Queue objects provide a blocking, thread-safe message-passing object to Qore programs More...

Public Member Functions
nothing	clear ()
	Clears the Queue of all data. More...

	constructor (int max=-1)
	Creates the Queue object. More...

	copy ()
	Creates a new Queue object with the same elements and maximum size as the original.

	destructor ()
	Destroys the Queue object. More...

bool	empty ()
	Returns True if the Queue is empty, False if not. More...

any	get (timeout timeout_ms=0)
	Blocks until at least one entry is available on the queue, then returns the first entry in the queue. If a timeout occurs, an exception is thrown. If the timeout is less than or equal to zero, then the call does not timeout until data is available. More...

int	getReadWaiting ()
	Returns the number of threads currently blocked on this queue for reading. More...

int	getWaiting ()
	Returns the number of threads currently blocked on this queue for reading. More...

int	getWriteWaiting ()
	Returns the number of threads currently blocked on this queue for writing. More...

nothing	insert (any arg, timeout timeout_ms=0)
	Inserts a value at the beginning of the queue. More...

int	max ()
	Returns the upper limit of the number of elements in the Queue. More...

any	pop (timeout timeout_ms=0)
	Blocks until at least one entry is available on the queue, then returns the last entry in the queue. If a timeout occurs, an exception is thrown. If the timeout is less than or equal to zero, then the call does not timeout until data is available. More...

nothing	push (any arg, timeout timeout_ms=0)
	Pushes a value on the end of the queue. More...

int	size ()
	Returns the number of elements in the Queue. More...

Detailed Description

Queue objects provide a blocking, thread-safe message-passing object to Qore programs

Restrictions:: Qore::PO_NO_THREAD_CLASSES

Queue objects can also be used as a stack or as a blocking message channel, if a maximum size is given to Queue::constructor() when the object is created. In this case when the Queue is full, adding new elements to the Queue will block until the Queue shrinks below the maximum size. All read and write methods to Queue also take timeout values; if a timeout occurs a QUEUE-TIMEOUT exception is thrown.

Note: This class is not available with the PO_NO_THREAD_CLASSES parse option

Member Function Documentation

nothing Qore::Thread::Queue::clear ( )

Clears the Queue of all data.

Example:: $queue.clear();

Note: This method does not throw any exceptions, but exceptions could be thrown by in destructors of objects that go out of scope by being removed from the Queue

Qore::Thread::Queue::constructor ( int max = -1 )

Creates the Queue object.

Example:: my Queue $queue();

Parameters

max	the maximum size of the Queue; -1 means no limit; if 0 or a negative number other than -1 is passed then a `QUEUE-SIZE-ERROR` exception will be thrown

Exceptions

QUEUE-SIZE-ERROR the size cannot be zero or any negative number except for -1 or a number that cannot fit in 32 bits (signed)

See also: Queue::max()

Since: Qore 0.8.4 this method takes a maximum size parameter and can throw exceptions if the parameter is invalid

Qore::Thread::Queue::destructor ( )

Destroys the Queue object.

Note: It is a programming error to delete this object while other threads are blocked on it; in this case an exception is thrown in the deleting thread, and also in each thread blocked on this object when it is deleted

Exceptions

QUEUE-ERROR The queue was deleted while at least one thread was blocked on it

bool Qore::Thread::Queue::empty ( )

Returns True if the Queue is empty, False if not.

Code Flags:: CONSTANT

Example:: my bool $b = $queue.empty();

Returns: True if the Queue is empty, False if not

See also: Queue::size()

Since: Qore 0.8.8

any Qore::Thread::Queue::get ( timeout timeout_ms = 0 )

Blocks until at least one entry is available on the queue, then returns the first entry in the queue. If a timeout occurs, an exception is thrown. If the timeout is less than or equal to zero, then the call does not timeout until data is available.

Example:: my any $data = $queue.get();

Parameters

timeout_ms a timeout value to wait for data to become available on the queue; integers are interpreted as milliseconds; relative date/time values are interpreted literally with a maximum resolution of milliseconds. Values <= 0 mean do not timeout. If a non-zero timeout argument is passed, and no data is available in the timeout period, a "QUEUE-TIMEOUT" exception is thrown. If no value or a value that converts to integer 0 is passed as the argument, then the call does not timeout until data is available on the queue.

Returns: the first entry on the queue

Note: This method throws a "QUEUE-TIMEOUT" exception on timeout, in order to enable the case where NOTHING was pushed on the queue to be differentiated from a timeout

Exceptions

QUEUE-TIMEOUT	The timeout value was exceeded
QUEUE-ERROR	The queue was deleted while at least one thread was blocked on it

int Qore::Thread::Queue::getReadWaiting ( )

Returns the number of threads currently blocked on this queue for reading.

