Other Library Functions

function

vfLock

Library: omvfile - virtual file access and locking Include: omvfile.xin

Return type: String Returns:        A lock-id string.

Declaration

  define external integer function vfLock
              value      omVFile    this-vfile
      from    value      integer    start-location optional
      to      value      integer    end-location   optional
      timeout	value      integer    time-out       optional
      id      modifiable int32      lock-id        optional

Where:
this-vfile

the omVFile object we want to lock

the start position for the lock and including the address to lock

the end position for the lock and including the address to lock

the maximum time to wait for the lock, in milliseconds

lock-id number to be returned by the function

You can use this function to lock an omVFile object or a specific area of it.

Results depend on which combination of the optional parameters you use. For example:

• If neither "start-location" nor "end-location" are defined, the function attempts to lock the entire object.
• If only "start-location" is defined, the function attempts to lock from and including the address to the end of the object.
• If only "end-location" is defined, the function attempts to lock from the start of the object up to and including the address.
• If "lock-id" is defined, the function returns a lock-id.
• If no timeout value is specified, the function waits indefinitely for a lock.

Sample function call:

   vfLock vfile to 4

The above code locks the first 4 bytes of a vfile.