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

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.

== Synopsis

Declared in `<ball_fixedsizerecordbuffer.h>`

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

== 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 such that at any time the sum of sizes of all records contained _plus_ the amount of memory allocated by this object is guaranteed to be less than or equal to the specified `maxTotalSize`. Optionally specify a `basicAllocator` used to supply memory. If `basicAllocator` is 0, the currently installed default allocator is used. The behavior is undefined unless `maxTotalSize > 0`.
| 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 of the shared pointer referring to the record positioned at the back end of this record buffer. The behavior is undefined unless this record buffer has been locked by the `beginSequence` method and unless `0 < length()`.
| xref:BloombergLP/ball/FixedSizeRecordBuffer/beginSequence.adoc[`beginSequence`]  [.small]#[virtual]#
| _Lock_ this record buffer so that a sequence of method invocations on this record buffer can occur uninterrupted by other threads. The buffer will remain _locked_ until `endSequence` is called. It is valid to invoke other methods on this record buffer between the calls to `beginSequence` and `endSequence` (the implementation guarantees this by employing a recursive mutex).
| 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 of the shared pointer referring to the record positioned at the front end of this record buffer. The behavior is undefined unless this record buffer has been locked by the `beginSequence` method and unless `0 < length()`.
| 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. Return 0 on success, and a non‐zero value otherwise. In order to accommodate a record, the records from the front end of the buffer may be removed. If a record can not be accommodated in the buffer, it is silently discarded.
| xref:BloombergLP/ball/FixedSizeRecordBuffer/pushFront.adoc[`pushFront`]  [.small]#[virtual]#
| Push the specified `handle` at the front end of this record buffer. Return 0 on success, and a non‐zero value otherwise. In order to accommodate a record, the records from the end end of the buffer may be removed. If a record can not be accommodated in the buffer, it is silently discarded.
| 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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