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<h1>EPICS pvAccessCPP</h1>
<!-- Maturity: Working Draft or Request for Comments, or Recommendation, and date. -->
<h2 class="nocount">EPICS v4 Working Group, Working Draft, 05-June-2011</h2>
<h2 class="nocount" id="L50">EPICS v4 Working Group, Working Draft, 09-July-2011</h2>
<dl>
<dt>Latest version:</dt>
<dd><a
@ -46,11 +46,11 @@
</a></dd>
<dt>This version:</dt>
<dd><a
href="pvAccessCPP_20150505.html">pvAccessCPP_20150505.html
href="pvAccessCPP_20140709.html">pvAccessCPP_20140709.html
</a></dd>
<dt>Previous version:</dt>
<dd><a
href="pvAccessCPP_20140709.html">pvAccessCPP_20140709.html
href="pvAccessCPP_20111220.html">pvAccessCPP_20111220.html
</a></dd>
<dt>Editors:</dt>
<dd>Marty Kraimer, BNL<br />
@ -59,77 +59,40 @@
<hr />
<h2 class="nocount">Abstract</h2>
<p>pvAccessCPP is the C++ implementation of pvAccess,
which is network support for transporting structured data as defined by pvData.
</p>
<p>
pvAccess is one of a related
set of products:
<p>pvAccessCPP is the C++ implementation of pvAccess, which is one of a related
set of products:</br >
<a href="http://epics-pvdata.sourceforge.net/relatedDocumentsV4.html">relatedDocumentsV4.html</a>
</p>
<h2 class="nocount">Status of this Document</h2>
<p>This is the 05-June-2011 version of the C++ implementation of pvAccess. The
code is a complete implementation of pvAccess.</p>
<p>This is the 09-July-2011 version of the C++ implementation of pvAccess. The
code is a complete implementation of pvAccess as currently defined. This
overview is NOT written.</p>
</div>
<div id="toc">
<h2 class="nocount">Table of Contents</h2>
<h2 class="nocount" style="page-break-before: always">Table of Contents</h2>
</div>
<!-- Place what you would like in the Table of Contents, inside the contents div -->
<div id="contents" class="contents">
<h2 id="L88">Introduction</h2>
<hr />
<h2>Preface</h2>
<p>This document describes the pvAccess Application Program Interface (API).
The reader is assumed to have a basic understanding of EPICS V4 as described in:</p>
<a
href="http://epics-pvdata.sourceforge.net/informative/developerGuide/developerGuide.html">
EPICS V4 Developer's Guide
</a>
<p>The pvAccess API is callback based and uses Status to report problem to the
client, which means that it can be complex to use.
If your primary interest is client access then, instead of reading this document,
read:</p>
<a
href="pva.html">
EPICS pva
</a>
<p>If your primary interest is implementing pvAccess services then,
before reading this documement read:</p>
<a
href="http://epics-pvdata.sourceforge.net/docbuild/pvDatabaseCPP/tip/documentation/pvDatabaseCPP.html">
pvDatabaseCPP
</a>
<p>This product is available via an <a
href="http://epics-pvdata.sourceforge.net/LICENSE.html">open source
license</a></p>
<p>This overview for pvAccessCPP. Doxygen documentation is available at <a
href="./html/index.html">doxygenDoc</a></p>
<h2>Introduction</h2>
<p>This product is available via an
<a
href="http://epics-pvdata.sourceforge.net/LICENSE.html">open source license
</a>
</p>
<p>
A user overview is available via
<a
href="./pvAccessOverview.html">pvAccessOverview.html
</a>
</p>
<p>
Doxygen documentation is available at
<a
href="./html/index.html">doxygenDoc
</a>
<h2>???</h2>
<p>Matej decide what else should go in this document</p>
<p><b>THIS IS NOT WRITTEN</b> For now please consult pvAccessJava.html.
