Re: [PATCH] pack-format: correct multi-pack-index description

[Derrick Stolee <stolee@gmail.com>]

On 2/7/2020 5:16 PM, Johannes Berg wrote:
> The description of the multi-pack-index contains a small bug,
> if all offsets are < 2^32 then there will be no LOFF chunk,
> not only if they're all < 2^31 (since the highest bit is only
> needed as the "LOFF-escape" when that's actually needed.)
> 
> Correct this, and clarify that in that case only offsets up
> to 2^31-1 can be stored in the OOFF chunk.
> 
> Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
> ---
>  Documentation/technical/pack-format.txt | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/technical/pack-format.txt b/Documentation/technical/pack-format.txt
> index cab5bdd2ff0f..d3a142c65202 100644
> --- a/Documentation/technical/pack-format.txt
> +++ b/Documentation/technical/pack-format.txt
> @@ -315,10 +315,11 @@ CHUNK DATA:
>  	    Stores two 4-byte values for every object.
>  	    1: The pack-int-id for the pack storing this object.
>  	    2: The offset within the pack.
> -		If all offsets are less than 2^31, then the large offset chunk
> +		If all offsets are less than 2^32, then the large offset chunk
>  		will not exist and offsets are stored as in IDX v1.
>  		If there is at least one offset value larger than 2^32-1, then
> -		the large offset chunk must exist. If the large offset chunk
> +		the large offset chunk must exist, and offsets larger than
> +		2^31-1 must be stored in it instead. If the large offset chunk
>  		exists and the 31st bit is on, then removing that bit reveals
>  		the row in the large offsets containing the 8-byte offset of
>  		this object.

Thank you for finding this doc bug. This is a very subtle point,
and you have described it very clearly.

-Stolee