[#BloombergLP-bsls-BslOnceGuard]
= xref:BloombergLP.adoc[BloombergLP]::xref:BloombergLP/bsls.adoc[bsls]::BslOnceGuard
:relfileprefix: ../../
:mrdocs:

This class provides a guard for managing a `BslOnce` for the purpose of executing a block of code (only) once.

== Synopsis

Declared in `<bsls_bslonce.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
class BslOnceGuard;
----

== Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:BloombergLP/bsls/BslOnceGuard/2constructor.adoc[`BslOnceGuard`]         [.small]#[constructor]#
| Create a guard to manage a block of code that is executed once.
| xref:BloombergLP/bsls/BslOnceGuard/2destructor.adoc[`~BslOnceGuard`] [.small]#[destructor]#
| Destroy this guard, and if `enter` had been called on this object without a subsequent call to `leave`, then call `leave` to signal the completion of the one‐time block of code.
| xref:BloombergLP/bsls/BslOnceGuard/enter.adoc[`enter`] 
| Enter the one‐time block of code that is managed by the specified `once`. Return `true` if the one‐time block of code has been entered, and `false` if the one‐time block of code has already been executed. If this function returns `false` then the thread of execution in which `enter` returned `true` has already called `leave` ‐‐ i.e., the one‐time block of code is guaranteed to have _completed_ execution. The behavior is undefined unless `once` was originally initialized to `BSLS_BSLONCE_INITIALIZER`. Note that a successful `enter` locks a spin‐lock; it is imperative that `leave` be called quickly.
| xref:BloombergLP/bsls/BslOnceGuard/leave.adoc[`leave`] 
| Exit the one‐time block of code. The behavior is undefined unless the caller had previously called `enter`, and `enter` had returned `true`.
|===



[.small]#Created with https://www.mrdocs.com[MrDocs]#