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>

class MultipoolAllocator
    : public ManagedAllocator

Base Classes

Name

Description

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

Name

Description

size_type

Alias for an unsigned integral type capable of representing the number of bytes in this platform's virtual address space.

Member Functions

Name

Description

MultipoolAllocator [constructor]

Constructors

~MultipoolAllocator [destructor] [virtual]

Destroy this multipool allocator. All memory allocated from this allocator is released.

operator=

allocate

allocate overloads

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.

deleteObject

deleteObject overloads

deleteObjectRaw

deleteObjectRaw overloads

is_equal

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.

numPools

Return the number of pools managed by this multipool allocator.

release [virtual]

Release all memory currently allocated through this multipool allocator.

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

Name

Description

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

Name

Description

do_allocate [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.

do_deallocate [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.

do_is_equal [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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