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digitalmars.D.learn - GetAndSet function (corresponding to cas function)

reply Adrian Mercieca <amercieca gmail.com> writes:
Hi folks,

Is there a GetAndSet function (corresponding to cas (compare and set) 
function) in D?

Thanks.
Dec 25 2011
parent reply Mike Wey <mike-wey example.com> writes:
On 12/25/2011 09:25 AM, Adrian Mercieca wrote:

 Hi folks,

 Is there a GetAndSet function (corresponding to cas (compare and set)
 function) in D?

 Thanks.


core.atomic.cas

http://dlang.org/phobos/core_atomic.html#cas

-- 
Mike Wey
Dec 25 2011
parent reply Adrian Mercieca <amercieca gmail.com> writes:
On Sun, 25 Dec 2011 13:37:32 +0100, Mike Wey wrote:


 On 12/25/2011 09:25 AM, Adrian Mercieca wrote:

 Hi folks,

 Is there a GetAndSet function (corresponding to cas (compare and set)
 function) in D?

 Thanks.


 
 core.atomic.cas
 
 http://dlang.org/phobos/core_atomic.html#cas


I know of the cas function in D.

I was asking if there was a getAndSet function.

Tks.
Dec 25 2011
parent reply Adrian Mercieca <amercieca gmail.com> writes:
Hi folks,

Would anyone answer me on this please?

To clarify, in Java there is are getAndSet methods on Atomic type objects 
(along with compareAndSet).

I know that in D there is the cas function (equivalent to Java's 
compareAndSet); is there an equivalent D function for Java's getAndSet 
please?


Thanks.
Dec 26 2011
next sibling parent reply Andrew Wiley <wiley.andrew.j gmail.com> writes:
On Mon, Dec 26, 2011 at 2:34 PM, Adrian Mercieca <amercieca gmail.com> wrote:

 Hi folks,

 Would anyone answer me on this please?

 To clarify, in Java there is are getAndSet methods on Atomic type objects
 (along with compareAndSet).

 I know that in D there is the cas function (equivalent to Java's
 compareAndSet); is there an equivalent D function for Java's getAndSet
 please?


 Thanks.



From Java:


---
    public final boolean getAndSet(boolean newValue) {
        for (;;) {
            boolean current = get();
            if (compareAndSet(current, newValue))
                return current;
        }
    }
---

getAndSet is just a wrapped version of compareAndSet.
Dec 26 2011
next sibling parent Adrian Mercieca <amercieca gmail.com> writes:
On Mon, 26 Dec 2011 15:06:57 -0600, Andrew Wiley wrote:


 On Mon, Dec 26, 2011 at 2:34 PM, Adrian Mercieca <amercieca gmail.com>
 wrote:

 Hi folks,

 Would anyone answer me on this please?

 To clarify, in Java there is are getAndSet methods on Atomic type
 objects (along with compareAndSet).

 I know that in D there is the cas function (equivalent to Java's
 compareAndSet); is there an equivalent D function for Java's getAndSet
 please?


 Thanks.


 

From Java:


 ---
     public final boolean getAndSet(boolean newValue) {
         for (;;) {
             boolean current = get();
             if (compareAndSet(current, newValue))
                 return current;
         }
     }
 ---
 
 getAndSet is just a wrapped version of compareAndSet.



Hi Andrew,

It is indeed; should have thought of that.

Anyway, thanks for pointing it out.

Regards.
Dec 27 2011
prev sibling parent Adrian Mercieca <amercieca gmail.com> writes:
Hi Andrew,

Actually, what would be the equivalent of the 'get' function in D?

Thanks.
Dec 27 2011
prev sibling next sibling parent Jonathan M Davis <jmdavisProg gmx.com> writes:
On Monday, December 26, 2011 20:34:39 Adrian Mercieca wrote:

 Hi folks,
 
 Would anyone answer me on this please?
 
 To clarify, in Java there is are getAndSet methods on Atomic type objects
 (along with compareAndSet).
 
 I know that in D there is the cas function (equivalent to Java's
 compareAndSet); is there an equivalent D function for Java's getAndSet
 please?


If it's not in core.atomic, then probably not. It has atomicLoad and 
atomicStore, but I don't see anything that tries to combine the two, assuming 
that that's what you want be getAndSet.

- Jonathan M Davis
Dec 26 2011
prev sibling parent Andrew Wiley <wiley.andrew.j gmail.com> writes:
On Mon, Dec 26, 2011 at 4:05 PM, Jonathan M Davis <jmdavisProg gmx.com> wrote:

 On Monday, December 26, 2011 20:34:39 Adrian Mercieca wrote:

 Hi folks,

 Would anyone answer me on this please?

 To clarify, in Java there is are getAndSet methods on Atomic type objects
 (along with compareAndSet).

 I know that in D there is the cas function (equivalent to Java's
 compareAndSet); is there an equivalent D function for Java's getAndSet
 please?


 If it's not in core.atomic, then probably not. It has atomicLoad and
 atomicStore, but I don't see anything that tries to combine the two, assuming
 that that's what you want be getAndSet.


getAndSet can easily be implemented as a utility method using cas and
atomicLoad. It's not a primitive atomic operation, it's just a
convenience function.

T getAndSet(T)(shared(T)* location, T newValue) {
    while(1) {
        auto current = atomicLoad(*location);
        if(cas(location, current, newValue))
            return current;
    }
}

Someone who knows more about the options to atomicLoad could probably
make this faster, but because we're using cas, it's guaranteed to be
correct.
Dec 26 2011