Exit Program for Open Stream File (QHFOPNSF) API

Before applications can use the Open Stream File (QHFOPNSF) API with your file system, you must:

1. Write an exit program that performs the open stream file operation on behalf of the API. For a detailed description of the API and its calling parameters, see Open Stream File (QHFOPNSF) API.
   
   
2. Give the exit program's name when you register the file system with the Register File System (QHFRGFS) API.

After that, when an application calls the QHFOPNSF API, the API calls your exit program and passes it the parameters specified by the application. Your exit program performs the work and returns any data to the API. The API passes the data back to the calling application.

Authorities and Locks

None.

Required Parameter Group

The following shows the input parameters that the API passes to your exit program and the output parameters that the exit program must pass back to the API:

Operation (OPNSF)

INPUT; CHAR(5)

The abbreviation for the operation being performed (OPNSF).

File system job handle

INPUT; CHAR(16)

The work area or job identifier for use by the file system.

Reserved

INPUT; CHAR(20)

Reserved for future use. This parameter is set to blanks.

Except as noted, the following parameters are the same as the parameters for the API.

Open file handle

OUTPUT; CHAR(16)

Path name

INPUT; CHAR(*)

The API removes the file system name before passing the path name to the exit program.

Path name length

INPUT; BINARY(4)

Open information

INPUT; CHAR(10)

The exit program can ignore character 7, which describes the type of open operation to perform. This field is used by i5/OS HFS support during job cleanup if the job ends before the file is closed.

Attribute information table

INPUT; CHAR(*)

Length of the attribute information table

INPUT; BINARY(4)

Action taken

OUTPUT; CHAR(1)

API Functions

The QHFOPNSF API performs the standard functions described in Standard HFS API Functions and these additional functions:

• Verifies that the length of the attribute information table is not negative.
  
  
• Ensures that the file is closed during normal job cleanup, in case the user forgets to close it before ending the job.
  
  
• Handles the type-of-open value represented by character 7 of the open information parameter. The file system does not need to take any action on the basis of this value.

Exit Program Requirements

You must create an exit program that performs the standard functions described in Standard HFS Exit Program Requirements and these additional functions:

• Checks for previous open operations that have lock modes conflicting with the requested access mode for this file.
  
  
• Attempts to take the action designated by the open information. The action can be opening an existing file, opening and replacing an existing file, or creating and opening a new file.
  
  
• If the action is successful, assigns a file handle, locks the file and its attributes, and returns the handle and action taken to the API. The API does not return this handle to the application. The API creates a handle of its own to return to the application. This procedure improves API performance and ensures that handles are unique across file systems.

Error Messages for Exit Program Use

This section lists the messages that the exit program can return to the API.