working on iterator
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54ec710f10
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@ -1,19 +1,19 @@
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const std = @import("std");
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const std = @import("std");
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const assert = std.debug.assert;
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const assert = std.debug.assert;
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// rounds up a u12 to the nearest factor of 4 and returns the difference
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// rounds up an int to the nearest factor of nbits.
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// (padding)
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pub fn roundUpPadding(comptime T: type, comptime nbits: u8, n: T) T {
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return roundUp(T, nbits, n) - n;
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}
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// rounds up a u12 to the nearest factor of 4.
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pub fn roundUp(comptime T: type, comptime nbits: u8, n: T) T {
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pub fn roundUp(comptime T: type, comptime nbits: u8, n: T) T {
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comptime assert(nbits < @bitSizeOf(T));
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comptime assert(nbits < @bitSizeOf(T));
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const factor = comptime (1 << nbits) - 1;
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const factor = comptime (1 << nbits) - 1;
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return ((n + factor) & ~@as(T, factor));
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return ((n + factor) & ~@as(T, factor));
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}
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}
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// rounds up an integer to the nearest factor of nbits and returns the
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// difference (padding)
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pub fn roundUpPadding(comptime T: type, comptime nbits: u8, n: T) T {
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return roundUp(T, nbits, n) - n;
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}
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const testing = std.testing;
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const testing = std.testing;
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test "padding" {
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test "padding" {
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@ -25,7 +25,7 @@ pub const ShellReader = struct {
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}
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}
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// get returns a shell at the given index.
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// get returns a shell at the given index.
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pub fn get(self: *const ShellReader, idx: u10) []const u8 {
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pub fn get(self: *const ShellReader, idx: u6) []const u8 {
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const shellIndex = self.sectionIndex[idx];
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const shellIndex = self.sectionIndex[idx];
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const start = shellIndex.offset << 2;
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const start = shellIndex.offset << 2;
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const end = start + shellIndex.len + 1;
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const end = start + shellIndex.len + 1;
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112
src/user.zig
112
src/user.zig
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@ -17,6 +17,21 @@ pub const PackedUser = packed struct {
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name_is_a_suffix: bool,
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name_is_a_suffix: bool,
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name_len: u5,
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name_len: u5,
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gecos_len: u8,
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gecos_len: u8,
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wip_padding: u8, // https://github.com/ziglang/zig/pull/10941
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// blobSize returns the length of the blob storing string values.
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pub fn blobLength(self: *const PackedUser) usize {
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var result: usize = self.home_len;
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if (!self.name_is_a_suffix) {
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result += self.name_len;
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}
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result += self.gecos_len;
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if (self.shell_here) {
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result += self.shell_len_or_idx;
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}
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return result;
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}
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};
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};
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const PackedUserAlignmentBits = 3;
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const PackedUserAlignmentBits = 3;
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@ -71,6 +86,7 @@ pub const UserWriter = struct {
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.name_is_a_suffix = std.mem.endsWith(u8, user.home, user.name),
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.name_is_a_suffix = std.mem.endsWith(u8, user.home, user.name),
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.name_len = name_len,
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.name_len = name_len,
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.gecos_len = gecos_len,
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.gecos_len = gecos_len,
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.wip_padding = 0,
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};
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};
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try self.appendTo.appendSlice(std.mem.asBytes(&puser));
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try self.appendTo.appendSlice(std.mem.asBytes(&puser));
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@ -92,37 +108,52 @@ pub const UserWriter = struct {
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};
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};
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pub const UserReader = struct {
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pub const UserReader = struct {
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const shellIndexProto = fn (u10) []const u8;
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const shellIndexProto = fn (u6) []const u8;
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blob: []u8,
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shellIndex: shellIndexProto,
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shellIndex: shellIndexProto,
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blob: []const u8,
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pub const PackedUserEntry = struct {
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const PackedEntry = struct {
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packed_user: *PackedUser,
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packed_user: *PackedUser,
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blob: []const u8,
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blob: []const u8,
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};
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};
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pub fn init(shellIndex: shellIndexProto, blob: []const u8) UserReader {
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pub fn init(blob: []u8, shellIndex: shellIndexProto) UserReader {
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return UserReader{
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return UserReader{
