[#BloombergLP-ball-FixedSizeRecordBuffer]
= xref:BloombergLP.adoc[BloombergLP]::xref:BloombergLP/ball.adoc[ball]::FixedSizeRecordBuffer
:relfileprefix: ../../
:mrdocs:

Concrete, thread‐safe fixed‐size buffer of record handles.

== Synopsis

Declared in `<ball_fixedsizerecordbuffer.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
class FixedSizeRecordBuffer
    : public xref:BloombergLP/ball/RecordBuffer.adoc[RecordBuffer]
----

== Description

This class provides a concrete, thread‐safe implementation of the `RecordBuffer` protocol. This class is a mechanism. At any time, the sum of sizes of all records contained in a `FixedSizeRecordBuffer` object _plus_ the amount of memory allocated by the `FixedSizeRecordBuffer` object itself is guaranteed to be less than or equal to an upper bound specified at creation. The class is thread‐safe, except that the methods `front` and `back` must be called after locking the buffer by invoking `beginSequence`. In order to accommodate a `pushBack` request, the records from the front end of the buffer may be removed. Similarly, in order to accommodate a `pushFront` request, the records from the back end of the buffer may be removed. If a record can not accommodate in the buffer, it is silently (but otherwise safely) discarded.

== Base Classes

[cols="1,4"]
|===
| Name| Description
| `xref:BloombergLP/ball/RecordBuffer.adoc[RecordBuffer]`
| Provide a protocol (or pure interface) for managing record handles (specifically instances of `bsl::shared_ptr<Record>`).
|===

== Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:BloombergLP/ball/FixedSizeRecordBuffer/2constructor.adoc[`FixedSizeRecordBuffer`]         [.small]#[constructor]#
| Create a limited record buffer with the specified `maxTotalSize`.
| xref:BloombergLP/ball/FixedSizeRecordBuffer/2destructor.adoc[`~FixedSizeRecordBuffer`] [.small]#[destructor]# [.small]#[virtual]#
| Remove all record handles from this record buffer and destroy this record buffer.
| xref:BloombergLP/ball/FixedSizeRecordBuffer/back.adoc[`back`]  [.small]#[virtual]#
| Return a reference to the shared pointer at the back of this buffer.
| xref:BloombergLP/ball/FixedSizeRecordBuffer/beginSequence.adoc[`beginSequence`]  [.small]#[virtual]#
| _Lock_ this record buffer for an uninterrupted sequence of calls.
| xref:BloombergLP/ball/FixedSizeRecordBuffer/endSequence.adoc[`endSequence`]  [.small]#[virtual]#
| _Unlock_ this record buffer, thus allowing other threads to access it. The behavior is undefined unless the buffer is already _locked_ by `beginSequence`.
| xref:BloombergLP/ball/FixedSizeRecordBuffer/front.adoc[`front`]  [.small]#[virtual]#
| Return a reference to the shared pointer at the front of this buffer.
| xref:BloombergLP/ball/FixedSizeRecordBuffer/length.adoc[`length`]  [.small]#[virtual]#
| Return the number of record handles in this record buffer.
| xref:BloombergLP/ball/FixedSizeRecordBuffer/popBack.adoc[`popBack`]  [.small]#[virtual]#
| Remove from this record buffer the record handle positioned at the back end of the buffer. The behavior is undefined unless `0 < length()`.
| xref:BloombergLP/ball/FixedSizeRecordBuffer/popFront.adoc[`popFront`]  [.small]#[virtual]#
| Remove from this record buffer the record handle positioned at the front end of the buffer. The behavior is undefined unless `0 < length()`.
| xref:BloombergLP/ball/FixedSizeRecordBuffer/pushBack.adoc[`pushBack`]  [.small]#[virtual]#
| Push the specified `handle` at the back end of this record buffer.
| xref:BloombergLP/ball/FixedSizeRecordBuffer/pushFront.adoc[`pushFront`]  [.small]#[virtual]#
| Push the specified `handle` at the front end of this record buffer.
| xref:BloombergLP/ball/FixedSizeRecordBuffer/removeAll.adoc[`removeAll`]  [.small]#[virtual]#
| Remove all record handles stored in this record buffer. Note that `length()` is now 0.
| xref:BloombergLP/ball/FixedSizeRecordBuffer/2conversion.adoc[`operator BloombergLP::bslmf::NestedTraitDeclaration<FixedSizeRecordBuffer, UsesBslmaAllocator>`] 
| Declare that this type uses a `bslma` allocator.
|===



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