Messages

Messages contains the keys described below.

JSON key: <message type value>

JSON key	Required?	Type	Value description
This is the message type and must be in the format described by the "type" of the msg type field. For integers, it must be a number e.g. "1". For strings, it is a string of the specified string size e.g. "A" or "AE" etc.	Yes	String or Integer	This a JSON object containing additional key/values. See Additional Values below.

Additional values

JSON key	Required?	Type	Value description
name	Yes	String	The name of the message being decoded.
fields	Yes	Array	The set of fields for the message type value.
message_types	No	Array	If the protocol being implemented contains multiple values which map to the same message, then we can specify a JSON array of values as shown in the Messages example below, where the message "SymbolNationalBestOfferUpdate" will be decoded if the message type is 17, 18 or 19.

Messages example:

   "Messages" : {
     "1" : {
        "name" : "SymbolMemxTradingStateUpdate",
        "fields" : [
          { "name":"TradingState", "type": "SymbolTradingState" },
          { "name":"StateChangeReason", "type": "SymbolStateReason" },
        ]
      },
 
     "2" : {
        "name" : "Delete Order",
        "fields" : [
          { "name":"SymbolId", "type":"ASCII64" },
          { "name":"OpeningState", "type": "SymbolOpeningState" },
          { "name":"MatchPrice", "type": "INT64_BE" },
        ]
      },
 
     "17" : {
        "name" : "SymbolNationalBestOfferUpdate",
        "message_types": [ "18", "19"],
        "fields" : [
          { "name":"SymbolId", "type":"ASCII64" },
          { "name":"MarketDataTimestamp", "type": "timestamp" },
          { "name":"MarketDataSequence", "type": "UINT64_BE" },
          { "name":"NationalAskPrice", "type": "INT64_BE" },
          { "name":"AwayAskPrice", "type": "INT64_BE" },
        ]
      },
 
   }

How the decoder decodes Message Definition datafields

Once the decoder has decoded the Message Header and Message Type, its selects a message definition using the Message Type. The internal offset counter is set to 0 again as it decodes each "field" defined for the selected message definition.