In addition look at the Doxygen documentation for this project.</p>
</div>
</body>

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<?xml version="1.0" encoding="iso-8859-1"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="content-type" content="text/html; charset=iso-8859-1" />
<title>EPICS pvAccessCPP</title>
<link rel="stylesheet" type="text/css"
href="http://epics-pvdata.sourceforge.net/base.css" />
<link rel="stylesheet" type="text/css"
href="http://epics-pvdata.sourceforge.net/epicsv4.css" />
<style type="text/css">
/*<![CDATA[*/
.about { margin-left: 3em; margin-right: 3em; font-size: .83em}
table { margin-left: auto; margin-right: auto }
.diagram { text-align: center; margin: 2.5em 0 }
span.opt { color: grey }
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p.ed.priv { display: inline; }
span.ed.priv { display: inline; }
/*]]>*/</style>
<!-- Script that generates the Table of Contents -->
<script type="text/javascript"
src="http://epics-pvdata.sourceforge.net/script/tocgen.js">
</script>
</head>
<body>
<div class="head">
<h1>EPICS pvAccessCPP</h1>
<!-- Maturity: Working Draft or Request for Comments, or Recommendation, and date. -->
<h2 class="nocount">EPICS v4 Working Group, Working Draft, 05-June-2011</h2>
<dl>
<dt>Latest version:</dt>
<dd><a
href="pvAccessCPP.html">pvAccessCPP.html
</a></dd>
<dt>This version:</dt>
<dd><a
href="pvAccessCPP_20150505.html">pvAccessCPP_20150505.html
</a></dd>
<dt>Previous version:</dt>
<dd><a
href="pvAccessCPP_20140709.html">pvAccessCPP_20140709.html
</a></dd>
<dt>Editors:</dt>
<dd>Marty Kraimer, BNL<br />
Matej Sekoranja, CosyLab</dd>
</dl>
<hr />
<h2 class="nocount">Abstract</h2>
<p>pvAccessCPP is the C++ implementation of pvAccess,
which is network support for transporting structured data as defined by pvData.
</p>
<p>
pvAccess is one of a related
set of products:
<a href="http://epics-pvdata.sourceforge.net/relatedDocumentsV4.html">relatedDocumentsV4.html</a>
</p>
<h2 class="nocount">Status of this Document</h2>
<p>This is the 05-June-2011 version of the C++ implementation of pvAccess. The
code is a complete implementation of pvAccess.</p>
</div>
<div id="toc">
<h2 class="nocount">Table of Contents</h2>
</div>
<!-- Place what you would like in the Table of Contents, inside the contents div -->
<div id="contents" class="contents">
<hr />
<h2>Preface</h2>
<p>This document describes the pvAccess Application Program Interface (API).
The reader is assumed to have a basic understanding of EPICS V4 as described in:</p>
<a
href="http://epics-pvdata.sourceforge.net/informative/developerGuide/developerGuide.html">
EPICS V4 Developer's Guide
</a>
<p>The pvAccess API is callback based and uses Status to report problem to the
client, which means that it can be complex to use.
