custom Layer

The <custom> layer represent any other protocol specific layer, functionality of which cannot be impelemented using other provided layers. The code generator must allow injection of the externally implemented code of the layer functionality when generating code relevant to the transport framing.

<?xml version="1.0" encoding="UTF-8"?>
<schema endian="big" ...>
    <frame name="ProtocolFrame">
        <size name="Size">
            ...
        </size>
        <custom name="SomeCustomLayer">
            <int name="SomeField" type="uint8" />
        </custom>
        <id name="Id">
            ...  
        </id>
        <payload name="Data" />
    </frame>
</schema>

The <value> layer has all the common properties as well as extra properties and elements described below.

ID Replacement

Most protocol frames are expected to use <id> layer to process numeric ID of the message. However, there are protocols that may use the same field not only for numeric ID, but also for some extra flags. In this case <id> layer cannot be used, because it expects the whole field to be dedicated to storage of the numeric ID. In such case <custom> layer needs to be used but marked as one replacing the <id> with idReplacement property.

<?xml version="1.0" encoding="UTF-8"?>
<schema endian="big" ...>
    <frame name="ProtocolFrame">
        <size name="Size">
            ...
        </size>
        <custom name="IdAndFlags" idReplacement="true">
            <bitfield name="IdAndFlagsField">
                <int name="Id" type="uint16" bitLength="12" />
                <set name="Flags" bitLength="4">
                    ...
                </set>
            </bitfield>
        </custom>
        <payload name="Data" />
    </frame>
</schema>

Use properties table for future references.