59 lines
2.4 KiB
HTML
59 lines
2.4 KiB
HTML
<h1>Release 4.0 IN DEVELOPMENT</h1>
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<p>The main changes since release 3.0.2 are:</p>
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<ul>
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<li>array semantics now enforce Copy On Write.</li>
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<li>String no longer defined.</li>
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<li>timeStamp and valueAlarm name changes</li>
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<li>toString replaced by stream I/O </li>
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<li>union is new type.</li>
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<li>copy is new.</li>
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<li>monitorPlugin is new.</li>
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</ul>
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<h2>New Semantics for Arrays</h2>
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<p>PVScalarArray, PVStructureArray, and PVUnionArray all enforce COW (Copy On Write) Semantics.
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In order to limit memory usage the storage for raw data is managed via a new shared_vector facility.
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This allows multiple instances of array data to use the shared raw data.
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COW is implemented via shared_vectors of const data, i. e. data that can not be modified.</p>
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<h2>String no longer defined</h2>
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<p>This is replaced by std::string.</p>
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<h2>timeStamp and valueAlarm name changes</h2>
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<p>In timeStamp nanoSeconds is changed to nanoseconds.</p>
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<p>In valueAlarm hystersis is changed to hysteresis</p>
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<h2>toString replaced by stream I/O</h2>
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<p>pvData.h and pvIntrospect no longer defines toString
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Instead they have stream support.
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pvIntrospect uses method dump and pvData uses dumpValue.
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For example:</p>
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<pre><code> PVDoublePtr pvValue;
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String buffer;
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pvValue->toString(&buffer);
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cout << buffer << endl;
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buffer.clear();
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pvValue->getField()->toString(&buffer);
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cout << buffer << evdl;
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</code></pre>
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<p>is replaced by</p>
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<pre><code> PVDoublePtr pvValue;
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cout << *pvValue << endl
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cout << *pvValue->getField() << endl;
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</code></pre>
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<h2>union is a new basic type.</h2>
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<p>There are two new basic types: union_t and unionArray.</p>
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<p>A union is like a structure that has a single subfield.
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There are two flavors:</p>
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<ul>
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<li><b>varient union</b> The field can have any type.</li>
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<li><b>union</b> The field can any of specified set of types.</li>
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</ul>
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<p>The field type can be dynamically changed.</p>
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<h2>copy</h2>
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<p>This consists of createRequest and pvCopy.
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createRequest was moved from pvAccess to here.
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pvCopy is moved from pvDatabaseCPP and now depends
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only on pvData, i. e. it no longer has any knowledge of PVRecord.</p>
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<h2>monitorPlugin</h2>
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<p>This is for is for use by code that implements pvAccess monitors.
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This is prototype and is subject to debate.</p>
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<h1>Release 3.0.2</h1>
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<p>This was the starting point for RELEASE_NOTES</p>
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