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

This class implements the `ManagedAllocator` protocol to provide a fast allocator that dispenses heterogeneous blocks of memory (of varying, user‐specified sizes) from an external buffer whose address and size (in bytes) are supplied at construction. If an allocation request exceeds the remaining free memory space in the external buffer, memory will be supplied by an (optional) allocator also supplied at construction; if no allocator is supplied, the currently installed default allocator is used. This class is _exception_ _neutral_: If memory cannot be allocated, the behavior is defined by the (optional) allocator supplied at construction. Note that in no case will the buffered sequential allocator attempt to deallocate the external buffer.

== Synopsis

Declared in `<bdlma_bufferedsequentialallocator.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
class BufferedSequentialAllocator
    : 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/BufferedSequentialAllocator/2constructor-00.adoc[`BufferedSequentialAllocator`]         [.small]#[constructor]#
| Constructors
| xref:BloombergLP/bdlma/BufferedSequentialAllocator/2destructor.adoc[`~BufferedSequentialAllocator`] [.small]#[destructor]# [.small]#[virtual]#
| Destroy this buffered sequential allocator. All memory allocated from this allocator is released.
| xref:BloombergLP/bslma/Allocator/operator_assign.adoc[`operator=`] 
| 
| xref:BloombergLP/bdlma/BufferedSequentialAllocator/allocate-0f.adoc[`allocate`] 
| Return a block of memory of the specified `size` (in bytes).
| xref:BloombergLP/bdlma/BufferedSequentialAllocator/allocator.adoc[`allocator`] 
| Return the allocator passed at construction.
| xref:BloombergLP/bdlma/BufferedSequentialAllocator/deallocate-0c3.adoc[`deallocate`] 
| This method has no effect on the specified memory block.
| 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/BufferedSequentialAllocator/release.adoc[`release`]  [.small]#[virtual]#
| Release all memory allocated through this allocator and return to the underlying allocator _all_ memory except the external buffer supplied at construction. The allocator is reset to its default‐constructed state, making the memory from the entire external buffer supplied at construction available for subsequent allocations, retaining the alignment and growth strategies, and the initial and maximum buffer sizes in effect following construction. The effect of subsequently ‐ to this invokation of `release` ‐ using a pointer obtained from this object prior to this call to `release` is undefined.
| xref:BloombergLP/bdlma/BufferedSequentialAllocator/rewind.adoc[`rewind`]  [.small]#[virtual]#
| Release all memory allocated through this allocator and return to the underlying allocator _only_ memory that was allocated outside of the typical internal buffer growth of this allocator (i.e., large blocks). All retained memory will be used to satisfy subsequent allocations. The effect of subsequently ‐ to this invokation of `rewind` ‐ using a pointer obtained from this object prior to this call to `rewind` is undefined.
|===


== 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`.
|===


== Derived Classes

[cols="1,4"]
|===
| Name| Description
| xref:BloombergLP/bdlma/LocalSequentialAllocator.adoc[`LocalSequentialAllocator`] 
| This class implements the `ManagedAllocator` protocol to provide a fast allocator that dispenses heterogeneous blocks of memory (of varying, user‐specified sizes) from a local buffer whose capacity is the specified `t_SIZE` (in bytes). If an allocation request exceeds the remaining free memory space in the local buffer, memory will be supplied by an (optional) allocator supplied at construction; if no allocator is supplied, the currently installed default allocator is used. This class is _exception_ _neutral_; if memory cannot be allocated, the behavior is defined by the (optional) allocator supplied at construction.
|===


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