1 files changed, 17 insertions, 3 deletions
diff --git a/crates/shirabe-external-packages/src/symfony/string/byte_string.rs b/crates/shirabe-external-packages/src/symfony/string/byte_string.rs
index ab17c1e..cd8eae8 100644
--- a/crates/shirabe-external-packages/src/symfony/string/byte_string.rs
+++ b/crates/shirabe-external-packages/src/symfony/string/byte_string.rs
@@ -8,11 +8,25 @@ pub struct ByteString {
 }
 
 impl ByteString {
-    pub fn new(_string: &str) -> Self {
-        todo!()
+    pub fn new(string: &str) -> Self {
+        Self {
+            string: string.to_string(),
+        }
     }
 
-    pub fn to_code_point_string(&self, _encoding: &str) -> CodePointString {
+    pub fn to_code_point_string(&self, from_encoding: &str) -> CodePointString {
+        // The source `string` is always valid UTF-8 (Rust `String`/`&str` guarantee). PHP takes the
+        // early-return branch whenever `preg_match('//u', ...)` holds for a UTF-8/null encoding, so
+        // the result mirrors the input bytes verbatim. The `mb_detect_encoding`/`iconv` conversion
+        // path only applies to genuinely non-UTF-8 byte strings, which cannot occur here.
+        if matches!(from_encoding, "" | "utf8" | "utf-8" | "UTF8" | "UTF-8") {
+            return CodePointString {
+                string: self.string.clone(),
+            };
+        }
+
+        // TODO(phase-d): non-UTF-8 source encodings would require mb_convert_encoding/iconv-style
+        // decoding, which is unreachable for the UTF-8-only inputs Shirabe currently produces.
         todo!()
     }
 }