Add std.atomic support

Author: rymrg

std/atomic.d

@@ -0,0 +1,205 @@
+/**
+ * The atomic module provides atomic struct support for lock-free
+ * concurrent programming.
+ *
+ * Copyright: Copyright Roy David Margalit 2022 - 2025.
+ * License:   $(LINK2 http://www.boost.org/LICENSE_1_0.txt, Boost License 1.0)
+ * Authors:   Roy David Margalit
+ * Source:    $(DRUNTIMESRC core/_atomic.d)
+ */
+module std.atomic;
+
+/// Atomic data like std::atomic
+struct Atomic(T) if (__traits(isIntegral, T) || isPointer!T) {
+	import core.atomic : atomicLoad, atomicStore, atomicExchange, atomicFetchAdd,
+		atomicFetchSub, atomicCas = cas, atomicCasWeak = casWeak, atomicOp;
+
+	private T val;
+
+	/// Constructor
+	this(T init) shared {
+		val.atomicStore(init);
+	}
+
+	private shared(T)* ptr() shared {
+		return &val;
+	}
+
+	/// Load the value from the atomic location with SC access
+	alias load this;
+
+	/// ditto
+	T load(MemoryOrder mo = MemoryOrder.seq)() shared {
+		return val.atomicLoad!(mo.toCore);
+	}
+
+	/// Store the value to the atomic location
+	void store(MemoryOrder mo = MemoryOrder.seq)(T newVal) shared {
+		return val.atomicStore!(mo.toCore)(newVal);
+	}
+
+	/// Store using SC access
+	alias opAssign = store;
+
+	/// Atomically increment the value
+	T fadd(MemoryOrder mo = MemoryOrder.seq)(T mod) shared {
+		return atomicFetchAdd!(mo.toCore)(val, mod);
+	}
+
+	/// Atomically decrement the value
+	T fsub(MemoryOrder mo = MemoryOrder.seq)(T mod) shared {
+		return atomicFetchSub!(mo.toCore)(val, mod);
+	}
+
+	/// Atomically swap the value
+	T exchange(MemoryOrder mo = MemoryOrder.seq)(T desired) shared {
+		return atomicExchange!(mo.toCore)(&val, desired);
+	}
+
+	/// Compare and swap
+	bool cas(MemoryOrder mo = MemoryOrder.seq, MemoryOrder fmo = MemoryOrder.seq)(T oldVal, T newVal) shared {
+		return atomicCas!(mo.toCore, fmo.toCore)(ptr, oldVal, newVal);
+	}
+
+	/// ditto
+	bool casWeak(MemoryOrder mo = MemoryOrder.seq, MemoryOrder fmo = MemoryOrder.seq)(T oldVal,
+			T newVal) shared {
+		return atomicCasWeak!(mo.toCore, fmo.toCore)(ptr, oldVal, newVal);
+	}
+
+	/// Op assign with SC semantics
+	T opOpAssign(string op)(T rhs) shared {
+		return val.atomicOp!(op ~ `=`)(rhs);
+	}
+
+	/// Implicit conversion to FADD and FSUB
+	T opUnary(string op)() shared if (op == `++`) {
+		return val.atomicOp!`+=`(1);
+	}
+
+	T opUnary(string op)() shared if (op == `--`) {
+		return val.atomicOp!`-=`(1);
+	}
+
+	auto ref opUnary(string op)() shared if (op == `*`) {
+		return *(load);
+	}
+}
+
+static import core.atomic;
+enum MemoryOrder{
+    /**
+     * Corresponds to $(LINK2 https://llvm.org/docs/Atomics.html#monotonic, LLVM AtomicOrdering.Monotonic)
+     * and C++11/C11 `memory_order_relaxed`.
+     */
+    rlx = cast(int)core.atomic.MemoryOrder.raw,
+    /**
+     * Corresponds to $(LINK2 https://llvm.org/docs/Atomics.html#acquire, LLVM AtomicOrdering.Acquire)
