DDS ISO C++ PSM

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ISO C++ DDS PSM

Angelo CorsaroOMG DDS Co-Chair

[email protected]

Rick WarrenRTI

[email protected]

POC: Angelo Corsaro <[email protected]>

mailto:[email protected]






Copyright 2010, PrismTech / RTI

Agenda

- Status Update

- Submission Scope

- API Overview

- Resource Management

- Code Example

- Type Mapping Example

- Next Steps


Status Update

- Tuesday 20th Sept. 2010, after a “conclave” of 4+ hours PrismTech and RTI have resolved all open issues and points of divergence!

- This presentation provides a unified view of what the joint final submission will be.


Agenda

- Status Update

- Submission Scope

- API Overview


- Code Example


- Next Steps


Submission Scope

The ISO C++ DDS PSM has the following scope:

- Full API for DCPS v1.2 PIM

- Full API for Extensible Topics

- ISO C++ mapping of DDS Type System (as defined in xtypes)


Agenda

- Status Update

- Submission Scope

- API Overview


- Code Example


- Next Steps


Key Highlights

- Simple, safe, efficient, extensible and portable C++ API

- Well defined and safe resource management

- Use of C++ templates to ensure type safety and improve compile time error detection

- Consistent use of Standard C++ types and idioms, such as, std::string, std::vector, iterators, RAII Pattern, etc., throughout the API


API Organization

dds

iddstdds

ANSI/ISO C++ PSM

Vendor Implementation for the DELEGATE layer

DELEGATE

Standard API instantiated from the parametrized API and the vendor implementation of the DELEGATE layer.

DDS type constructors.


Agenda

- Status Update

- Submission Scope

- API Overview


- Code Example


- Next Steps


Resource Management- Principles

Safety: Never access uninitialized, freed, or undefined state

Determinism: Applications control when local and remote resources are allocated and released

Expressiveness: Maintain capabilities from PIM


Resource Management

- Expression of principles differ for different kinds of types Reference types: Identity based on reference

• DDS Entities• Wait sets and conditions

Value types: Identity based on state• Entity QoS and QoS policies• Status• Time and duration


Reference Type Usage- Access is through smart pointers, allocated by

factory methods. These: Provide null initialization Throw exception on access to “closed” object May automatically manage resources

- Examples: Null pointer:

• Publisher pub;• if (pub == dds::core::null) { … }

Initialization:• pub = dp.create_publisher();

Copying reference:• Publisher pub2 = pub1; —or— Publisher pub2(pub1);

// 2 references to same object Polymorphism & Down-Casting:

• Entity e = pub; // Publisher pub• Publisher pub = dds::core::polymorphic_cast<Publisher>(e);


Reference Type Mgmt

- Reference types have close() method Disposes object and its contained objects

- Service may automatically close objects no longer in use “May” gives vendors flexibility to balance determinism,

convenience for their users Similar to resource management practice in JMS Common-sense rules:

• If I keep a reference to it, I intend to call it: still in use• If I set a listener, I want it to call me: still in use• If I call retain(): still in use

- Summary: Deterministic way to halt communication, reclaim resources Deterministic way to continue communication, maintain resources Flexibility for vendors


Agenda

- Status Update

- Submission Scope

- API Overview



- Code Example

- Next Steps


DDS Types Mapping

- The ISO C++ API is independent from the specific mapping used for DDS Topic Types, as far as generated types have value semantics The ISO C++ API can be used with the existing

IDL2C++ type mapping, or It can be used with the ISO C++ mapping for

DDS Types as defined in the DDS-XTypes specification


ISO C++ Mapping

-Main Characteristics Use of ISO C++ / StdLib types Full Attribute Encapsulation via accessors Container Safe

- Example... see next slide


DDS Type Mapping

struct TelephoneNumber { string prefix; string number;};

DDS Topic Type ISO C++ Mappingclass TelephoneNumber {

public: TelephoneNumber();

explicit TelephoneNumber(const std::string& prefix,

const std::string& number);

virtual ~TelephoneNumber()public: const std::string& prefix() const; void prefix(const std::string& s); const std::string& number() const; void number(const std::string& s);

// State representation // is implementation dependent};


DDS Type MappingDDS Topic Type

enum MarrialStatus { SINGLE, MARRIED, DIVORCED };

struct Person { long age; //@id(1) wstring name; MarrialStatus married; sequence<TelephoneNumber> tel; sequence<TelefoneNumber, 2> fax; double height; //@optional double weight; //@optional sequence<byte> photo; //@shared };





class Person {public: int32_t age() const; void age(int32_t i);};

ISO C++ Mapping





class Person {public: std::wstring name() const; void name(const std::wstring s);};

ISO C++ Mapping





class Person {public: const std::vector<TelephoneNumber>& tel() const; void tel(const std::vector<TelephoneNumber>& s);};

ISO C++ Mapping





class Person {public: const dds::core::optional<double>& height() const; void height(double d); void height(const dds::core::optional<double>& o);};

ISO C++ Mapping





class Person {public: std::vector<uint8_t>* photo() const; void photo(std::vector<uint8_t>* v);};

ISO C++ Mapping


Agenda

- Status Update

- Submission Scope

- API Overview



- Code Example

- Next Steps


Code Example

struct RadarTrack { string id; long x; long y;};

DDS Topic Type


Data Writer

- Create DataWriter

using dds::core; using dds::domain; using dds::pub; using dds::topic;

DomainId id = 0;

DomainParticipant dp = theParticipantFactory().create_participant(id);

Publisher pub = dp.create_publisher();

Topic<RadarTrack> topic = dp.create_topic("RadarTrackTopic");DataWriter<RadarTrack> dw = pub.create_datawriter();RadarTrack t("T101", 100, 200);dw.write(t);


Data Reader

using dds::core; using dds::domain; using dds::pub; using dds::topic;

DomainId id = 0;DomainParticipant dp(id);

DomainParticipant dp = theParticipantFactory().create_participant();

Publisher sub = dp.create_publisher();

Topic<RadarTrack> topic = dp.create_topic("RadarTrackTopic");DataReader<RadarTrack> reader = sub.create_datareader();


Data Reader

- User Provided Container

dr.take(t.begin(), i.begin(), maxsize);

std::vector<RadarTrack> t;std::vector<SampleInfo> i;

RadarTrack at[MSIZE];SampleInfo ai[MSIZE];

dr.take(at, ai, MSIZE);


Data Reader

- Loaned Data

LoanedSamples<RadarTrack> dt = dr.take(); for (LoanedSamples<RadarTrack>::Iterator it = dt.begin(); it != dt.end(); ++it) { const Sample<RadarTrack>& sample = *it; if (sample.is_valid_data()) { const RadarTrack& data = sample.data(); // … } }


Agenda

- Status Update

- Submission Scope

- API Overview



- Code Example

- Next Steps


Next Steps

- XTopics API Add support for the XTopics API Complete the Type Mapping to include the full

DDS-XTypes Type System

- Vote for Adoption December Meeting

THANKS

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DDS ISO C++ PSM

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