constructing header

src/sections.zig

@@ -95,11 +95,11 @@ const Corpus = struct {
         defer baseAllocator.free(user2groups);
         mem.set(ArrayListUnmanaged(u32), user2groups, ArrayListUnmanaged(u32){});
 
-        for (groups.items(.members)) |group_members, i| {
+        for (groups.items(.members)) |groupmembers, i| {
-            var members = try allocator.alloc(u32, group_members.count());
+            var members = try allocator.alloc(u32, groupmembers.count());
             members.len = 0;
 
-            var it = group_members.iterator();
+            var it = groupmembers.iterator();
             while (it.next()) |memberName| {
                 if (name2user.get(memberName.*)) |user_idx| {
                     members.len += 1;
@@ -148,7 +148,7 @@ pub fn shellSections(
     return popcon.toOwnedSections(max_shells);
 }
 
-pub const UserGids = struct {
+pub const AdditionalGids = struct {
     // user index -> offset in blob
     idx2offset: []const u64,
     // compressed user gids blob. A blob contains N <= users.len items,
@@ -158,7 +158,7 @@ pub const UserGids = struct {
     // ... and the gid list is delta-compressed.
     blob: []const u8,
 
-    pub fn deinit(self: *UserGids, allocator: Allocator) void {
+    pub fn deinit(self: *AdditionalGids, allocator: Allocator) void {
         allocator.free(self.idx2offset);
         allocator.free(self.blob);
         self.* = undefined;
@@ -168,7 +168,7 @@ pub const UserGids = struct {
 pub fn userGids(
     allocator: Allocator,
     corpus: *const Corpus,
-) error{ OutOfMemory, Overflow }!UserGids {
+) error{ OutOfMemory, Overflow }!AdditionalGids {
     var blob = ArrayList(u8).init(allocator);
     errdefer blob.deinit();
     var idx2offset = try allocator.alloc(u64, corpus.users.len);
@@ -198,13 +198,15 @@ pub fn userGids(
             try compress.appendUvarint(&blob, gid);
     }
 
-    return UserGids{
+    return AdditionalGids{
         .idx2offset = idx2offset,
         .blob = blob.toOwnedSlice(),
     };
 }
 
 pub const UsersSection = struct {
+    // number of users in this section
+    len: u32,
     // user index -> offset in blob
     idx2offset: []const u32,
     blob: []const u8,
@@ -219,7 +221,7 @@ pub const UsersSection = struct {
 pub fn usersSection(
     allocator: Allocator,
     corpus: *const Corpus,
-    gids: *const UserGids,
+    gids: *const AdditionalGids,
     shells: *const ShellSections,
 ) error{ OutOfMemory, Overflow, InvalidRecord }!UsersSection {
     var idx2offset = try allocator.alloc(u32, corpus.users.len);
@@ -244,6 +246,7 @@ pub fn usersSection(
         try pad.arrayList(&blob, PackedUser.alignment_bits);
     }
     return UsersSection{
+        .len = @intCast(u32, corpus.users.len),
         .idx2offset = idx2offset,
         .blob = blob.toOwnedSlice(),
     };
@@ -303,6 +306,8 @@ pub fn groupMembers(
 }
 
 pub const GroupsSection = struct {
+    // number of groups in this section
+    len: u32,
     // group index -> offset in blob
     idx2offset: []const u32,
     blob: []const u8,
@@ -342,6 +347,7 @@ pub fn groupsSection(
     }
 
     return GroupsSection{
+        .len = @intCast(u32, corpus.groups.len),
         .idx2offset = idx2offset,
         .blob = blob.toOwnedSlice(),
     };
@@ -416,8 +422,8 @@ pub const AllSections = struct {
     users: UsersSection,
     shell_sections: ShellSections,
     shell_reader: ShellReader,
-    user_gids: UserGids,
+    additional_gids: AdditionalGids,
-    group_members: GroupMembers,
+    groupmembers: GroupMembers,
     groups: GroupsSection,
     idx_gid2group: []const u32,
     idx_groupname2group: []const u32,
@@ -449,16 +455,16 @@ pub const AllSections = struct {
         var shell_sections = try shellSections(allocator, corpus);
         errdefer shell_sections.deinit();
 
-        var user_gids = try userGids(allocator, corpus);
+        var additional_gids = try userGids(allocator, corpus);
-        errdefer user_gids.deinit(allocator);
+        errdefer additional_gids.deinit(allocator);
 
-        var users = try usersSection(allocator, corpus, &user_gids, &shell_sections);
+        var users = try usersSection(allocator, corpus, &additional_gids, &shell_sections);
         errdefer users.deinit(allocator);
 
-        var group_members = try groupMembers(allocator, corpus, users.idx2offset);
+        var groupmembers = try groupMembers(allocator, corpus, users.idx2offset);
-        errdefer group_members.deinit(allocator);
+        errdefer groupmembers.deinit(allocator);
 
