emplace ~master

emplace

C++-grade, GC-free data structures and smart pointers for D.

Writing @nogc D today usually means falling back to C-isms — raw pointers, manual malloc/free, hand-rolled containers. emplace closes that gap: the containers and smart pointers you expect from C++'s <memory>/<vector>/<map>, allocator-aware (Alexandrescu's std.experimental.allocator), @nogc when the allocator is, and correct on current LDC/DMD.

Install

dub add emplace

import emplace.smartptr : Uniq, Shared, Weak;
import emplace.vector : Vector;
import emplace.map : Map, OrderedSet;

What's in the box

Smart pointers (emplace.smartptr) — modeled on libc++'s <memory>

• `Uniq!(T, Alloc = Mallocator)` — unique_ptr: single ownership, move-only, plus Rust-flavored borrow / take (Option::take) / intoInner (Box::into_inner).
• `Shared!(T, Alloc = Mallocator)` — shared_ptr: reference counted, copy bumps the count, make_shared-style inline control block (one allocation), with a weak count.
• `Weak!(T, Alloc = Mallocator)` — weak_ptr: non-owning observer, lock() / expired.

Containers

• `emplace.vector.Vector!(T, Alloc = Mallocator)` — a dynamic array; bulk put(slice) is a single memcpy (not a per-element loop). shrinkToFit (shrink_to_fit). `Vector!bool` is bit-packed (std::vector<bool>): one bit per element, opIndex returns an assignable proxy bit-reference.
• `emplace.deque.Deque!(T, Alloc = Mallocator)` — a double-ended queue: a circular buffer over one contiguous block, O(1) push/pop at both ends and O(1) random access. Releases memory as it drains (halves capacity at ¼ load, frees at empty) — safe for long-running FIFOs.
• `emplace.map.Map!(K, V)` — an ordered map on a hand-rolled red-black tree (O(log n) insert/lookup/remove, sorted iteration, leftBound/rightBound floor/ceiling + foreachRange, removeRight consuming prefix range).
• `emplace.map.OrderedSet!T` — the ordered set: the valueless companion (union / intersection / difference / symmetric difference, subset / superset).
• `emplace.hashmap.HashMap!(K, V)` — unordered_map: open-addressed hash table, linear probing with backward-shift deletion (no tombstones).
• `emplace.hashmap.HashSet!K` — unordered_set.

Every container is RAII and smart-pointer safe: elements are moved into place, and popBack/clear/~this release each one (its .free() or destructor), so a Vector!(Uniq!T) or Deque!(Shared!T) never leaks. Each is copyable exactly when its element is (a deep, independent copy — Map deep- clones its tree like std::map); an element with a move-only type (e.g. Uniq) makes the whole container move-only, so a bitwise copy can never double-free. All expose D ranges (opSlice).

Allocators

Everything is parameterized on an std.experimental.allocator allocator, defaulting to Mallocator. Attributes are inferred, so with Mallocator the whole surface is @nogc nothrow; plug GCAllocator, FreeList, Region, InSituRegion, or your own — unchanged.

import std.experimental.allocator.building_blocks.free_list : FreeList;
import std.experimental.allocator.mallocator : Mallocator;

// a node pool: ~10-16x cheaper per allocation than malloc in our benchmarks
alias Pool = FreeList!(Mallocator, 64);

Example

import emplace.smartptr : Uniq, Shared;
import emplace.vector : Vector;

@nogc nothrow:

auto box = Uniq!int.make(42);      // owns a heap int, freed on scope exit
int taken = box.intoInner();       // move the value out (Box::into_inner)

auto rc = Shared!string.make("hi");
auto rc2 = rc;                     // refcount == 2, freed when the last dies

Vector!ubyte buf;
buf.put(cast(const(ubyte)[]) "hello");  // one memcpy, no per-byte loop

Acknowledgements

emplace was originally built for [dreads](https://github.com/caetanus/dreads), a GC-free Redis/Valkey-compatible database in D, whose data plane runs with the collector disabled — so it needed exactly these containers without C-isms. It is extracted here as a standalone, reusable package.

It is inspired by [automem](https://github.com/atilaneves/automem) by Atila Neves, which pioneered allocator-aware smart pointers and a vector for D. emplace carries that idea forward with a wider container set, libc++/Rust semantics, and fixes for issues that surface on current compilers. Credit for the original direction is his.

License

MIT — see LICENSE. Copyright © 2026 Marcelo Aires Caetano.