precompose;
> @@ -75,11 +75,19 @@ void precompose_argv(int argc, const char **argv)
>  	if (precomposed_unicode != 1)
>  		return;
>  
> +	/* Avoid iconv_open()/iconv_close() if there is nothing to convert */
> +	for (i = 0; i < argc; i++) {
> +		if (has_utf8(argv[i], (size_t)-1, NULL))
> +			break;
> +	}
> +	if (argc <= i)
> +		return; /* no utf8 found */
> +
>  	ic_precompose = iconv_open(repo_encoding, path_encoding);
>  	if (ic_precompose == (iconv_t) -1)
>  		return;
>  
> -	while (i < argc) {
> +	for (i = 0; i < argc; i++) {
>  		size_t namelen;
>  		oldarg = argv[i];
>  		if (has_utf8(oldarg, (size_t)-1, &namelen)) {
> @@ -87,7 +95,6 @@ void precompose_argv(int argc, const char **argv)
>  			if (newarg)
>  				argv[i] = newarg;
>  		}
> -		i++;
>  	}
>  	iconv_close(ic_precompose);
>  }
> @@ -106,8 +113,7 @@ PREC_DIR *precompose_utf8_opendir(const char *dirname)
>  		return NULL;
>  	} else {
>  		int ret_errno = errno;
> -		prec_dir->ic_precompose = iconv_open(repo_encoding, path_encoding);
> -		/* if iconv_open() fails, die() in readdir() if needed */
> +		prec_dir->ic_precompose = (iconv_t)-1;
>  		errno = ret_errno;
>  	}
>  
> @@ -136,6 +142,9 @@ struct dirent_prec_psx *precompose_utf8_readdir(PREC_DIR *prec_dir)
>  		prec_dir->dirent_nfc->d_type = res->d_type;
>  
>  		if ((precomposed_unicode == 1) && has_utf8(res->d_name, (size_t)-1, NULL)) {
> +			if (prec_dir->ic_precompose == (iconv_t)-1)
> +				prec_dir->ic_precompose =
> +					iconv_open(repo_encoding, path_encoding);
>  			if (prec_dir->ic_precompose == (iconv_t)-1) {
>  				die("iconv_open(%s,%s) failed, but needed:\n"
>  						"    precomposed unicode is not supported.\n"