Library Reference

version 2.112.0

Internal API

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core.atomic

The atomic module provides basic support for lock-free concurrent programming.

Note: Use the-preview=nosharedaccess compiler flag to detect unsafe individual read or write operations on shared data.

License:

Boost License 1.0

Authors:

Sean Kelly, Alex Rønne Petersen, Manu Evans

Sourcecore/atomic.d

Examples:

int y = 2;sharedint x = y;// OK//x++; // read modify write errorx.atomicOp!"+="(1);// OK//y = x; // read error with preview flagy = x.atomicLoad();// OKassert(y == 3);//x = 5; // write error with preview flagx.atomicStore(5);// OKassert(x.atomicLoad() == 5);

enumMemoryOrder: int;

Specifies the memory ordering semantics of an atomic operation.

raw: Not sequenced. Corresponds toLLVM AtomicOrdering.Monotonic and C++11/C11memory_order_relaxed.
acq: Hoist-load + hoist-store barrier. Corresponds toLLVM AtomicOrdering.Acquire and C++11/C11memory_order_acquire.
rel: Sink-load + sink-store barrier. Corresponds toLLVM AtomicOrdering.Release and C++11/C11memory_order_release.
acq_rel: Acquire + release barrier. Corresponds toLLVM AtomicOrdering.AcquireRelease and C++11/C11memory_order_acq_rel.
seq: Fully sequenced (acquire + release). Corresponds toLLVM AtomicOrdering.SequentiallyConsistent and C++11/C11memory_order_seq_cst.

pure nothrow @nogc @trusted TatomicLoad(MemoryOrder ms = MemoryOrder.seq, T)(auto ref return scope const Tval) if (!is(T == shared(U), U) && !is(T == shared(inout(U)), U) && !is(T == shared(const(U)), U)); pure nothrow @nogc @trusted TatomicLoad(MemoryOrder ms = MemoryOrder.seq, T)(auto ref return scope const shared Tval) if (!hasUnsharedIndirections!T); pure nothrow @nogc @trusted TailShared!TatomicLoad(MemoryOrder ms = MemoryOrder.seq, T)(auto ref const shared Tval) if (hasUnsharedIndirections!T);

Loads 'val' from memory and returns it. The memory barrier specified by 'ms' is applied to the operation, which is fully sequenced by default. Valid memory orders are MemoryOrder.raw, MemoryOrder.acq, and MemoryOrder.seq.

Parameters:

Tval The target variable.

Returns:

The value of 'val'.

pure nothrow @nogc @trusted voidatomicStore(MemoryOrder ms = MemoryOrder.seq, T, V)(ref Tval, Vnewval) if (!is(T == shared) && !is(V == shared)); pure nothrow @nogc @trusted voidatomicStore(MemoryOrder ms = MemoryOrder.seq, T, V)(ref shared Tval, Vnewval) if (!is(T == class)); pure nothrow @nogc @trusted voidatomicStore(MemoryOrder ms = MemoryOrder.seq, T, V)(ref shared Tval, auto ref shared Vnewval) if (is(T == class));

Writes 'newval' into 'val'. The memory barrier specified by 'ms' is applied to the operation, which is fully sequenced by default. Valid memory orders are MemoryOrder.raw, MemoryOrder.rel, and MemoryOrder.seq.

Parameters:

T`val`	The target variable.
V`newval`	The value to store.

pure nothrow @nogc @trusted TatomicFetchAdd(MemoryOrder ms = MemoryOrder.seq, T)(ref return scope Tval, size_tmod) if ((__traits(isIntegral, T) || is(T == U*, U)) && !is(T == shared)); pure nothrow @nogc @trusted TatomicFetchAdd(MemoryOrder ms = MemoryOrder.seq, T)(ref return scope shared Tval, size_tmod) if (__traits(isIntegral, T) || is(T == U*, U));

Atomically addsmod to the value referenced byval and returns the valueval held previously. This operation is both lock-free and atomic.

Parameters:

T`val`	Reference to the value to modify.
size_t`mod`	The value to add.

Returns:

The value held previously byval.

pure nothrow @nogc @trusted TatomicFetchSub(MemoryOrder ms = MemoryOrder.seq, T)(ref return scope Tval, size_tmod) if ((__traits(isIntegral, T) || is(T == U*, U)) && !is(T == shared)); pure nothrow @nogc @trusted TatomicFetchSub(MemoryOrder ms = MemoryOrder.seq, T)(ref return scope shared Tval, size_tmod) if (__traits(isIntegral, T) || is(T == U*, U));

Atomically subtractsmod from the value referenced byval and returns the valueval held previously. This operation is both lock-free and atomic.

Parameters:

T`val`	Reference to the value to modify.
size_t`mod`	The value to subtract.

Returns:

The value held previously byval.

pure nothrow @nogc @trusted TatomicExchange(MemoryOrder ms = MemoryOrder.seq, T, V)(T*here, VexchangeWith) if (!is(T == shared) && !is(V == shared)); pure nothrow @nogc @trusted TailShared!TatomicExchange(MemoryOrder ms = MemoryOrder.seq, T, V)(shared(T)*here, VexchangeWith) if (!is(T == class) && !is(T == interface)); pure nothrow @nogc @trusted shared(T)atomicExchange(MemoryOrder ms = MemoryOrder.seq, T, V)(shared(T)*here, shared(V)exchangeWith) if (is(T == class) || is(T == interface));

ExchangeexchangeWith with the memory referenced byhere. This operation is both lock-free and atomic.

Parameters:

T*`here`	The address of the destination variable.
V`exchangeWith`	The value to exchange.

