Refactor InputSource to use abstract position method

Author: Glavo

src/main/java/org/glavo/nbt/internal/input/InputSource.java

@@ -23,12 +23,13 @@
 
 public sealed abstract class InputSource implements Closeable {
     private boolean closed = false;
-    protected long bytesRead = 0L;
 
     public boolean supportDirectBuffer() {
         return false;
     }
 
+    public abstract long position() throws IOException;
+
     @Override
     public final void close() throws IOException {
         if (!closed) {
@@ -73,12 +74,18 @@ public final void fillBuffer(InputBuffer buffer, int required) throws IOExceptio
     public static final class OfInputStream extends InputSource {
         private final InputStream inputStream;
         private final boolean closeInputStream;
+        private long position;
 
         public OfInputStream(InputStream inputStream, boolean closeInputStream) {
             this.inputStream = inputStream;
             this.closeInputStream = closeInputStream;
         }
 
+        @Override
+        public long position() throws IOException {
+            return position;
+        }
+
         @Override
         protected void closeImpl() throws IOException {
             if (closeInputStream) {
@@ -99,7 +106,7 @@ protected void fillBufferImpl(ByteBuffer target, int required) throws IOExceptio
                     throw new EOFException("Unexpected end of stream");
                 }
                 target.limit(target.limit() + read);
-                bytesRead += read;
+                position += read;
             }
         }
     }

src/main/java/org/glavo/nbt/internal/input/NBTReader.java

@@ -23,7 +23,6 @@
 import java.io.Closeable;
 import java.io.IOException;
 import java.nio.ByteBuffer;
-import java.nio.ByteOrder;
 import java.nio.charset.StandardCharsets;
 
 public final class NBTReader implements Closeable {
@@ -37,14 +36,16 @@ public final class NBTReader implements Closeable {
     private final InputSource source;
     private final InputBuffer buffer;
     private final MinecraftEdition edition;
+    private final long initialPosition;
 
     /// Used for reading UTF-8 strings
     private @Nullable StringBuilder charsBuffer;
 
-    public NBTReader(InputSource source, MinecraftEdition edition) {
+    public NBTReader(InputSource source, MinecraftEdition edition) throws IOException {
         this.source = source;
         this.buffer = InputBuffer.allocate(IOUtils.DEFAULT_BUFFER_SIZE, source.supportDirectBuffer(), edition.byteOrder());
         this.edition = edition;
+        this.initialPosition = source.position();
     }
 
     public MinecraftEdition getEdition() {