If your primary interest is client access then, instead of reading this document,
read:</p>
<a
href="pva.html">
EPICS pva
</a>
<p>If your primary interest is implementing pvAccess services then,
before reading this documement read:</p>
<a
href="http://epics-pvdata.sourceforge.net/docbuild/pvDatabaseCPP/tip/documentation/pvDatabaseCPP.html">
pvDatabaseCPP
</a>
<h2>Introduction</h2>
<p>This product is available via an
<a
href="http://epics-pvdata.sourceforge.net/LICENSE.html">open source license
</a>
</p>
<p>
A user overview is available via
<a
href="./pvAccessOverview.html">pvAccessOverview.html
</a>
</p>
<p>
Doxygen documentation is available at
<a
href="./html/index.html">doxygenDoc
</a>
<h2>???</h2>
<p>Matej decide what else should go in this document</p>
</div>
</body>
</html>

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<?xml version="1.0" encoding="iso-8859-1"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="content-type" content="text/html; charset=iso-8859-1" />
<title>EPICS pva</title>
<link rel="stylesheet" type="text/css"
href="http://epics-pvdata.sourceforge.net/base.css" />
<link rel="stylesheet" type="text/css"
href="http://epics-pvdata.sourceforge.net/epicsv4.css" />
<style type="text/css">
/*<![CDATA[*/
.about { margin-left: 3em; margin-right: 3em; font-size: .83em}
table { margin-left: auto; margin-right: auto }
.diagram { text-align: center; margin: 2.5em 0 }
body { margin-right: 10% }
/*]]>*/</style>
<!-- Script that generates the Table of Contents -->
<script type="text/javascript" src="http://epics-pvdata.sourceforge.net/script/tocgen.js"></script>
</head>
<body>
<div class="head">
<h1>EPICS pva</h1>
<!-- Maturity: Working Draft or Request for Comments, or Recommendation, and date. -->
<h2 class="nocount">EPICS V4 Working Group, Working Draft,
29-May-2015</h2>
<dl>
<dt>This version:</dt>
<dd><a
href="pva.html">pva.html
</a> </dd>
<dt>Latest version:</dt>
<dd><a
href="pva_20150529.html">pva_20150529.html</a>
</dd>
<dt>Previous version:</dt>
<dd>none</dd>
<dt>Editors:</dt>
<dd>Marty Kraimer, BNL</dd>
<dd>Matej Sekoranja, Cosylab</dd>
</dl>
<h2 class="nocount">Abstract</h2>
<p>Pva (Pva PVAccess) is a software library that provides to an EPICS client programmer, a friendly
client side programming interface to the data of an EPICS based control system. It is intended
for such uses as rapid development of ad hoc programs by controls engineers, or to provide
scientists a way to directly develop analytical applications.</p>
<p>Specifically, pva provides a synchronous interface for pvAccess, which is the
software support for high speed controls network communications used in EPICS version 4.
PvAccess provides a callback based interface, which can be hard to use.
Pva provides an interface that does not require callbacks even for monitors.
</p>
<p>
PvaChannel provides many "convenience" methods to directly get and put
scalar and scalarArray data types.
Additional methods provide access to the full features of pvAccess.
</p>
<p>
PvaMultiChannel provides access to data from multiple channels.
It can be used directly by a client or via PvaMultiDouble or PvaNTMultiChannel.
PvaMultiDouble allows the client to get and put data to multiple channels.
But each channel must have a value field that is a numeric scalar.
PvaNTMultiChannel allows the client to get and put data to multiple channels.
Each channel must have a value field.
The data for the channels is presented via normative type NTMultiChannel.
</p>
<!-- last para of Abstract is boilerplate reference to EPICS -->
<p>For more information about EPICS generally, please refer to the home page of the <a
href="http://www.aps.anl.gov/epics/">Experimental Physics and Industrial
Control System</a>.</p>
<h2 class="nocount">Status of this Document and of the Pva Software</h2>
<p>PvaCPP is ready for use.</p>
</div> <!-- head -->
<div id="toc">
<h2 class="nocount">Table of Contents</h2>
</div>
<!-- Place what you would like in the Table of Contents, inside the contents div -->
<div id="contents" class="contents">
<hr />
<h2>Introduction</h2>
<p>Pva is a synchronous API for accessing PVData via PVAccess. It provides
an interface to many of the features provided by pvData and pvAccess.</p>
<p>This document describes the layout of the source files in this project.</p>
<p>
A user overview is available via
<a
href="./pvaOverview.html">pvaOverview.html
</a>
</p>
<p>
Doxygen documentation is available at
<a
href="./html/index.html">doxygenDoc
</a>
</p>
<h2>Example and Test Database</h2>
<p>The examples and tests require that an example pvAccess server is runnimg.
This distribution has a file <b>exampleDatabasePva.zip</b>.
When unzipped this is used to create an example IOC database.
The database has the record used by the examples are tests that come with pvaJava.
It uses pvDatabaseCPP to build the database.
