offsets are u64

README.md

@@ -197,13 +197,13 @@ const PackedGroup = packed struct {
 pub const PackedUser = packed struct {
     uid: u32,
     gid: u32,
-    additional_gids_offset: u29,
-    shell_here: bool,
+    padding: u2 = 0,
     shell_len_or_idx: u6,
-    home_len: u6,
+    shell_here: bool,
     name_is_a_suffix: bool,
+    home_len: u6,
     name_len: u5,
-    gecos_len: u8,
+    gecos_len: u11,
     // pseudocode: variable-sized array that will be stored immediately after
     // this struct.
     stringdata []u8;
@@ -215,6 +215,7 @@ pub const PackedUser = packed struct {
 - name (optional).
 - gecos.
 - shell (optional).
+- `additional_gids_offset`: varint.
 
 First byte of home is stored right after the `gecos_len` field, and it's
 length is `home_len`. The same logic applies to all the `stringdata` fields:
@@ -232,6 +233,9 @@ Additionally, there are two "easy" optimizations:
   2. `name_is_a_suffix=false`: name begins one byte after home, and it's length
   is `name_len`.
 
+The last field, `additional_gids_offset`, which is needed least frequently,
+is stored at the end.
+
 Shells
 ------