use omit_members sometimes

src/DB.zig

@@ -279,6 +279,28 @@ pub fn fromBytes(buf: []align(8) const u8) InvalidHeader!DB {
     return result;
 }
 
+pub fn packCGroupNoMembers(group: PackedGroup, buf: []u8) error{BufferTooSmall}!CGroup {
+    // first word in buf will be a pointer to null. that probably can be
+    // simplified by writing (0)**word_size to the buffer, but let's pretend
+    // type safety for a moment.
+    const name_start = @sizeOf(?[*:0]const u8);
+    if (name_start > buf.len) return error.BufferTooSmall;
+    var member_ptrs = mem.bytesAsSlice(?[*:0]const u8, buf[0..name_start]);
+    member_ptrs[0] = null;
+
+    // write name
+    const name = group.name();
+    if (name_start + name.len + 1 > buf.len) return error.BufferTooSmall;
+    mem.copy(u8, buf[name_start..], name);
+    buf[name_start + name.len] = 0;
+
+    return CGroup{
+        .gid = group.gid(),
+        .name = buf[name_start .. name_start + name.len :0].ptr,
+        .members = member_ptrs.ptr,
+    };
+}
+
 // dumps PackedGroup to []u8 and returns a CGroup.
 pub fn packCGroup(self: *const DB, group: PackedGroup, buf: []u8) error{BufferTooSmall}!CGroup {
     const members_slice = self.groupmembers[group.members_offset..];
@@ -321,25 +343,41 @@ pub fn packCGroup(self: *const DB, group: PackedGroup, buf: []u8) error{BufferTo
 }
 
 // get a CGroup entry by name.
-pub fn getgrnam(self: *const DB, name: []const u8, buf: []u8) error{BufferTooSmall}!?CGroup {
+pub fn getgrnam(
+    self: *const DB,
+    name: []const u8,
+    buf: []u8,
+    omit_members: bool,
+) error{BufferTooSmall}!?CGroup {
     const idx = bdz.search(self.bdz_groupname, name);
     if (idx >= self.header.num_groups) return null;
     const offset = self.idx_groupname2group[idx];
     const nbits = PackedGroup.alignment_bits;
     const group = PackedGroup.fromBytes(self.groups[offset << nbits ..]).group;
     if (!mem.eql(u8, name, group.name())) return null;
-    return try self.packCGroup(group, buf);
+    return if (omit_members)
+        try packCGroupNoMembers(group, buf)
+    else
+        try self.packCGroup(group, buf);
 }
 
 // get a CGroup entry by it's gid.
-pub fn getgrgid(self: *const DB, gid: u32, buf: []u8) error{BufferTooSmall}!?CGroup {
+pub fn getgrgid(
+    self: *const DB,
+    gid: u32,
+    buf: []u8,
+    omit_members: bool,
+) error{BufferTooSmall}!?CGroup {
     const idx = bdz.search_u32(self.bdz_gid, gid);
     if (idx >= self.header.num_groups) return null;
     const offset = self.idx_gid2group[idx];
     const nbits = PackedGroup.alignment_bits;
     const group = PackedGroup.fromBytes(self.groups[offset << nbits ..]).group;
     if (gid != group.gid()) return null;
-    return try self.packCGroup(group, buf);
+    return if (omit_members)
+        try packCGroupNoMembers(group, buf)
+    else
+        try self.packCGroup(group, buf);
 }
 
 fn pushStr(str: []const u8, buf: []u8, offset: *usize) [*:0]const u8 {
@@ -708,8 +746,8 @@ test "getgrnam/getgrgid" {
     defer testing.allocator.free(buf);
 
     {
-        try testing.expectEqual(try db.getgrnam("doesnotexist", buf), null);
+        try testing.expectEqual(try db.getgrnam("doesnotexist", buf, false), null);
-        const all = (try db.getgrnam("all", buf)).?;
+        const all = (try db.getgrnam("all", buf, false)).?;
         try testing.expectEqual(all.gid, 9999);
         try testing.expectEqualStrings(all.name[0..4], "all\x00");
         const members = all.members;
@@ -721,16 +759,23 @@ test "getgrnam/getgrgid" {
     }
 
