LibCompress: Move loading XZ stream headers into its own function

Userland/Libraries/LibCompress/Xz.cpp

@@ -191,12 +191,12 @@ static Optional<size_t> size_for_check_type(XzStreamCheckType check_type)
     }
 }
 
-ErrorOr<Bytes> XzDecompressor::read_some(Bytes bytes)
+ErrorOr<bool> XzDecompressor::load_next_stream()
 {
+    // If we already determined to have found the last stream footer, there is nothing more to do.
     if (m_found_last_stream_footer)
-        return bytes.trim(0);
+        return false;
 
-    if (!m_stream_flags.has_value()) {
     // This assumes that we can just read the Stream Header into memory as-is. Check that this still holds up for good measure.
     static_assert(AK::Traits<XzStreamHeader>::is_trivially_serializable());
 
@@ -239,7 +239,7 @@ ErrorOr<Bytes> XzDecompressor::read_some(Bytes bytes)
 
         if (m_stream->is_eof()) {
             m_found_last_stream_footer = true;
-                return bytes.trim(0);
+            return false;
         }
     }
 
@@ -248,6 +248,15 @@ ErrorOr<Bytes> XzDecompressor::read_some(Bytes bytes)
 
     m_stream_flags = stream_header.flags;
     m_found_first_stream_header = true;
+
+    return true;
+}
+
+ErrorOr<Bytes> XzDecompressor::read_some(Bytes bytes)
+{
+    if (!m_stream_flags.has_value()) {
+        if (!TRY(load_next_stream()))
+            return bytes.trim(0);
     }
 
     if (!m_current_block_stream.has_value() || (*m_current_block_stream)->is_eof()) {

Userland/Libraries/LibCompress/Xz.h

@@ -111,6 +111,8 @@ public:
 private:
     XzDecompressor(NonnullOwnPtr<CountingStream>);
 
+    ErrorOr<bool> load_next_stream();
+
     NonnullOwnPtr<CountingStream> m_stream;
     Optional<XzStreamFlags> m_stream_flags;
     bool m_found_first_stream_header { false };