Guardian Procedure Calls Reference Manual

count-read := $MIN(read-count,EOF - next-record - next-record pointer)
◦ Number of bytes read
If the unstructured file is created with the odd unstructured attribute (also known as
ODDUNSTR) set, the number of bytes read is exactly the number specified with
read-count. If the odd unstructured attribute is not set when the file is created, the value
of read-count is rounded up to an even value before the FILE_READUPDATE64_ is
executed.
You set the odd unstructured attribute with the FILE_CREATE_, FILE_CREATELIST_, or
CREATE procedure, or with the File Utility Program (FUP) SET and CREATE commands.
Interprocess Communication Considerations
• Replying to messages
Each message read in a call to FILE_READUPDATE64_, including system messages, must be
replied to in a corresponding call to the FILE_REPLY64_ procedure.
• Queuing several messages before replying
Several interprocess messages can be read and queued by the application process before a
reply must be made. The maximum number of messages that the application process expects
to read before a corresponding reply is made must be specified in the receive-depth
parameter to the FILE_OPEN_ or OPEN procedure.
• If $RECEIVE is opened with receive-depth = 0, only FILE_READ64_ calls can be performed,
and FILE_READUPDATE64_ and FILE_REPLY64_ will fail with error 2 ("operation not allowed
on this type of file").
• Message tags when replying to queued messages
If more than one message is to be queued by the application process (that is, receive-depth
> 1), a message tag that is associated with each incoming message must be obtained in a
call to the FILE_GETRECEIVEINFOL_ (or FILE_GETRECEIVEINFO_ or LASTRECEIVE or
RECEIVEINFO) procedure following each call to FILE_READUPDATE64_. To direct a reply
back to the originator of the message, the message tag associated with the incoming message
is passed to the system in a parameter to the FILE_REPLY64_ procedure. If messages are not
to be queued, it is not necessary to call FILE_GETRECEIVEINFOL_ or FILE_GETRECEIVEINFO_.
Related Programming Manuals
For programming information about the FILE_READUPDATE64_ procedure, see the Guardian
Programmer's Guide and the Enscribe Programmer's Guide.
FILE_READUPDATE64_ Procedure 491