user packing

README.md

@@ -67,9 +67,9 @@ Tight packing places some constraints on the underlying data:
 
 - Maximum database size: 4GB.
 - Permitted length of username and groupname: 1-32 bytes.
-- Permitted length of shell and homedir: 1-64 bytes.
+- Permitted length of shell and home: 1-64 bytes.
 - Permitted comment ("gecos") length: 0-255 bytes.
-- Username, groupname and gecos must be utf8-encoded.
+- User name, groupname and gecos must be utf8-encoded.
 
 Checking out and building
 -------------------------
@@ -219,11 +219,11 @@ const User = struct {
     // pointer to a separate structure that contains a list of gids
     additional_gids_offset: u29,
     // shell is a different story, documented elsewhere.
-    shell_here: u1,
+    shell_here: bool,
     shell_len_or_idx: u6,
-    homedir_len: u6,
-    username_is_a_suffix: u1,
-    username_offset_or_len: u5,
+    home_len: u6,
+    name_is_a_suffix: bool,
+    name_len: u5,
     gecos_len: u8,
     // a variable-sized array that will be stored immediately after this
     // struct.
@@ -232,27 +232,27 @@ const User = struct {
 ```
 
 `stringdata` contains a few string entries:
-- homedir.
-- username.
+- home.
+- name.
 - gecos.
 - shell (optional).
 
-First byte of the homedir is stored right after the `gecos_len` field, and it's
-length is `homedir_len`. The same logic applies to all the `stringdata` fields:
+First byte of the 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:
 there is a way to calculate their relative position from the length of the
 fields before them.
 
 Additionally, two optimizations for special fields are made:
 - shells are often shared across different users, see the "Shells" section.
-- username is frequently a suffix of the homedir. For example, `/home/motiejus`
-  and `motiejus`. In which case storing both username and homedir strings is
-  wasteful. For that cases, username has two options:
-  1. `username_is_a_suffix=true`: username is a suffix of the home dir. In that
-  case, the username starts at the `username_offset_or_len`'th byte of the
-  homedir, and ends at the same place as the homedir.
-  2. `username_is_a_suffix=false`: username is stored separately. In that case,
-  it begins one byte after homedir, and it's length is
-  `username_offset_or_len`.
+- name is frequently a suffix of the home. For example, `/home/motiejus`
+  and `motiejus`. In which case storing both name and home strings is
+  wasteful. For that cases, name has two options:
+  1. `name_is_a_suffix=true`: name is a suffix of the home dir. In that
+     case, the name starts at the `home_len - name_len`'th
+     byte of the home, and ends at the same place as the home.
+  2. `name_is_a_suffix=false`: name is stored separately. In that case,
+  it begins one byte after home, and it's length is
+  `name_len`.
 
 Shells
 ------
@@ -315,8 +315,7 @@ const AdditionalGids = PackedList;
 
 An entry in `members` field points to the offset into a respective `User` or
 `Group` entry (number of bytes relative to the first entry of the type).
-`members` in `PackedList` is sorted by the name (`username` or `groupname`) of
-the record it is pointing to.
+`members` in `PackedList` are sorted the same way as in the input.
 
 A packed list is a list of varints.