</p>
<p>
After unzipping the file:
</p>
<pre>
cd configure
cp ExampleRELEASE.local RELEASE.local
edit RELEASE.local
cd ..
make
cd iocBoot/exampleDatabase
../../bin/&lt;arch:&gt;/exampleDatabase st.cmd
</pre>
<h2>Testing</h2>
<p>The tests will fail unless the example database is running.</p>
<p>Once it is running:</p>
<pre>
make runtests
</pre>
<h2>Examples</h2>
<p>Examples are in directory <b>pvaExample/src</b>.
An example of how to run them is:</p>
<pre>
mrk&gt; pwd
/home/epicsv4/pvAccessCPP/pvaExample
mrk&gt; bin/linux-x86_64/examplePvaGet
</pre>
<p>The following is a brief description of each example.
In order to understand each example it
helps to also look at the source for the example.</p>
<h2>examplePvaGet</h2>
<p>This has a number of examples:</p>
<dl>
<dt>exampleDouble</dt>
<dd>
This shows two methods for getting data from a channel that has a numeric
scalar value field.
</dd>
<dt>exampleDoubleArray</dt>
<dd>
This shows two methods for getting data from a channel that has a
double array value field.
</dd>
<dt>exampleCADouble</dt>
<dd>
This is like exampleDouble except it uses provider <b>ca</b>.
</dd>
<dt>exampleCADoubleArray</dt>
<dd>
This is like exampleDoubleArray except it uses provider <b>ca</b>.
</dd>
<dt>examplePowerSupply</dt>
<dd>
This is an example of getting data from a channel that does not
have a value field.
</dd>
</dl>
<h2>examplePvaMonitor</h2>
<p>This is an example of creating a monitor on a channel.
It monitors a channel that models a powerSupply, i. e. it is not a "standard" record.
It does not have a value field.
</p>
<p>After starting the example a change can be made to the powerSupply by issuing:</p>
<pre>
pvput -r "power.value,voltage.value" examplePowerSupply 6 6
</pre>
<h2>examplePvaPut</h2>
<p>This example gets and puts to channel exampleDouble.</p>
<h2>examplePvaProcess</h2>
<p>This example makes a process request to channel exampleDouble.</p>
<h2>helloWorldPutGet</h2>
<p>This is an example of issuing a channelPutGet.</p>
<h2>examplePvaMultiDouble</h2>
<p>This is an example of issuing gets and puts to multiple channels where each
channel has a numeric scalar value field.</p>
<h2>examplePvaNTMultiChannel</h2>
<p>This is an example of using NDMultiChannel to obtain data from multiple channels.
</p>
<h2>helloWorldRPC</h2>
<p>This is an example of issuing a channelRPC request.
It does <b>not</b> use pva.</p>
</div> <!-- class="contents" -->
</body>
</html>

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<?xml version="1.0" encoding="iso-8859-1"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="content-type" content="text/html; charset=iso-8859-1" />
<title>pva C++ Overview</title>
<link rel="stylesheet" type="text/css"
href="http://epics-pvdata.sourceforge.net/base.css" />
<link rel="stylesheet" type="text/css"
href="http://epics-pvdata.sourceforge.net/epicsv4.css" />
<style type="text/css">
/*<![CDATA[*/
.about { margin-left: 3em; margin-right: 3em; font-size: .83em}
table { margin-left: auto; margin-right: auto }
.diagram { text-align: center; margin: 2.5em 0 }
body { margin-right: 10% }
/*]]>*/</style>
<!-- Script that generates the Table of Contents -->
<script type="text/javascript" src="http://epics-pvdata.sourceforge.net/script/tocgen.js"></script>
</head>
<body>
<div class="head">
<h1>Pva C++ Overview</h1>
</div> <!-- head -->
<div id="toc">
<h2 class="nocount">Table of Contents</h2>
</div>
<!-- Place what you would like in the Table of Contents, inside the contents div -->
<div id="contents" class="contents">
<hr />
<h2>Introduction</h2>
<p>Pva is a synchronous API for accessing PVData via PVAccess.
It also provides a number of convenience methods.
