groovyx.gpars.dataflow.stream
[Java] Class DataflowStream

java.lang.Object
  groovyx.gpars.dataflow.stream.DataflowStream

All Implemented Interfaces:

FList

@SuppressWarnings({"rawtypes", "TailRecursion", "unchecked", "StaticMethodNamingConvention", "ClassWithTooManyMethods"})
public final class DataflowStream
extends java.lang.Object

Represents a deterministic dataflow channel. Unlike a DataflowQueue, DataflowStream allows multiple readers each to read all the messages. Essentially, you may think of DataflowStream as a 1 to many communication channel, since when a reader consumes a messages, other readers will still be able to read the message. Also, all messages arrive to all readers in the same order. DataflowStream is implemented as a functional queue, which impacts the API in that users have to traverse the values in the stream themselves. On the other hand in offers handy methods for value filtering or transformation together with interesting performance characteristics. For convenience and for the ability to use DataflowStream with other dataflow constructs, like e.g. operators, you can wrap DataflowStreams with DataflowReadAdapter for read access or DataflowWriteAdapter for write access.

The DataflowStream class is designed for single-threaded producers and consumers. If multiple threads are supposed to read or write values to the stream, their access to the stream must be serialized externally or the adapters should be used.

Parameters:

- Type for values to pass through the stream

Authors:

Johannes Link, Vaclav Pech

first

private final DataflowVariable first

rest

private final java.util.concurrent.atomic.AtomicReference rest

wheneverBoundListeners

private final java.util.Collection wheneverBoundListeners

A collection of listeners who need to be informed each time the stream is bound to a value

DataflowStream

public DataflowStream()

Creates an empty stream

DataflowStream

public DataflowStream(groovy.lang.Closure toBeApplied)

Creates a stream while applying the supplied initialization closure to it

Parameters:

toBeApplied - The closure to use for initialization

DataflowStream

@SuppressWarnings({"AssignmentToCollectionOrArrayFieldFromParameter"})
private DataflowStream(java.util.Collection wheneverBoundListeners)

appendingString

@Override
public java.lang.String appendingString()

apply

public final DataflowStream apply(groovy.lang.Closure closure)

Calls the supplied closure with the stream as a parameter

Parameters:

closure - The closure to call

Returns:

This instance of DataflowStream

bind

private void bind(T value)

eos

public static T eos()

equals

@Override
public boolean equals(java.lang.Object obj)

eval

private static T eval(java.lang.Object valueOrDataflowVariable)

filter

@Override
public FList filter(groovy.lang.Closure filterClosure)

Builds a filtered stream using the supplied filter closure

Parameters:

filterClosure - The closure to decide on inclusion of elements

Returns:

The first item of the filtered stream

filter

private void filter(DataflowStream rest, groovy.lang.Closure filterClosure, DataflowStream result)

generate

public DataflowStream generate(T seed, groovy.lang.Closure generator, groovy.lang.Closure condition)

Populates the stream with generated values

Parameters:

seed - The initial element to evaluate and add as the first value of the stream

generator - A closure generating stream elements from the previous values

condition - A closure indicating whether the generation should continue based on the last generated value

Returns:

This stream

generateNext

private void generateNext(T value, DataflowStream stream, groovy.lang.Closure generator, groovy.lang.Closure condition)

getFirst

@Override
public T getFirst()

Retrieved the first element in the stream, blocking until a value is available

Returns:

The first item in the stream

getFirstDFV

DataflowVariable getFirstDFV()

getRest

@Override
public FList getRest()

Retrieves a DataflowStream representing the rest of this Stream after removing the first element

Returns:

The remaining stream elements

hashCode

@Override
public int hashCode()

hookWheneverBoundListeners

private DataflowExpression hookWheneverBoundListeners(DataflowExpression expr)

Hooks the registered when bound handlers to the supplied dataflow expression

Parameters:

expr - The expression to hook all the when bound listeners to

Returns:

The supplied expression handler to allow method chaining

isEmpty

@Override
public boolean isEmpty()

Indicates, whether the first element in the stream is an eos

iterator

@Override
public java.util.Iterator iterator()

Builds an iterator to iterate over the stream

Returns:

A new FListIterator instance

leftShift

public DataflowStream leftShift(DataflowReadChannel ref)

Adds a dataflow variable value to the stream, once the value is available

Parameters:

ref - The DataflowVariable to check for value

Returns:

The rest of the stream

leftShift

public DataflowStream leftShift(T value)

Adds a value to the stream

Parameters:

value - The value to add

Returns:

The rest of the stream

map

@Override
public FList map(groovy.lang.Closure mapClosure)

Builds a modified stream using the supplied map closure

Parameters:

mapClosure - The closure to transform elements

Returns:

The first item of the transformed stream

map

private void map(FList rest, groovy.lang.Closure mapClosure, DataflowStream result)

reduce

@Override
public T reduce(groovy.lang.Closure reduceClosure)

Reduces all elements in the stream using the supplied closure

Parameters:

reduceClosure - The closure to reduce elements of the stream gradually into an accumulator. The accumulator is seeded with the first stream element.

Returns:

The result of reduction of the whole stream

reduce

@Override
public T reduce(T seed, groovy.lang.Closure reduceClosure)

Reduces all elements in the stream using the supplied closure

Parameters:

reduceClosure - The closure to reduce elements of the stream gradually into an accumulator.

seed - The value to initialize the accumulator with.

Returns:

The result of reduction of the whole stream

reduce

private T reduce(T current, FList rest, groovy.lang.Closure reduceClosure)

toString

@Override
public java.lang.String toString()

wheneverBound

public void wheneverBound(groovy.lang.Closure closure)

wheneverBound

public void wheneverBound(MessageStream stream)

Copyright © 2008–2010 Václav Pech. All Rights Reserved.