nxt.allocator_traits source code

1 /** Extra traits for `std.experimental.allocator`;
2  */
3 module nxt.allocator_traits;
4 
5 /** Is `true` iff `T` is an allocator, otherwise `false`.
6  *
7  * Only members and `alignment` and `allocate` are required.
8  *
9  * See_Also: https://dlang.org/phobos/std_experimental_allocator_building_blocks.html
10  * See_Also: https://forum.dlang.org/post/uiavxptceyxsjulkxlec@forum.dlang.org
11  *
12  * TODO: Move to Phobos.
13  */
14 enum isAllocator(T) = (is(typeof(T.allocate(size_t.init)) == void[])
15 					   && is(typeof(T.alignment) : size_t)); // currently either uint or size_t. TODO shall we require T.alignment to be known at compile-time?
16 
17 version(unittest)
18 {
19     static assert(isAllocator!NullAllocator);
20     static assert(isAllocator!Mallocator);
21     static assert(isAllocator!GCAllocator);
22     static assert(isAllocator!MmapAllocator);
23     static assert(!isAllocator!int);
24 }
25 
26 /** State of an allocator or pointer to an allocator.
27  *
28  * State is zero for `Mallocator`, `GCAllocator`, and `MMapAllocator` and
29  * typically non-zero for the other.
30  *
31  * EMSI containers has this state as their first field.
32  *
33  * TODO: Move to Phobos and put beside
34  * std.experimental.allocator.common.stateSize.
35  */
36 mixin template AllocatorState(Allocator) // TODO: add string fieldName parameter
37 if (isAllocator!Allocator ||
38 	isAllocator!(typeof(*Allocator.init)))
39 {
40 	private import std.experimental.allocator.common : stateSize;
41 	static if (stateSize!Allocator == 0)
42 		alias allocator = Allocator.instance;
43 	else
44 		Allocator allocator;
45 }
46 
47 version(unittest)
48 {
49 	@safe pure nothrow @nogc unittest
50 	{
51 		mixin AllocatorState!NullAllocator n;
52 		mixin AllocatorState!GCAllocator g;
53 		mixin AllocatorState!Mallocator m;
54 		mixin AllocatorState!MmapAllocator p;
55 		mixin AllocatorState!(MmapAllocator*) pi;
56 	}
57 }
58 
59 version(unittest)
60 {
61     import std.experimental.allocator.building_blocks.null_allocator : NullAllocator;
62     import std.experimental.allocator.mallocator : Mallocator;
63     import std.experimental.allocator.gc_allocator : GCAllocator;
64     import std.experimental.allocator.mmap_allocator : MmapAllocator;
65 }