Michael Davidsaver
78 lines
2.0 KiB
ReStructuredText
78 lines
2.0 KiB
ReStructuredText
SharedPV and StaticSource
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=========================
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A SharedPV is a single data value which may be accessed by multiple clients through a Server.
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It is "shared" in the sense that all clients are manipulating a single variable.
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.. code-block:: c++
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#include <pvxs/sharedpv.h>
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namespace pvxs { namespace server { ... } }
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Each SharedPV instance has (after open() ) an associated data structure
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which is later manipulated with post().
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A simple usage is:
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.. code-block:: c++
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using namespace pvxs;
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auto initial = nt::NTScalar{TypeCode::Float64}.create();
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initial["value"] = 42.0;
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auto src(server::StaticSource::build());
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auto pv(server::SharedPV::buildMailbox());
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pv.open(initial);
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src.add(argv[1], pv);
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auto serv = server::Server::Config::from_env()
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.build()
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.addSource("box", src.source());
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serv.run();
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In this context "mailbox" refers to the default onPut() handler, which simply post()s whatever
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the client sends.
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An example of a SharedPV with a custom Put handler
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.. code-block:: c++
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auto pv(server::SharedPV::buildMailbox());
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pv.opPut([](server::SharedPV& pv,
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std::unique_ptr<server::ExecOp>&& op,
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Value&& top)
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{
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// We decide that .value will be present with .open()
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auto val = top["value"];
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// is client trying to change .value ?
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if(val.isMarked(true, true)) {
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auto val = top["value"].as<double>();
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// clip to range [0, 10]
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top["value"] = std::max(0.0, std::min(val, 10.0));
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}
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// update and send to subscribers
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pv.post(std::move(top));
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// notify client of success (or call op->error() if not)
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op->reply();
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});
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auto initial = nt::NTScalar{TypeCode::Float64}.create();
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initial["value"] = 42.0;
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auto src(server::StaticSource::build());
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pv.open(initial);
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.. doxygenstruct:: pvxs::server::SharedPV
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:members:
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.. doxygenstruct:: pvxs::server::StaticSource
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:members:
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