Implement basic SNBT reader and testsuite

lib/nbt/SnbtIo.dart

@@ -5,7 +5,7 @@ import 'Tag.dart';
 import 'impl/CompoundTag.dart';
 
 class SnbtIo {
-  static void write(String file, CompoundTag tag) {
+  static void writeToFile(String file, CompoundTag tag) {
     File handle = File(file);
 
     if (handle.existsSync())
@@ -15,4 +15,22 @@ class SnbtIo {
     Tag.writeStringifiedNamedTag(tag, builder, 0);
     handle.writeAsString(builder.toString());
   }
+
+  static Future<Tag> readFromFile(String file) async {
+    File fi = File(file);
+    String data = await fi.readAsString();
+    StringReader reader = StringReader(data);
+
+    return Tag.readStringifiedNamedTag(reader);
+  }
+
+  static String writeToString(CompoundTag tag) {
+    StringBuilder builder = StringBuilder();
+    Tag.writeStringifiedNamedTag(tag, builder, 0);
+    return builder.toString();
+  }
+
+  static Future<Tag> readFromString(String data) async {
+    return Tag.readStringifiedNamedTag(StringReader(data));
+  }
 }

lib/nbt/Stream.dart

@@ -408,3 +408,124 @@ class StringBuilder {
     return "${_buffer}";
   }
 }
+
+class StringReader {
+  final String _buffer;
+  int _position = 0;
+  int _lastPostion = 0;
+
+  StringReader(this._buffer);
+
+  // Check if there's more to read
+  bool get canRead => _position < _buffer.length;
+
+  // Read the next character
+  String next() {
+    if (canRead) {
+      skipWhitespace();
+      return _buffer[_position++];
+    } else {
+      throw Exception("End of buffer reached");
+    }
+  }
+
+  // Peek the next character without advancing the position
+  String peek() {
+    skipWhitespace();
+    if (canRead) {
+      return _buffer[_position];
+    } else {
+      throw Exception("End of buffer reached");
+    }
+  }
+
+  // Skip any whitespace characters
+  void skipWhitespace() {
+    while (canRead && isWhitespace(_buffer[_position])) {
+      _position++;
+    }
+  }
+
+  // Check if a character is a whitespace
+  bool isWhitespace(String char) {
+    return char.trim().isEmpty;
+  }
+
+  // Read until a specific character is found
+  String readUntil(String stopChar) {
+    StringBuffer result = StringBuffer();
+    while (canRead && peek() != stopChar) {
+      result.write(next());
+    }
+    return result.toString();
+  }
+
+  // Read a string enclosed in double quotes
+  String readQuotedString() {
+    if (next() != '"') {
+      throw Exception('Expected double quotes at the start of a string');
+    }
+    StringBuffer result = StringBuffer();
+    while (canRead) {
+      String char = next();
+      if (char == '"') {
+        break;
+      }
+      result.write(char);
+    }
+    return result.toString();
+  }
+
+  // Read a number (int or double)
+  String readNumber() {
+    StringBuffer result = StringBuffer();
+    while (canRead && (isDigit(peek()) || peek() == '.' || peek() == '-')) {
+      result.write(next());
+    }
+    return result.toString();
+  }
+
+  // Check if a character is a digit
+  bool isDigit(String char) {
+    return int.tryParse(char) != null;
+  }
+
+  // Read an unquoted string (used for keys in SNBT)
+  String readUnquotedString() {
+    StringBuffer result = StringBuffer();
+    while (canRead &&
+        !isWhitespace(peek()) &&
+        peek() != ':' &&
+        peek() != ',' &&
+        peek() != '{' &&
+        peek() != '}' &&
+        peek() != '[' &&
+        peek() != ']') {
+      result.write(next());
+    }
+    return result.toString();
+  }
+
+  String readString() {
+    if (peek() == "\"") {
+      return readQuotedString();
+    } else
+      return readUnquotedString();
+  }
+
+  // Read a specific character and throw an exception if it's not found
+  void expect(String expectedChar) {
+    if (next().toLowerCase() != expectedChar.toLowerCase()) {
+      throw Exception('Expected $expectedChar');
+    }
+  }
+
+  void startSeek() {
+    _lastPostion = _position;
+  }
+
+  void endSeek() {
+    _position = _lastPostion;
+    _lastPostion = 0;
+  }
+}