+     * and C++11/C11 `memory_order_acquire`.
+     */
+    acq = cast(int)core.atomic.MemoryOrder.acq,
+    /**
+     * Corresponds to $(LINK2 https://llvm.org/docs/Atomics.html#release, LLVM AtomicOrdering.Release)
+     * and C++11/C11 `memory_order_release`.
+     */
+    rel = cast(int)core.atomic.MemoryOrder.rel,
+    /**
+     * Corresponds to $(LINK2 https://llvm.org/docs/Atomics.html#acquirerelease, LLVM AtomicOrdering.AcquireRelease)
+     * and C++11/C11 `memory_order_acq_rel`.
+     */
+    acq_rel = cast(int)core.atomic.MemoryOrder.acq_rel,
+    /**
+     * Corresponds to $(LINK2 https://llvm.org/docs/Atomics.html#sequentiallyconsistent, LLVM AtomicOrdering.SequentiallyConsistent)
+     * and C++11/C11 `memory_order_seq_cst`.
+     */
+    seq = cast(int)core.atomic.MemoryOrder.seq,
+}
+
+private auto toCore(MemoryOrder mo){
+    static import core.atomic;
+    return cast(core.atomic.MemoryOrder) mo;
+}
+
+@safe unittest {
+	shared Atomic!int a;
+	assert(a == 0);
+	assert(a.load == 0);
+	assert(a.fadd!(MemoryOrder.rlx)(5) == 0);
+	assert(a.load!(MemoryOrder.acq) == 5);
+	assert(!a.casWeak(4, 5));
+	assert(!a.cas(4, 5));
+	assert(a.cas!(MemoryOrder.rel, MemoryOrder.acq)(5, 4));
+	assert(a.fsub!(MemoryOrder.acq_rel)(2) == 4);
+	assert(a.exchange!(MemoryOrder.acq_rel)(3) == 2);
+	assert(a.load!(MemoryOrder.rlx) == 3);
+	a.store!(MemoryOrder.rel)(7);
+	assert(a.load == 7);
+	a = 32;
+	assert(a == 32);
+	a += 5;
+	assert(a == 37);
+	assert(a++ == 37);
+	assert(a == 38);
+}
+
+// static array of shared atomics
+@safe unittest {
+	static shared(Atomic!int)[5] arr;
+	arr[4] = 4;
+	assert(arr[4].load == 4);
+}
+
+unittest {
+	import core.thread : Thread;
+
+	shared(Atomic!int)[2] arr;
+
+	void reltest() @safe {
+		arr[0].store!(MemoryOrder.rel)(1);
+		arr[1].store!(MemoryOrder.rel)(1);
+	}
+
+	void acqtest() @safe {
+		while (arr[1].load!(MemoryOrder.acq) != 1) {
+		}
+		assert(arr[0].load!(MemoryOrder.acq) == 1);
+	}
+
+	auto t1 = new Thread(&acqtest);
+	auto t2 = new Thread(&reltest);
+	t2.start;
+	t1.start;
+	t2.join;
+	t1.join;
+}
+
+@safe unittest {
+	shared Atomic!(shared(int)) a = 5;
+	assert(a.load == shared(int)(5));
+	a = 2;
+	assert(a == 2);
+}
+
+@safe unittest {
+	shared Atomic!(shared(int)*) ptr = new shared(int);
+	*ptr.load!(MemoryOrder.rlx)() = 5;
+	assert(*ptr.load == 5);
+	*(ptr.load) = 42;
+	assert(*ptr.load == 42);
+}
+
+@safe unittest {
+	shared Atomic!(shared(int)*) ptr = new shared(int);
+	*ptr = 5;
+	assert(*ptr == 5);
+	*ptr = 42;
+	assert(*ptr == 42);
+}
+
+unittest {
+	//shared Atomic!(shared(Atomic!(int))*) ptr = new shared(Atomic!int);
+}
+
+private enum bool isAggregateType(T) = is(T == struct) || is(T == union)
+	|| is(T == class) || is(T == interface);
+private enum bool isPointer(T) = is(T == U*, U) && !isAggregateType!T;