SIP Codec Overview

• Purpose

• Architectural relationships

• Description of the interface class structure

• Memory overhead

The SIP Codec API provides services for encoding and decoding SIP headers and their fields. It also helps convert SIP messages from the UTF-8 ASCII format to the API implementation’s internal structure, and vice versa.

The API implementation verifies the SIP message syntax according to the SIP BNF definition.

The API implementation supports serialization and deserialization of objects belonging to the SIP message structure.

The implementation of the API is provided in a shared DLL that is executed in the user’s context. The API implementation creates class instances in the user’s heap area so that these instances cannot be shared between different users.

You must have a good understanding of the SIP protocol. Refer to SIP: Session Initiation Protocol, RFC 3261 for more information.

The SIP Codec API does not require any interfaces.

Capability information

No capabilities are required when using the SIP Codec API. This API is valid for all platforms running Symbian OS version 9.1.

Extending the API

There are no extensions to the SIP Codec API.

The logical type of the SIP Codec API is Library API. The interface contains synchronous functions that do not block, but return immediately. The interface uses only local objects.

The subsequent figures illustrate the relationships of the SIP Codec classes.

The SIP Codec API defines the functions required to create the SIP headers of a SIP message. CSIPHeaderBase is the base class for all SIP headers. A client creates a new instance of the CSIPXHeader class, where “X” is the name of the header required, and sets the values of the header with the setter functions of this class.

The amount of overhead memory used by every header object of the SIP Codec API is at least the same as the memory used by the header as text (class + the size of SIP headers).