wip writing of users

src/sections.zig

@@ -232,14 +232,13 @@ pub fn userGids(allocator: Allocator, corpus: *const Corpus) userGidsErr!UserGid
     var name2offset = StringHashMap(u32).init(allocator);
     errdefer name2offset.deinit();
 
+    // zero'th entry is empty, so groupless users can refer to it.
+    try compress.appendUvarint(&blob, 0);
+
     var scratch = try allocator.alloc(u32, 256);
     defer allocator.free(scratch);
     for (corpus.users) |user| {
-        const usergroups_maybe = corpus.username2groups.get(user.name);
-        if (usergroups_maybe == null)
-            continue;
-        const usergroups = usergroups_maybe.?;
-
+        if (corpus.username2groups.get(user.name)) |usergroups| {
             try name2offset.putNoClobber(user.name, try math.cast(u32, blob.items.len));
             scratch = try allocator.realloc(scratch, usergroups.len);
             scratch.len = usergroups.len;
@@ -251,6 +250,9 @@ pub fn userGids(allocator: Allocator, corpus: *const Corpus) userGidsErr!UserGid
             try compress.appendUvarint(&blob, usergroups.len);
             for (scratch) |gid|
                 try compress.appendUvarint(&blob, gid);
+        } else {
+            try name2offset.putNoClobber(user.name, 0);
+        }
     }
 
     return UserGids{
@@ -259,18 +261,25 @@ pub fn userGids(allocator: Allocator, corpus: *const Corpus) userGidsErr!UserGid
     };
 }
 
-pub const usersSectionErr = Allocator.Error || error{Overflow};
 pub fn usersSection(
     allocator: Allocator,
     corpus: *const Corpus,
     gids: *const UserGids,
     shells: *const ShellSections,
-) usersSectionErr![]const u8 {
+) error{ OutOfMemory, Overflow }![]const u8 {
     // as of writing each user takes 15 bytes + strings + padding, padded to
-    // 8 bytes. 24 is a very optimistic lower bound.
+    // 8 bytes. 24 is an optimistic lower bound for an average record size.
     var buf = try ArrayList(u8).initCapacity(allocator, 24 * corpus.users.len);
-    _ = gids;
-    _ = shells;
+    for (corpus.users) |user| {
+        const offset = gids.name2offset.get(user.name).?;
+        std.debug.assert(offset & 7 == 0);
+        try userImport.PackedUserConst.packTo(
+            &buf,
+            user,
+            @truncate(u29, @shrExact(offset, 3)),
+            shells.indices.get,
+        );
+    }
     return buf.toOwnedSlice();
 }
 

src/user.zig

@@ -6,6 +6,7 @@ const InvalidRecord = validate.InvalidRecord;
 
 const assert = std.debug.assert;
 const mem = std.mem;
+const math = std.math;
 const Allocator = mem.Allocator;
 const ArrayList = std.ArrayList;
 
@@ -196,6 +197,7 @@ fn packedUser(immutable: bool) type {
         pub fn packTo(
             arr: *ArrayList(u8),
             user: User,
+            additional_gids_offset: u29,
             idxFn: shell2idxProto,
         ) packErr!void {
             // function arguments are consts. We need to mutate the underlying
@@ -213,7 +215,7 @@ fn packedUser(immutable: bool) type {
             const inner = Inner{
                 .uid = user.uid,
                 .gid = user.gid,
-                .additional_gids_offset = std.math.maxInt(u29),
+                .additional_gids_offset = additional_gids_offset,
                 .shell_here = idxFn(user.shell) == null,
                 .shell_len_or_idx = idxFn(user.shell) orelse shell_len,
                 .home_len = home_len,
@@ -241,10 +243,10 @@ fn packedUser(immutable: bool) type {
         pub fn maxSize() usize {
             comptime {
                 const unpadded = InnerSize +
-                    std.math.maxInt(u6) + 1 + // home
-                    std.math.maxInt(u5) + 1 + // name
-                    std.math.maxInt(u6) + 1 + // shell
-                    std.math.maxInt(u8); // gecos
+                    math.maxInt(u6) + 1 + // home
+                    math.maxInt(u5) + 1 + // name
+                    math.maxInt(u6) + 1 + // shell
+                    math.maxInt(u8); // gecos
                 return pad.roundUp(u64, alignmentBits, unpadded);
             }
         }
@@ -346,7 +348,7 @@ test "construct PackedUser section" {
         .shell = "/usr/bin/nologin",
     }, User{
         .uid = 0,
-        .gid = std.math.maxInt(u32),
+        .gid = math.maxInt(u32),
         .name = "Name" ** 8,
         .gecos = "Gecos" ** 51,
         .home = "Home" ** 16,
@@ -360,7 +362,7 @@ test "construct PackedUser section" {
         .shell = "/",
     } };
     for (users) |user|
-        try PackedUserConst.packTo(&buf, user, testShellIndex);
+        try PackedUserConst.packTo(&buf, user, math.maxInt(u29), testShellIndex);
 
     var i: u29 = 0;
     var it1 = PackedUserConst.iterator(buf.items, testShell);
@@ -368,7 +370,7 @@ test "construct PackedUser section" {
         try testing.expectEqual(users[i].uid, user.uid());
         try testing.expectEqual(users[i].gid, user.gid());
         try testing.expectEqual(
-            @as(u29, std.math.maxInt(u29)),
+            @as(u29, math.maxInt(u29)),
             user.additionalGidsOffset(),
         );
         try testing.expectEqualStrings(users[i].name, user.name());
@@ -405,14 +407,14 @@ test "PackedUser.maxSize()" {
     defer buf.deinit();
 
     const largeUser = User{
-        .uid = std.math.maxInt(u32),
-        .gid = std.math.maxInt(u32),
+        .uid = math.maxInt(u32),
+        .gid = math.maxInt(u32),
         .name = "Name" ** 8, // 32
         .gecos = "Gecos" ** 51, // 255
         .home = "Home" ** 16, // 64
         .shell = "She.LllL" ** 8, // 64
     };
-    try PackedUserConst.packTo(&buf, largeUser, testShellIndex);
+    try PackedUserConst.packTo(&buf, largeUser, math.maxInt(u29), testShellIndex);
     try testing.expectEqual(PackedUserConst.maxSize(), buf.items.len);
 }