It allows the client to request access without checking for failure,
but throws an exception if a request fails.
A client can also check for failues and thus prevent exceptions.</p>
<p>The Pva API has the following features:</p>
<ol>
<li>Provides a synchronous API rather than the callback API provided by pvAccess.</li>
<li>Makes common requests pva.</li>
<li>Provides full access to the pvAccess API for more demanding
applications</li>
<li>Allows efficient client side programs.</li>
<li>Takes care of most object resource management problems.</li>
</ol>
<p>Simple examples of using pva:</p>
<pre>
// pvaGet
PvaPtr pva = Pva::create();
double value = pva-&gt;channel("exampleDouble")-&gt;get()-&gt;getData()-&gt;getDouble();
// pvaPut
PvaChannelPtr channel = pva-&gt;channel("exampleDouble");
PvaPutPtr put = channel-&gt;put();
PvaPutDataPtr putData = put-&gt;getData();
putData-&gt;putDouble(3.0); put-&gt;put();
// pvaMonitor
PvaMonitorPtr monitor = pva-&gt;channel("examplePowerSupply")-&gt;monitor("");
PvaMonitorDataPtr pvaData = monitor-&gt;getData();
while(true) {
monitor-&gt;waitEvent();
cout &lt;&lt; "changed\n";
pvaData-&gt;showChanged(cout);
cout &lt;&lt; "overrun\n";
pvaData-&gt;showOverrun(cout);
monitor-&gt;releaseEvent();
}
// pvaProcess
PvaChannelPtr channel = pva-&gt;channel("exampleDouble");
PvaProcessPtr process = channel-&gt;createProcess();
process-&gt;process();
</pre>
<p><b>pvaExample</b> includes a number of examples.</p>
<p>pva does <b>not</b> provide support for:</p>
<dl>
<dt>ChannelArray</dt>
<dd>TBD</dd>
<dt>ChannelRPC</dt>
<dd>pvAccess itself already provides a synchronous interface.
The examples include helloWorldRPC, which is an example of using channelRP.
</dd>
</dl>
<h2>Pva</h2>
<p>An instance of Pva is obtained via the call:</p>
<pre>
PvaPtr pva = Pva::create();
</pre>
<p>Pva has methods to create instances of <b>PvaChannel</b>.
The client can specify the provider name or use the default provider.
The client can manage it's own channels or can let pva cache channels.
An example of using the cached method is:</p>
<pre>
PvaChannelPtr pvaChannel = pva-&gt;channel("exampleDouble");
</pre>
<p>This will attempt to connect to channel exampleDouble.
Since the client did not specify a timeout an exception wll be thrown if
the connection request fails.
The client will block until the connection is made or an exception is thrown.
If the request succeeds, pva caches the pvaChannel so that if the
client makes another request for the same channel the cached object is
returned to the client.
</p>
<p>An example of using a non cached method is:</p>
<pre>
PvaChannelPtr pvaChannel = pva-&gt;createChannel("exampleDouble");
</pre>
<p>This will create an PvaChannel and return it to the client.
The client must itself connect.
This is useful if the client wants to connect to multiple channels in parallel.
</p>
<h2>PvaChannel - Wrapper For Single Channel</h2>
<h3>PvaChannel</h3>
<p>This provides methods for connecting to a channel and for creating instances of
PvaField, PvaProcess, ..., PvaPutGet.</p>
<p>Connection must be made before any create method is called or
an exception is raised.
The following is a synchronous connection request:</p>
<pre>
pvaChannel-&gt;connect(5.0); // BLOCKS AND THROWS IF NO CONNECT
</pre>
<p>This blocks until then connection is made or until timout occurs.
An exception is raised if the connection request fails.
</p>
<p>The same request can be made without blocking and without exceptions.</p>
<pre>
pvaChannel-&gt;issueConnect(); // DOES NOT BLOCK
.....
Status status =pvaChannel-&gt;waitConnect(5.0); // BLOCKS DOES NOT THROW
if(!status.isOK()) {
// failure do something
}
</pre>
<p>Once the channel is connected other Pva objects can be created.
