dueca::DataReader< T, S > Class Template Reference

Lightweight class for accessing data in a channel. More...

#include <DataReader.hxx>

Inheritance diagram for dueca::DataReader< T, S >:

Collaboration diagram for dueca::DataReader< T, S >:

Public Member Functions
	DataReader (ChannelReadToken &token, const DataTimeSpec &ts)
	Constructor. More...
	DataReader (ChannelReadToken &token, const TimeSpec &ts)
	Constructor with TimeSpec. More...
	DataReader (ChannelReadToken &token, TimeTickType ts=MAX_TIMETICK)
	Constructor with time tick. More...
const T &	data ()
	Access to the data. More...
const DataTimeSpec &	timeSpec ()
	Return the time specification of the data.
const GlobalId &	origin ()
	Return the origin.
	~DataReader ()
	Destructor. More...

Additional Inherited Members
Protected Member Functions inherited from dueca::DataReaderBase
	DataReaderBase (ChannelReadToken &token, const DataTimeSpec &t_request)
	Constructor.
Protected Attributes inherited from dueca::DataReaderBase
ChannelReadToken &	token
	Reference to the channel access token.
DataTimeSpec	t_request
	Time span or point requested.
DataTimeSpec	ts_data
	Time specification as realised.
GlobalId	data_origin
	Data origin.
bool	firstaccess
	First access flag.

Detailed Description

template<class T, template< class > class S = MatchIntervalStart>
class dueca::DataReader< T, S >

Lightweight class for accessing data in a channel.

The DataReader accesses the data in a channel. These objects should be created on the stack, and when they go out of scope, the access to the channel is released again.

Example:

{
  DataReader<MyData> r(r_mydata, ts);
  cout << r.data() << endl;
} // out of scope, access to data in channel released again

Parameters:

Template Parameters

T	Class of the data to be read.
S	Data time selector.

Typical data time selectors are:

MatchIntervalStart. Data is read that matches the start of the time specification interval. When reading all datapoints (with Channel::ReadAllData, Channel::ReadReservation, or Channel::AdaptEventStream in combination with Channel::Events), older data is also returned.

MatchIntervalStartOrEarlier. If data is not available for the requested time, but older data is available, then that older data is returned.

VirtualJoin. Produces a combined reading of all entries in a channel, typically only selected for event data. Note that it might be necessary for channels with many entries and a higher frequency of data writing, to repeatedly try reading to prevent data buildup in the channel.

Constructor & Destructor Documentation

DataReader() [1/3]

template<class T , template< class > class S = MatchIntervalStart>

dueca::DataReader< T, S >::DataReader ( ChannelReadToken &  token, const DataTimeSpec &  ts  )

inline

Constructor.

Note that these objects are light-weight, and meant to be constructed (on the stack) and discarded.

Parameters

token	Read token
ts	Time specification. Exact interpretation depends on the S template parameter.

DataReader() [2/3]

template<class T , template< class > class S = MatchIntervalStart>

dueca::DataReader< T, S >::DataReader ( ChannelReadToken &  token, const TimeSpec &  ts  )

inline

Constructor with TimeSpec.

Parameters

token	Read token.
ts	Time specification. Accessed data point will not be newer than ts.getValidityStart()

DataReader() [3/3]

template<class T , template< class > class S = MatchIntervalStart>

dueca::DataReader< T, S >::DataReader ( ChannelReadToken &  token, TimeTickType  ts = MAX_TIMETICK  )

inline

Constructor with time tick.

Parameters

token	Read token.
ts	Time tick. Accessed data point will not be newer than the tick. Note that the default (not specifying this parameter) simply gives you the latest data in the channel, if JumpToMatchTime is selected for the read token.

~DataReader()

template<class T , template< class > class S = MatchIntervalStart>

dueca::DataReader< T, S >::~DataReader ( )

inline

Destructor.

Releases the access again with a token.

Member Function Documentation

data()

template<class T , template< class > class S = MatchIntervalStart>

const T & dueca::DataReader< T, S >::data ( )

inline

Access to the data.

Note that the constructors are lazy. The getAccess() call will perform the actual access.

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The documentation for this class was generated from the following file:

• /home/abuild/rpmbuild/BUILD/dueca-4.0.2/dueca/DataReader.hxx