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<== Date ==> <== Thread ==>

Subject: javaIOC
From: Marty Kraimer <mrkraimer@comcast.net>
To: tech-talk@aps.anl.gov
Date: Thu, 11 Jan 2007 06:10:13 -0500
A new release of the javaIOC is now available. See

http://epics-doc.desy.de/ioc/javaIOC/index.html

Attached is an html file giving a brief status of the current state of javaIOC.

Marty Kraimer
Title: No title

Status javaIOC

A new release of the javaIOC is now available. See
http://epics-doc.desy.de/ioc/javaIOC/index.html

With the major exception of remote access, the basic functionality required for a working javaIOC is now implemented. Because remote access and no support, except for testing, is implemented the javaIOC is not ready for real applications.

The following is a brief summary of what is implemented.

Process Variable Database

A javaIOC is a Process Variable (PV) database, which is a "smart" database, i.e. a database consisting of records that can be processed. Each record instance has support code the implements record processing.

A PV record is a set of structured data. Each record has a recordType, which is just a top level structure. A structure is a set of fields that can have any of the following types:

  • boolean,byte,short,int,long,double
    All java primitive types except char.
  • string
    A java String.
  • enum,menu
    An enum is an array of choices and an index that selects a choice. A choice is a string. A menu is an enum that has a menuName and the array of choices is immutable.
  • link
    A link has no data but can have support and optionally have an associated configuration structure.
  • structure
    A structure contains a set of fields that can be any of the supported types. Since a field can be a structure, complex hierarchies can be created.
  • array
    An array is a 1 dimensional array that has a elementType, which can be any of the supported types.

Each field can optionaly have associated support, which is identified by a supportName.

A simple example of how these data types with associated support can be used is linkArray. A linkArray is an array of links with associated support. Any recordType can have an arrayLink field. When a record instances is defined the array of links can be created. An output record can have the array be a combination of process and output links. Thus any output record can also have builtin the capability of the V3 fanout and dfanout records.

Record Processing

Record processing is implemented. Each record instance can have only a single process requestor, i.e. code must register to be the process requestor.

Records can be periodically or event scanned. For periodic scanning the rate and priority is specified. The rate can be any value desired, with the restriction that the fastest rate is determined by the underlying java/os implementation. For event scanning, each event is identified by an eventName, which allows event scanning to replace the V3 event and I/O Intr scanning.

Database Listener

A listener can be attached to an field of a record. If the field is a structure than the listener is notified whenever any field within the structure is modified. In particular if the listener attaches to the record itself then the listener is notofied when any filed in the record is modified.

Channel Access

Local channel access is implemented. The CA client can issue process, get, put, and monitor requests. The client can modify the supportName associated with any field and also the configuration structure of a link field. When this is done the old support is automatically stopped and new support attached. Monitoring is implemented via ChannelData, which holds modified data, and ChannelDataQueue, which is a queue of ChannelDatas.

Channel Access Links

Support is implemented for process, input, output, and monitor links. It will work for both local and remote channel access but for now only local access is available.


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