std.experimental.allocator.building_blocks.bucketizer

Source

std/experimental/allocator/building_blocks/bucketizer.d

struct Bucketizer(Allocator, size_t min, size_t max, size_t step);

A Bucketizer uses distinct allocators for handling allocations of sizes in the intervals [min, min + step - 1], [min + step, min + 2 * step - 1], [min + 2 * step, min + 3 * step - 1], ..., [max - step + 1, max].

Bucketizer holds a fixed-size array of allocators and dispatches calls to them appropriately. The size of the array is (max + 1 - min) / step, which must be an exact division.

Allocations for sizes smaller than min or larger than max are illegal for Bucketizer. To handle them separately, Segregator may be of use.

Examples:

import std.algorithm.comparison : max;
import std.experimental.allocator.building_blocks.allocator_list : AllocatorList;
import std.experimental.allocator.building_blocks.free_list : FreeList;
import std.experimental.allocator.building_blocks.region : Region;
import std.experimental.allocator.common : unbounded;
import std.experimental.allocator.mallocator : Mallocator;
import std.typecons : Ternary;
Bucketizer!(
    FreeList!(
        AllocatorList!(
            (size_t n) => Region!Mallocator(max(n, 1024 * 1024))),
        0, unbounded),
    65, 512, 64) a;
auto b = a.allocate(400);
writeln(b.length); // 400
writeln(a.owns(b)); // Ternary.yes
a.deallocate(b);

Allocator[(max + 1 - min) / step] buckets;

The array of allocators is publicly available for e.g. initialization and inspection.

enum uint alignment;

The alignment offered is the same as Allocator.alignment.

const pure nothrow @nogc @safe size_t goodAllocSize(size_t bytes);

Rounds up to the maximum size of the bucket in which bytes falls.

void[] allocate(size_t bytes);

Directs the call to either one of the buckets allocators.

void[] alignedAllocate(size_t bytes, uint alignment);

Allocates the requested bytes of memory with specified alignment. Directs the call to either one of the buckets allocators. Defined only if Allocator defines alignedAllocate.

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

This method allows expansion within the respective bucket range. It succeeds if both b.length and b.length + delta fall in a range of the form [min + k * step, min + (k + 1) * step - 1].

bool reallocate(ref void[] b, size_t size);

This method allows reallocation within the respective bucket range. If both b.length and size fall in a range of the form [min + k * step, min + (k + 1) * step - 1], then reallocation is in place. Otherwise, reallocation with moving is attempted.

bool alignedReallocate(ref void[] b, size_t size, uint a);

Similar to reallocate, with alignment. Defined only if Allocator defines alignedReallocate.

Ternary owns(void[] b);

Defined only if Allocator defines owns. Finds the owner of b and forwards the call to it.

bool deallocate(void[] b);

This method is only defined if Allocator defines deallocate.

bool deallocateAll();

This method is only defined if all allocators involved define deallocateAll, and calls it for each bucket in turn. Returns true if all allocators could deallocate all.

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

This method is only defined if all allocators involved define resolveInternalPointer, and tries it for each bucket in turn.