libluna: Simplify the API for Utf8StateDecoder by splitting it into multiple methods

kernel/src/video/TextConsole.cpp

@@ -127,12 +127,12 @@ namespace TextConsole
     {
         auto guard = make_scope_guard([] { utf8_decoder.reset(); });
 
-        const Option<wchar_t> maybe_wchar = TRY(utf8_decoder.feed(c));
+        bool is_ready = TRY(utf8_decoder.feed(c));
+
+        if (is_ready) putwchar(TRY(utf8_decoder.extract()));
 
         guard.deactivate();
 
-        if (maybe_wchar.has_value()) putwchar(maybe_wchar.value());
-
         return {};
     }
 

libluna/include/luna/Utf8.h

@@ -52,13 +52,16 @@ class Utf8StateDecoder
   public:
     Utf8StateDecoder();
 
-    Result<Option<wchar_t>> feed(char c);
+    Result<bool> feed(char c);
+    Result<wchar_t> extract();
     void reset();
 
   private:
     char m_state[4];
     usize m_state_len = 0;
     usize m_state_index = 0;
+    wchar_t m_decoded_character;
+    bool m_has_character_ready { false };
 };
 
 class Utf8Encoder

libluna/src/Utf8.cpp

@@ -217,19 +217,23 @@ Utf8StateDecoder::Utf8StateDecoder() : m_state_len(0), m_state_index(0)
 {
 }
 
-Result<Option<wchar_t>> Utf8StateDecoder::feed(char c)
+Result<bool> Utf8StateDecoder::feed(char c)
 {
+    check(!m_has_character_ready);
+
     if (m_state_len == 0)
     {
         m_state_len = TRY(utf8_char_length(c));
         if (m_state_len == 1)
         {
             m_state_len = 0;
-            return Option<wchar_t> { c & 0x7f };
+            m_decoded_character = c & 0x7f;
+            m_has_character_ready = true;
+            return true;
         }
         m_state_index = 0;
         m_state[m_state_index] = c;
-        return { {} };
+        return false;
     }
 
     m_state_index++;
@@ -238,12 +242,20 @@ Result<Option<wchar_t>> Utf8StateDecoder::feed(char c)
     if (m_state_index == m_state_len - 1)
     {
         usize len = m_state_len;
-        const wchar_t wc = TRY(encode_utf8_as_wide_char(m_state, len));
+        m_decoded_character = TRY(encode_utf8_as_wide_char(m_state, len));
+        m_has_character_ready = true;
         m_state_len = 0;
-        return Option<wchar_t> { wc };
+        return true;
     }
 
-    return { {} };
+    return false;
+}
+
+Result<wchar_t> Utf8StateDecoder::extract()
+{
+    check(m_has_character_ready);
+    m_has_character_ready = false;
+    return m_decoded_character;
 }
 
 void Utf8StateDecoder::reset()