Implemented new Anvil saving format, fixed old chunk saving format.

- Added 'Chunk' Interface.
 - Moved old 'Chunk' to 'OldChunk' and replaced dynamic world height reference with '128.
 - Added 'AnvilChunk' implementing the new anvil chunk format.
 - Added temp fixes to FileMcRegionChunkStore.java, TrueZipMcRegionChunkStore.java and ZippedMcRegionChunkStore.java too allow them to read .mca files.
 - Added the new 'IntArrayTag' since the new heightmap tag wasn't recognized.
 - Moved 'getChildTag' to 'NBTUtils'.

src/main/java/com/sk89q/jnbt/NBTUtils.java

@@ -1,5 +1,7 @@
 package com.sk89q.jnbt;
 
+import java.util.Map;
+
 import com.sk89q.jnbt.ByteArrayTag;
 import com.sk89q.jnbt.ByteTag;
 import com.sk89q.jnbt.CompoundTag;
@@ -13,6 +15,7 @@ import com.sk89q.jnbt.NBTConstants;
 import com.sk89q.jnbt.ShortTag;
 import com.sk89q.jnbt.StringTag;
 import com.sk89q.jnbt.Tag;
+import com.sk89q.worldedit.data.InvalidFormatException;
 
 /*
  * JNBT License
@@ -85,6 +88,8 @@ public final class NBTUtils {
             return "TAG_Short";
         } else if (clazz.equals(StringTag.class)) {
             return "TAG_String";
+        } else if (clazz.equals(IntArrayTag.class)) {
+            return "TAG_Int_Array";
         } else {
             throw new IllegalArgumentException("Invalid tag classs ("
                     + clazz.getName() + ").");
@@ -123,6 +128,8 @@ public final class NBTUtils {
             return NBTConstants.TYPE_SHORT;
         } else if (clazz.equals(StringTag.class)) {
             return NBTConstants.TYPE_STRING;
+        } else if (clazz.equals(IntArrayTag.class)) {
+            return NBTConstants.TYPE_INT_ARRAY;  
         } else {
             throw new IllegalArgumentException("Invalid tag classs ("
                     + clazz.getName() + ").");
@@ -162,6 +169,8 @@ public final class NBTUtils {
             return ListTag.class;
         case NBTConstants.TYPE_COMPOUND:
             return CompoundTag.class;
+        case NBTConstants.TYPE_INT_ARRAY:
+            return IntArrayTag.class;
         default:
             throw new IllegalArgumentException("Invalid tag type : " + type
                     + ".");
@@ -174,5 +183,26 @@ public final class NBTUtils {
     private NBTUtils() {
 
     }
+    
+    /**
+     * Get child tag of a NBT structure.
+     *
+     * @param items
+     * @param key
+     * @param expected
+     * @return child tag
+     * @throws InvalidFormatException
+     */
+    public static <T extends Tag> T getChildTag(Map<String,Tag> items, String key,
+            Class<T> expected) throws InvalidFormatException {
+        if (!items.containsKey(key)) {
+            throw new InvalidFormatException("Missing a \"" + key + "\" tag");
+        }
+        Tag tag = items.get(key);
+        if (!expected.isInstance(tag)) {
+            throw new InvalidFormatException(key + " tag is not of tag type " + expected.getName());
+        }
+        return expected.cast(tag);
+    }
 
 }