This is a "synonym" for Queue::getWaiting()

Code Flags:: CONSTANT

Example:: my int $waiting = $queue.numReadWaiting();

Returns: the number of threads currently blocked on this queue for reading

See also: Queue::getWriteWaiting()

Since: Qore 0.8.4

int Qore::Thread::Queue::getWaiting ( )

Returns the number of threads currently blocked on this queue for reading.

This is a "synonym" for Queue::getReadWaiting()

Code Flags:: CONSTANT

Example:: my int $waiting = $queue.numWaiting();

Returns: the number of threads currently blocked on this queue for reading

See also: Queue::getWriteWaiting()

int Qore::Thread::Queue::getWriteWaiting ( )

Returns the number of threads currently blocked on this queue for writing.

Code Flags:: CONSTANT

Example:: my int $waiting = $queue.getWriteWaiting();

Returns: the number of threads currently blocked on this queue for writing

See also: Queue::getReadWaiting()

Since: Qore 0.8.4

nothing Qore::Thread::Queue::insert	(	any	arg,
		timeout	timeout_ms = `0`
	)

Inserts a value at the beginning of the queue.

Example:: $queue.insert($value);

Parameters

arg value to be put on the queue

timeout_ms a timeout value to wait for a free entry to become available on the queue; integers are interpreted as milliseconds; relative date/time values are interpreted literally with a maximum resolution of milliseconds. Values <= 0 mean do not timeout. If a non-zero timeout argument is passed, and no data is available in the timeout period, a "QUEUE-TIMEOUT" exception is thrown. If no value or a value that converts to integer 0 is passed as the argument, then the call does not timeout until a slot becomes available on the queue. Queue slots are only limited if a maximum size is passed to Queue::constructor().

Exceptions

QUEUE-TIMEOUT	The timeout value was exceeded
QUEUE-ERROR	The queue was deleted while at least one thread was blocked on it

Since: Qore 0.8.4 this method takes a timeout parameter

int Qore::Thread::Queue::max ( )

Returns the upper limit of the number of elements in the Queue.

Code Flags:: CONSTANT

Example:: my int $max = $queue.max();

Returns: the upper limit of the number of elements in the Queu

See also: Queue::size()

any Qore::Thread::Queue::pop ( timeout timeout_ms = 0 )

Blocks until at least one entry is available on the queue, then returns the last entry in the queue. If a timeout occurs, an exception is thrown. If the timeout is less than or equal to zero, then the call does not timeout until data is available.

Example:: my any $data = $queue.pop();

Parameters

timeout_ms a timeout value to wait for data to become available on the queue; integers are interpreted as milliseconds; relative date/time values are interpreted literally with a maximum resolution of milliseconds. Values <= 0 mean do not timeout. If a non-zero timeout argument is passed, and no data is available in the timeout period, a "QUEUE-TIMEOUT" exception is thrown. If no value or a value that converts to integer 0 is passed as the argument, then the call does not timeout until data is available on the queue.

Returns: the last entry on the queue

Note: This method throws a "QUEUE-TIMEOUT" exception on timeout, in order to enable the case where NOTHING was pushed on the queue to be differentiated from a timeout

Exceptions

QUEUE-TIMEOUT	The timeout value was exceeded
QUEUE-ERROR	The queue was deleted while at least one thread was blocked on it

nothing Qore::Thread::Queue::push	(	any	arg,
		timeout	timeout_ms = `0`
	)

Pushes a value on the end of the queue.

Example:: $queue.push($value);

Parameters

arg value to be put on the queue

timeout_ms a timeout value to wait for a free entry to become available on the queue; integers are interpreted as milliseconds; relative date/time values are interpreted literally with a maximum resolution of milliseconds. Values <= 0 mean do not timeout. If a non-zero timeout argument is passed, and no data is available in the timeout period, a "QUEUE-TIMEOUT" exception is thrown. If no value or a value that converts to integer 0 is passed as the argument, then the call does not timeout until a slot becomes available on the queue. Queue slots are only limited if a maximum size is passed to Queue::constructor().

Exceptions

QUEUE-TIMEOUT	The timeout value was exceeded
QUEUE-ERROR	The queue was deleted while at least one thread was blocked on it

Since: Qore 0.8.4 this method takes a timeout parameter

int Qore::Thread::Queue::size ( )

Returns the number of elements in the Queue.

Code Flags:: CONSTANT

Example:: my int $size = $queue.size();

Returns: the number of elements in the Queue

See also: Queue::max()

Public Member Functions

Detailed Description

Member Function Documentation