[#BloombergLP-bslma-BufferAllocator]
= xref:BloombergLP.adoc[BloombergLP]::xref:BloombergLP/bslma.adoc[bslma]::BufferAllocator
:relfileprefix: ../../
:mrdocs:

This `class` provides a concrete buffer allocator that implements the `Allocator` interface, and allocates memory blocks from a fixed‐size buffer that is supplied by the user at construction. The allocator can supply memory that can be maximally (default) or naturally aligned.

== Synopsis

Declared in `<bslma_bufferallocator.h>`

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

== Base Classes

[cols="1,4"]
|===
| Name| Description
| `xref:BloombergLP/bslma/Allocator.adoc[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/bslma/BufferAllocator/AllocCallback.adoc[`AllocCallback`] 
| `AllocCallback` is an alias for (the address of) a function that takes an integer argument and returns `void *`.
| 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.
|===


== Enums

[cols="1,4"]
|===
| Name| Description
| xref:BloombergLP/bslma/BufferAllocator/AlignmentStrategy.adoc[`AlignmentStrategy`] 
| Types of alignment strategy to allocate memory.
|===


== Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:BloombergLP/bslma/BufferAllocator/2constructor-0fb.adoc[`BufferAllocator`]         [.small]#[constructor]#
| Constructors
| xref:BloombergLP/bslma/BufferAllocator/2destructor.adoc[`~BufferAllocator`] [.small]#[destructor]# [.small]#[virtual]#
| Destroy this buffer allocator.
| xref:BloombergLP/bslma/Allocator/operator_assign.adoc[`operator=`] 
| 
| xref:BloombergLP/bslma/BufferAllocator/allocate-05.adoc[`allocate`] 
| Return a newly allocated block of memory of (at least) the specified positive `size` (in bytes). If `size` is 0, a null pointer is returned with no other effect. If this allocator cannot return the requested number of bytes, then it will return the result of invoking an optional callback function (supplied at construction); if no callback function was specified, throw a `std::bad_alloc` exception in an exception‐enabled build, or else abort the program in a non‐exception build. The behavior is undefined unless `0 <= size`. Note that the alignment of the address returned depends on the alignment strategy (`MAXIMUM_ALIGNMENT` or `NATURAL_ALIGNMENT`) specified at construction of this buffer allocator. Also note that it is up to the callback function whether to return zero or throw an exception if this buffer allocator is unable to satisfy the request.
| xref:BloombergLP/bslma/BufferAllocator/deallocate-06.adoc[`deallocate`] 
| This function has no effect for this buffer allocator.
| 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/bslma/BufferAllocator/print.adoc[`print`] 
| Write formatted debugging information to `stdout` describing the internal state of this buffer allocator.
|===


== Static Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:BloombergLP/bslma/BufferAllocator/allocateFromBuffer-0a.adoc[`allocateFromBuffer`] 
| `allocateFromBuffer` overloads
| 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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