77 lines
2.1 KiB
Zig
77 lines
2.1 KiB
Zig
const std = @import("std");
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const Allocator = std.mem.Allocator;
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pub const PackedUserSize = @sizeOf(PackedUser);
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pub const PackedUser = packed struct {
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uid: u32,
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gid: u32,
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additional_gids_offset: u29,
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shell_here: u1,
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shell_len_or_place: u6,
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homedir_len: u6,
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username_is_a_suffix: u1,
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username_offset_or_len: u5,
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gecos_len: u8,
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};
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pub const User = struct {
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uid: u32,
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gid: u32,
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name: []const u8,
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gecos: []const u8,
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home: []const u8,
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shell: []const u8,
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};
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// UserWriter accepts a naive User struct and returns a PackedUser
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pub const UserWriter = struct {
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// shellIndexFnType is a signature for a function that accepts a shell
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// string and returns it's index in the global shell section. Passing a
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// function makes tests easier, and removes the Shell dependency of this
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// module.
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const shellIndexFnType = fn ([]const u8) ?u10;
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allocator: Allocator,
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shellIndexFn: shellIndexFnType,
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pub fn init(allocator: Allocator, shellIndexFn: shellIndexFnType) UserWriter {
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return UserWriter{
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.allocator = allocator,
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.shellIndexFn = shellIndexFn,
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};
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}
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pub fn fromUser(self: *UserWriter, user: User) !PackedUser {
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var shell_here: u1 = undefined;
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var shell_len_or_place: u6 = undefined;
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if (self.shellIndexFn(user.shell)) |idx| {
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shell_here = false;
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shell_len_or_place = idx;
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} else {
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shell_here = true;
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shell_len_or_place = user.shell.len;
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}
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var puser = PackedUser{
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.uid = user.uid,
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.gid = user.gid,
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.additional_gids_offset = 0, // second pass
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.shell_here = shell_here,
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.shell_len_or_place = shell_len_or_place,
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.homedir_len = undefined,
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.username_is_a_suffix = undefined,
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.username_offset_or_len = undefined,
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.gecos_len = undefined,
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};
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return puser;
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}
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};
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const testing = std.testing;
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test "PackedUser is byte-aligned" {
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try testing.expectEqual(0, @rem(@bitSizeOf(PackedUser), 8));
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}
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