Subject: Re: [PATCH 01/12] Make starts_with() a wrapper of skip_prefix()

From: Junio C Hamano <[email-masked]>
Date: Wed, 18 Dec 2013 09:50:07 -0800

Nguyễn Thái Ngọc Duy  <[email-masked]> writes:

> starts_with() started out as a copy of prefixcmp(). But if we don't
> care about the sorting order, the logic looks closer to
> skip_prefix(). This looks like a good thing to do.
>
> Signed-off-by: Nguyễn Thái Ngọc Duy <[email-masked]>
> ---

Sure, but the implementation of skip_prefix() scans the prefix
string twice, while prefixcmp() aka starts_with() does it only once.

I'd expect a later step in this series would rectify this micro
regression in the performance, though ;-)

>  git-compat-util.h | 6 +++++-
>  strbuf.c          | 9 ---------
>  2 files changed, 5 insertions(+), 10 deletions(-)
>
> diff --git a/git-compat-util.h b/git-compat-util.h
> index b73916b..84f1078 100644
> --- a/git-compat-util.h
> +++ b/git-compat-util.h
> @@ -350,7 +350,6 @@ extern void set_die_routine(NORETURN_PTR void (*routine)(const char *err, va_lis
>  extern void set_error_routine(void (*routine)(const char *err, va_list params));
>  extern void set_die_is_recursing_routine(int (*routine)(void));
>  
> -extern int starts_with(const char *str, const char *prefix);
>  extern int prefixcmp(const char *str, const char *prefix);
>  extern int ends_with(const char *str, const char *suffix);
>  extern int suffixcmp(const char *str, const char *suffix);
> @@ -361,6 +360,11 @@ static inline const char *skip_prefix(const char *str, const char *prefix)
>  	return strncmp(str, prefix, len) ? NULL : str + len;
>  }
>  
> +static inline int starts_with(const char *str, const char *prefix)
> +{
> +	return skip_prefix(str, prefix) != NULL;
> +}
> +
>  #if defined(NO_MMAP) || defined(USE_WIN32_MMAP)
>  
>  #ifndef PROT_READ
> diff --git a/strbuf.c b/strbuf.c
> index 83caf4a..bd4c0d8 100644
> --- a/strbuf.c
> +++ b/strbuf.c
> @@ -1,15 +1,6 @@
>  #include "cache.h"
>  #include "refs.h"
>  
> -int starts_with(const char *str, const char *prefix)
> -{
> -	for (; ; str++, prefix++)
> -		if (!*prefix)
> -			return 1;
> -		else if (*str != *prefix)
> -			return 0;
> -}
> -
>  int prefixcmp(const char *str, const char *prefix)
>  {
>  	for (; ; str++, prefix++)