     {
-        try testing.expectEqual(try db.getgrgid(42, buf), null);
+        const all = (try db.getgrnam("all", buf, true)).?;
-        const all = (try db.getgrgid(9999, buf)).?;
+        try testing.expectEqual(all.gid, 9999);
+        try testing.expectEqualStrings(all.name[0..4], "all\x00");
+        try testing.expectEqual(all.members[0], null);
+    }
+
+    {
+        try testing.expectEqual(try db.getgrgid(42, buf, false), null);
+        const all = (try db.getgrgid(9999, buf, false)).?;
         try testing.expectEqual(all.gid, 9999);
         try testing.expectEqualStrings(all.name[0..3], "all");
     }
     try testing.expectEqualStrings("", errc.unwrap().constSlice());
 
-    _ = try db.getgrnam("all", buf);
+    _ = try db.getgrnam("all", buf, false);
     buf.len -= 1;
-    try testing.expectError(error.BufferTooSmall, db.getgrnam("all", buf));
+    try testing.expectError(error.BufferTooSmall, db.getgrnam("all", buf, false));
 }
 
 test "getpwnam/getpwuid" {

src/libnss.zig

@@ -160,8 +160,12 @@ export fn _nss_turbo_getgrgid_r(
     buflen: usize,
     errnop: *c_int,
 ) c.enum_nss_status {
-    const db = getDBErrno(errnop) orelse return c.NSS_STATUS_UNAVAIL;
+    const state = getStateErrno(errnop) orelse return c.NSS_STATUS_UNAVAIL;
-    var cgroup = db.getgrgid(gid, buffer[0..buflen]) catch |err| switch (err) {
+    const db = state.file.db;
+    const omit_members = state.omit_members;
+
+    var buf = buffer[0..buflen];
+    var cgroup = db.getgrgid(gid, buf, omit_members) catch |err| switch (err) {
         error.BufferTooSmall => {
             errnop.* = @enumToInt(os.E.RANGE);
             return c.NSS_STATUS_TRYAGAIN;
@@ -184,10 +188,13 @@ export fn _nss_turbo_getgrnam_r(
     buflen: usize,
     errnop: *c_int,
 ) c.enum_nss_status {
-    const db = getDBErrno(errnop) orelse return c.NSS_STATUS_UNAVAIL;
+    const state = getStateErrno(errnop) orelse return c.NSS_STATUS_UNAVAIL;
+    const db = state.file.db;
+    const omit_members = state.omit_members;
+
     const nameSlice = mem.sliceTo(name, 0);
     var buf = buffer[0..buflen];
-    var cgroup = db.getgrnam(nameSlice, buf) catch |err| switch (err) {
+    var cgroup = db.getgrnam(nameSlice, buf, omit_members) catch |err| switch (err) {
         error.BufferTooSmall => {
             errnop.* = @enumToInt(os.E.RANGE);
             return c.NSS_STATUS_TRYAGAIN;
@@ -267,16 +274,20 @@ export fn _nss_turbo_getgrent_r(
         return c.NSS_STATUS_NOTFOUND;
     };
 
-    const buf = buffer[0..buflen];
+    const cgroup1 = if (state.omit_members)
-    const cgroup = state.file.db.packCGroup(group, buf) catch |err| switch (err) {
+        DB.packCGroupNoMembers(group, buffer[0..buflen])
+    else
+        state.file.db.packCGroup(group, buffer[0..buflen]);
+
+    if (cgroup1) |cgroup| {
+        result.* = cgroup;
+        return c.NSS_STATUS_SUCCESS;
+    } else |err| switch (err) {
         error.BufferTooSmall => {
             errnop.* = @enumToInt(os.E.RANGE);
             return c.NSS_STATUS_TRYAGAIN;
         },
-    };
+    }
-
-    result.* = cgroup;
-    return c.NSS_STATUS_SUCCESS;
 }
 
 export fn _nss_turbo_getpwent_r(