98 lines
2.4 KiB
Zig
98 lines
2.4 KiB
Zig
const std = @import("std");
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const mem = std.mem;
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const math = std.math;
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const native_endian = @import("builtin").target.cpu.arch.endian();
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const max_shells = @import("shell.zig").max_shells;
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const magic = [4]u8{ 0xf0, 0x9f, 0xa4, 0xb7 };
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const version = 0;
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const Endian = enum(u8) {
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big,
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little,
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fn native() Endian {
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return switch (native_endian) {
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.Little => Endian.little,
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.Big => Endian.big,
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};
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}
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};
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pub const section_length_bits = 6;
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pub const section_length = 1 << section_length_bits;
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pub const Invalid = error{
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InvalidMagic,
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InvalidVersion,
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InvalidEndianess,
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};
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pub const Header = packed struct {
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magic: [4]u8 = magic,
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version: u8 = version,
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endian: Endian = Endian.native(),
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nblocks_shell_blob: u8,
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num_shells: u8,
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num_groups: u32,
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num_users: u32,
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nblocks_bdz_gid: u32,
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nblocks_bdz_groupname: u32,
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nblocks_bdz_uid: u32,
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nblocks_bdz_username: u32,
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nblocks_groups: u64,
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nblocks_users: u64,
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nblocks_groupmembers: u64,
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nblocks_additional_gids: u64,
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pub fn fromBytes(blob: *const [@sizeOf(Header)]u8) Invalid!*const Header {
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const self = mem.bytesAsValue(Header, blob);
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if (!mem.eql(u8, magic[0..4], blob[0..4]))
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return error.InvalidMagic;
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if (self.version != 0)
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return error.InvalidVersion;
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if (self.endian != Endian.native())
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return error.InvalidEndianess;
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return self;
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}
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};
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const testing = std.testing;
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test "Section length is a power of two" {
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try testing.expect(std.math.isPowerOfTwo(section_length));
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}
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test "Header fits into a section" {
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try testing.expect(@sizeOf(Header) <= section_length);
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}
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test "bit header size is equal to @sizeOf(Header)" {
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try testing.expectEqual(@sizeOf(Header) * 8, @bitSizeOf(Header));
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}
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test "header pack and unpack" {
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const header1 = Header{
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.nblocks_shell_blob = 0,
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.num_shells = 0,
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.num_groups = 0,
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.num_users = 0,
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.nblocks_bdz_gid = 0,
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.nblocks_bdz_groupname = 0,
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.nblocks_bdz_uid = 0,
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.nblocks_bdz_username = 0,
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.nblocks_groups = 0,
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.nblocks_users = 0,
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.nblocks_groupmembers = 0,
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.nblocks_additional_gids = 1,
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};
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const bytes = mem.asBytes(&header1);
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const header = try Header.fromBytes(bytes);
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try testing.expectEqual(header1, header.*);
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}
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