1 files changed, 80 insertions, 1 deletions
diff --git a/include/cru/win/string.hpp b/include/cru/win/string.hpp
index 7a12e47e..75395052 100644
--- a/include/cru/win/string.hpp
+++ b/include/cru/win/string.hpp
@@ -1,10 +1,89 @@
+/*
+Because the text encoding problem on Windows, here I write some functions
+related to text encoding. The utf-8 and utf-16 conversion function is provided
+by win32 api. However win32 api does not provide any function about charactor
+iteration or index by code point. (At least I haven't found.) I don't use icu
+because it is not easy to build it on Windows and the bundled version in Windows
+(https://docs.microsoft.com/en-us/windows/win32/intl/international-components-for-unicode--icu-)
+is only available after Windows 10 Creators Update.
+
+Luckily, both utf-8 and utf-16 encoding are easy to learn and program with if we
+only do simple iteration rather than do much sophisticated work about
+complicated error situations. (And I learn the internal of the encoding by the
+way.)
+*/
+
 #pragma once
 #include "win_pre_config.hpp"
 
+#include "cru/common/base.hpp"
+
+#include <cstdint>
+#include <stdexcept>
 #include <string>
 #include <string_view>
 
 namespace cru::platform::win {
 std::string ToUtf8String(const std::wstring_view& string);
 std::wstring ToUtf16String(const std::string_view& string);
-}
+
+using CodePoint = std::int32_t;
+constexpr CodePoint k_code_point_end = -1;
+
+class TextEncodeException : public std::runtime_error {
+ public:
+  using runtime_error::runtime_error;
+};
+
+class Utf8Iterator : public Object {
+ public:
+  Utf8Iterator(const std::string_view& string) : string_(string) {}
+
+  CRU_DEFAULT_COPY(Utf8Iterator)
+  CRU_DEFAULT_MOVE(Utf8Iterator)
+
+  ~Utf8Iterator() = default;
+
+ public:
+  void SetToHead() { position_ = 0; }
+
+  // Advance current position and get next code point. Return k_code_point_end
+  // if there is no next code unit(point). Throw TextEncodeException if decoding
+  // fails.
+  CodePoint Next();
+
+  int CurrentPosition() const { return this->position_; }
+
+ private:
+  std::string_view string_;
+  int position_ = 0;
+};
+
+class Utf16Iterator : public Object {
+  static_assert(sizeof(wchar_t) == 2,
+                "Emmm, according to my knowledge, wchar_t should be 2-length on "
+                "Windows. If not, Utf16 will be broken.");
+
+ public:
+  Utf16Iterator(const std::wstring_view& string) : string_(string) {}
+
+  CRU_DEFAULT_COPY(Utf16Iterator)
+  CRU_DEFAULT_MOVE(Utf16Iterator)
+
+  ~Utf16Iterator() = default;
+
+ public:
+  void SetToHead() { position_ = 0; }
+
+  // Advance current position and get next code point. Return k_code_point_end
+  // if there is no next code unit(point). Throw TextEncodeException if decoding
+  // fails.
+  CodePoint Next();
+
+  int CurrentPosition() const { return this->position_; }
+
+ private:
+  std::wstring_view string_;
+  int position_ = 0;
+};
+}  // namespace cru::platform::win