YamlDotNet !!binary type - yamldotnet

Question

I am trying to send binary data, i.e. byte arrays, using yaml. According to the yaml documentation, Yaml Binary Type, this is supported. On the Java side I use SnakeYaml and if a value of byte[] is passed, then the yaml correctly gives !!binary.
This functionality does not seem to be supported "out of the box" in YamlDotNet. The below code snippet creates a sequence of integer values:
IDictionary<string, object> data = new Dictionary<string, object>();
const string value = ":| value: <XML> /n\n C:\\cat";
byte[] bytes = Encoding.UTF8.GetBytes(value);
data.Add(ValueKey, bytes);
// Turn the object representation into text
using (var output = new StringWriter())
{
var serializer = new Serializer();
serializer.Serialize(output, data);
return output.ToString();
}
Output like:
val:\r- 58\r- 124\r- 32\r- 118\r- 97\r- 108\r- 117\r- 101\r- 58\r- 32\r- 60\r- 88\r- 77\r- 76\r- 62\r- 32\r- 47\r- 110\r- 10\r- 32\r- 67\r- 58\r- 92\r- 99\r- 97\r- 116\r
But I would like something more like:
val: !!binary |-
OnwgdmFsdWU6IDxYTUw+IC9uCiBDOlxjYXQ=
Can anyone recommend a workaround?

Answer 1

The preferred way to add support for custom types is to use a custom IYamlTypeConverter. A possible implementation for the !!binary type would be:
public class ByteArrayConverter : IYamlTypeConverter
{
public bool Accepts(Type type)
{
// Return true to indicate that this converter is able to handle the byte[] type
return type == typeof(byte[]);
}
public object ReadYaml(IParser parser, Type type)
{
var scalar = (YamlDotNet.Core.Events.Scalar)parser.Current;
var bytes = Convert.FromBase64String(scalar.Value);
parser.MoveNext();
return bytes;
}
public void WriteYaml(IEmitter emitter, object value, Type type)
{
var bytes = (byte[])value;
emitter.Emit(new YamlDotNet.Core.Events.Scalar(
null,
"tag:yaml.org,2002:binary",
Convert.ToBase64String(bytes),
ScalarStyle.Plain,
false,
false
));
}
}
To use the converter in the Serializer, you simply need to register it using the following code:
var serializer = new Serializer();
serializer.RegisterTypeConverter(new ByteArrayConverter());
For the Deserializer, you also need to register the converter, but you also need to add a tag mapping to resolve the !!binary tag to the byte[] type:
var deserializer = new Deserializer();
deserializer.RegisterTagMapping("tag:yaml.org,2002:binary", typeof(byte[]));
deserializer.RegisterTypeConverter(new ByteArrayConverter());
A fully working example can be tried here

Answer 2

For anyone that's interested.... I fixed this by creating the string myself and adding the !!binary tag, and also doing some clean up. Below is the code.
ToYaml:
IDictionary<string, string> data = new Dictionary<string, string>();
string byteAsBase64Fromat = Convert.ToBase64String("The string to convert");
byteAsBase64Fromat = "!!binary |-\n" + byteAsBase64Fromat + "\n";
data.Add(ValueKey, byteAsBase64Fromat);
string yaml;
using (var output = new StringWriter())
{
var serializer = new Serializer();
serializer.Serialize(output, data);
yaml = output.ToString();
}
string yaml = yaml.Replace(">", "");
return yaml.Replace(Environment.NewLine + Environment.NewLine, Environment.NewLine);
And then back by:
string binaryText = ((YamlScalarNode)data.Children[new YamlScalarNode(ValueKey)]).Value
String value = Convert.FromBase64String(binaryText);