[#BloombergLP-ball-Log-obtainMessageBuffer-04]
= xref:BloombergLP.adoc[BloombergLP]::xref:BloombergLP/ball.adoc[ball]::xref:BloombergLP/ball/Log.adoc[Log]::obtainMessageBuffer
:relfileprefix: ../../../
:mrdocs:

Obtain exclusive access to this thread's message‐formatting buffer.

== Synopsis

Declared in `<ball_log.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
static
char*
obtainMessageBuffer(
    xref:BloombergLP/bslmt/Mutex.adoc[bslmt::Mutex]** mutex,
    int* bufferSize);
----

== Description

Block until access to the buffer used for formatting messages in this thread of execution is available. Return the address of the modifiable buffer to which this thread of execution has exclusive access, load the address of the mutex that protects the buffer into the specified `*mutex` address, and load the size (in bytes) of the buffer into the specified `bufferSize` address. The address remains valid, and the buffer remains locked by this thread of execution, until the `Log::releaseMessageBuffer` method is called. The behavior is undefined if this thread of execution currently holds a lock on the buffer. Note that the buffer is intended to be used _only_ for formatting log messages immediately before a call to `Log::logMessage`; other use may adversely affect performance for the entire program.

== Return Value

address of this thread's exclusive message‐formatting buffer

== Parameters

[cols="1,4"]
|===
| Name| Description
| *mutex*
| address at which to store the buffer‐guarding mutex
| *bufferSize*
| address at which to store the buffer size in bytes
|===


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