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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.
Accessing a stream in your UDR

Accessing a stream in your UDR

About this task

To access a stream in your UDR:

Procedure

Open the stream with the appropriate type-specific stream-open function.
The stream-open function is the stream I/O function that opens the stream, making the data available for a read or write operation. It returns a pointer to a stream descriptor, which the C UDR uses to access the stream. For more information, see The stream-open function.
Access the opened stream with the appropriate generic stream I/O function.
After a particular stream is open, a UDR can use the generic functions of the stream I/O interface to access the associated I/O object. Each of the generic stream I/O functions requires a stream descriptor for the stream on which the function is to operate. The usual sequence of access is to seek to the desired location in the stream, read or write the desired number of bytes, and close the stream.

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