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mrkraimer
2017-07-06 15:33:08 -04:00
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documentation/htmldoxygen/pvaClient.html
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<h1>PvaClient</h1>
<p>
<b>Not Yet Written</b>
</p>
<h2>Overview</h2>
<p>
@@ -45,6 +42,81 @@ pvaClient is a synchronous wrapper for the pvAccess API, which is a callback bas
Thus it is easier to use than pvAccess itself.
In addition pvaClient provides many convenience methods.
</p>
<p>
Class <b>PvaClient</b> is a class that is used by all the other pvaClient classes.
An application that uses pvaClient must call:</p>
<pre>
PvaClientPtr pvaClient = PvaClient::get(providers);
</pre>
<p>
before it uses any other pvaClient classes.
</p>
<p>
This is a singleton method, i. e. only one instance of PvaClient is created.
</p>
<p>
<b>pvaClient</b> must not be deleted until the client no longer wants to use any part
of pvaClient.
</p>
<p>
<b>providers</b> is a blank separated set of provider names.
For example:</p>
<pre>
PvaClientPtr pvaClient = PvaClient::get("ca pva");
</pre>
<p>
The providers <b>ca</b> and <b>pva</b> are special.
For each of these a client context is created when the <b>PvaClient</b>
is constructed and the context destroyed when <b>PvaClient</b> is deleted.
</p>
<h2>Channel Caching</h2>
<p>
<b>PvaClient</b> has a method:
</p>
<pre>
PvaClientChannelPtr channel(
string const &amp; channelName,
string const &amp;providerName = "pva",
double timeOut = 5.0);
</pre>
<p>
This method creates a
<b>PvaClientChannel</b> and then connects to the channel.
</p>
<p>
If a call is successful then multiple calls to the same channelName and providerName
share the same PvaClientChannel, i. e. the PvaClientChannel is cached.
</p>
<p>
<b>pvaClientChannelGet</b> and <b>pvaClientChannelPut</b> also implement caching.
</p>
<p>
For example consider a client that makes multiple calls like:
</p>
<pre>
double value;
value = pva->channel(channelName)->get()->getData()->getDouble();
...
value = pva->channel(channelName)->get()->getData()->getDouble();
</pre>
<p>
Only the first call creates a new PvaClientChannel and a new PvaClientGet.
The second call reuses the cached PvaClientChannel and PvaClientGet.
</p>
<h2>Non Cached Channels</h2>
<p>
<b>PvaClient</b> has a method:
</p>
<pre>
PvaClientChannelPtr createChannel(
string const &amp; channelName,
string const &amp;providerName = "pva");
</pre>
<p>
This method is just creates a new PvaClientChannel and returns it to the caller.
The caller must call the PvaClientChannel connect methods.
</p>
</body>
</html>