PackedGroup

README.md

@@ -358,7 +358,7 @@ STATUS  SECTION               SIZE             DESCRIPTION
         idx_username2gids     len(user)*29/8   bdz->offset Username2gids
 ✅      ShellIndex            len(shells)*2    Shell index array
 ✅      ShellBlob             <= 4032          Shell data blob (max 63*64 bytes)
-        Groups                ?                packed Group entries (8b padding)
+✅      Groups                ?                packed Group entries (8b padding)
 ✅      Users                 ?                packed User entries (8b padding)
         Groupmembers          ?                per-group memberlist (32b padding)
         Username2gids         ?                Per-user gidlist entries (8b padding)

src/compress.zig

@@ -13,7 +13,7 @@ pub const Varint = struct {
     bytesRead: usize,
 };
 
-const MaxVarintLen64 = 10;
+const maxVarintLen64 = 10;
 
 // https://golang.org/pkg/encoding/binary/#Uvarint
 pub fn uvarint(buf: []const u8) error{Overflow}!Varint {
@@ -21,14 +21,14 @@ pub fn uvarint(buf: []const u8) error{Overflow}!Varint {
     var s: u6 = 0;
 
     for (buf) |b, i| {
-        if (i == MaxVarintLen64) {
+        if (i == maxVarintLen64) {
-            // Catch byte reads past MaxVarintLen64.
+            // Catch byte reads past maxVarintLen64.
             // See issue https://golang.org/issues/41185
             return error.Overflow;
         }
 
         if (b < 0x80) {
-            if (i == MaxVarintLen64 - 1 and b > 1) {
+            if (i == maxVarintLen64 - 1 and b > 1) {
                 return error.Overflow;
             }
             return Varint{ .value = x | (@as(u64, b) << s), .bytesRead = i + 1 };
@@ -80,7 +80,7 @@ const tests = [_]u64{
 
 test "uvarint" {
     for (tests) |x| {
-        var buf: [MaxVarintLen64]u8 = undefined;
+        var buf: [maxVarintLen64]u8 = undefined;
         const n = putUvarint(buf[0..], x);
         const got = try uvarint(buf[0..n]);
 
@@ -89,10 +89,6 @@ test "uvarint" {
     }
 }
 
-const overflowTest = struct {
-    arr: []const u8,
-};
-
 test "overflow" {
     for ([_][]const u8{
         &[_]u8{ 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x2 },

src/group.zig

@@ -1,15 +1,114 @@
 const std = @import("std");
 
-const PackedGroup = packed struct {
+const pad = @import("padding.zig");
-    gid: u32,
+const validate = @import("validate.zig");
-    members_offset: u27,
+const InvalidRecord = validate.InvalidRecord;
-    groupname_len: u5,
+
-};
+const mem = std.mem;
+const Allocator = mem.Allocator;
+const ArrayList = std.ArrayList;
 
 const Group = struct {
     gid: u32,
     name: []const u8,
-    members: std.BufSet,
+    members_offset: u32,
+};
+
+const PackedGroup = struct {
+    const alignmentBits = 3;
+
+    const Inner = packed struct {
+        gid: u32,
+        members_offset: u32,
+        groupname_len: u8,
+
+        pub fn groupnameLen(self: *const Inner) usize {
+            return self.groupname_len + 1;
+        }
+    };
+
+    inner: *const Inner,
+    groupdata: []const u8,
+
+    pub const Entry = struct {
+        group: PackedGroup,
+        next: ?[]const u8,
+    };
+
+    pub fn fromBytes(bytes: []const u8) Entry {
+        const inner = mem.bytesAsValue(Inner, bytes[0..@sizeOf(Inner)]);
+        const endBlob = @sizeOf(Inner) + inner.groupnameLen();
+        const nextStart = pad.roundUp(usize, alignmentBits, endBlob);
+
+        var next: ?[]const u8 = null;
+        if (nextStart < bytes.len) {
+            next = bytes[nextStart..];
+        }
+
+        return Entry{
+            .group = PackedGroup{
+                .inner = inner,
+                .groupdata = bytes[@sizeOf(Inner)..endBlob],
+            },
+            .next = next,
+        };
+    }
+
+    const packErr = validate.InvalidRecord || Allocator.Error;
+    fn validateUtf8(s: []const u8) InvalidRecord!void {
+        if (!std.unicode.utf8ValidateSlice(s)) {
+            return error.InvalidRecord;
+        }
+    }
+
+    pub const Iterator = struct {
+        section: ?[]const u8,
+
+        pub fn next(it: *Iterator) ?PackedGroup {
+            if (it.section) |section| {
+                const entry = fromBytes(section);
+                it.section = entry.next;
+                return entry.group;
+            }
+            return null;
+        }
+    };
+
+    pub fn iterator(section: []const u8) Iterator {
+        return Iterator{ .section = section };
+    }
+
+    pub fn gid(self: *const PackedGroup) u32 {
+        return self.inner.gid;
+    }
+
+    pub fn membersOffset(self: *const PackedGroup) u32 {
+        return self.inner.members_offset;
+    }
+
+    pub fn name(self: *const PackedGroup) []const u8 {
+        return self.groupdata;
+    }
+
+    pub fn packTo(
+        arr: *ArrayList(u8),
+        group: Group,
+    ) packErr!void {
+        const groupname_len = try validate.downCast(u5, group.name.len - 1);
+
+        try validate.utf8(group.name);
+
+        const inner = Inner{
+            .gid = group.gid,
+            .members_offset = group.members_offset,
+            .groupname_len = groupname_len,
+        };
+
+        try arr.*.appendSlice(mem.asBytes(&inner));
+        try arr.*.appendSlice(group.name);
+
+        try pad.arrayList(arr, alignmentBits);
+    }
 };
 
