Support NBT files with roots of any tag type

Author: tryashtar

fNbt/NbtFile.cs

@@ -25,7 +25,7 @@ public sealed class NbtFile {
         /// <summary> Root tag of this file. Must be a named CompoundTag. Defaults to an empty-named tag. </summary>
         /// <exception cref="ArgumentException"> If given tag is unnamed. </exception>
         [NotNull]
-        public NbtCompound RootTag {
+        public NbtTag RootTag {
             get { return rootTag; }
             set {
                 if (value == null) throw new ArgumentNullException("value");
@@ -34,8 +34,10 @@ public NbtCompound RootTag {
             }
         }
 
+        public T GetRootTag<T>() where T : NbtTag => RootTag as T;
+
         [NotNull]
-        NbtCompound rootTag;
+        NbtTag rootTag;
 
         /// <summary> Whether new NbtFiles should default to big-endian encoding (default: true). </summary>
         public static bool BigEndianByDefault { get; set; }
@@ -94,7 +96,7 @@ public NbtFile() {
         /// <summary> Creates a new NBT file with the given root tag. </summary>
         /// <param name="rootTag"> Compound tag to set as the root tag. May be <c>null</c>. </param>
         /// <exception cref="ArgumentException"> If given <paramref name="rootTag"/> is unnamed. </exception>
-        public NbtFile([NotNull] NbtCompound rootTag)
+        public NbtFile([NotNull] NbtTag rootTag)
             : this() {
             if (rootTag == null) throw new ArgumentNullException("rootTag");
             RootTag = rootTag;
@@ -317,7 +319,18 @@ static NbtCompression DetectCompression([NotNull] Stream stream) {
                 case -1:
                     throw new EndOfStreamException();
 
-                case (byte)NbtTagType.Compound: // 0x0A
+                case (byte)NbtTagType.Byte:
+                case (byte)NbtTagType.Short:
+                case (byte)NbtTagType.Int:
+                case (byte)NbtTagType.Long:
+                case (byte)NbtTagType.Float:
+                case (byte)NbtTagType.Double:
+                case (byte)NbtTagType.String:
+                case (byte)NbtTagType.ByteArray:
+                case (byte)NbtTagType.IntArray:
+                case (byte)NbtTagType.LongArray:
+                case (byte)NbtTagType.Compound:
+                case (byte)NbtTagType.List:
                     compression = NbtCompression.None;
                     break;
 
@@ -345,16 +358,14 @@ void LoadFromStreamInternal([NotNull] Stream stream, [CanBeNull] TagSelector tag
             if (firstByte < 0) {
                 throw new EndOfStreamException();
             }
-            if (firstByte != (int)NbtTagType.Compound) {
-                throw new NbtFormatException("Given NBT stream does not start with a TAG_Compound");
-            }
             var reader = new NbtBinaryReader(stream, BigEndian) {
                 Selector = tagSelector
             };
 
-            var rootCompound = new NbtCompound(reader.ReadString());
-            rootCompound.ReadTag(reader);
-            RootTag = rootCompound;
+            var rootValue = NbtCompound.CreateTag((NbtTagType)firstByte);
+            rootValue.Name = reader.ReadString();
+            rootValue.ReadTag(reader);
+            RootTag = rootValue;
         }
 
         #endregion

fNbt/Tags/NbtCompound.cs

@@ -292,6 +292,37 @@ public IEnumerable<NbtTag> Tags {
 
         #region Reading / Writing
 
+        internal static NbtTag CreateTag(NbtTagType type) {
+            switch (type) {
+                case NbtTagType.Byte:
+                    return  new NbtByte();
+                case NbtTagType.Short:
+                    return new NbtShort();
+                case NbtTagType.Int:
+                    return new NbtInt();
+                case NbtTagType.Long:
+                    return new NbtLong();
+                case NbtTagType.Float:
+                    return new NbtFloat();
+                case NbtTagType.Double:
+                    return new NbtDouble();
+                case NbtTagType.ByteArray:
+                    return new NbtByteArray();
+                case NbtTagType.String:
+                    return new NbtString();
+                case NbtTagType.List:
+                    return new NbtList();
+                case NbtTagType.Compound:
+                    return new NbtCompound();
+                case NbtTagType.IntArray:
+                    return new NbtIntArray();
+                case NbtTagType.LongArray:
+                    return new NbtLongArray();
+                default:
+                    throw new NbtFormatException("Unsupported tag type found: " + type);
+            }
+        }
+
         internal override bool ReadTag(NbtBinaryReader readStream) {
             if (Parent != null && readStream.Selector != null && !readStream.Selector(this)) {
                 SkipTag(readStream);
@@ -300,62 +331,10 @@ internal override bool ReadTag(NbtBinaryReader readStream) {
 
             while (true) {
                 NbtTagType nextTag = readStream.ReadTagType();
-                NbtTag newTag;
-                switch (nextTag) {
-                    case NbtTagType.End:
-                        return true;
-
-                    case NbtTagType.Byte:
-                        newTag = new NbtByte();
-                        break;
-
-                    case NbtTagType.Short:
-                        newTag = new NbtShort();
-                        break;
-
-                    case NbtTagType.Int:
-                        newTag = new NbtInt();
-                        break;
-
-                    case NbtTagType.Long:
-                        newTag = new NbtLong();
-                        break;
-
-                    case NbtTagType.Float:
-                        newTag = new NbtFloat();
-                        break;
-
-                    case NbtTagType.Double:
-                        newTag = new NbtDouble();
-                        break;
-
-                    case NbtTagType.ByteArray:
-                        newTag = new NbtByteArray();
-                        break;
-
-                    case NbtTagType.String:
-                        newTag = new NbtString();
-                        break;
-
-                    case NbtTagType.List:
-                        newTag = new NbtList();
-                        break;
-
-                    case NbtTagType.Compound:
-                        newTag = new NbtCompound();
-                        break;
-
-                    case NbtTagType.IntArray:
-                        newTag = new NbtIntArray();
-                        break;
-                    
-                    case NbtTagType.LongArray:
-                        newTag = new NbtLongArray();
-                        break;
+                if (nextTag == NbtTagType.End)
+                    return true;
 
-                    default:
-                        throw new NbtFormatException("Unsupported tag type found in NBT_Compound: " + nextTag);
-                }
+                NbtTag newTag = CreateTag(nextTag);
                 newTag.Parent = this;
                 newTag.Name = readStream.ReadString();
                 if (newTag.ReadTag(readStream)) {