Re: [PATCH v3] skip_prefix: rewrite so that prefix is scanned once

From: Duy Nguyen <pclouds@gmail.com>
Date: Mar 3, 2014, 23:37 UTC
Message-ID: <CACsJy8ASBeravdk67pbOJbrFUbwg21JwYcLtSbDDMJOu9-F=yA@mail.gmail.com>
In-Reply-To: <xmqq61nuoqd5.fsf@gitster.dls.corp.google.com>

On Tue, Mar 4, 2014 at 5:43 AM, Junio C Hamano <gitster@pobox.com> wrote:

Show 10 quoted lines

> diff --git a/git-compat-util.h b/git-compat-util.h
> index cbd86c3..68ffaef 100644
> --- a/git-compat-util.h
> +++ b/git-compat-util.h
> @@ -357,8 +357,14 @@ extern int suffixcmp(const char *str, const char *suffix);
>
>  static inline const char *skip_prefix(const char *str, const char *prefix)
>  {
> -       size_t len = strlen(prefix);
> -       return strncmp(str, prefix, len) ? NULL : str + len;

Just a note. gcc does optimize strlen("abcdef") to 6, and with that information at compile time built-in strncmp might do better.

Show 11 quoted lines

> +       while (1) {
> +               if (!*prefix)
> +                       return str;
> +               if (*str != *prefix)
> +                       return NULL;
> +               prefix++;
> +               str++;
> +       }
>  }
>
>  #if defined(NO_MMAP) || defined(USE_WIN32_MMAP)

-- 
Duy