1 files changed, 21 insertions, 0 deletions
diff --git a/include/unicode/predicate.h b/include/unicode/predicate.h
new file mode 100644
index 0000000..5f8c6a4
--- /dev/null
+++ b/include/unicode/predicate.h
@@ -0,0 +1,21 @@
+#pragma once
+
+namespace unicode {
+
+ // bits_to_compare: limit bits to consider even further than defined by T
+ // T: usually, char32_t, uint32_t etc.
+ template<size_t bits_to_compare = 32, typename T>
+ static inline bool is_valid_unicode(const T& value) noexcept
+ {
+  if constexpr(sizeof(T) == 1 || bits_to_compare <= 15)
+   return true;
+  else if constexpr(sizeof(T) == 2 || bits_to_compare <= 20)
+   //return value <= 0xD7FF || value >= 0xE000;
+   return (value & 0xF800) != 0xD800;
+  else
+   //return (value & 0xFFFFF800) != 0x0000D800 && (value >> 16) <= 0x10;
+   return value <= 0xD7FF || (value >= 0xE000 && value <= 0x10FFFF);
+ }
+
+} // namespace unicode
+