linux-kernel - Re: [PATCH 4/5] logger: clarify code in clock

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Message-ID: <CAPz4a6DpEUN_0wHdLdDT3fxmFr3j38sMn379+0hMFTdWRFDcFw@mail.gmail.com>
Date:	Wed, 8 Feb 2012 22:09:52 -0800
From:	Dima Zavin <dima@...roid.com>
To:	Tim Bird <tim.bird@...sony.com>
Cc:	Greg KH <gregkh@...uxfoundation.org>,
	linux-embedded <linux-embedded@...r.kernel.org>,
	linux kernel <linux-kernel@...r.kernel.org>,
	Brian Swetland <swetland@...gle.com>,
	Andrew Morton <akpm@...l.org>
Subject: Re: [PATCH 4/5] logger: clarify code in clock_interval

To be honest, i don't find the new logic code much different or
cleaner than the old code. I think just documenting (as well as the
function rename) as you've done without inverting the logic would be
sufficient. The ascii art helps immensely.

--Dima

On Tue, Feb 7, 2012 at 6:32 PM, Tim Bird <tim.bird@...sony.com> wrote:
> Add commentary, rename the function and make the code easier to read.
>
> Signed-off-by: Tim Bird <tim.bird@...sony.com>
> ---
>  drivers/staging/android/logger.c |   28 ++++++++++++++++++++--------
>  1 files changed, 20 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/staging/android/logger.c b/drivers/staging/android/logger.c
> index 54b7cdf..8d9d4f1 100644
> --- a/drivers/staging/android/logger.c
> +++ b/drivers/staging/android/logger.c
> @@ -242,16 +242,28 @@ static size_t get_next_entry(struct logger_log *log, size_t off, size_t len)
>  }
>
>  /*
> - * clock_interval - is a < c < b in mod-space? Put another way, does the line
> - * from a to b cross c?
> + * is_between - is a < c < b, accounting for wrapping of a, b, and c
> + *    positions in the buffer
> + *
> + * That is, if a<b, check for c between a and b
> + * and if a>b, check for c outside (not between) a and b
> + *
> + * |------- a xxxxxxxx b --------|
> + *               c^
> + *
> + * |xxxxx b --------- a xxxxxxxxx|
> + *    c^
> + *  or                    c^
>  */
> -static inline int clock_interval(size_t a, size_t b, size_t c)
> +static inline int is_between(size_t a, size_t b, size_t c)
>  {
> -       if (b < a) {
> -               if (a < c || b >= c)
> +       if (a < b) {
> +               /* is c between a and b? */
> +               if (a < c && c <= b)
>                        return 1;
>        } else {
> -               if (a < c && b >= c)
> +               /* is c outside of b through a? */
> +               if (c <= b || a < c)
>                        return 1;
>        }
>
> @@ -272,11 +284,11 @@ static void fix_up_readers(struct logger_log *log, size_t len)
>        size_t new = logger_offset(log, old + len);
>        struct logger_reader *reader;
>
> -       if (clock_interval(old, new, log->head))
> +       if (is_between(old, new, log->head))
>                log->head = get_next_entry(log, log->head, len);
>
>        list_for_each_entry(reader, &log->readers, list)
> -               if (clock_interval(old, new, reader->r_off))
> +               if (is_between(old, new, reader->r_off))
>                        reader->r_off = get_next_entry(log, reader->r_off, len);
>  }
>
> --
> 1.7.2.3
>
--
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