Add Tag decoding

src/cbor/lexer.cr

@@ -79,6 +79,8 @@ class CBOR::Lexer
       map_start(read_size(byte - 0xa0))
     when 0xbf
       Token::MapT.new
+    when 0xc0..0xdb
+      consume_tag(read_size(byte - 0xc0))
       ##################
     when 0xf4
       Token::BoolT.new(value: false)
@@ -170,6 +172,11 @@ class CBOR::Lexer
     Token::MapT.new(size: size.to_i32)
   end
 
+  private def consume_tag(size) : Token::TagT
+    raise ParseError.new("Maximum size for tag exceeded") if size > UInt32::MAX
+    Token::TagT.new(id: size.to_u32)
+  end
+
   # Creates a method overloaded for each UInt sizes to convert the UInt into
   # the respective Int capable of containing the value
 

src/cbor/tag.cr

@@ -0,0 +1,21 @@
+module CBOR::Tag
+  enum Kind
+    Unassigned
+    RFC3339Time
+    EpochTime
+    PositiveBigNum
+    NegativeBigNum
+    DecimalFraction
+    BigFloat
+    ExpectBase64URLConversion
+    ExpectBase64Conversion
+    ExpectBase16Conversion
+    EncodedCBOR
+    URI
+    Base64URL
+    Base64
+    RegularExpresion
+    MIME
+    SelfDescribeCBOR
+  end
+end

src/cbor/token.cr

@@ -7,6 +7,7 @@ module CBOR::Token
   record StringT, value : String, chunks : Array(Int32)? = nil
   record ArrayT, size : Int32? = nil
   record MapT, size : Int32? = nil
+  record TagT, id : UInt32
 
   alias T = NullT |
             BoolT |
@@ -15,5 +16,6 @@ module CBOR::Token
             BytesT |
             StringT |
             ArrayT |
-            MapT
+            MapT |
+            TagT
 end