benchmark-update.d

extern (C) void* _aaGetX(void** paa, const TypeInfo_AssociativeArray ti, in size_t valuesize, in void* pkey, out bool found) pure nothrow;

V* slot(K, V)(ref V[K] aa, K key, out bool found)
{
    return cast(V*) _aaGetX(cast(void**)&aa, typeid(V[K]), V.sizeof, &key, found);
}

void update(K, V, C, U)(ref V[K] aa, K key, C create, U update)
if (is(C : V delegate()) || is(C : V function()) && (is(U : V delegate(ref V)) || is(U : V function(ref V))))
{
    bool found = true;
    auto p = cast(V*) _aaGetX(cast(void**)&aa, typeid(V[K]), V.sizeof, &key, found);
    if (!found)
        *p = create();
    else
        *p = update(*p);
}

void test1()
{
    class C
    {
    }

    C[string] aa;

    C orig = new C;
    aa["foo"] = orig;

    C newer;
    C older;

    bool found;
    auto p = aa.slot("foo", found);
    if(!found)
    {
        newer = new C;
        *p = newer;
    } else {
        older = *p;
        newer = new C;
        *p = newer;
    }
    assert(older is orig);
    assert(newer is aa["foo"]);
}

void test2()
{
    class C
    {
    }

    C[string] aa;

    C orig = new C;
    aa["foo"] = orig;

    C newer;
    C older;
    aa.update("foo",
    {
        newer = new C;
        return newer;
    }, (C c) {
        older = c;
        newer = new C;
        return newer;
    });
    assert(older is orig);
    assert(newer is aa["foo"]);
}

void main()
{
    import std.datetime.stopwatch, std.stdio;

    auto r1 = benchmark!test1(100_000);
    writeln("test1 ", r1);
    auto r2 = benchmark!test2(100_000);
    writeln("test2 ", r2);

    getchar();
}