linux-kernel - Re: [PATCH 1/2] docs: lzo: fix first byte interpretation off-by-one

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Message-ID: <ED8A0242-10D3-4280-815F-BB38AB80251D@arm.com>
Date:   Fri, 22 May 2020 15:22:29 +0000
From:   Dave Rodgman <dave.rodgman@....com>
To:     "C. Masloch" <pushbx@...kai.org>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Jonathan Corbet <corbet@....net>, Willy Tarreau <w@....eu>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 1/2] docs: lzo: fix first byte interpretation off-by-one

Your update looks correct to me, thanks.

Dave

On 22/05/2020, 15:11, "C. Masloch" <pushbx@...kai.org> wrote:

    There was an error in the description of the initial byte's
    interpretation. While "18..21" was listed as  "copy 0..3 literals",
    it should actually be interpreted as "copy 1..4 literals".

    The "byte - 17" part is correct. 17 would encode copying "zero"
    literals, but does not occur. 18 encodes copying 1 literal,
    19 then 2 literals, 20 for 3 literals, 21 for 4 literals.
    The description should read "18..21" as "copy 1..4 literals".
    Likewise, 22 indicates "copying 5 literals", not "4 literals".
    However, the state is indeed always set to "byte - 17" (which
    for 21 results in 4 too).

    Signed-off-by: C. Masloch <pushbx@...kai.org>
    ---
     Documentation/lzo.txt | 6 +++---
     1 file changed, 3 insertions(+), 3 deletions(-)

    diff --git a/Documentation/lzo.txt b/Documentation/lzo.txt
    index ca9833289..f839d104d 100644
    --- a/Documentation/lzo.txt
    +++ b/Documentation/lzo.txt
    @@ -108,12 +108,12 @@ Byte sequences
                     (version 1 only).
                     Otherwise, the bitstream version is 0.

    -      18..21  : copy 0..3 literals
    -                state = (byte - 17) = 0..3  [ copy <state> literals ]
    +      18..21  : copy 1..4 literals
    +                state = (byte - 17) = 1..4  [ copy <state> literals ]
                     skip byte

           22..255 : copy literal string
    -                length = (byte - 17) = 4..238
    +                length = (byte - 17) = 5..238
                     state = 4 [ don't copy extra literals ]
                     skip byte

    --
    2.26.2


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