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.shellIndex = shellIndex,
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.blob = blob,
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.blob = blob,
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.shellIndex = shellIndex,
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};
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};
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}
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}
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pub const PackedUserIterator = struct {
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pub const PackedIterator = struct {
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ur: *const UserReader,
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ur: *UserReader,
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index: u32 = 0,
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index: usize = 0,
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pub fn next(it: *PackedUserIterator) ?PackedUserEntry {
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pub fn next(it: *PackedIterator) ?PackedEntry {
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if (it.index == it.ur.blob.len) return null;
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if (it.index == it.ur.blob.len) return null;
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assert(it.index < it.blob.len);
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assert(it.index < it.ur.blob.len);
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const start = it.index;
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const endUser = it.index + PackedUserSize;
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const end = it.index + it.index + @sizeOf(PackedUser);
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var packedUser = std.mem.bytesAsValue(
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var pu = std.mem.bytesAsValue(it.ur.blob[start..end]);
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PackedUser,
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_ = pu;
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it.ur.blob[it.index..endUser][0..PackedUserSize],
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);
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const startBlob = endUser + 1;
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const endBlob = startBlob + packedUser.blobLength();
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it.index = pad.roundUp(usize, PackedUserAlignmentBits, endBlob + 1);
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return PackedEntry{
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.packed_user = packedUser,
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.blob = it.ur.blob[startBlob..endBlob],
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};
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}
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}
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};
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};
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pub fn packedIterator(self: *UserReader) PackedIterator {
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return .{ .ur = self };
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}
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};
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};
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const testing = std.testing;
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const testing = std.testing;
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@ -140,27 +171,46 @@ fn testShellIndex(shell: []const u8) ?u6 {
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return null;
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return null;
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}
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}
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fn testShell(index: u6) []const u8 {
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return switch (index) {
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0 => "/bin/bash",
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1 => "/bin/zsh",
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else => unreachable,
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};
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}
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test "construct PackedUser blob" {
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test "construct PackedUser blob" {
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var buf = ArrayList(u8).init(testing.allocator);
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var buf = ArrayList(u8).init(testing.allocator);
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defer buf.deinit();
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defer buf.deinit();
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var writer = UserWriter.init(&buf, testShellIndex);
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var writer = UserWriter.init(&buf, testShellIndex);
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const user1 = User{
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const users = [_]User{
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.uid = 1000,
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User{
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.gid = 1000,
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.uid = 1000,
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.name = "vidmantas",
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.gid = 1000,
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.gecos = "Vidmantas Kaminskas",
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.name = "vidmantas",
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.home = "/home/vidmantas",
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.gecos = "Vidmantas Kaminskas",
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.shell = "/bin/bash",
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.home = "/home/vidmantas",
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.shell = "/bin/bash",
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},
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User{
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.uid = 1001,
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.gid = 1001,
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.name = "svc-foo",
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.gecos = "Service Account",
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.home = "/home/service1",
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.shell = "/usr/bin/nologin",
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},
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};
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};
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const user2 = User{
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for (users) |user| {
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.uid = 1001,
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try writer.appendUser(user);
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.gid = 1001,
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}
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.name = "svc-foo",
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.gecos = "Service Account",
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var rd = UserReader.init(buf.items, testShell);
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.home = "/home/service1",
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var it = rd.packedIterator();
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.shell = "/usr/bin/nologin",
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var i: u32 = 0;
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};
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while (it.next()) |entry| : (i += 1) {
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try writer.appendUser(user1);
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try testing.expectEqual(users[i].uid, entry.packed_user.uid);
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try writer.appendUser(user2);
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try testing.expectEqual(users[i].gid, entry.packed_user.gid);
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}
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}
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}
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