start packed group

README.md

@@ -180,10 +180,10 @@ referred by their byte offset in the `Users` and `Groups` section relative to
 the beginning of the section.
 
 ```
-const PackedGroup = struct {
+const PackedGroup = packed struct {
     gid: u32,
     // index to a separate structure with a list of members. The memberlist is
-    // always 2^5-byte aligned (32b), this is an index there.
+    // 2^5-byte aligned (32b), this is an index there.
     members_offset: u27,
     groupname_len: u5,
     // a groupname_len-sized string
@@ -347,10 +347,10 @@ Each section is padded to 64 bytes.
 ```
 STATUS  SECTION               SIZE             DESCRIPTION
 ✅      Header                48               see "Turbonss header" section
-        bdz_gid               ?                bdz(gid)
-        bdz_groupname         ?                bdz(groupname)
-        bdz_uid               ?                bdz(uid)
-        bdz_name              ?                bdz(username)
+✅      bdz_gid               ?                bdz(gid)
+✅      bdz_groupname         ?                bdz(groupname)
+✅      bdz_uid               ?                bdz(uid)
+✅      bdz_name              ?                bdz(username)
         idx_gid2group         len(group)*29/8  bdz->offset Groups
         idx_groupname2group   len(group)*29/8  bdz->offset Groups
         idx_uid2user          len(user)*29/8   bdz->offset Users

src/bdz.zig

@@ -5,7 +5,7 @@ const c = @cImport({
     @cInclude("bdz.h");
 });
 
-pub fn search_packed(packed_mphf: []const u8, key: []const u8) error{Overflow}!u32 {
+pub fn search(packed_mphf: []const u8, key: []const u8) error{Overflow}!u32 {
     const bdz_start = @intToPtr(?*anyopaque, @ptrToInt(&packed_mphf[0]));
     const len = try std.math.cast(c_uint, key.len);
     return @as(u32, c.bdz_search_packed(bdz_start, key.ptr, len));

src/cmph.zig

@@ -59,7 +59,7 @@ test "basic pack/unpack" {
     var used: [items_len]bool = undefined;
 
     inline for (items) |elem| {
-        const hashed = try bdz.search_packed(buf, elem);
+        const hashed = try bdz.search(buf, elem);
         used[hashed] = true;
     }
 

src/group.zig

@@ -1,7 +1,19 @@
 const std = @import("std");
 
+const PackedGroup = packed struct {
+    gid: u32,
+    members_offset: u27,
+    groupname_len: u5,
+};
+
 const Group = struct {
     gid: u32,
     name: []const u8,
     members: std.BufSet,
 };
+
+const testing = std.testing;
+
+test "PackedGroup alignment" {
+    try testing.expectEqual(@sizeOf(PackedGroup) * 8, @bitSizeOf(PackedGroup));
+}

src/user.zig

@@ -248,7 +248,7 @@ test "PackedUser internal and external alignment" {
     // cannot be converted from/to [@bitSizeOf(PackedUser)/8]u8;
     // asBytes/bytesAsValue use @sizeOf, which is larger. Now we are putting no
     // more than 1, but it probably could be higher.
-    try testing.expect(@bitSizeOf(PackedUser) - @sizeOf(PackedUser) * 8 <= 8);
+    try testing.expect(@sizeOf(PackedUser) * 8 - @bitSizeOf(PackedUser) <= 8);
 }
 
 fn testShellIndex(shell: []const u8) ?u6 {