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Extending Informix®Beyond standard relational database objects, HCL Informix® can be extended to handle specialized data types, access methods, routines, and other objects. Informix® includes many built-in extensions that are fully integrated in the database server. Informix® also provides DataBlade® modules, which are packages of extended database objects for a particular purpose and that are installed separately from the database server. Alternatively, you can create your own user-defined objects for Informix®.
Creating extensionsYou can create user-defined data types, routines, access methods, and other database objects to suit your needs. You can use application programming interfaces to write user-defined routines and applications that access data in Informix® databases.
DataBlade® API Programmer's GuideThe Informix® DataBlade® API Programmer's Guide describes information about the DataBlade® API, the C-language application programming interface (API) provided with HCL Informix®.
Create user-defined routines
Write a user-defined routineThis section outlines some implementation issues for C user-defined routines (UDRs). This section also describes the specific features and tasks of a C UDR.
Perform input and outputBecause a C UDR executes in the context of the database server, it must not use the standard input/output (I/O) calls such as scanf() and printf(). The DataBlade® API provides support for I/O on a generic stream and I/O on an operating-system file from a UDR.
Access to a stream (Server)The DataBlade® API provides a stream I/O interface, which enables you to use the same function calls to access different objects. Stream is a generic term for an object that can be written to or read from.
Create a user-defined stream classYou can provide a stream I/O interface to create your own protocol for reciprocal reading and writing of SQL data and other data streams.
Initialization of the stream descriptorAfter your type-specific stream-open function has prepared the arguments for the mi_stream_init() function, it must call mi_stream_init() to initialize the stream descriptor.

Initialization of the stream descriptor

After your type-specific stream-open function has prepared the arguments for the mi_stream_init() function, it must call mi_stream_init() to initialize the stream descriptor.

Tip: Whether the mi_stream_init() function actually allocates the stream descriptor depends on the value of its third argument. For more information, see The stream descriptor.

The stream descriptor, MI_STREAM, holds information about the data stream such as the data and its seek position. For the most current definition of the MI_STREAM structure, see the mistream.h header file.

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