lib/nbt/Tag.dart

@@ -40,6 +40,79 @@ enum TagType {
 
     return TagType.End;
   }
+
+  static TagType getStringifiedTagType(StringReader reader) {
+    reader.startSeek();
+    TagType ret = TagType.End;
+
+    // Start to determine the next tag type
+    while (reader.canRead && ret == TagType.End) {
+      var val = reader.next().toUpperCase();
+      switch (val) {
+        case "{":
+          {
+            ret = TagType.Compound;
+            break;
+          }
+        case "[":
+          {
+            // Check for a type Prefix
+            var X = reader.readUntil(";");
+            switch (X.toUpperCase()) {
+              case "B":
+                {
+                  ret = TagType.ByteArray;
+                  break;
+                }
+              case "I":
+                {
+                  ret = TagType.IntArray;
+                  break;
+                }
+              case "L":
+                {
+                  ret = TagType.LongArray;
+                  break;
+                }
+              default:
+                {
+                  ret = TagType.List;
+                  break;
+                }
+            }
+            break;
+          }
+        case "B":
+          {
+            ret = TagType.Byte;
+            break;
+          }
+        case "D":
+          {
+            ret = TagType.Double;
+            break;
+          }
+        case "F":
+          {
+            ret = TagType.Float;
+            break;
+          }
+        case "L":
+          {
+            ret = TagType.Long;
+            break;
+          }
+        case "S":
+          {
+            ret = TagType.Short;
+            break;
+          }
+      }
+    }
+
+    reader.endSeek();
+    return ret;
+  }
 }
 
 abstract class Tag {
@@ -100,6 +173,23 @@ abstract class Tag {
     }
   }
 
+  static Tag readStringifiedNamedTag(StringReader string) {
+    String name = "";
+    if (string.peek() == "{" || string.peek() == "[") {
+      // No name
+      name = "";
+    } else {
+      name = string.readString();
+      string.expect(":");
+    }
+    TagType type = TagType.getStringifiedTagType(string);
+    Tag tag = Tag.makeTagOfType(type);
+    tag._key = name;
+    tag.readStringifiedValue(string);
+
+    return tag;
+  }
+
   bool shouldQuoteName() {
     if (getKey() == "") {
       return false;
@@ -116,6 +206,7 @@ abstract class Tag {
   }
 
   void writeStringifiedValue(StringBuilder builder, int indent, bool isList);
+  void readStringifiedValue(StringReader reader);
 
   bool equals(dynamic object) {
     if (object == null || object is! Tag) return false;

lib/nbt/impl/ByteArrayTag.dart

@@ -52,4 +52,16 @@ class ByteArrayTag extends Tag {
     builder.append(
         "${isList ? "".padLeft(indent, '\t') : ""}[B; ${value.join("B, ")}B]");
   }
+
+  @override
+  void readStringifiedValue(StringReader reader) {
+    reader.expect("[");
+    while (reader.peek() != "]") {
+      value.add(int.parse(reader.readNumber()));
+      reader.expect("b");
+
+      if (reader.peek() == ",") reader.next();
+    }
+    reader.expect("]");
+  }
 }

lib/nbt/impl/ByteTag.dart

@@ -39,4 +39,12 @@ class ByteTag extends Tag {
   void writeStringifiedValue(StringBuilder builder, int indent, bool isList) {
     builder.append("${value}b");
   }
+
+  @override
+  void readStringifiedValue(StringReader reader) {
+    String val = reader.readNumber();
+    value = int.parse(val);
+
+    reader.expect("b");
+  }
 }

lib/nbt/impl/CompoundTag.dart

@@ -190,4 +190,16 @@ class CompoundTag extends Tag implements Map<String, Tag> {
 
   @override
   Iterable<Tag> get values => value.values;
+
+  @override
+  void readStringifiedValue(StringReader reader) {
+    reader.expect("{");
+
+    while (reader.peek() != "}") {
+      Tag tag = Tag.readStringifiedNamedTag(reader);
+      put(tag.getKey(), tag);
+    }
+
+    reader.expect("}");
+  }
 }

lib/nbt/impl/DoubleTag.dart

@@ -39,4 +39,12 @@ class DoubleTag extends Tag {
   void writeStringifiedValue(StringBuilder builder, int indent, bool isList) {
     builder.append("${isList ? "".padLeft(indent, '\t') : ""}${value}d");
   }
+
+  @override
+  void readStringifiedValue(StringReader reader) {
+    double val = double.parse(reader.readNumber());
+    value = val;
+
+    reader.expect("d");
+  }
 }

lib/nbt/impl/EndTag.dart

@@ -22,4 +22,7 @@ class EndTag extends Tag {
 
   @override
   void writeStringifiedValue(StringBuilder builder, int indent, bool isList) {}
+
+  @override
+  void readStringifiedValue(StringReader reader) {}
 }

