4 files changed, 61 insertions, 7 deletions
diff --git a/include/cru/common/Exception.hpp b/include/cru/common/Exception.hpp
index 861bf5e9..8864f4df 100644
--- a/include/cru/common/Exception.hpp
+++ b/include/cru/common/Exception.hpp
@@ -18,4 +18,9 @@ class CRU_BASE_API Exception {
  private:
   String message_;
 };
+
+class CRU_BASE_API TextEncodeException : public Exception {
+ public:
+  using Exception::Exception;
+};
 }  // namespace cru
diff --git a/include/cru/common/Range.hpp b/include/cru/common/Range.hpp
new file mode 100644
index 00000000..ecc61243
--- /dev/null
+++ b/include/cru/common/Range.hpp
@@ -0,0 +1,43 @@
+#pragma once
+#include "Base.hpp"
+
+namespace cru {
+struct Range final {
+  constexpr static Range FromTwoSides(gsl::index start, gsl::index end) {
+    return Range(start, end - start);
+  }
+
+  constexpr static Range FromTwoSides(gsl::index start, gsl::index end,
+                                      gsl::index offset) {
+    return Range(start + offset, end - start);
+  }
+
+  constexpr Range() = default;
+  constexpr Range(const gsl::index position, const gsl::index count = 0)
+      : position(position), count(count) {}
+
+  gsl::index GetStart() const { return position; }
+  gsl::index GetEnd() const { return position + count; }
+
+  void ChangeEnd(gsl::index new_end) { count = new_end - position; }
+
+  Range Normalize() const {
+    auto result = *this;
+    if (result.count < 0) {
+      result.position += result.count;
+      result.count = -result.count;
+    }
+    return result;
+  }
+
+  Range CoerceInto(gsl::index min, gsl::index max) const {
+    auto coerce = [min, max](gsl::index index) {
+      return index > max ? max : (index < min ? min : index);
+    };
+    return Range::FromTwoSides(coerce(GetStart()), coerce(GetEnd()));
+  }
+
+  gsl::index position = 0;
+  gsl::index count = 0;
+};
+}  // namespace cru
diff --git a/include/cru/common/String.hpp b/include/cru/common/String.hpp
index 563e1606..4211a160 100644
--- a/include/cru/common/String.hpp
+++ b/include/cru/common/String.hpp
@@ -1,7 +1,9 @@
 #pragma once
-
 #include "Base.hpp"
 
+#include "StringUtil.hpp"
+#include "Range.hpp"
+
 #include <cstdint>
 #include <iterator>
 
@@ -127,6 +129,16 @@ class CRU_BASE_API String {
   }
 
  public:
+  Utf16CodePointIterator CodePointIterator() const {
+    return Utf16CodePointIterator(
+        std::u16string_view(reinterpret_cast<char16_t*>(buffer_), size_));
+  }
+
+  Index IndexFromCodeUnitToCodePoint(Index code_unit_index) const;
+  Index IndexFromCodePointToCodeUnit(Index code_point_index) const;
+  Range RangeFromCodeUnitToCodePoint(Range code_unit_range) const;
+  Range RangeFromCodePointToCodeUnit(Range code_point_range) const;
+
   const char16_t* Char16CStr() const {
     return reinterpret_cast<const char16_t*>(c_str());
   }
diff --git a/include/cru/common/StringUtil.hpp b/include/cru/common/StringUtil.hpp
index 985f0032..5c230898 100644
--- a/include/cru/common/StringUtil.hpp
+++ b/include/cru/common/StringUtil.hpp
@@ -1,6 +1,5 @@
 #pragma once
 #include "Base.hpp"
-#include "Exception.hpp"
 
 #include <functional>
 #include <string>
@@ -10,11 +9,6 @@ namespace cru {
 using CodePoint = std::int32_t;
 constexpr CodePoint k_invalid_code_point = -1;
 
-class CRU_BASE_API TextEncodeException : public Exception {
- public:
-  using Exception::Exception;
-};
-
 inline bool IsUtf16SurrogatePairCodeUnit(char16_t c) {
   return c >= 0xD800 && c <= 0xDFFF;
 }