1 files changed, 12 insertions, 2 deletions

diff --git a/src/FoldData.zig b/src/FoldData.zig
index 139c677..2a9a1f5 100644
--- a/src/FoldData.zig
+++ b/src/FoldData.zig
@@ -5,6 +5,7 @@ const mem = std.mem;
 
 allocator: mem.Allocator,
 fold: [][]u21 = undefined,
+cwcf: []bool = undefined,
 
 const Self = @This();
 
@@ -20,18 +21,21 @@ pub fn init(allocator: mem.Allocator) !Self {
     var self = Self{
         .allocator = allocator,
         .fold = try allocator.alloc([]u21, 0x110000),
+        .cwcf = try allocator.alloc(bool, 0x110000),
     };
 
     @memset(self.fold, &.{});
+    @memset(self.cwcf, false);
 
     while (true) {
         const len: u8 = try reader.readInt(u8, endian);
         if (len == 0) break;
         const cp = try reader.readInt(u24, endian);
-        self.fold[cp] = try allocator.alloc(u21, len - 1);
+        self.fold[cp >> 1] = try allocator.alloc(u21, len - 1);
         for (0..len - 1) |i| {
-            self.fold[cp][i] = @intCast(try reader.readInt(u24, endian));
+            self.fold[cp >> 1][i] = @intCast(try reader.readInt(u24, endian));
         }
+        self.cwcf[cp >> 1] = cp & 1 == 1;
     }
 
     return self;
@@ -40,9 +44,15 @@ pub fn init(allocator: mem.Allocator) !Self {
 pub fn deinit(self: *Self) void {
     for (self.fold) |slice| self.allocator.free(slice);
     self.allocator.free(self.fold);
+    self.allocator.free(self.cwcf);
 }
 
 /// Returns the case fold for `cp`.
 pub inline fn caseFold(self: Self, cp: u21) []const u21 {
     return self.fold[cp];
 }
+
+/// Returns true when caseFold(NFD(`cp`)) != NFD(`cp`).
+pub inline fn changesWhenCaseFolded(self: Self, cp: u21) bool {
+    return self.cwcf[cp];
+}