Zitat von Vicente Botet Escriba <vicente.botet@wanadoo.fr>:
Peter Dimov-5 wrote:
Vicente Botet Escriba wrote:
For me it is unacceptable to use reallocation of the vector on the operator*.
Operator* has a non-NULL precondition and doesn't need to reallocate. reset() does, but only if you set a thread_specific_ptr that has been created after the thread has started.
I was responding to the proposition of Stefan, not to the current implementation.
peter´s right, no reallocation in operator*. thread_specific_ptr::operator*(){ BOOST_ASSERT(tss_vec.size() > this->index); return *tss_vec[this->index]; } thread_specific_ptr::get(){ if(tss_vec.size() > this->index) return tss_vec[this->index]; else return 0; } thread_specific_ptr::reset(T *ptr){ auto_ptr aptr(ptr); if(tss_vec.size() <= this->index) tss_vec.resize(this->index+1); tss_vec[this->index]=aptr.release(); }
My concrete example is to access the current transaction on a Software Transaction Memory. This operation can be required frequently. You should
but reallocation only happens once per thread, on first call to reset().
I have no access to the code now. Please,could you show where the current implementation allocates and use a mutex on the operator*.
probably also only on reset(), the code is in libs/src/pthread/thread.cpp. it inserts an element into a std::map, which allocates, which acquires a mutex.
A library could not know if its users work on a Boost.Thread or on a native thread. So thread_specific_ptr needs to work in both cases. The current implementation of thread_specific_ptr satisfy already this. Any alternative proposal need to satisfy this requirement also.
ok, I wasn´t sure.