Refactor decompression readers to factory methods

Author: Glavo

src/main/java/org/glavo/nbt/chunk/ChunkRegion.java

@@ -91,16 +91,10 @@ static ChunkRegion readRegion(RawDataReader rawReader) throws IOException {
             }
 
             BoundedDataReader reader = switch (compressType) {
-                case 1 -> throw new IOException("GZip compression is not supported yet.");
+                case 1 -> DecompressStreamDataReader.newGZipDataReader(rawReader, chunkRawContentLength);
                 case 2 -> new ZlibDataReader(rawReader, chunkRawContentLength);
                 case 3 -> new UncompressedDataReader(rawReader, chunkRawContentLength);
-                case 4 -> {
-                    try {
-                        yield new LZ4DataReader(rawReader, chunkRawContentLength);
-                    } catch (NoClassDefFoundError e) {
-                        throw new IOException("Missing dependency for LZ4 compression: " + e.getMessage(), e);
-                    }
-                }
+                case 4 -> DecompressStreamDataReader.newLZ4DataReader(rawReader, chunkRawContentLength);
                 default -> throw new IOException("Unsupported compression type: " + compressType);
             };
 

…vo/nbt/internal/input/LZ4DataReader.java …al/input/DecompressStreamDataReader.javasrc/main/java/org/glavo/nbt/internal/input/LZ4DataReader.java renamed to src/main/java/org/glavo/nbt/internal/input/DecompressStreamDataReader.java src/main/java/org/glavo/nbt/internal/input/LZ4DataReader.java renamed to src/main/java/org/glavo/nbt/internal/input/DecompressStreamDataReader.java

@@ -18,24 +18,59 @@
 package org.glavo.nbt.internal.input;
 
 import net.jpountz.lz4.LZ4BlockInputStream;
-import org.jetbrains.annotations.Nullable;
 
 import java.io.EOFException;
 import java.io.IOException;
 import java.io.InputStream;
 import java.nio.ByteBuffer;
-import java.util.Objects;
+import java.util.zip.GZIPInputStream;
 
-public final class LZ4DataReader extends BoundedDataReader {
-    private final LZ4BlockInputStream lz4Stream;
+public abstract class DecompressStreamDataReader extends BoundedDataReader {
+    private static final boolean LZ4_AVAILABLE;
 
-    public LZ4DataReader(RawDataReader rawReader, long limit) {
+    static {
+        boolean lz4Available = false;
+        try {
+            Class.forName("net.jpountz.lz4.LZ4BlockInputStream", false, DecompressStreamDataReader.class.getClassLoader());
+            lz4Available = true;
+        } catch (ClassNotFoundException ignored) {
+        }
+        LZ4_AVAILABLE = lz4Available;
+    }
+
+    public static DecompressStreamDataReader newGZipDataReader(RawDataReader rawReader, long limit) throws IOException {
+        return new DecompressStreamDataReader(rawReader, limit) {
+            @Override
+            protected InputStream newDecompressStream(InputStream rawInputStream) throws IOException {
+                return new GZIPInputStream(rawInputStream);
+            }
+        };
+    }
+
+    public static DecompressStreamDataReader newLZ4DataReader(RawDataReader rawReader, long limit) throws IOException {
+        if (!LZ4_AVAILABLE) {
+            throw new IOException("Missing LZ4 library, please add it to your classpath.");
+        }
+
+        return new DecompressStreamDataReader(rawReader, limit) {
+            @Override
+            protected InputStream newDecompressStream(InputStream rawInputStream) {
+                return LZ4BlockInputStream.newBuilder().build(rawInputStream);
+            }
+        };
+    }
+
+    private final InputStream decompressStream;
+
+    public DecompressStreamDataReader(RawDataReader rawReader, long limit) throws IOException {
         super(rawReader, rawReader.getDecompressBuffer(), limit);
-        this.lz4Stream = LZ4BlockInputStream.newBuilder().build(asInputStream());
+        this.decompressStream = newDecompressStream(asInputStream());
 
         assert getBuffer().getByteBuffer().hasArray();
     }
 
+    protected abstract InputStream newDecompressStream(InputStream rawInputStream) throws IOException;
+
     @Override
     public void ensureBufferRemaining(int required) throws IOException {
         if (getBuffer().remaining() >= required) {
@@ -54,7 +89,7 @@ public void ensureBufferRemaining(int required) throws IOException {
         byte[] array = output.array();
         try {
             while (output.position() < required) {
-                int n = lz4Stream.read(array, output.arrayOffset() + output.position(), output.remaining());
+                int n = decompressStream.read(array, output.arrayOffset() + output.position(), output.remaining());
                 if (n <= 0) {
                     throw new EOFException("Not enough data to read, required: " + required + ", remaining: " + (endPosition - getRawReader().position()));
                 }