[Vm-dev] Re: Method invocation in Slang
andreas.raab at gmx.de
Wed Feb 6 18:21:19 UTC 2008
Robert Krahn wrote:
>> What are you actually trying to accomplish? Possibly Andreas' callback
>> support is what you need.
> We are actually trying to find an easy way to use callbacks. The method
> invocation would be triggered from outside the VM. But since the
> callbacks are probably synchronous we don't have to use callbacks into
> the VM at all. If that will not work, we will follow Andreas' proposal
> and use semaphores. One thing I am interested in concerning this is how
> are parameters normally passed to the callbacks when using semaphores?
> By manipulating the stack?
No, by writing primitives which pick them up. For exampe:
"Run the callback process"
[self handleCallback] ensure:[self callbackReturn].
"Handle a callback from Python"
| nArgs rcvr selector args result |
nArgs := self callbackGetArgCount.
nArgs < 2 ifTrue:[^nil].
rcvr := self resolveReceiver: (self callbackGetArg: 1).
selector := self callbackGetArg: 2.
selector isString ifFalse:[^nil].
args := (3 to: nArgs) collect:[:i| self callbackGetArg: i].
"Transcript cr; show: selector; space; show: args."
result := [rcvr pyCallback: selector asSymbol args: args] on: Error
Transcript cr; show: ex description.
Transcript cr; show: ex signalerContext longStack.
ex return: nil.
"Transcript show:' ==> '; show: result."
self callbackResult: result.
"Primitive. Answer the number of args for the current callback."
<primitive: 'primitivePyCallbackGetArgCount' module: 'PyBridge'>
"Primitive. Answer the n-th argument of the current callback"
<primitive: 'primitivePyCallbackGetArg' module: 'PyBridge'>
"Primitive. Set the return value from the callback."
<primitive: 'primitivePyCallbackSetResult' module: 'PyBridge'>
"Primitive. Return from the callback."
<primitive: 'primitivePyCallbackReturn' module: 'PyBridge'>
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