LibAudio: Allow the MP3 plugin to be constructed from a byte buffer

Userland/Libraries/LibAudio/Loader.cpp

@@ -42,6 +42,9 @@ Result<NonnullOwnPtr<LoaderPlugin>, LoaderError> Loader::try_create(Bytes& buffe
     if (auto initstate = plugin->initialize(); !initstate.is_error())
         return plugin;
     plugin = adopt_own(*new FlacLoaderPlugin(buffer));
+    if (auto initstate = plugin->initialize(); !initstate.is_error())
+        return plugin;
+    plugin = adopt_own(*new MP3LoaderPlugin(buffer));
     if (auto initstate = plugin->initialize(); !initstate.is_error())
         return plugin;
     return LoaderError { "No loader plugin available" };

Userland/Libraries/LibAudio/MP3Loader.cpp

@@ -15,13 +15,19 @@ DSP::MDCT<12> MP3LoaderPlugin::s_mdct_12;
 DSP::MDCT<36> MP3LoaderPlugin::s_mdct_36;
 
 MP3LoaderPlugin::MP3LoaderPlugin(StringView path)
-    : m_path(path)
+    : LoaderPlugin(path)
+{
+}
+
+MP3LoaderPlugin::MP3LoaderPlugin(Bytes buffer)
+    : m_backing_memory(buffer)
 {
 }
 
 MaybeLoaderError MP3LoaderPlugin::initialize()
 {
-    m_stream = LOADER_TRY(Core::Stream::File::open(m_path, Core::Stream::OpenMode::Read));
+    LOADER_TRY(LoaderPlugin::initialize());
+
     m_bitstream = LOADER_TRY(Core::Stream::BigEndianInputBitStream::construct(*m_stream));
 
     TRY(synchronize());

Userland/Libraries/LibAudio/MP3Loader.h

@@ -11,6 +11,7 @@
 #include <AK/MemoryStream.h>
 #include <AK/Tuple.h>
 #include <LibCore/InputBitStream.h>
+#include <LibCore/MemoryStream.h>
 #include <LibCore/Stream.h>
 #include <LibDSP/MDCT.h>
 
@@ -23,6 +24,7 @@ struct ScaleFactorBand;
 class MP3LoaderPlugin : public LoaderPlugin {
 public:
     explicit MP3LoaderPlugin(StringView path);
+    explicit MP3LoaderPlugin(Bytes buffer);
     virtual ~MP3LoaderPlugin() = default;
 
     virtual MaybeLoaderError initialize() override;
@@ -72,6 +74,7 @@ private:
     u32 m_current_frame_read;
     StringView m_path;
     OwnPtr<Core::Stream::SeekableStream> m_stream;
+    Optional<Bytes const&> m_backing_memory;
     OwnPtr<Core::Stream::BigEndianInputBitStream> m_bitstream;
     DuplexMemoryStream m_bit_reservoir;
 };