-        var groups = try groupsSection(allocator, corpus, group_members.idx2offset);
+        var groups = try groupsSection(allocator, corpus, groupmembers.idx2offset);
         errdefer groups.deinit(allocator);
 
         var idx_gid2group = try bdzIdx(u32, allocator, bdz_gid, gids, groups.idx2offset);
@@ -474,18 +480,18 @@ pub const AllSections = struct {
         errdefer allocator.free(idx_name2user);
 
         const header = Header{
-            .nblocks_shell_blob = undefined,
+            .nblocks_shell_blob = nblocks(u8, shell_sections.blob.constSlice()),
-            .num_shells = undefined,
+            .num_shells = shell_sections.len,
-            .num_groups = undefined,
+            .num_groups = groups.len,
-            .num_users = undefined,
+            .num_users = users.len,
-            .nblocks_bdz_gid = undefined,
+            .nblocks_bdz_gid = nblocks(u32, bdz_gid),
-            .nblocks_bdz_groupname = undefined,
+            .nblocks_bdz_groupname = nblocks(u32, bdz_groupname),
-            .nblocks_bdz_uid = undefined,
+            .nblocks_bdz_uid = nblocks(u32, bdz_uid),
-            .nblocks_bdz_username = undefined,
+            .nblocks_bdz_username = nblocks(u32, bdz_username),
-            .nblocks_groups = undefined,
+            .nblocks_groups = nblocks(u64, groups.blob),
-            .nblocks_users = undefined,
+            .nblocks_users = nblocks(u64, users.blob),
-            .nblocks_groupmembers = undefined,
+            .nblocks_groupmembers = nblocks(u64, groupmembers.blob),
-            .nblocks_additional_gids = undefined,
+            .nblocks_additional_gids = nblocks(u64, additional_gids.blob),
         };
 
         return AllSections{
@@ -499,9 +505,9 @@ pub const AllSections = struct {
                 mem.sliceAsBytes(shell_sections.index.constSlice()),
                 mem.sliceAsBytes(shell_sections.blob.constSlice()),
             ),
-            .user_gids = user_gids,
+            .additional_gids = additional_gids,
             .users = users,
-            .group_members = group_members,
+            .groupmembers = groupmembers,
             .groups = groups,
             .idx_gid2group = idx_gid2group,
             .idx_groupname2group = idx_groupname2group,
@@ -517,9 +523,9 @@ pub const AllSections = struct {
         self.allocator.free(self.bdz_uid);
         self.allocator.free(self.bdz_username);
         self.shell_sections.deinit();
-        self.user_gids.deinit(self.allocator);
+        self.additional_gids.deinit(self.allocator);
         self.users.deinit(self.allocator);
-        self.group_members.deinit(self.allocator);
+        self.groupmembers.deinit(self.allocator);
         self.groups.deinit(self.allocator);
         self.allocator.free(self.idx_gid2group);
         self.allocator.free(self.idx_groupname2group);
@@ -657,10 +663,10 @@ test "test groups, group members and users" {
     var sections = try AllSections.init(allocator, &corpus);
     defer sections.deinit();
 
-    const blob = sections.group_members.blob;
+    const blob = sections.groupmembers.blob;
     var i: usize = 0;
     while (i < corpus.groups.len) : (i += 1) {
-        const offset = sections.group_members.idx2offset[i];
+        const offset = sections.groupmembers.idx2offset[i];
         var vit = try compress.VarintSliceIterator(blob[offset..]);
         var it = compress.DeltaDecompressionIterator(&vit);
         for (corpus.group2users[i]) |user_idx| {
@@ -690,18 +696,18 @@ test "userGids" {
     var corpus = try testCorpus(allocator);
     defer corpus.deinit();
 
-    var user_gids = try userGids(allocator, &corpus);
+    var additional_gids = try userGids(allocator, &corpus);
-    defer user_gids.deinit(allocator);
+    defer additional_gids.deinit(allocator);
 
     var user_idx: usize = 0;
     while (user_idx < corpus.users.len) : (user_idx += 1) {
         const groups = corpus.user2groups[user_idx];
-        const offset = user_gids.idx2offset[user_idx];
+        const offset = additional_gids.idx2offset[user_idx];
         if (groups.len == 0) {
             try testing.expect(offset == 0);
             continue;
         }
-        var vit = try compress.VarintSliceIterator(user_gids.blob[offset..]);
+        var vit = try compress.VarintSliceIterator(additional_gids.blob[offset..]);
         var it = compress.DeltaDecompressionIterator(&vit);
         try testing.expectEqual(it.remaining(), groups.len);
         var i: u64 = 0;

src/shell.zig

@@ -38,6 +38,8 @@ pub const ShellWriter = struct {
     };
 
     pub const ShellSections = struct {
+        // len is the number of shells in this section.
+        len: u8,
         // index points the i'th shell to it's offset in blob. The last
         // byte of the i'th shell is index[i+1].
         index: BoundedArray(u16, max_shells),
@@ -55,6 +57,7 @@ pub const ShellWriter = struct {
             shells: BoundedArray([]const u8, max_shells),
         ) error{ Overflow, OutOfMemory }!ShellSections {
             var self = ShellSections{
+                .len = @intCast(u8, shells.len),
                 .index = try BoundedArray(u16, max_shells).init(shells.len),
                 .blob = try BoundedArray(u8, (max_shells + 1) * max_shell_len).init(0),
                 .shell2idx = StringHashMap(u8).init(allocator),