FallbackAllocator

FallbackAllocator is the allocator equivalent of an "or" operator in algebra. An allocation request is first attempted with the Primary allocator. If that returns null, the request is forwarded to the Fallback allocator. All other requests are dispatched appropriately to one of the two allocators.

In order to work, FallbackAllocator requires that Primary defines the owns method. This is needed in order to decide which allocator was responsible for a given allocation.

FallbackAllocator is useful for fast, special-purpose allocators backed up by general-purpose allocators. The example below features a stack region backed up by the GCAllocator.

struct FallbackAllocator (

Primary

Fallback

) {

T min(T a, U b) via import std.algorithm.comparison : min;;

eponymoustemplate hasMember(T, string name) via import std.traits : hasMember;;

struct Ternary via import std.typecons : Ternary;;

static if(stateSize!Primary)

Primary primary;

static if(stateSize!Fallback)

Fallback fallback;

static

static if(!stateSize!Primary && !stateSize!Fallback)

FallbackAllocator instance;

enum uint alignment;

void[] allocate(size_t s);

static if(hasMember!(Primary, "alignedAllocate") || hasMember!(Fallback, "alignedAllocate"))

void[] alignedAllocate(size_t s, uint a);

static if(hasMember!(Primary, "owns") && (hasMember!(Primary, "expand") || hasMember!(Fallback, "expand")))

bool expand(void[] b, size_t delta);

static if(hasMember!(Primary, "owns"))

bool reallocate(void[] b, size_t newSize);

static if(hasMember!(Primary, "owns") && hasMember!(Fallback, "owns"))

Ternary owns(void[] b);

static if(hasMember!(Primary, "resolveInternalPointer") && hasMember!(Fallback, "resolveInternalPointer"))

Ternary resolveInternalPointer(void* p, void[] result);

static if(hasMember!(Primary, "owns") && (hasMember!(Primary, "deallocate") || hasMember!(Fallback, "deallocate")))

bool deallocate(void[] b);

static if(hasMember!(Primary, "empty") && hasMember!(Fallback, "empty"))

Ternary empty();

}

Members

Functions

alignedAllocate void[] alignedAllocate(size_t s, uint a): FallbackAllocator offers alignedAllocate iff at least one of the allocators also offers it. It attempts to allocate using either or both.
allocate void[] allocate(size_t s): Allocates memory trying the primary allocator first. If it returns null, the fallback allocator is tried.
deallocate bool deallocate(void[] b): deallocate is defined if and only if at least one of the allocators define deallocate. It works as follows. If primary.owns(b), then the request is forwarded to primary.deallocate if it is defined, or is a no-op otherwise. If primary does not own b, then the request is forwarded to fallback.deallocate if it is defined, or is a no-op otherwise.
empty Ternary empty(): empty is defined if both allocators also define it.
expand bool expand(void[] b, size_t delta): expand is defined if and only if at least one of the allocators defines expand. It works as follows. If primary.owns(b), then the request is forwarded to primary.expand if it is defined, or fails (returning false) otherwise. If primary does not own b, then the request is forwarded to fallback.expand if it is defined, or fails (returning false) otherwise.
owns Ternary owns(void[] b): owns is defined if and only if both allocators define owns. Returns primary.owns(b) | fallback.owns(b).
reallocate bool reallocate(void[] b, size_t newSize): reallocate works as follows. If primary.owns(b), then primary.reallocate(b, newSize) is attempted. If it fails, an attempt is made to move the allocation from primary to fallback.
resolveInternalPointer Ternary resolveInternalPointer(void* p, void[] result): resolveInternalPointer is defined if and only if both allocators define it.

Static variables

instance FallbackAllocator instance;: If both Primary and Fallback are stateless, FallbackAllocator defines a static instance called instance.

Variables

alignment enum uint alignment;: The alignment offered is the minimum of the two allocators' alignment.
fallback Fallback fallback;: The fallback allocator.
primary Primary primary;: The primary allocator.

FallbackAllocator

Members

Functions

Static variables

Variables

Meta

Source