 const testing = std.testing;
@@ -17,3 +116,36 @@ const testing = std.testing;
 test "PackedGroup alignment" {
     try testing.expectEqual(@sizeOf(PackedGroup) * 8, @bitSizeOf(PackedGroup));
 }
+
+test "construct PackedGroups" {
+    var buf = ArrayList(u8).init(testing.allocator);
+    defer buf.deinit();
+
+    const groups = [_]Group{
+        Group{
+            .gid = 1000,
+            .name = "sudo",
+            .members_offset = 1,
+        },
+        Group{
+            .gid = std.math.maxInt(u32),
+            .name = "Name" ** 8, // 32
+            .members_offset = std.math.maxInt(u32),
+        },
+    };
+
+    for (groups) |group| {
+        try PackedGroup.packTo(&buf, group);
+    }
+
+    var i: u29 = 0;
+    {
+        var it = PackedGroup.iterator(buf.items);
+        while (it.next()) |group| : (i += 1) {
+            try testing.expectEqual(groups[i].gid, group.gid());
+            try testing.expectEqualStrings(groups[i].name, group.name());
+            try testing.expectEqual(groups[i].members_offset, group.membersOffset());
+        }
+        try testing.expectEqual(groups.len, i);
+    }
+}

src/test_main.zig

@@ -4,8 +4,9 @@ test "turbonss test suite" {
     _ = @import("header.zig");
     _ = @import("user.zig");
     _ = @import("group.zig");
+    _ = @import("validate.zig");
     _ = @import("padding.zig");
-    _ = @import("varint.zig");
+    _ = @import("compress.zig");
     _ = @import("cmph.zig");
     _ = @import("bdz.zig");
 }

src/user.zig

@@ -1,11 +1,13 @@
 const std = @import("std");
+
 const pad = @import("padding.zig");
+const validate = @import("validate.zig");
+const InvalidRecord = validate.InvalidRecord;
 
 const assert = std.debug.assert;
 const mem = std.mem;
 const Allocator = mem.Allocator;
 const ArrayList = std.ArrayList;
-
 // Idx2ShellProto is a function prototype that, given a shell's index (in
 // global shell section), will return a shell string. Matches ShellReader.get.
 const Idx2ShellProto = fn (u6) []const u8;
@@ -28,20 +30,20 @@ fn packedUser(immutable: bool) type {
     return struct {
         const Self = @This();
 
-        const AlignmentBits = 3;
+        const alignmentBits = 3;
         const shell2idxProto = fn ([]const u8) ?u6;
 
         const InnerSize = @divExact(@bitSizeOf(Inner), 8);
         const Inner = packed struct {
             uid: u32,
             gid: u32,
-            shell_here: bool,
+            additional_gids_offset: u29,
             shell_len_or_idx: u6,
+            shell_here: bool,
             home_len: u6,
             name_is_a_suffix: bool,
             name_len: u5,
             gecos_len: u8,
-            additional_gids_offset: u29,
 
             fn homeLen(self: *const Inner) usize {
                 return @as(u32, self.home_len) + 1;
@@ -118,7 +120,7 @@ fn packedUser(immutable: bool) type {
             const startBlob = InnerSize;
             const endBlob = startBlob + inner.blobLength();
 
-            const nextStart = pad.roundUp(usize, AlignmentBits, endBlob);
+            const nextStart = pad.roundUp(usize, alignmentBits, endBlob);
             var next: ?Bytes = null;
             if (nextStart < bytes.len) {
                 next = bytes[nextStart..];
@@ -133,25 +135,31 @@ fn packedUser(immutable: bool) type {
             };
         }
 
-        pub const errInvalid = error{InvalidRecord};
+        pub const Iterator = struct {
-        fn downCast(comptime T: type, n: u64) errInvalid!T {
+            section: ?Bytes,
-            return std.math.cast(T, n) catch |err| switch (err) {
+            shellIndex: Idx2ShellProto,
-                error.Overflow => {
-                    return error.InvalidRecord;
-                },
-            };
-        }
 
