storing getgr_max and getpw_max

lib/Corpus.zig

@@ -26,6 +26,9 @@ name2group: StringHashMap(u32),
 group2users: []const []const u32,
 user2groups: []const []const u32,
 
+getgr_max: usize,
+getpw_max: usize,
+
 pub fn init(
     baseAllocator: Allocator,
     usersConst: []const User,
@@ -38,12 +41,18 @@ pub fn init(
     var allocator = arena.allocator();
     errdefer arena.deinit();
 
-    var users_arr = try allocator.alloc(User, usersConst.len);
     var groups_arr = try allocator.alloc(Group, groupsConst.len);
-    for (usersConst) |*user, i|
-        users_arr[i] = try user.clone(allocator);
-    for (groupsConst) |*group, i|
+    var users_arr = try allocator.alloc(User, usersConst.len);
+    var getgr_max: usize = 0;
+    for (groupsConst) |*group, i| {
         groups_arr[i] = try group.clone(allocator);
+        getgr_max = math.max(getgr_max, groups_arr[i].strlenZ());
+    }
+    var getpw_max: usize = 0;
+    for (usersConst) |*user, i| {
+        users_arr[i] = try user.clone(allocator);
+        getpw_max = math.max(getpw_max, users_arr[i].strlenZ());
+    }
 
     sort.sort(User, users_arr, {}, cmpUser);
     sort.sort(Group, groups_arr, {}, cmpGroup);
@@ -114,6 +123,8 @@ pub fn init(
         .name2group = name2group,
         .group2users = group2users,
         .user2groups = user2groups_final,
+        .getgr_max = getgr_max,
+        .getpw_max = getpw_max,
     };
 }
 

lib/DB.zig

@@ -119,8 +119,8 @@ pub fn fromCorpus(
         .nblocks_users = nblocks(u64, users.blob),
         .nblocks_groupmembers = nblocks(u64, groupmembers.blob),
         .nblocks_additional_gids = nblocks(u64, additional_gids.blob),
-        .getgr_max = 0,
-        .getpw_max = 0,
+        .getgr_max = corpus.getgr_max,
+        .getpw_max = corpus.getpw_max,
     };
 
     return DB{

lib/Group.zig

@@ -54,6 +54,13 @@ pub fn deinit(self: *Group, allocator: Allocator) void {
     self.* = undefined;
 }
 
+// buffer size in bytes if all strings were zero-terminated.
+pub fn strlenZ(self: *const Group) usize {
+    return self._buf.len +
+        self.members.len + // each membername sentinel
+        1; // name sentinel
+}
+
 const testing = std.testing;
 
 test "Group.clone" {

lib/User.zig

@@ -103,6 +103,14 @@ fn strlen(self: *const User) usize {
         self.shell.len;
 }
 
+// length of all string-data fields, assuming they are zero-terminated.
+// Includes one character for "password".
+pub fn strlenZ(self: *const User) usize {
+    return self.strlen() +
+        4 + // '\0' of name, gecos, home and shell
+        2; // password: 'x\0'
+}
+
 pub fn deinit(self: *User, allocator: Allocator) void {
     const slice = self.home.ptr[0..self.strlen()];
     allocator.free(slice);

lib/header.zig

@@ -92,8 +92,8 @@ test "header pack and unpack" {
         .nblocks_users = 0,
         .nblocks_groupmembers = 0,
         .nblocks_additional_gids = 1,
-        .getgr_max = 0,
-        .getpw_max = 0,
+        .getgr_max = 16,
+        .getpw_max = 32,
     };
 
     const bytes = mem.asBytes(&header1);