On Mon, 12 Nov 2012 02:30:17 -0000, Walter Bright
<[email protected]> wrote:
To make a shared type work in an algorithm, you have to:
1. ensure single threaded access by aquiring a mutex
2. cast away shared
3. operate on the data
4. cast back to shared
5. release the mutex
So what we actually want, in order to make the above "nice" is a "scoped"
struct wrapping the mutex and shared object which does all the "dirty"
work for you. I'm thinking..
// (0)
with(ScopedLock(obj,lock)) // (1)
{
obj.foo = 2; // (2)
} // (3)
// (4)
(0) obj is a "shared" reference, lock is a global mutex
(1) mutex is acquired here, shared is cast away
(2) 'obj' is not "shared" here so data access is allowed
(3) ScopedLock is "destroyed" and the mutex released
(4) obj is shared again
I think most of the above can be done without any compiler support but it
would be "nice" if the compiler did something clever with 'obj' such that
it knew it wasn't 'shared' inside the the 'with' above. If not, if a full
library solution is desired we could always have another temporary
"unshared" variable referencing obj.
R
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