Implement region file reading and chunk structure

Author: Glavo

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

@@ -16,7 +16,17 @@
 package org.glavo.nbt.chunk;
 
 import org.glavo.nbt.NBTElement;
+import org.jetbrains.annotations.Nullable;
 
 public final class Chunk implements NBTElement {
-    // TODO
+    private int index = -1;
+    private @Nullable Region region;
+
+    public Chunk() {
+    }
+
+    /// Return the region of this chunk, or `null` if this chunk is not in any region.
+    public @Nullable Region getRegion() {
+        return region;
+    }
 }

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

@@ -15,16 +15,41 @@
  */
 package org.glavo.nbt.chunk;
 
+import org.glavo.nbt.MinecraftEdition;
 import org.glavo.nbt.NBTElement;
+import org.glavo.nbt.internal.input.InputContext;
 
+import java.io.IOException;
 import java.util.Objects;
 
 /// @see <a href="https://minecraft.wiki/w/Region_file_format">Region file format - Minecraft Wiki</a>
 /// @see <a href="https://minecraft.wiki/w/Anvil_file_format">Anvil file format - Minecraft Wiki</a>
 public final class Region implements NBTElement {
     private static final int CHUNKS_PER_REGION_SIDE = 32;
 
-    // TODO
+    static Region readRegion(InputContext context) throws IOException {
+        if (context.edition != MinecraftEdition.JAVA_EDITION) {
+            throw new IllegalArgumentException("Only Java Edition supports region file format");
+        }
+
+        int[] diskInfo = context.rawReader.readIntArray(CHUNKS_PER_REGION_SIDE * CHUNKS_PER_REGION_SIDE);
+        int[] timestamps = context.rawReader.readIntArray(CHUNKS_PER_REGION_SIDE * CHUNKS_PER_REGION_SIDE);
+
+        for (int y = 0; y < CHUNKS_PER_REGION_SIDE; y++) {
+            for (int x = 0; x < CHUNKS_PER_REGION_SIDE; x++) {
+                int index = x + y * CHUNKS_PER_REGION_SIDE;
+
+                int info = diskInfo[index];
+                int sectorOffset = info >>> 8;
+                int sectorCount = info & 0xFF;
+                int timestamp = timestamps[index];
+
+            }
+        }
+
+        throw new AssertionError("Not implemented yet");
+    }
+
     private final Chunk[] chunks = new Chunk[CHUNKS_PER_REGION_SIDE * CHUNKS_PER_REGION_SIDE];
 
     public Chunk getChunk(int x, int z) {

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

@@ -52,12 +52,20 @@ public byte[] readByteArray() throws IOException {
             throw new IOException("Array length too large");
         }
 
+        return readBYteArray(len);
+    }
+
+    public byte[] readByteArray(int len) throws IOException {
         ensureBufferRemaining(len);
         return buffer.getByteArray(len);
     }
 
     public int[] readIntArray() throws IOException {
         int len = readInt();
+        return readIntArray(len);
+    }
+
+    public int[] readIntArray(int len) throws IOException {
         if (len < 0 || len > Integer.MAX_VALUE / Integer.BYTES - 8) {
             throw new IOException("Array length too large");
         }
@@ -76,6 +84,15 @@ public long[] readLongArray() throws IOException {
         return buffer.getLongArray(len);
     }
 
+    public long[] readLongArray(int len) throws IOException {
+        if (len < 0 || len > Integer.MAX_VALUE / Long.BYTES - 8) {
+            throw new IOException("Array length too large");
+        }
+
+        ensureBufferRemaining(len * Long.BYTES);
+        return buffer.getLongArray(len);
+    }
+
     /// Read a byte from the input stream.
     public byte readByte() throws IOException {
         ensureBufferRemaining(Byte.BYTES);