feat: add matchExact to the APIi

TODO: write doc comment

src/lib.zig

@@ -121,8 +121,6 @@ pub fn extract(comptime bit_string: []const u8, value: anytype) Bitfield(bit_str
     };
     comptime verify(ValT, bit_string);
 
-    std.debug.assert(match(bit_string, value)); // prevents branchless impl in ReleaseSafe
-
     var ret: ReturnT = undefined;
 
     inline for (@typeInfo(ReturnT).Struct.fields) |field| {
@@ -148,6 +146,11 @@ pub fn extract(comptime bit_string: []const u8, value: anytype) Bitfield(bit_str
     return ret;
 }
 
+pub fn matchExtract(comptime bit_string: []const u8, value: anytype) ?Bitfield(bit_string) {
+    if (!match(bit_string, value)) return null;
+    return extract(bit_string, value);
+}
+
 test "extract" {
     // doc tests
     {