On Wed, Jul 15, 2015 at 5:16 PM, Matthieu Lacaton
<matthieu.laca...@gmail.com> wrote:
> Hello Igor,
>
> Thanks for your answer.
>
> I implemented something like that for the printf function:
> Basically, it generates a method with matching arguments and executes it.
>
>> printf: stringFormat args: tab
>>
>> | argNumber functionArgs functionPrototype methodCorpse methodSelector
>> argsArray |
>>
>> ((tab size % 2) = 0) ifFalse: [
>> Transcript show: 'error'.
>> ^self.
>> ].
>>
>> argNumber := 0.
>> functionPrototype := 'printf: stringFormat'.
>> functionArgs := ''.
>> methodCorpse := ''.
>> argsArray := (Array new: (tab size / 2) + 1).
>> argsArray at: 1 put: stringFormat.
>>
>> 1 to: tab size by: 2 do: [ :i |
>> functionPrototype := functionPrototype, ' arg', argNumber
>> asString, ': ', (tab at: i) asString, argNumber asString.
>> functionArgs := functionArgs, ' ', (tab at: i) asString, ' ', (tab
>> at: i) asString, argNumber asString, ','.
>> argsArray at: argNumber + 2 put: (tab at: i + 1).
>> argNumber := argNumber + 1.
>> ].
>> functionArgs := functionArgs allButLast.
>>
>> methodCorpse := functionPrototype, Character cr asString, '
>> <primitive: #primitiveNativeCall module: #NativeBoostPlugin>', Character cr
>> asString, Character cr asString, ' ^self nbCall: #( void printf ( String
>> stringFormat,', functionArgs asString, ' ) )', Character cr asString, '
>> module: NativeBoost CLibrary'.
>>
>> methodSelector := self class compile: methodCorpse.
>>
>> self perform: methodSelector withArguments: argsArray.
>
>
>
> Then you can call it like that :
>
> MyClass printf: 'Test of printf. String: %s, Int : %d, Long: %ld, Char: %c,
> Double: %lf' args: { 'String'. 'This is a string'. 'int'. 100. 'long'.
> 10000000. 'char'. 89. 'double'. 3.14159 }.
>
>
> I also tried it for some other variadic functions and, on my computer (I am
> running archlinux), it seemed to work for every type of argument except
> "float".
Maybe NativeBoost does not do implicit type conversions that a C
compiler would do?
[1] "Because C will promote floats to doubles for functions that take
variable arguments"
More info search [2] for:
* "implicit type conversion"
* "guess wrongly when the program uses floating-point formats in
scanf() or printf()"
[1]
http://stackoverflow.com/questions/210590/why-does-scanf-need-lf-for-doubles-when-printf-is-okay-with-just-f
[2] http://www.electroons.com/8051/ebooks/expert%20C%20programming.pdf
cheers -ben
> It works fine for "double" though.
> For "char" you need to pass the integer ASCII value directly for it to work.
> I tried with "Character value: xxx" but it didn't work.
>
> I know that this is very hackish and very bad, and I am aware it has some
> drawbacks. Moreover I am not even sure it will work everytime.
> But for now it seems to work ...
>
> 2015-07-13 19:24 GMT+02:00 Igor Stasenko <siguc...@gmail.com>:
>>
>>
>>
>> On 10 July 2015 at 10:18, Matthieu Lacaton <matthieu.laca...@gmail.com>
>> wrote:
>>>
>>> Hello,
>>>
>>> Is it possible with NativeBoost to create a binding for a variadic
>>> function ?
>>>
>>> I've seen the printf example in NBCPrinter but this implementation is
>>> kind of cheating since it always pass just a %s as format and one already
>>> formatted string to the C function.
>>>
>>> I've written a simple variadic function which adds every integer it
>>> receives as argument (first argument is for the number of following
>>> arguments) :
>>>
>>> int add(int number,...);
>>>
>>> In Pharo I've tried something like this :
>>>
>>>> add: number arg1: first arg2: second
>>>> <primitive: #primitiveNativeCall module: #NativeBoostPlugin>
>>>>
>>>> ^ self nbCall: #( int add (int number, int first, int second))
>>>> module: 'libMyLib.so'
>>>
>>>
>>> and it works fine with two arguments.
>>>
>>> Basically, doing so, I would need one method per number of arguments so
>>> it's not very cool.
>>>
>>> I thought that maybe I could pass an array as argument to my Pharo method
>>> but I didn't really find a way to figure out how to define the nbCall
>>> without having a "Generic failure".
>>>
>>>> add: number args: anArray
>>>> <primitive: #primitiveNativeCall module: #NativeBoostPlugin>
>>>>
>>>> ^ self nbCall: #( int add (int number, ??? anArray))
>>>> module: 'libMyLib.so'
>>>
>>>
>>> Do you have an idea ?
>>>
>>
>> In short, there's no marshaller for converting an array of items, to same
>> number of things on stack. That could solve the problem with your example:
>> passing array of objects of *same* type. But in general, it is not what C
>> variadic function(s) standing for. Because they stand for any number of
>> arguments, of any type.
>> In C, since all program is compiled statically, compiler knows the number
>> of passed arguments and their types through compiling each particular call
>> site(s) to variadic function. Which means that in fact, you are still
>> supplying all information needed by compiler *before* run time.
>>
>> In variadic functions, you can pass any arguments of any type,
>> but for converting each of them, you must tell NB what kind of marshaller
>> should be used for it , which means, that it is impossible to know before
>> run time, since you cannot know how many arguments you may pass, not
>> speaking about their types.
>>
>>
>>
>>>
>>> Thanks,
>>>
>>> Matthieu
>>>
>>>
>>
>>
>>
>> --
>> Best regards,
>> Igor Stasenko.
>
>
