MessagePackObject

MessagePackObject is low level representation of message pack object. It is lightweight from the space efficiency perspective, and it has a lot of conversion operators. You can represent 'dynamic' type entry using it.

Type Conversion

MessagePackObject allows you to dynamic casting. If you used boxing, you cannot cast from a boxed Int32 value to an UInt32 value because unboxing itself does not handle any type conversion. In contrast, if you cast an Int32 value to a MessagePackObject, then you can cast it to an UInt32 as long as the value is not negative.

Conversion Operators

• From CLI primitive type to MessagePackObject is always safe, so conversion is done with implicit conversion. (Note that native int (void* in C#), pointers are not supported. And also, note that IntPtr, UIntPtr, Decimal are not CLI primitive.)

• From MessagePackObject is not always safe, so conversion is done with explicit conversion.

• System.String is same as CLI primitives. Note that MessagePack APIs uses UTF-8 encoding (without BOM) as default.

• From a collection of MessagePackObject (IList<T>), map (dictionary) of MessagePackObject (MessagePackDictionary), or bytes array to single MessagePackObject is actually always safe, but there is an immutability related issue (see following "Immutability" section). So, it is done with explicit conversion. Note that constructor is better because it takes boolean parameter which hints collection immutability.

• There are constructors which take acceptable CLI objects. They correspond to implicit operators. (However, collection taking ones have extra immutable hints.)

• There are AsXxx() methods which correspond to explicit operators.

• There are IsTypeOf() methods which allow you to check type compatibility.

String Representation

MessagePackObject.ToString() returns JSON style string for its content. Note that when the object represents very large collections or binary, it will cause significant resource consumption (CPU and memory).

Immutability

MessagePackObject is value type object, so it is immutable compliant to Framework Design Guidelines. Therefore, the constructor and conversion operator copy entire collection which is passed to as the parameter. As you can see, it causes performance problem for large collection. MessagePackObject has constructors which take second boolean type parameter which indicates the first argument can be considered as immutable. If the value is true, the constructor just store passed collection without copying, so you can avoid extra collection copying.