Thanks a lot for the answer. In fact, I am trying to associate data (std::vector<int> and Widget objects) with a boost::mutex by wrapping its interface [ lock(), try_lock() and unlock() ] as follows:
class Widget { ... }; // data to be associated with
class MyData {
public:
MyData(std::vector<int>& v) : v_(v), w_(new Widget) { }
~MyData() {
m_.~mutex();
delete w_;
}
bool is_held() { // test if current thread has locked the thread
return id_ == boost::this_thread::get_id();
}
std::vector<int>& v() {
assert( is_held() ); // lock before accessing data
return v_;
}
Widget* w() {
assert( is_held() ); // lock before accessing data
return w_;
}
void lock() {
id_ = boost::this_thread::get_id();
m_.lock();
}
bool trylock() {
bool b = m_.try_lock();
if (b)
id_ = boost::this_thread::get_id();
return b;
}
void unlock() {
id_ = 0; // reset it, does not compile
m_.unlock();
}
private:
boost::mutex m_;
std::vector<int>& v_;
Widget* w_;
boost::thread::id id_;
};
In the MyData::unlock(), I want to reset id_ to some initial value, but it does not compile. What should I do with it?
Thanks in advance,
Robert
On Tue, Jun 8, 2010 at 12:55 PM, Anthony Williams
<anthony.ajw@gmail.com> wrote:
Boost lzw <
boostlzw@gmail.com> writes:
> class X {
> public:
> X() : id_(0) // does not compile
> { }
>
> void f() {
> if (operation_failed)
> id_ = 0; // does not compile
> else
> id_ = boost::this_thread::get_id(); // get which thread is
> sucessfully executing f()
> }
> bool compare() { // compare current thread with the one that has
> sucessfully executed f()
> return id_ == boost::this_thread::get_id();
> }
> private:
> boost::thread::id id_;
> };
>
> My questions are:
>
> How can I set the id_ to an initial value (e.g., 0 here) for compare() function
> to get correct result
> , assuming multiple threads might be executing f() and
> compare() at the same time? Is there a way to do this:
> atomic<boost::thread::id> id_;
> to make them thread-safe?
If you want to protect a value for safe access from multiple threads,
use a mutex.
Anthony
--
Author of C++ Concurrency in Action http://www.stdthread.co.uk/book/
just::thread C++0x thread library http://www.stdthread.co.uk
Just Software Solutions Ltd http://www.justsoftwaresolutions.co.uk
15 Carrallack Mews, St Just, Cornwall, TR19 7UL, UK. Company No. 5478976