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Revert "wip groupmembers is 2-alloc away."

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This reverts commit 7c41cbabe7.

Not doing this now.
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Motiejus Jakštys
2022-04-08 16:08:03 +03:00
committed by Motiejus Jakštys
parent 7c41cbabe7
commit c343bf64fb
3 changed files with 31 additions and 67 deletions
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README.md
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@@ -274,25 +274,20 @@ Similarly, when user's groups are resolved in (2), they are not always necessary
(i.e. not part of `struct user*`), therefore the memberships themselves are
stored out of bound.
`groupmembers` and `additional_gids` store group and user memberships
respectively. Membership IDs are packed — not necessitating random access, thus
suitable for compression.
`groupmembers` and `additional_gids` store group and user memberships respectively.
Membership IDs are packed — not necessitating random access, thus suitable for
compression.
- `groupmembers` consists of a number X followed by a list of offsets to User
records, because `getgr*_r` returns pointers to membernames, thus a name has
to be immediately resolvable.
- `additional_gids` is a list of gids, because `initgroups_dyn` (and friends)
returns an array of gids.
- `groupmembers` is a list of pointers (offsets) to User records, because
`getgr*_r` returns pointers to membernames, thus a name has to be immediately
resolvable.
- `additional_gids` is a list of gids, because `initgroups_dyn` (and friends) returns
an array of gids.
Each entry of `groupmembers` and `additional_gids` starts with a varint N,
which is the number of upcoming elements. Then depending on the type:
- **additional_gids** stores N delta-compressed varints. These varints
correspond to a list of gids.
- **groupmembers** stores a total length of the member names, followed by N,
followed by N offsets. These are byte-offsets to the User records in the
`users` section. Having the length of membernames saves some CPU cycles when
decompressing the members in the hot path.
Each entry of `groupmembers` and `additional_gids` starts with a varint N, which is
the number of upcoming elements, followed by N delta-compressed varints. These
N delta-compressed varints are sorted the same way entries in `users` (in
`groupmembers`) and `groups`.
Indices
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