For example:</p>
<pre>
PvaGetPtr pvaGet = pvaChannel-&gt;get(); // DOES BLOCK
</pre>
<p>This is a caching request.
If the client already has made an identical request the client will receive the
cached object.
If a new pvaGet is created than it is connected before it is returned to the client.
</p>
<p>The client can also managed it's own objects:</p>
<pre>
PvaGetPtr pvaGet = pvaChannel-&gt;createGet(); // DOES NOT BLOCK
</pre>
<p>The client must connect the pvaGet.</p>
<h3>PvaGetData</h3>
<p>This provides the data returned by pvaGet and pvaPutGet.
It is obtained via:</p>
<pre>
PvaGetDataPtr pvaData = pvaGet-&gt;getData();
</pre>
<p>It provides methods to get everything returned by channelGet.
In addition there are methods that make it easier to handle a value
field that is a scalar or a scalarArray.
Also for a scalar that is a double or a scalarArray with element type double.
</p>
<p>An example is:</p>
<pre>
double value = pvaData-&gt;getDouble();
</pre>
<p>It also keeps a bitSet showing which fields have changed since the last channelGet or channelPutGet.</p>
<h3>PvaMonitorData</h3>
<p>To the client this looks identical to PvaGetData except that
it provides two BitSets: changedBitSet and overrrunBitSet.
It is used by pvaMonitor.
</p>
<h3>PvaPutData</h3>
<p>This is used to provided data for pvaPut and pvaPutGet.
It has many of the same methods as pvaGetData.
It does not have a bitSet.
It also has put methods like:</p>
<pre>
void pvaData-&gt;putDouble(5.0);
</pre>
<h3>PvaGet</h3>
<p>This provides methods to connect to channelGet and to issue get request.
To connect via a single synchronous call:</p>
<pre>
eastGet-&gt;connect(); // BLOCKS AND CAN THROW
</pre>
<p>This can also be done in two steps:</p>
<pre>
pvaGet-&gt;issueConnect(); // DOES NOT BLOCK
...
Status status = pvaGet-&gt;waitConnect(); // BLOCKS AND DOES NOT HROW
</pre>
<p>Once connected gets are issued via either:</p>
<pre>
void pvaGet-&gt;get(); // BLOCKS AND CAN THROW
</pre>
or
<pre>
pvaGet-&gt;issueGet(); // DOES NOT BLOCK
...
Status status = pvaGet-&gt;waitGet(); // BLOCKS AND DOES NOT THROW
</pre>
<h3>PvaPut</h3>
<p>This is similar to pvaGet except that it wraps channelPut instead of channelGet.
</p>
<p>Once connected puts are issued via either:</p>
<pre>
void pvaPut-&gt;put(); // BLOCKS AND CAN THROW
</pre>
or
<pre>
pvaPut-&gt;issuePut(); // DOES NOT BLOCK
...
Status status = pvaPut-&gt;waitPut(); // BLOCKS AND DOES NOT THROW
</pre>
<h3>PvaMonitor</h3>
<p>Connecting is similar to pvaGet and pvaPut.
The other methods are:</p>
<dl>
<dt>start</dt>
<dd>Starts monitoring</dd>
<dt>stop</dt>
<dd>Stops monitoring</dd>
<dt>poll</dt>
<dd>polls for a monitorEvent.
The data is avalable via pvaMonitorData.
</dd>
<dt>releaseEvent</dt>
<dd>Release the data from the last poll.
Note that this must be called before another poll is requested.
</dd>
<dt>waitEvent</dt>
<dd>Block until a monitorEvent is available.
If true is returned a poll has already been issued.
</dd>
<dt>setRequester</dt>
<dd>A client callback is registered to receive notice of monitorEvents.</dd>
</dl>
<h3>PvaProcess</h3>
<p>Connecting is similar to pvaGet.
It has methods:</p>
<dl>
<dt>process</dt>
<dd>call issueProcess and waitProcess.</dd>
<dt>issueProcess</dt>
<dd>call channelProcess-&gt;process() and return immediately.
