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

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Message-Id: <20200522141040.1353769-1-pushbx@ulukai.org>
Date:   Fri, 22 May 2020 16:10:39 +0200
From:   "C. Masloch" <pushbx@...kai.org>
To:     linux-doc@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, Jonathan Corbet <corbet@....net>,
        Dave Rodgman <dave.rodgman@....com>, Willy Tarreau <w@....eu>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH 1/2] docs: lzo: fix first byte interpretation off-by-one

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