Returns:

The value held previously byhere.

templatecas(MemoryOrder succ = MemoryOrder.seq, MemoryOrder fail = MemoryOrder.seq)

Performs either compare-and-set or compare-and-swap (or exchange).

There are two categories of overloads in this template: The first category does a simple compare-and-set. The comparison value (ifThis) is treated as an rvalue.

The second category does a compare-and-swap (a.k.a. compare-and-exchange), and expectsifThis to be a pointer type, where the previous value ofhere will be written.

This operation is both lock-free and atomic.

Parameters:

T* here	The address of the destination variable.
V2 writeThis	The value to store.
V1 ifThis	The comparison value.

Returns:

true if the store occurred, false if not.

pure nothrow @nogc @trusted boolcas(T, V1, V2)(T*here, V1ifThis, V2writeThis) if (!is(T == shared) && is(T : V1));: Compare-and-set for non-shared values
pure nothrow @nogc @trusted boolcas(T, V1, V2)(shared(T)*here, V1ifThis, V2writeThis) if (!is(T == class) && (is(T : V1) || is(shared(T) : V1)));: Compare-and-set for shared value type
pure nothrow @nogc @trusted boolcas(T, V1, V2)(shared(T)*here, shared(V1)ifThis, shared(V2)writeThis) if (is(T == class));: Compare-and-set forshared reference type (class)
pure nothrow @nogc @trusted boolcas(T, V)(T*here, T*ifThis, VwriteThis) if (!is(T == shared) && !is(V == shared));: Compare-and-exchange for non-shared types
pure nothrow @nogc @trusted boolcas(T, V1, V2)(shared(T)*here, V1*ifThis, V2writeThis) if (!is(T == class) && (is(T : V1) || is(shared(T) : V1)));: Compare and exchange for mixed-sharedness types
pure nothrow @nogc @trusted boolcas(T, V)(shared(T)*here, shared(T)*ifThis, shared(V)writeThis) if (is(T == class));: Compare-and-exchange forclass

pure nothrow @nogc @trusted boolcasWeak(MemoryOrder succ = MemoryOrder.seq, MemoryOrder fail = MemoryOrder.seq, T, V1, V2)(T*here, V1ifThis, V2writeThis) if (!is(T == shared) && is(T : V1)); pure nothrow @nogc @trusted boolcasWeak(MemoryOrder succ = MemoryOrder.seq, MemoryOrder fail = MemoryOrder.seq, T, V1, V2)(shared(T)*here, V1ifThis, V2writeThis) if (!is(T == class) && (is(T : V1) || is(shared(T) : V1))); pure nothrow @nogc @trusted boolcasWeak(MemoryOrder succ = MemoryOrder.seq, MemoryOrder fail = MemoryOrder.seq, T, V1, V2)(shared(T)*here, shared(V1)ifThis, shared(V2)writeThis) if (is(T == class));

Stores 'writeThis' to the memory referenced by 'here' if the value referenced by 'here' is equal to 'ifThis'. The 'weak' version of cas may spuriously fail. It is recommended to usecasWeak only whencas would be used in a loop. This operation is both lock-free and atomic.

Parameters:

T*`here`	The address of the destination variable.
V2`writeThis`	The value to store.
V1`ifThis`	The comparison value.

Returns:

true if the store occurred, false if not.

pure nothrow @nogc @trusted boolcasWeak(MemoryOrder succ = MemoryOrder.seq, MemoryOrder fail = MemoryOrder.seq, T, V)(T*here, T*ifThis, VwriteThis) if (!is(T == shared(S), S) && !is(V == shared(U), U)); pure nothrow @nogc @trusted boolcasWeak(MemoryOrder succ = MemoryOrder.seq, MemoryOrder fail = MemoryOrder.seq, T, V1, V2)(shared(T)*here, V1*ifThis, V2writeThis) if (!is(T == class) && (is(T : V1) || is(shared(T) : V1))); pure nothrow @nogc @trusted boolcasWeak(MemoryOrder succ = MemoryOrder.seq, MemoryOrder fail = MemoryOrder.seq, T, V)(shared(T)*here, shared(T)*ifThis, shared(V)writeThis) if (is(T == class));

Stores 'writeThis' to the memory referenced by 'here' if the value referenced by 'here' is equal to the value referenced by 'ifThis'. The prior value referenced by 'here' is written toifThis and returned to the user. The 'weak' version of cas may spuriously fail. It is recommended to usecasWeak only whencas would be used in a loop. This operation is both lock-free and atomic.

Parameters:

T*`here`	The address of the destination variable.
V`writeThis`	The value to store.
T*`ifThis`	The address of the value to compare, and receives the prior value of`here` as output.

Returns:

true if the store occurred, false if not.

pure nothrow @nogc @safe voidatomicFence(MemoryOrder order = MemoryOrder.seq)();

Inserts a full load/store memory fence (on platforms that need it). This ensures that all loads and stores before a call to this function are executed before any loads and stores after the call.

pure nothrow @nogc @safe voidpause();

Gives a hint to the processor that the calling thread is in a 'spin-wait' loop, allowing to more efficiently allocate resources.

pure nothrow @nogc @safe TailShared!TatomicOp(string op, T, V1)(ref shared Tval, V1mod) if (__traits(compiles, mixin("*cast(T*)&val" ~ op ~ "mod")));

Performs the binary operation 'op' on val using 'mod' as the modifier.

Parameters:

T`val`	The target variable.
V1`mod`	The modifier to apply.

Returns:

The result of the operation.

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Library Reference

core.atomic