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

This class implements the `bdlma::ManagedAllocator` protocol to provide an allocator that maintains a configurable number of `bdlma::Pool` objects, each dispensing memory blocks of a unique size. The `bdlma::Pool` objects are placed in an array, with each successive pool managing memory blocks of size twice that of the previous pool. Each multipool allocation (deallocation) request allocates memory from (returns memory to) the internal pool having the smallest block size not less than the requested size, or, if no pool manages memory blocks of sufficient sized, from a separately managed list of memory blocks. Both the `release` method and the destructor of a `bdlma::MultipoolAllocator` release all memory currently allocated via the object.

== Synopsis

Declared in `<bdlma_multipoolallocator.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
class MultipoolAllocator
    : public xref:BloombergLP/bdlma/ManagedAllocator.adoc[ManagedAllocator]
----

== Base Classes

[cols="1,4"]
|===
| Name| Description
| `xref:BloombergLP/bdlma/ManagedAllocator.adoc[ManagedAllocator]`
| This protocol class extends `bslma::Allocator` for allocators with the ability to `release` all memory currently allocated through the protocol back to the memory supplier of the derived concrete allocator object.
|===

== Type Aliases

[cols="1,4"]
|===
| Name| Description
| xref:BloombergLP/bslma/Allocator/size_type.adoc[`size_type`] 
| Alias for an unsigned integral type capable of representing the number of bytes in this platform's virtual address space.
|===


== Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:BloombergLP/bdlma/MultipoolAllocator/2constructor-0a7.adoc[`MultipoolAllocator`]         [.small]#[constructor]#
| Constructors
| xref:BloombergLP/bdlma/MultipoolAllocator/2destructor.adoc[`~MultipoolAllocator`] [.small]#[destructor]# [.small]#[virtual]#
| Destroy this multipool allocator. All memory allocated from this allocator is released.
| xref:BloombergLP/bslma/Allocator/operator_assign.adoc[`operator=`] 
| 
| xref:BloombergLP/bdlma/MultipoolAllocator/allocate-01.adoc[`allocate`] 
| `allocate` overloads
| xref:BloombergLP/bdlma/MultipoolAllocator/deallocate-08.adoc[`deallocate`] 
| Return the memory block at the specified `address` back to this allocator for reuse. If `address` is 0, this method has no effect. The behavior is undefined unless `address` was allocated by 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/MultipoolAllocator/maxPooledBlockSize.adoc[`maxPooledBlockSize`] 
| Return the maximum size of memory blocks that are pooled by this multipool allocator. Note that the maximum value is defined as: ` 2 ˆ (numPools + 2) ` where `numPools` is either specified at construction, or an implementation‐defined value.
| xref:BloombergLP/bdlma/MultipoolAllocator/numPools.adoc[`numPools`] 
| Return the number of pools managed by this multipool allocator.
| xref:BloombergLP/bdlma/MultipoolAllocator/release.adoc[`release`]  [.small]#[virtual]#
| Release all memory currently allocated through this multipool allocator.
| xref:BloombergLP/bdlma/MultipoolAllocator/reserveCapacity.adoc[`reserveCapacity`] 
| Reserve memory from this multipool allocator to satisfy memory requests for at least the specified `numObjects` having the specified `size` (in bytes) before the pool replenishes. If `size` is 0, this method has no effect. The behavior is undefined unless `size <= maxPooledBlockSize()` and `0 <= numObjects`.
|===


== 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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