Exit Program for Write to Stream File (QHFWRTSF) API

Before applications can use the Write to Stream File (QHFWRTSF) API with your file system, you must:

1. Write an exit program that performs the write operation on behalf of the API. For a detailed description of the API and its calling parameters, see Write to Stream File (QHFWRTSF) 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 QHFWRTSF 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 (WRTSF)

INPUT; CHAR(5)

The abbreviation for the operation being performed (WRTSF).

File system job handle

INPUT; CHAR(16)

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

The following parameters are the same as the parameters for the API.

Open file handle

INPUT; CHAR(16)

Data buffer

INPUT; CHAR(*)

Bytes to write

INPUT; BINARY(4)

Bytes actually written

OUTPUT; BINARY(4)

API Functions

The QHFWRTSF API performs the standard functions described in Standard HFS API Functions.

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:

• Verifies that the file was previously opened with an access mode of write or read/write.
  
  
• Makes sure that no part of the range of bytes being written is locked in a way that denies access to this operation.
  
  
• Writes the number of bytes specified in the data buffer to the file, starting at the current file pointer position.
  
  
• Records the number of bytes actually written. Unless an error occurs, this number must be the same as the number specified in the bytes-to-write parameter.
  
  
• Increases the value of the file pointer by the number of bytes written.
  
  
• If the write operation is not successful, sets the bytes actually written to zero and signals an exception describing the error to the API.

Error Messages for Exit Program Use

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