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Future-proof QGenericRunnableHelper

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Collapse the two function pointers into a single one, taking an Op
enum. Add a possible return value (void*) and extra argument (also
void*). The intent is to allow extensions in a BC way,
e.g. cloning. We can't add new function pointers (sizeof changes), so
we need to fold everything into a single function.

Change-Id: Id0f3f74149c61e4e65622aeabfd2fcea3c6d7fb3
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
This commit is contained in:
Marc Mutz 2023-05-04 14:51:15 +02:00
parent fb2fccc534
commit 3c4743c66c
1 changed files with 21 additions and 10 deletions
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31
src/corelib/thread/qrunnable.h
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@ -38,27 +38,38 @@ protected:
// Type erasure, to only instantiate a non-virtual class per Callable: // Type erasure, to only instantiate a non-virtual class per Callable:
class QGenericRunnableHelperBase class QGenericRunnableHelperBase
{ {
using OpFn = void(*)(QGenericRunnableHelperBase *);
OpFn runFn;
OpFn destroyFn;
protected: protected:
constexpr explicit QGenericRunnableHelperBase(OpFn fn, OpFn del) noexcept : runFn(fn), destroyFn(del) {} enum class Op {
Run,
Destroy,
};
using OpFn = void* (*)(Op, QGenericRunnableHelperBase *, void*);
OpFn fn;
protected:
constexpr explicit QGenericRunnableHelperBase(OpFn f) noexcept : fn(f) {}
~QGenericRunnableHelperBase() = default; ~QGenericRunnableHelperBase() = default;
public: public:
void run() { runFn(this); } void run() { fn(Op::Run, this, nullptr); }
void destroy() { destroyFn(this); } void destroy() { fn(Op::Destroy, this, nullptr); }
}; };
template <typename Callable> template <typename Callable>
class QGenericRunnableHelper : public QGenericRunnableHelperBase class QGenericRunnableHelper : public QGenericRunnableHelperBase
{ {
Callable m_functionToRun; Callable m_functionToRun;
static void *impl(Op op, QGenericRunnableHelperBase *that, [[maybe_unused]] void *arg)
{
const auto _this = static_cast<QGenericRunnableHelper*>(that);
switch (op) {
case Op::Run: _this->m_functionToRun(); break;
case Op::Destroy: delete _this; break;
}
return nullptr;
}
public: public:
template <typename UniCallable> template <typename UniCallable>
QGenericRunnableHelper(UniCallable &&functionToRun) noexcept : explicit QGenericRunnableHelper(UniCallable &&functionToRun) noexcept
QGenericRunnableHelperBase( : QGenericRunnableHelperBase(&impl),
[](QGenericRunnableHelperBase *that) { static_cast<QGenericRunnableHelper*>(that)->m_functionToRun(); },
[](QGenericRunnableHelperBase *that) { delete static_cast<QGenericRunnableHelper*>(that); }),
m_functionToRun(std::forward<UniCallable>(functionToRun)) m_functionToRun(std::forward<UniCallable>(functionToRun))
{ {
} }