[#BloombergLP-bdlma-ConcurrentPoolAllocator]
= xref:BloombergLP.adoc[BloombergLP]::xref:BloombergLP/bdlma.adoc[bdlma]::ConcurrentPoolAllocator
:relfileprefix: ../../
:mrdocs:

This class implements the `bslma::Allocator` protocol to provide an allocator that manages pooled memory blocks of some uniform size, specified either at construction, or at the first invocation of the `allocate` method. This allocator maintains an internal linked list of free memory blocks, and dispenses one block for each `allocate` method invocation. When a memory block is deallocated, it is returned to the free list for potential reuse.

== Synopsis

Declared in `<bdlma_concurrentpoolallocator.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
class ConcurrentPoolAllocator
    : public xref:BloombergLP/bslma/Allocator.adoc[bslma::Allocator]
----

== Description

This class guarantees thread‐safety while allocating or releasing memory.

== Base Classes

[cols="1,4"]
|===
| Name| Description
| `xref:BloombergLP/bslma/Allocator.adoc[bslma::Allocator]`
| This protocol class provides a pure abstract interface and contract for clients and suppliers of raw memory. If the requested memory cannot be returned, the contract requires that an `std::bad_alloc` exception be thrown. Note that memory is guaranteed to be sufficiently aligned for any object of the requested size on the current platform, which may be less than the maximal alignment guarantee afforded by global `operator new`.
|===

== Type Aliases

[cols="1,4"]
|===
| Name| Description
| xref:BloombergLP/bdlma/ConcurrentPoolAllocator/size_type.adoc[`size_type`] 
| This `typedef` is an alias for the block size type.
|===


== Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:BloombergLP/bdlma/ConcurrentPoolAllocator/2constructor-00fc.adoc[`ConcurrentPoolAllocator`]         [.small]#[constructor]#
| Constructors
| xref:BloombergLP/bdlma/ConcurrentPoolAllocator/2destructor.adoc[`~ConcurrentPoolAllocator`] [.small]#[destructor]# [.small]#[virtual]#
| Destroy this pool allocator.
| xref:BloombergLP/bslma/Allocator/operator_assign.adoc[`operator=`] 
| 
| xref:BloombergLP/bdlma/ConcurrentPoolAllocator/allocate-08.adoc[`allocate`] 
| Return a newly allocated block of memory of (at least) the specified positive `size` (in bytes), and having alignment conforming to the platform requirement for any object having `size` bytes. If `size` is 0, a null pointer is returned with no effect. If the block size is not supplied at construction, then the `size` specified in the first call to this method fixes the block size. If `size` is greater than the value returned by `blockSize`, the allocation request will be satisfied directly by the external allocator supplied at construction (or the default allocator, if no allocator was supplied).
| xref:BloombergLP/bdlma/ConcurrentPoolAllocator/blockSize.adoc[`blockSize`] 
| Return the size (in bytes) of the memory blocks allocated from this allocator. Note that all blocks dispensed by this allocator have the same size.
| xref:BloombergLP/bdlma/ConcurrentPoolAllocator/deallocate-010.adoc[`deallocate`] 
| Return the memory at the specified `address` back to this allocator. If `address` is 0, this method has no effect. The behavior is undefined unless `address` was allocated using this allocator and has not already been deallocated.
| xref:BloombergLP/bslma/Allocator/deleteObject-09.adoc[`deleteObject`] 
| `deleteObject` overloads
| xref:BloombergLP/bslma/Allocator/deleteObjectRaw-06f.adoc[`deleteObjectRaw`] 
| `deleteObjectRaw` overloads
| xref:BloombergLP/bslma/Allocator/is_equal.adoc[`is_equal`] 
| 
| xref:BloombergLP/bdlma/ConcurrentPoolAllocator/release.adoc[`release`] 
| Relinquish all memory currently allocated through this pool allocator.
| xref:BloombergLP/bdlma/ConcurrentPoolAllocator/reserveCapacity.adoc[`reserveCapacity`] 
| Reserve memory from this pool allocator to satisfy memory requests for at least the specified `numObjects` before the pool replenishes. The behavior is undefined unless `0 <= numObjects`. Note that this operation has no effect unless block size was supplied at construction, or `allocate` was invoked.
|===


== Static Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:BloombergLP/bslma/Allocator/throwBadAlloc.adoc[`throwBadAlloc`] 
| Throw `std::bad_alloc` if exceptions are enabled or abort the program otherwise. Derived classes and helper functions will typically call this function when they are unable to satisfy an allocation request. This function never returns.
|===


== Protected Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:BloombergLP/bslma/Allocator/do_allocate.adoc[`do_allocate`]  [.small]#[virtual]#
| Return a newly allocated block of memory of (at least) the specified positive `bytes` and having at least the specified `alignment`. Unless overriden in a derived class, the return value is `this‐>allocate(bytes)`. If this allocator cannot return the requested number of bytes or cannot satisfy the alignment request, then it will throw a `std::bad_alloc` exception in an exception‐enabled build, or else will abort the program in a non‐exception build. Unless overriden in a derived class, this function will forward the allocation request to the `allocate` virtual function, padding `bytes` and adjusting the return value as necessary to ensure sufficient alignment. Note that if `bytes` is `0`, the same non‐null value will be returned every time.
| xref:BloombergLP/bslma/Allocator/do_deallocate.adoc[`do_deallocate`]  [.small]#[virtual]#
| Return the memory block at the specified `p` address, having the specified `bytes` and specified `alignment`, back to this allocator. Unless overriden in a derived class, this function will forward the deallocation request to the `deallocate` virtual function, padding `bytes` and adjusting `p` as necessary to account for `alignment` values other than the natural alignment for an object of size `bytes`. The behavior is undefined unless `address` is a block allocated from this allocator object using the same `bytes` and `alignment` and not already deallocated.
| xref:BloombergLP/bslma/Allocator/do_is_equal.adoc[`do_is_equal`]  [.small]#[virtual]#
| Return `true` if this allocator is equal to the specified `other` allocator, meaning (at least) that a memory block allocated by one can be deallocated by the other; otherwise return `false`. Unless overriden, this method returns `this == &other`.
|===



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