LibMedia: Add a method to get the available bytes from a MediaStream

This will be used to determine the buffered time ranges.

Libraries/LibMedia/IncrementallyPopulatedStream.cpp

@@ -101,6 +101,15 @@ void IncrementallyPopulatedStream::add_chunk_at(u64 offset, ReadonlyBytes data)
     m_state_changed.broadcast();
 }
 
+Vector<MediaStream::ByteRange> IncrementallyPopulatedStream::available_byte_ranges() const
+{
+    Sync::MutexLocker locker { m_mutex };
+    Vector<ByteRange> ranges;
+    for (auto it = m_chunks.begin(); it != m_chunks.end(); ++it)
+        ranges.empend(it->offset(), it->end());
+    return ranges;
+}
+
 void IncrementallyPopulatedStream::close()
 {
     Sync::MutexLocker locker { m_mutex };

Libraries/LibMedia/IncrementallyPopulatedStream.h

@@ -43,6 +43,8 @@ public:
 
     void close();
 
+    virtual Vector<ByteRange> available_byte_ranges() const override;
+
     u64 size();
     void set_expected_size(u64);
     Optional<u64> expected_size() const;

Libraries/LibMedia/MediaStream.h

@@ -32,9 +32,16 @@ public:
 
 class MediaStream : public AtomicRefCounted<MediaStream> {
 public:
+    struct ByteRange {
+        size_t start { 0 };
+        size_t end { 0 };
+    };
+
     virtual ~MediaStream() = default;
 
     virtual NonnullRefPtr<MediaStreamCursor> create_cursor() = 0;
+
+    virtual Vector<ByteRange> available_byte_ranges() const = 0;
 };
 
 }