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Writing a User-Defined Routine

In This Chapter

Defining Routine Parameters

Routines with No Arguments

MI_DATUM Arguments

MI_FPARAM Argument

Obtaining Argument Values

Handling Character Arguments

Handling NULL Arguments

Handling Opaque-Type Arguments

Modifying Argument Values

Defining a Return Value

Returning a Value

Returning Multiple Values

Coding the Routine Body

Using Virtual Processors

Creating a Well-Behaved Routine

Preserving Availability of the CPU VP

Writing Threadsafe Code

Avoiding Restricted System Calls

Choosing the User-Defined VP Class

Defining a User-Defined VP

Assigning a C UDR to a User-Defined VP Class

Managing Virtual Processors

Initializing a VP Class

Adding and Dropping VPs

Monitoring Virtual Processors

Controlling the VP Environment

Obtaining VP-Environment Information

Identifying the Current VP

Identifying a VP Class

Changing the VP Environment

Executing on Another VP

Forking and Executing a Process

Locking a Routine Instance to a VP

Locking a Shared-Object File in Memory

Performing Input and Output

Access to a Stream (Server)

Using Predefined Stream Classes

Creating a User-Defined Stream Class

Registering a UDR That Accesses a Stream

Releasing Stream Resources

Access to Operating-System Files

Sample File-Access UDR

Accessing the UDR Execution Environment

Accessing the Session Environment

Accessing the Server Environment

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