3 files changed, 62 insertions, 6 deletions
diff --git a/src/base/Osx.cpp b/src/base/Osx.cpp
index 46b923fe..d979f542 100644
--- a/src/base/Osx.cpp
+++ b/src/base/Osx.cpp
@@ -1,19 +1,22 @@
 #include "cru/base/Osx.h"
+#include "cru/base/StringUtil.h"
 
 namespace cru {
-CFWrapper<CFStringRef> ToCFString(StringView string) {
+CFWrapper<CFStringRef> ToCFString(std::string_view string) {
   return CFWrapper<CFStringRef>(CFStringCreateWithBytes(
       nullptr, reinterpret_cast<const UInt8*>(string.data()),
-      string.size() * sizeof(std::uint16_t), kCFStringEncodingUTF16, false));
+      string.size() * sizeof(char), kCFStringEncodingUTF8, false));
 }
 
-String FromCFStringRef(CFStringRef string) {
+std::string FromCFStringRef(CFStringRef string) {
   auto length = CFStringGetLength(string);
 
-  String result;
+  std::string result;
 
   for (int i = 0; i < length; i++) {
-    result.AppendCodePoint(CFStringGetCharacterAtIndex(string, i));
+    cru::string::Utf8EncodeCodePointAppend(
+        CFStringGetCharacterAtIndex(string, i),
+        [&result](char c) { result += c; });
   }
 
   return result;
diff --git a/src/base/StringUtil.cpp b/src/base/StringUtil.cpp
index 581ebcab..4cd662d1 100644
--- a/src/base/StringUtil.cpp
+++ b/src/base/StringUtil.cpp
@@ -357,4 +357,51 @@ Index Utf16NextWord(const Utf16CodeUnit* ptr, Index size, Index position,
       ptr, size, position, is_space);
 }
 
+template <typename CharType,
+          NextCodePointFunctionType<CharType> NextCodePointFunction>
+static Index IndexCodeUnitToCodePoint(const CharType* ptr, Index size,
+                                      Index position) {
+  CodePointIterator<CharType, NextCodePointFunction> iter(ptr, size);
+  Index result = 0;
+  while (!iter.IsPastEnd() && iter.GetPosition() < position) {
+    ++iter;
+    ++result;
+  }
+  return result;
+}
+
+template <typename CharType,
+          NextCodePointFunctionType<CharType> NextCodePointFunction>
+static Index IndexCodePointToCodeUnit(const CharType* ptr, Index size,
+                                      Index position) {
+  CodePointIterator<CharType, NextCodePointFunction> iter(ptr, size);
+  for (Index i = 0; i < position; i++) {
+    ++iter;
+  }
+  return iter.GetPosition();
+}
+
+Index Utf8IndexCodeUnitToCodePoint(const Utf8CodeUnit* ptr, Index size,
+                                   Index position) {
+  return IndexCodeUnitToCodePoint<Utf8CodeUnit, Utf8NextCodePoint>(ptr, size,
+                                                                   position);
+}
+
+Index Utf8IndexCodePointToCodeUnit(const Utf8CodeUnit* ptr, Index size,
+                                   Index position) {
+  return IndexCodePointToCodeUnit<Utf8CodeUnit, Utf8NextCodePoint>(ptr, size,
+                                                                   position);
+}
+
+Index Utf16IndexCodeUnitToCodePoint(const Utf16CodeUnit* ptr, Index size,
+                                    Index position) {
+  return IndexCodeUnitToCodePoint<Utf16CodeUnit, Utf16NextCodePoint>(ptr, size,
+                                                                     position);
+}
+Index Utf16IndexCodePointToCodeUnit(const Utf16CodeUnit* ptr, Index size,
+                                    Index position) {
+  return IndexCodePointToCodeUnit<Utf16CodeUnit, Utf16NextCodePoint>(ptr, size,
+                                                                     position);
+}
+
 }  // namespace cru::string
diff --git a/src/base/io/Stream.cpp b/src/base/io/Stream.cpp
index 1aafc839..e07f2899 100644
--- a/src/base/io/Stream.cpp
+++ b/src/base/io/Stream.cpp
@@ -1,7 +1,9 @@
 #include "cru/base/io/Stream.h"
 #include "cru/base/Exception.h"
 
+#include <algorithm>
 #include <format>
+#include <iterator>
 #include <utility>
 
 namespace cru::io {
@@ -193,6 +195,10 @@ Buffer Stream::ReadToEnd(Index grow_size) {
 
 std::string Stream::ReadToEndAsUtf8String() {
   auto buffer = ReadToEnd();
-  return std::string(buffer.GetUsedBeginPtr(), buffer.GetUsedEndPtr());
+  std::string result;
+  std::transform(buffer.GetUsedBeginPtr(), buffer.GetUsedEndPtr(),
+                 std::back_inserter(result),
+                 [](std::byte c) { return static_cast<char>(c); });
+  return result;
 }
 }  // namespace cru::io