From: Glen Choo <chooglen@google.com>
To: git@vger.kernel.org
Cc: Glen Choo <chooglen@google.com>, Junio C Hamano <gitster@pobox.com>
Subject: [PATCH] docs: document zero bits in index "mode"
Date: Wed, 1 Feb 2023 10:40:41 +0800 [thread overview]
Message-ID: <20230201024041.29401-1-chooglen@google.com> (raw)
In-Reply-To: xmqqmt5yy08d.fsf@gitster.g
Documentation/gitformat-index.txt describes the "mode" as 32 bits, but
only documents 16 bits. Document the missing 16 bits and specify that
'unused' bits must be zero.
Signed-off-by: Glen Choo <chooglen@google.com>
---
> The existing explanation starts with "32-bit mode,
> split into (high to low bits)", followed by "4-bit object type", as
> if the "4-bit object type" occupies bits 29-32, which is not quite
> what we want to say.
If I am understanding you correctly (which I'm not sure, since I am
honestly clueless about bit numbering and big endianness and whatnot),
you're saying that highest 16 bits are zero, not the lowest? If so, then
I genuinely made that mistake, hah.
(We're storing 16 bits as bigendian 32 bits, so they would occupy the
lower 16 bits, right..?)
Perhaps something like this would be better. I took the "unused, must be
zero" phrasing from elsewhere in the doc. And if I am completely
off-base, feel free to patch it without waiting for my reroll if you
think that's easier.
Documentation/gitformat-index.txt | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/Documentation/gitformat-index.txt b/Documentation/gitformat-index.txt
index 015cb21bdc..0773e5c380 100644
--- a/Documentation/gitformat-index.txt
+++ b/Documentation/gitformat-index.txt
@@ -83,11 +83,13 @@ Git index format
32-bit mode, split into (high to low bits)
+ 16-bit unused, must be zero
+
4-bit object type
valid values in binary are 1000 (regular file), 1010 (symbolic link)
and 1110 (gitlink)
- 3-bit unused
+ 3-bit unused, must be zero
9-bit unix permission. Only 0755 and 0644 are valid for regular files.
Symbolic links and gitlinks have value 0 in this field.
--
2.39.1.456.gfc5497dd1b-goog
next reply other threads:[~2023-02-01 2:40 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-01 2:40 Glen Choo [this message]
2023-02-01 2:46 ` [PATCH] docs: document zero bits in index "mode" Glen Choo
2023-02-01 16:56 ` Junio C Hamano
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