[#BloombergLP-bdlcc-SingleProducerQueueImpl]
= xref:BloombergLP.adoc[BloombergLP]::xref:BloombergLP/bdlcc.adoc[bdlcc]::SingleProducerQueueImpl
:relfileprefix: ../../
:mrdocs:

This class provides a thread‐safe unbounded queue of values that assumes a single producer thread.

== Synopsis

Declared in `<bdlcc_singleproducerqueueimpl.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<
    class TYPE,
    class ATOMIC_OP,
    class MUTEX,
    class CONDITION>
class SingleProducerQueueImpl;
----

== Description

The types `ATOMIC_OP`, `MUTEX`, and `CONDITION` are exposed for testing. Typical usage is with `bsls::AtomicOperations` for `ATOMIC_OP`, `bslmt::Mutex` for `MUTEX`, and `bslmt::Condition` for `CONDITION`.

== Type Aliases

[cols="1,4"]
|===
| Name| Description
| xref:BloombergLP/bdlcc/SingleProducerQueueImpl/value_type.adoc[`value_type`] 
| The type for elements stored in this queue.
|===


== Enums

[cols="1,4"]
|===
| Name| Description
| xref:BloombergLP/bdlcc/SingleProducerQueueImpl/_04enum.adoc[`Unnamed enum`] 
| Status codes returned by queue operations.
|===


== Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:BloombergLP/bdlcc/SingleProducerQueueImpl/2constructor-0c.adoc[`SingleProducerQueueImpl`]         [.small]#[constructor]#
| Constructors
| xref:BloombergLP/bdlcc/SingleProducerQueueImpl/2destructor.adoc[`~SingleProducerQueueImpl`] [.small]#[destructor]#
| Destroy this object.
| xref:BloombergLP/bdlcc/SingleProducerQueueImpl/allocator.adoc[`allocator`] 
| Return the allocator used by this object to supply memory.
| xref:BloombergLP/bdlcc/SingleProducerQueueImpl/disablePopFront.adoc[`disablePopFront`] 
| Disable dequeueing from this queue. All subsequent invocations of `popFront` or `tryPopFront` will fail immediately. All blocked invocations of `popFront` and `waitUntilEmpty` will fail immediately. If the queue is already dequeue disabled, this method has no effect.
| xref:BloombergLP/bdlcc/SingleProducerQueueImpl/disablePushBack.adoc[`disablePushBack`] 
| Disable enqueueing into this queue. All subsequent invocations of `pushBack` or `tryPushBack` will fail immediately. All blocked invocations of `pushBack` will fail immediately. If the queue is already enqueue disabled, this method has no effect.
| xref:BloombergLP/bdlcc/SingleProducerQueueImpl/enablePopFront.adoc[`enablePopFront`] 
| Enable dequeueing. If the queue is not dequeue disabled, this call has no effect.
| xref:BloombergLP/bdlcc/SingleProducerQueueImpl/enablePushBack.adoc[`enablePushBack`] 
| Enable queuing. If the queue is not enqueue disabled, this call has no effect.
| xref:BloombergLP/bdlcc/SingleProducerQueueImpl/isEmpty.adoc[`isEmpty`] 
| Return `true` if this queue is empty (has no elements), or `false` otherwise.
| xref:BloombergLP/bdlcc/SingleProducerQueueImpl/isFull.adoc[`isFull`] 
| Return `true` if this queue is full (has no available capacity), or `false` otherwise. Note that for unbounded queues, this method always returns `false`.
| xref:BloombergLP/bdlcc/SingleProducerQueueImpl/isPopFrontDisabled.adoc[`isPopFrontDisabled`] 
| Return `true` if this queue is dequeue disabled, and `false` otherwise. Note that the queue is created in the "dequeue enabled" state.
| xref:BloombergLP/bdlcc/SingleProducerQueueImpl/isPushBackDisabled.adoc[`isPushBackDisabled`] 
| Return `true` if this queue is enqueue disabled, and `false` otherwise. Note that the queue is created in the "enqueue enabled" state.
| xref:BloombergLP/bdlcc/SingleProducerQueueImpl/numElements.adoc[`numElements`] 
| Returns the number of elements currently in this queue.
| xref:BloombergLP/bdlcc/SingleProducerQueueImpl/popFront.adoc[`popFront`] 
| Remove the element from the front of this queue and load that element into the specified `value`. If the queue is empty, block until it is not empty. Return 0 on success, and a non‐zero value otherwise. Specifically, return `e_DISABLED` if `isPopFrontDisabled()`. On failure, `value` is not changed. Threads blocked due to the queue being empty will return `e_DISABLED` if `disablePopFront` is invoked.
| xref:BloombergLP/bdlcc/SingleProducerQueueImpl/pushBack-04.adoc[`pushBack`] 
| `pushBack` overloads
| xref:BloombergLP/bdlcc/SingleProducerQueueImpl/removeAll.adoc[`removeAll`] 
| Remove all items currently in this queue. Note that this operation is not atomic; if other threads are concurrently pushing items into the queue the result of `numElements()` after this function returns is not guaranteed to be 0.
| xref:BloombergLP/bdlcc/SingleProducerQueueImpl/tryPopFront.adoc[`tryPopFront`] 
| Attempt to remove the element from the front of this queue without blocking, and, if successful, load the specified `value` with the removed element. Return 0 on success, and a non‐zero value otherwise. Specifically, return `e_DISABLED` if `isPopFrontDisabled()`, and `e_EMPTY` if `!isPopFrontDisabled()` and the queue was empty. On failure, `value` is not changed.
| xref:BloombergLP/bdlcc/SingleProducerQueueImpl/tryPushBack-08.adoc[`tryPushBack`] 
| `tryPushBack` overloads
| xref:BloombergLP/bdlcc/SingleProducerQueueImpl/waitUntilEmpty.adoc[`waitUntilEmpty`] 
| Block until all the elements in this queue are removed. Return 0 on success, and a non‐zero value otherwise. Specifically, return `e_DISABLED` if `!isEmpty() && isPopFrontDisabled()`. A blocked thread waiting for the queue to empty will return `e_DISABLED` if `disablePopFront` is invoked.
| xref:BloombergLP/bdlcc/SingleProducerQueueImpl/2conversion.adoc[`operator BloombergLP::bslmf::NestedTraitDeclaration<SingleProducerQueueImpl, UsesBslmaAllocator>`] 
| Declare that this type uses a `bslma` allocator.
|===


== Friends

[cols="1,4"]
|===
| Name| Description
| `xref:BloombergLP/bdlcc/SingleProducerQueueImpl_PopCompleteGuard.adoc[BloombergLP::bdlcc::SingleProducerQueueImpl_PopCompleteGuard]`
| This class implements a guard automatically invokes `popComplete` on a `NODE` upon destruction.
| `xref:BloombergLP/bdlcc/SingleProducerQueueImpl_ReleaseAllRawProctor.adoc[BloombergLP::bdlcc::SingleProducerQueueImpl_ReleaseAllRawProctor]`
| This class implements a proctor that, unless its `release` method has previously been invoked, automatically invokes `releaseAllRaw` on a `TYPE` upon destruction.
|===


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