motiejus
/
turbonss
1
Fork 0
Code Releases Activity

test and README tiny updates

main
Motiejus Jakštys 2022-02-18 17:24:22 +02:00 committed by Motiejus Jakštys
parent 80ec63b6a4
commit 411fb91fd1
2 changed files with 41 additions and 36 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

43
README.md
View File

@ -92,7 +92,10 @@ $ zig build test
Other commands will be documented as they are implemented. Other commands will be documented as they are implemented.
This project uses [git subtrac][git-subtrac] for managing dependencies. This project uses [git subtrac][git-subtrac] for managing dependencies. They
work just like regular submodules, except all the refs of the submodules are in
this repository. Repeat after me: all the submodules are in this repository.
So if you have a copy of this repo, dependencies will not disappear.
remarks on `id(1)` remarks on `id(1)`
------------------ ------------------
@ -131,12 +134,12 @@ understand which operations need to be fast; in order of importance:
3. lookup groupname -> group. 3. lookup groupname -> group.
4. lookup username -> user. 4. lookup username -> user.
These indices can use perfect hashing like [cmph][cmph]: a perfect hash hashes These indices can use perfect hashing like [bdz from cmph][cmph]: a perfect
a list of bytes to a sequential list of integers. Perfect hashing algorithms hash hashes a list of bytes to a sequential list of integers. Perfect hashing
require some space, and take some time to calculate ("hashing duration"). I've algorithms require some space, and take some time to calculate ("hashing
tested BDZ, which hashes [][]u8 to a sequential list of integers (not duration"). I've tested BDZ, which hashes [][]u8 to a sequential list of
preserving order) and CHM, preserves order. BDZ accepts an optional argument `3 integers (not preserving order) and CHM, preserves order. BDZ accepts an
<= b <= 10`. optional argument `3 <= b <= 10`.
* BDZ algorithm requires (b=3, 900KB, b=7, 338KB, b=10, 306KB) for 1M values. * BDZ algorithm requires (b=3, 900KB, b=7, 338KB, b=10, 306KB) for 1M values.
* Latency to resolve 1M keys: (170ms, 180ms, 230ms, respectively). * Latency to resolve 1M keys: (170ms, 180ms, 230ms, respectively).
@ -159,9 +162,9 @@ OFFSET TYPE NAME DESCRIPTION
u8 num_shells max value: 63. Padding is strange on little endian. u8 num_shells max value: 63. Padding is strange on little endian.
8 u32 num_users number of passwd entries 8 u32 num_users number of passwd entries
12 u32 num_groups number of group entries 12 u32 num_groups number of group entries
16 u32 offset_cmph_uid2user 16 u32 offset_bdz_uid2user
20 u32 offset_cmph_groupname2group 20 u32 offset_bdz_groupname2group
24 u32 offset_cmph_username2user 24 u32 offset_bdz_username2user
28 u32 offset_idx offset to the first idx_ section 28 u32 offset_idx offset to the first idx_ section
32 u32 offset_groups 32 u32 offset_groups
36 u32 offset_users 36 u32 offset_users
@ -182,7 +185,7 @@ all `offset_*` values could be `u26`. As `u32` is easier to visualize with xxd,
and the header block fits to 64 bytes anyway, we are keeping them as u32 now. and the header block fits to 64 bytes anyway, we are keeping them as u32 now.
Sections whose lengths can be calculated do not have a corresponding `offset_*` Sections whose lengths can be calculated do not have a corresponding `offset_*`
header field. For example, `cmph_gid2group` comes immediately after the header, header field. For example, `bdz_gid2group` comes immediately after the header,
and `idx_groupname2group` comes after `idx_gid2group`, whose offset is and `idx_groupname2group` comes after `idx_gid2group`, whose offset is
`offset_idx`, and size can be calculated. `offset_idx`, and size can be calculated.
@ -330,14 +333,14 @@ Each section is padded to 64 bytes.
``` ```
SECTION SIZE DESCRIPTION SECTION SIZE DESCRIPTION
Header 48 see "Turbonss header" section Header 48 see "Turbonss header" section
cmph_gid2group ? gid->group cmph bdz_gid2group ? gid->group bdz
cmph_uid2user ? uid->user cmph bdz_uid2user ? uid->user bdz
cmph_groupname2group ? groupname->group cmph bdz_groupname2group ? groupname->group bdz
cmph_username2user ? username->user cmph bdz_username2user ? username->user bdz
idx_gid2group len(group)*4*29/32 cmph->offset gid2group idx_gid2group len(group)*4*29/32 bdz->offset gid2group
idx_groupname2group len(group)*4*29/32 cmph->offset groupname2group idx_groupname2group len(group)*4*29/32 bdz->offset groupname2group
idx_uid2user len(user)*4*29/32 cmph->offset uid2user idx_uid2user len(user)*4*29/32 bdz->offset uid2user
idx_username2user len(user)*4*29/32 cmph->offset username2user idx_username2user len(user)*4*29/32 bdz->offset username2user
ShellIndex len(shells)*2 Shell index array ShellIndex len(shells)*2 Shell index array
ShellBlob <= 4032 Shell data blob (max 63*64 bytes) ShellBlob <= 4032 Shell data blob (max 63*64 bytes)
Groups ? packed Group entries (8b padding) Groups ? packed Group entries (8b padding)
@ -346,7 +349,7 @@ groupmembers ? per-group memberlist (32b padding)
additional_gids ? per-user grouplist (8b padding) additional_gids ? per-user grouplist (8b padding)
``` ```
[git-subtrac]: https://github.com/apenwarr/git-subtrac/ [git-subtrac]: https://apenwarr.ca/log/20191109
[cmph]: http://cmph.sourceforge.net/ [cmph]: http://cmph.sourceforge.net/
[id]: https://linux.die.net/man/1/id [id]: https://linux.die.net/man/1/id
[nsswitch]: https://linux.die.net/man/5/nsswitch.conf [nsswitch]: https://linux.die.net/man/5/nsswitch.conf

