Specifying of the SOFH for message handling

The SOFH specification is always used when the MessageSchema instance is created. The specification can be used implicitly (it is deprecated way, but it still can be used), or explicitly (the recommended way).

// Standard SBE header
MessageSchema schema = new MessageSchema(ParseUtil.parse(new File("SbeTemplate.xml")));

// Standard SBE header
MessageSchema schema = new MessageSchema(ParseUtil.parse(new File("SbeTemplate.xml")), false);

// MDP3 SOFH
MessageSchema schema = new MessageSchema(ParseUtil.parse(new File("CmeTemplate.xml")), true);

Explicit SOFH specification

You must explicitly specify the SOFH specification when using the MessageSchema constructor. In the example below, the B3 SBE header specification is used. (See the next chapter for a list of predefined SOFH specifications.)

// Custom header
MessageSchema schema = new MessageSchema(ParseUtil.parse(new File("B3Template.xml")),
        FramingHeaderPolicy.getCustomPolicy(FramingHeaderSpecification.B3_FRAMING_HEADER));

Predefined SOFH specifications

The OnixS SBE toolset contains a set of SOFHs for widely known venues.

Creating of custom SOFH

To create your own SOFH specification, ensure the following information is clearly defined:

• Which fields are included in the SOFH;
• The byte order for each field.

Additionally, adhere to these limitations:

• The SOFH may contain only two fields: one for the message size and an optional field for byte order specification.
• The SOFH must not include any additional non-standard or user-defined fields.

For example, consider an SOFH with the following structure:

• SOFH byte order: little-endian;
• Field 1: frame length, 2-byte unsigned integer;
• Field 2: standard 2-byte SBE byte order marker.

In this case, the SOFH specification should look like:

    public final static FramingHeaderSpecification MY_FRAMING_HEADER = new FramingHeaderSpecification(
            // Size field specification
            new FramingHeaderSpecification.FieldSpecification(
                    0, // Offset in the header
                    2, // Size of the field
                    false, // Unsigned
                    MessageSchema.Endianess.LittleEndian // Byte order of this field
            ),

            // Message byte order marker specification
            new FramingHeaderSpecification.EndianessFieldSpecification(
                    2, // Offset in the header
                    2, // Size of the field
                    false, // Unsigned
                    MessageSchema.Endianess.LittleEndian, // Byte order of the field
                    FramingHeaderSpecification.SBE_1_0_LE_LITTLEENDIAN_SIGN, // Mark for little-endian byte order of the message.
                    FramingHeaderSpecification.SBE_1_0_LE_BIGENDIAN_SIGN // Mark for big-endian byte order of the message.
            )
    );

Please note the following details:

• The field order is explicitly defined by the field offset parameters in the constructors of the relevant objects.
• The byte order marker field should have two variants: one for little-endian SBE messages and one for big-endian messages.
• The byte order of the header itself is specified explicitly and is independent of the SBE message's byte order.

This SOFH specification must be used in the MessageSchema constructor:

// Custom header
MessageSchema schema = new MessageSchema(ParseUtil.parse(new File("MyTemplate.xml")),
        FramingHeaderPolicy.getCustomPolicy(MY_FRAMING_HEADER));