uk.co.real_logic.sbe.ir

Class Token

java.lang.Object

uk.co.real_logic.sbe.ir.Token

public class Token
extends Object

Class to encapsulate a token of information for the message schema stream. This Intermediate Representation (IR) is intended to be language, schema, platform independent. Processing and optimization could be run over a list of Tokens to perform various functions

• re-ordering of fields based on size
• padding of fields in order to provide expansion room
• computing offsets of individual fields
• etc.

IR could be used to generate code or other specifications. It should be possible to do the following:

• generate a FIX/SBE schema from IR
• generate an ASN.1 spec from IR
• generate a GPB spec from IR
• etc.

IR could be serialized to storage or network via code generated by SBE. Then read back in to a List of Tokens. The entire IR of an entity is a List of Token objects. The order of this list is very important. Encoding of fields is done by nodes pointing to specific encoding PrimitiveType objects. Each encoding node contains size, offset, byte order, and Encoding. Entities relevant to the encoding such as fields, messages, repeating groups, etc. are encapsulated in the list as nodes themselves. Although, they will in most cases never be serialized. The boundaries of these entities are delimited by BEGIN and END Signal values in the node Encoding. A list structure like this allows for each concatenation of encodings as well as easy traversal. An example encoding of a message headerStructure might be like this.

• Token 0 - Signal = BEGIN_MESSAGE, schemaId = 100
• Token 1 - Signal = BEGIN_FIELD, schemaId = 25
• Token 2 - Signal = ENCODING, PrimitiveType = uint32, size = 4, offset = 0
• Token 3 - Signal = END_FIELD
• Token 4 - Signal = END_MESSAGE

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	Token.Builder
static class	Token.VersionContext Indicates how the version field should be interpreted.

Field Summary

Fields

Modifier and Type	Field and Description
static int	INVALID_ID Invalid ID value.
static int	UNKNOWN_OFFSET Offset not computed or set
static int	VARIABLE_SIZE Size not determined

Constructor Summary

Constructors

Constructor and Description
Token(Signal signal, String name, int id, int version, int size, int offset, Encoding encoding) Construct an Token by providing values for all fields.

Method Summary

Modifier and Type	Method and Description
int	arrayLength() The number of encoded primitives in this type.
Encoding	encoding() Return the Encoding of the Token.
int	id() Return the ID of the token assigned by the specification
String	name() Return the name of the token
int	offset() The offset for this token in the message.
Signal	signal() Signal the role of this token.
int	size() The size of this token in bytes.
String	toString()
int	version() The version context for this token.
Token.VersionContext	versionContext() The context in which the version field should be interpreted.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

INVALID_ID

public static final int INVALID_ID

Invalid ID value.

See Also:

Constant Field Values

VARIABLE_SIZE

public static final int VARIABLE_SIZE

Size not determined

See Also:

Constant Field Values

UNKNOWN_OFFSET

public static final int UNKNOWN_OFFSET

Offset not computed or set

See Also:

Constant Field Values

Constructor Detail

Token

public Token(Signal signal,
             String name,
             int id,
             int version,
             int size,
             int offset,
             Encoding encoding)

Construct an Token by providing values for all fields.

Parameters:

signal - for the token role

name - of the token in the message

id - as the identifier in the message declaration

version - application within the template

size - of the component part

offset - in the underlying message as octets

encoding - of the primitive field

Method Detail

signal

public Signal signal()

Signal the role of this token.

Returns:

the Signal for the token.

name

public String name()

Return the name of the token

Returns:

name of the token

id

public int id()

Return the ID of the token assigned by the specification

Returns:

ID of the token assigned by the specification

version

public int version()

The version context for this token.

Returns:

version context for this token.

See Also:

versionContext()

versionContext

public Token.VersionContext versionContext()

The context in which the version field should be interpreted.

Returns:

context in which the version field should be interpreted.

size

public int size()

The size of this token in bytes.

Returns:

the size of this node. A value of 0 means the node has no size when encoded. A value of VARIABLE_SIZE means this node represents a variable length field.

arrayLength

public int arrayLength()

The number of encoded primitives in this type.

Returns:

number of encoded primitives in this type.

offset

public int offset()

The offset for this token in the message.

Returns:

the offset of this Token. A value of 0 means the node has no relevant offset. A value of UNKNOWN_OFFSET means this nodes true offset is dependent on variable length fields ahead of it in the encoding.

encoding

public Encoding encoding()

Return the Encoding of the Token.

Returns:

encoding of the Token

toString

public String toString()

Overrides:

toString in class Object