34
src/header.zig
View File

@ -8,7 +8,7 @@ const Bom = 0x1234;
pub const SectionLength = 64; pub const SectionLength = 64;
const HeaderError = error{ const InvalidHeader = error{
InvalidMagic, InvalidMagic,
InvalidVersion, InvalidVersion,
InvalidBom, InvalidBom,
@ -23,16 +23,16 @@ const Header = packed struct {
num_shells: u8, num_shells: u8,
num_users: u32, num_users: u32,
num_groups: u32, num_groups: u32,
offset_cmph_uid2user: u32, offset_bdz_uid2user: u32,
offset_cmph_groupname2group: u32, offset_bdz_groupname2group: u32,
offset_cmph_username2user: u32, offset_bdz_username2user: u32,
offset_idx: u32, offset_idx: u32,
offset_groups: u32, offset_groups: u32,
offset_users: u32, offset_users: u32,
offset_groupmembers: u32, offset_groupmembers: u32,
offset_additional_gids: u32, offset_additional_gids: u32,
pub fn init(blob: [HeaderSize]u8) HeaderError!Header { pub fn init(blob: [HeaderSize]u8) InvalidHeader!Header {
const self = @bitCast(Header, blob); const self = @bitCast(Header, blob);
for (Magic) |item, index| { for (Magic) |item, index| {
if (self.magic[index] != item) return error.InvalidMagic; if (self.magic[index] != item) return error.InvalidMagic;
@ -48,9 +48,9 @@ const Header = packed struct {
} }
const offsets = [_]u32{ const offsets = [_]u32{
self.offset_cmph_uid2user, self.offset_bdz_uid2user,
self.offset_cmph_groupname2group, self.offset_bdz_groupname2group,
self.offset_cmph_username2user, self.offset_bdz_username2user,
self.offset_idx, self.offset_idx,
self.offset_groups, self.offset_groups,
self.offset_users, self.offset_users,
@ -73,12 +73,15 @@ const Header = packed struct {
const testing = std.testing; const testing = std.testing;
test "constants and types are reasonable" { test "header is byte-aligned" {
try testing.expectEqual(HeaderSize * 8, @bitSizeOf(Header)); try testing.expectEqual(HeaderSize * 8, @bitSizeOf(Header));
}
test "Section length is a power of two" {
try testing.expect(std.math.isPowerOfTwo(SectionLength)); try testing.expect(std.math.isPowerOfTwo(SectionLength));
} }
test "header pack and unpack" { test "header pack, unpack and validation" {
const goodHeader = Header{ const goodHeader = Header{
.magic = Magic, .magic = Magic,
.version = Version, .version = Version,
@ -86,9 +89,9 @@ test "header pack and unpack" {
.num_shells = 0, .num_shells = 0,
.num_users = 0, .num_users = 0,
.num_groups = 0, .num_groups = 0,
.offset_cmph_uid2user = 0, .offset_bdz_uid2user = 0,
.offset_cmph_groupname2group = 0, .offset_bdz_groupname2group = 0,
.offset_cmph_username2user = 0, .offset_bdz_username2user = 0,
.offset_idx = 0, .offset_idx = 0,
.offset_groups = 0, .offset_groups = 0,
.offset_users = 0, .offset_users = 0,
@ -96,8 +99,7 @@ test "header pack and unpack" {
.offset_additional_gids = 0, .offset_additional_gids = 0,
}; };
const blob = goodHeader.asArray(); const gotHeader = try Header.init(goodHeader.asArray());
const gotHeader = try Header.init(blob);
try testing.expectEqual(goodHeader, gotHeader); try testing.expectEqual(goodHeader, gotHeader);
{ {
@ -120,7 +122,7 @@ test "header pack and unpack" {
{ {
var header = goodHeader; var header = goodHeader;
header.offset_cmph_uid2user = 65; header.offset_bdz_uid2user = 65;
try testing.expectError(error.InvalidOffset, Header.init(header.asArray())); try testing.expectError(error.InvalidOffset, Header.init(header.asArray()));
} }
} }