</dd>
<dt>waitProcess</dt>
<dd>Wait for process to complete.</dd>
</dl>
<h3>PvaPutGet</h3>
<p>Connecting is similar to pvaGet.
It has methods:</p>
<dl>
<dt>putGet</dt>
<dd>calls issuePutGet and waitPutGet.
throws an exception if not successfull.
</dd>
<dt>issuePutGet</dt>
<dd>
Calls channel-&gt;putGet() and returns.
</dd>
<dt>waitPutGet</dt>
<dd>
Waits until putGet completes and returns status.
</dd>
<dt>getGet,issueGetGet, and waitGetGet</dt>
<dd>Gets the data for the get part of channelPutGet.</dd>
<dt>getPut,issueGetPut,and waitGetPut</dt>
<dd>Gets the data for the put part of channelPutGet.</dd>
<dt>getPutData</dt>
<dd>
Returns the PvaData for the put part of channelPutGet.
</dd>
<dt>getGetData</dt>
<dd>
Returns the PvaData for the get part of channelPutGet.
</dd>
</dl>
<p>Look at javaDoc for details.</p>
<h2>PvaMultiChannel - Wrapper For Multiple Channels</h2>
<h3>PvaMultiChannel</h3>
<p>This provides methods for connecting to multiple channels.
A client can either use PvaMultiChannel directly or use PvaMultiDouble or PvaNTMultiChannel.
But both impose restrictions on what can be accessed.
</p>
<h3>PvaMultiDouble</h3>
<p>This provides support for gets and puts to the value field of multiple channels.
Each channel must have a value field that is a numeric scalar.
The client always sees the data as a PVDoubleArray.
All channels must connect.
If any problems occur an exception is thrown.
</p>
<h3>PvaNTMultiChannel</h3>
<p>This provides support for gets and puts to the value field of multiple channels.
Each channel must have a value field.
The client always sees the data as a NTMultiChannel, which is one
of the types provided by normativeTypesCPP.
All channels must connect.
If any problems occur an exception is thrown.
</p>
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<h1>EPICS pva</h1>
<!-- Maturity: Working Draft or Request for Comments, or Recommendation, and date. -->
<h2 class="nocount">EPICS V4 Working Group, Working Draft,
29-May-2015</h2>
<dl>
<dt>This version:</dt>
<dd><a
href="pva.html">pva.html
</a> </dd>
<dt>Latest version:</dt>
<dd><a
href="pva_20150529.html">pva_20150529.html</a>
</dd>
<dt>Previous version:</dt>
<dd>none</dd>
<dt>Editors:</dt>
<dd>Marty Kraimer, BNL</dd>
<dd>Matej Sekoranja, Cosylab</dd>
</dl>
<h2 class="nocount">Abstract</h2>
<p>Pva (Pva PVAccess) is a software library that provides to an EPICS client programmer, a friendly
client side programming interface to the data of an EPICS based control system. It is intended
for such uses as rapid development of ad hoc programs by controls engineers, or to provide
scientists a way to directly develop analytical applications.</p>
<p>Specifically, pva provides a synchronous interface for pvAccess, which is the
software support for high speed controls network communications used in EPICS version 4.
PvAccess provides a callback based interface, which can be hard to use.
Pva provides an interface that does not require callbacks even for monitors.
</p>
<p>
PvaChannel provides many "convenience" methods to directly get and put
scalar and scalarArray data types.
Additional methods provide access to the full features of pvAccess.
</p>
<p>
PvaMultiChannel provides access to data from multiple channels.
It can be used directly by a client or via PvaMultiDouble or PvaNTMultiChannel.
PvaMultiDouble allows the client to get and put data to multiple channels.
But each channel must have a value field that is a numeric scalar.
PvaNTMultiChannel allows the client to get and put data to multiple channels.
Each channel must have a value field.
The data for the channels is presented via normative type NTMultiChannel.
