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Struct std.experimental.allocator.typed.TypedAllocator

TypedAllocator acts like a chassis on which several specialized allocators can be assembled. To let the system make a choice about a particular kind of allocation, use Default for the respective parameters.

struct TypedAllocator(PrimaryAllocator, Policies...) ;

There is a hierarchy of allocation kinds. When an allocator is implemented for a given combination of flags, it is used. Otherwise, the next down the list is chosen.

AllocFlag combination Description
`AllocFlag.threadLocal | AllocFlag.hasNoIndirections | AllocFlag.fixedSize` This is the most specific allocation policy: the memory being allocated is thread local, has no indirections at all, and will not be reallocated. Examples of types fitting this description: int, double, Tuple!(int, long), but not Tuple!(int, string), which contains an indirection.
`AllocFlag.threadLocal | AllocFlag.hasNoIndirections` As above, but may be reallocated later. Examples of types fitting this description are int[], double[], Tuple!(int, long)[], but not Tuple!(int, string)[], which contains an indirection.
`AllocFlag.threadLocal` As above, but may embed indirections. Examples of types fitting this description are int*[], Object[], Tuple!(int, string)[].
`AllocFlag.immutableShared | AllocFlag.hasNoIndirections | AllocFlag.fixedSize` The type being allocated is immutable and has no pointers. The thread that allocated it must also deallocate it. Example: immutable(int).
`AllocFlag.immutableShared | AllocFlag.hasNoIndirections` As above, but the type may be appended to in the future. Example: string.
`AllocFlag.immutableShared` As above, but the type may embed references. Example: immutable(Object)[].
`AllocFlag.hasNoIndirections | AllocFlag.fixedSize` The type being allocated may be shared across threads, embeds no indirections, and has fixed size.
`AllocFlag.hasNoIndirections` The type being allocated may be shared across threads, may embed indirections, and has variable size.
`AllocFlag.fixedSize` The type being allocated may be shared across threads, may embed indirections, and has fixed size.
`0` The most conservative/general allocation: memory may be shared, deallocated in a different thread, may or may not be resized, and may embed references.

Methods

NameDescription
allocatorFor () Given flags as a combination of AllocFlag values, or a type T, returns the allocator that's a closest fit in capabilities.
dispose (p) Destroys and then deallocates (using allocatorFor!T) the object pointed to by a pointer, the class object referred to by a class or interface reference, or an entire array. It is assumed the respective entities had been allocated with the same allocator.
expandArray (array, delta) Grows array by appending delta more elements. The needed memory is allocated using the same allocator that was used for the array type. The extra elements added are either default-initialized, filled with copies of init, or initialized with values fetched from range.
make (args) Dynamically allocates (using the appropriate allocator chosen with allocatorFor!T) and then creates in the memory allocated an object of type T, using args (if any) for its initialization. Initialization occurs in the memory allocated and is otherwise semantically the same as T(args). (Note that using make!(T[]) creates a pointer to an (empty) array of Ts, not an array. To allocate and initialize an array, use makeArray!T described below.)
makeArray (length) Create an array of T with length elements. The array is either default-initialized, filled with copies of init, or initialized with values fetched from range.
shrinkArray (arr, delta) Shrinks an array by delta elements using allocatorFor!(T[]).
type2flags () Given a type T, returns its allocation-related flags as a combination of AllocFlag values.

Parameters

NameDescription
PrimaryAllocator The default allocator.
Policies Zero or more pairs consisting of an AllocFlag and an allocator type.

Example

import std.experimental.allocator.gc_allocator : GCAllocator;
import std.experimental.allocator.mallocator : Mallocator;
import std.experimental.allocator.mmap_allocator : MmapAllocator;
alias MyAllocator = TypedAllocator!(GCAllocator,
    AllocFlag.fixedSize | AllocFlag.threadLocal, Mallocator,
    AllocFlag.fixedSize | AllocFlag.threadLocal
            | AllocFlag.hasNoIndirections,
        MmapAllocator,
);

MyAllocator a;
auto b = &a.allocatorFor!0();
static assert(is(typeof(*b) == shared const(GCAllocator)));
enum f1 = AllocFlag.fixedSize | AllocFlag.threadLocal;
auto c = &a.allocatorFor!f1();
static assert(is(typeof(*c) == Mallocator));
enum f2 = AllocFlag.fixedSize | AllocFlag.threadLocal;
static assert(is(typeof(a.allocatorFor!f2()) == Mallocator));
// Partial match
enum f3 = AllocFlag.threadLocal;
static assert(is(typeof(a.allocatorFor!f3()) == Mallocator));

int* p = a.make!int;
scope(exit) a.dispose(p);
int[] arr = a.makeArray!int(42);
scope(exit) a.dispose(arr);
assert(a.expandArray(arr, 3));
assert(a.shrinkArray(arr, 4));

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