-        fn validateUtf8(s: []const u8) errInvalid!void {
+            pub fn next(it: *Iterator) ?Self {
-            if (!std.unicode.utf8ValidateSlice(s)) {
+                if (it.section) |section| {
-                return error.InvalidRecord;
+                    const entry = Self.fromBytes(section);
+                    it.section = entry.next;
+                    return entry.user;
+                }
+                return null;
             }
+        };
+
+        pub fn iterator(section: Bytes, idxFn: Idx2ShellProto) Iterator {
+            return Iterator{
+                .section = section,
+                .shellIndex = idxFn,
+            };
         }
 
         // packTo packs the User record and copies it to the given byte slice. The
         // slice must have at least maxRecordSize() bytes available.
         // The slice is passed as a pointer, so it can be mutated.
-        const packErr = errInvalid || Allocator.Error;
+        const packErr = InvalidRecord || Allocator.Error;
         pub fn packTo(
             arr: *ArrayList(u8),
             user: User,
@@ -159,15 +167,15 @@ fn packedUser(immutable: bool) type {
         ) packErr!void {
             // function arguments are consts. We need to mutate the underlying
             // slice, so passing it via pointer instead.
-            const home_len = try downCast(u6, user.home.len - 1);
+            const home_len = try validate.downCast(u6, user.home.len - 1);
-            const name_len = try downCast(u5, user.name.len - 1);
+            const name_len = try validate.downCast(u5, user.name.len - 1);
-            const shell_len = try downCast(u6, user.shell.len - 1);
+            const shell_len = try validate.downCast(u6, user.shell.len - 1);
-            const gecos_len = try downCast(u8, user.gecos.len);
+            const gecos_len = try validate.downCast(u8, user.gecos.len);
 
-            try validateUtf8(user.home);
+            try validate.utf8(user.home);
-            try validateUtf8(user.name);
+            try validate.utf8(user.name);
-            try validateUtf8(user.shell);
+            try validate.utf8(user.shell);
-            try validateUtf8(user.gecos);
+            try validate.utf8(user.gecos);
 
             const inner = Inner{
                 .uid = user.uid,
@@ -196,7 +204,7 @@ fn packedUser(immutable: bool) type {
                 try arr.*.appendSlice(user.shell);
             }
 
-            try pad.arrayList(arr, AlignmentBits);
+            try pad.arrayList(arr, alignmentBits);
         }
 
         // maxSize is the maximum number of records a PackedUser can take
@@ -208,7 +216,7 @@ fn packedUser(immutable: bool) type {
                     std.math.maxInt(u5) + 1 + // name
                     std.math.maxInt(u6) + 1 + // shell
                     std.math.maxInt(u8); // gecos
-                return pad.roundUp(u64, AlignmentBits, unpadded);
+                return pad.roundUp(u64, alignmentBits, unpadded);
             }
         }
 
@@ -256,34 +264,13 @@ fn packedUser(immutable: bool) type {
             }
             self.inner.additional_gids_offset = new;
         }
-
-        pub const Iterator = struct {
-            section: ?Bytes,
-            shellIndex: Idx2ShellProto,
-
-            pub fn next(it: *Iterator) ?Self {
-                if (it.section) |section| {
-                    const entry = Self.fromBytes(section);
-                    it.section = entry.next;
-                    return entry.user;
-                }
-                return null;
-            }
-        };
-
-        pub fn iterator(section: Bytes, idxFn: Idx2ShellProto) Iterator {
-            return Iterator{
-                .section = section,
-                .shellIndex = idxFn,
-            };
-        }
     };
 }
 
 const testing = std.testing;
 
 test "PackedUser internal and external alignment" {
-    // External padding (AlignmentBits) must be higher or equal to
+    // External padding (alignmentBits) must be higher or equal to
     // the "internal" PackedUser alignment. By aligning PackedUser we are also
     // working around https://github.com/ziglang/zig/issues/10958 ; PackedUser
     // cannot be converted from/to [@bitSizeOf(PackedUser)/8]u8;
@@ -349,7 +336,6 @@ test "construct PackedUser section" {
     var i: u29 = 0;
     {
         var it = PackedUserConst.iterator(buf.items, testShell);
-        i = 0;
         while (it.next()) |user| : (i += 1) {
             try testing.expectEqual(users[i].uid, user.uid());
             try testing.expectEqual(users[i].gid, user.gid());

src/validate.zig

@@ -0,0 +1,17 @@
+const std = @import("std");
+
+pub const InvalidRecord = error{InvalidRecord};
+
+pub fn downCast(comptime T: type, n: u64) InvalidRecord!T {
+    return std.math.cast(T, n) catch |err| switch (err) {
+        error.Overflow => {
+            return error.InvalidRecord;
+        },
+    };
+}
+
+pub fn utf8(s: []const u8) InvalidRecord!void {
+    if (!std.unicode.utf8ValidateSlice(s)) {
+        return error.InvalidRecord;
+    }
+}