</p>
<!-- last para of Abstract is boilerplate reference to EPICS -->
<p>For more information about EPICS generally, please refer to the home page of the <a
href="http://www.aps.anl.gov/epics/">Experimental Physics and Industrial
Control System</a>.</p>
<h2 class="nocount">Status of this Document and of the Pva Software</h2>
<p>PvaCPP is ready for use.</p>
</div> <!-- head -->
<div id="toc">
<h2 class="nocount">Table of Contents</h2>
</div>
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<div id="contents" class="contents">
<hr />
<h2>Introduction</h2>
<p>Pva is a synchronous API for accessing PVData via PVAccess. It provides
an interface to many of the features provided by pvData and pvAccess.</p>
<p>This document describes the layout of the source files in this project.</p>
<p>
A user overview is available via
<a
href="./pvaOverview.html">pvaOverview.html
</a>
</p>
<p>
Doxygen documentation is available at
<a
href="./html/index.html">doxygenDoc
</a>
</p>
<h2>Example and Test Database</h2>
<p>The examples and tests require that an example pvAccess server is runnimg.
This distribution has a file <b>exampleDatabasePva.zip</b>.
When unzipped this is used to create an example IOC database.
The database has the record used by the examples are tests that come with pvaJava.
It uses pvDatabaseCPP to build the database.
</p>
<p>
After unzipping the file:
</p>
<pre>
cd configure
cp ExampleRELEASE.local RELEASE.local
edit RELEASE.local
cd ..
make
cd iocBoot/exampleDatabase
../../bin/&lt;arch:&gt;/exampleDatabase st.cmd
</pre>
<h2>Testing</h2>
<p>The tests will fail unless the example database is running.</p>
<p>Once it is running:</p>
<pre>
make runtests
</pre>
<h2>Examples</h2>
<p>Examples are in directory <b>pvaExample/src</b>.
An example of how to run them is:</p>
<pre>
mrk&gt; pwd
/home/epicsv4/pvAccessCPP/pvaExample
mrk&gt; bin/linux-x86_64/examplePvaGet
</pre>
<p>The following is a brief description of each example.
In order to understand each example it
helps to also look at the source for the example.</p>
<h2>examplePvaGet</h2>
<p>This has a number of examples:</p>
<dl>
<dt>exampleDouble</dt>
<dd>
This shows two methods for getting data from a channel that has a numeric
scalar value field.
</dd>
<dt>exampleDoubleArray</dt>
<dd>
This shows two methods for getting data from a channel that has a
double array value field.
</dd>
<dt>exampleCADouble</dt>
<dd>
This is like exampleDouble except it uses provider <b>ca</b>.
</dd>
<dt>exampleCADoubleArray</dt>
<dd>
This is like exampleDoubleArray except it uses provider <b>ca</b>.
</dd>
<dt>examplePowerSupply</dt>
<dd>
This is an example of getting data from a channel that does not
have a value field.
</dd>
</dl>
<h2>examplePvaMonitor</h2>
<p>This is an example of creating a monitor on a channel.
It monitors a channel that models a powerSupply, i. e. it is not a "standard" record.
It does not have a value field.
</p>
<p>After starting the example a change can be made to the powerSupply by issuing:</p>
<pre>
pvput -r "power.value,voltage.value" examplePowerSupply 6 6
</pre>
<h2>examplePvaPut</h2>
<p>This example gets and puts to channel exampleDouble.</p>
<h2>examplePvaProcess</h2>
<p>This example makes a process request to channel exampleDouble.</p>
<h2>helloWorldPutGet</h2>
<p>This is an example of issuing a channelPutGet.</p>
<h2>examplePvaMultiDouble</h2>
<p>This is an example of issuing gets and puts to multiple channels where each
channel has a numeric scalar value field.</p>
<h2>examplePvaNTMultiChannel</h2>
<p>This is an example of using NDMultiChannel to obtain data from multiple channels.
</p>
<h2>helloWorldRPC</h2>
<p>This is an example of issuing a channelRPC request.
It does <b>not</b> use pva.</p>
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