lib/nbt/impl/FloatTag.dart

@@ -38,4 +38,12 @@ class FloatTag extends Tag {
   void writeStringifiedValue(StringBuilder builder, int indent, bool isList) {
     builder.append("${isList ? "".padLeft(indent, '\t') : ""}${value}f");
   }
+
+  @override
+  void readStringifiedValue(StringReader reader) {
+    double val = double.parse(reader.readNumber());
+    value = val;
+
+    reader.expect("f");
+  }
 }

lib/nbt/impl/IntArrayTag.dart

@@ -51,4 +51,15 @@ class IntArrayTag extends Tag {
     builder.append(
         "${isList ? "".padLeft(indent, '\t') : ""}[I; ${value.join('I, ')}I]");
   }
+
+  @override
+  void readStringifiedValue(StringReader reader) {
+    reader.expect("[");
+    while (reader.peek() != "]") {
+      value.add(int.parse(reader.readNumber()));
+
+      if (reader.peek() == ",") reader.next();
+    }
+    reader.expect("]");
+  }
 }

lib/nbt/impl/IntTag.dart

@@ -38,4 +38,10 @@ class IntTag extends Tag {
   void writeStringifiedValue(StringBuilder builder, int indent, bool isList) {
     builder.append("${isList ? "".padLeft(indent, '\t') : ""}${value}i");
   }
+
+  @override
+  void readStringifiedValue(StringReader reader) {
+    String val = reader.readNumber();
+    value = int.parse(val);
+  }
 }

lib/nbt/impl/ListTag.dart

@@ -103,4 +103,15 @@ class ListTag extends Tag {
     }
     builder.append("\n${"".padLeft(indent - 1, '\t')}]");
   }
+
+  @override
+  void readStringifiedValue(StringReader reader) {
+    reader.expect("[");
+    while (reader.peek() != "]") {
+      value.add(Tag.readStringifiedNamedTag(reader));
+
+      if (reader.peek() == ",") reader.next();
+    }
+    reader.expect("]");
+  }
 }

lib/nbt/impl/LongArrayTag.dart

@@ -55,4 +55,16 @@ class LongArrayTag extends Tag {
     builder.append(
         "${isList ? "".padLeft(indent, '\t') : ""}[L; ${value.join('L, ')}L]");
   }
+
+  @override
+  void readStringifiedValue(StringReader reader) {
+    reader.expect("[");
+    while (reader.peek() != "]") {
+      value.add(int.parse(reader.readNumber()));
+      reader.expect("l");
+
+      if (reader.peek() == ",") reader.next();
+    }
+    reader.expect("]");
+  }
 }

lib/nbt/impl/LongTag.dart

@@ -38,4 +38,12 @@ class LongTag extends Tag {
   void writeStringifiedValue(StringBuilder builder, int indent, bool isList) {
     builder.append("${isList ? "".padLeft(indent, '\t') : ""}${value}L");
   }
+
+  @override
+  void readStringifiedValue(StringReader reader) {
+    int val = int.parse(reader.readNumber());
+    value = val;
+
+    reader.expect("l");
+  }
 }

lib/nbt/impl/ShortTag.dart

@@ -38,4 +38,12 @@ class ShortTag extends Tag {
   void writeStringifiedValue(StringBuilder builder, int indent, bool isList) {
     builder.append("${isList ? "".padLeft(indent, '\t') : ""}${value}S");
   }
+
+  @override
+  void readStringifiedValue(StringReader reader) {
+    int val = int.parse(reader.readNumber());
+    value = val;
+
+    reader.expect("s");
+  }
 }

lib/nbt/impl/StringTag.dart

@@ -38,4 +38,10 @@ class StringTag extends Tag {
   void writeStringifiedValue(StringBuilder builder, int indent, bool isList) {
     builder.append("${isList ? "".padLeft(indent, '\t') : ""}\"${value}\"");
   }
+
+  @override
+  void readStringifiedValue(StringReader reader) {
+    String str = reader.readString();
+    value = str;
+  }
 }

test/nbt_test.dart

@@ -82,12 +82,19 @@ void main() {
         await NbtIo.read("${Directory.current.path}/test/bigtest.nbt");
     String output = "${Directory.current.path}/build/bigtest.snbt";
     File file = File(output);
-    SnbtIo.write(output, ct);
+    SnbtIo.writeToFile(output, ct);
 
     // Expect that the file exists
     expect(file.existsSync(), true);
   });
 
+  test("Read BigTest from SNBT file", () async {
+    CompoundTag tag = await SnbtIo.readFromFile(
+        "${Directory.current.path}/build/bigtest.snbt") as CompoundTag;
+
+    expect(tag.containsKey("stringTest"), true);
+  });
+
   test("Write NULL UUID to NBT", () async {
     CompoundTag tag = CompoundTag();
     NbtUtils.writeUUID(tag, "test", NbtUUID.fromUUID(UUID.ZERO));