Add enum support

spec/cbor/from_cbor_spec.cr

@@ -1,5 +1,9 @@
 require "../spec_helper"
 
+enum TestEnum
+  Foo = 1
+end
+
 describe "CBOR helpers on basic types" do
   describe "#from_cbor" do
     tests = [
@@ -32,6 +36,7 @@ describe "CBOR helpers on basic types" do
       #  [1_i8, [2_i8, 3_i8], [4_i8, 5_i8]]},
       {Hash(UInt8, UInt8), Bytes[0xa0], {} of UInt8 => UInt8},
       {Hash(UInt8, UInt8), Bytes[0xa2, 0x01, 0x02, 0x03, 0x04], Hash(UInt8, UInt8){1 => 2, 3 => 4}},
+      {TestEnum, Bytes[0x1a, 0x00, 0x00, 0x00, 0x01], TestEnum::Foo},
     ]
 
     tests.each do |tt|

src/cbor/decoder.cr

@@ -82,7 +82,7 @@ class CBOR::Decoder
     end
   end
 
-  private def finish_token!
+  def finish_token!
     @current_token = @lexer.next_token
   end
 
@@ -115,7 +115,7 @@ class CBOR::Decoder
     end
   end
 
-  private def unexpected_token(token, expected = nil)
+  def unexpected_token(token, expected = nil)
     message = "Unexpected token #{token.class}"
     message += " expected #{expected}" if expected
     raise ParseError.new(message)

src/cbor/from_cbor.cr

@@ -60,6 +60,19 @@ def Hash.new(decoder : CBOR::Decoder)
   hash
 end
 
+def Enum.new(decoder : CBOR::Decoder)
+  case token = decoder.current_token
+  when CBOR::Token::IntT
+    decoder.finish_token!
+    from_value(token.value)
+  when CBOR::Token::StringT
+    decoder.finish_token!
+    parse(token.value)
+  else
+    decoder.unexpected_token(token, "IntT or StringT")
+  end
+end
+
 # Reads the CBOR values as a time. The value must be surrounded by a time tag as
 # specified by [Section 2.4.1 of RFC 7049][1].
 #