Hi, Thanks for help. OK, I've created a new ticket as below. https://www.macruby.org/trac/ticket/1080 Thanks&Regards. kyossi

Hi,

There is no way to do that for now. Could you file a ticket? I will introduce #size on C structs classes.

NSRect.size in MacRuby would be the same as sizeof(NSRect) in C.

Laurent

On Dec 24, 2010, at 12:19 PM, kyossi wrote:

Hi,

I'm trying to write some app in MacRuby with CoreAudio framework.

I've notices some framework's C-function require pointer manipulation, and for some cases, I need calculate size of C-struct, but don't know how to get sizeof(struct Foo).

Is there any way to calculate size of C-struct in MacRuby?

For example, to obtain available formats of audio stream,I have to call AudioStreamGetPropertyInfo() at first.

extern OSStatus AudioStreamGetPropertyInfo( AudioStreamID inStream, UInt32 inChannel, AudioDevicePropertyID inPropertyID, UInt32*outSize, Boolean*outWritable);

if I specify kAudioStreamPropertyAvailableVirtualFormats as 3rd argument(inPropertyID), outSize gives me total required byte size for [an array of AudioStreamRangedDescription struct] which describe available formats.

Then, AudioStreamGetProperty() will fill [an array of AudioStreamRangedDescription struct] with available formats

extern OSStatus AudioStreamGetProperty( AudioStreamID inStream, UInt32 inChannel, AudioDevicePropertyID inPropertyID, //again use kAudioStreamPropertyAvailableVirtualFormats UInt32*ioPropertyDataSize, void*outPropertyData); //filled by API

http://developer.apple.com/library/mac/#documentation/MusicAudio/Reference/C...

So, I need to write some code like

framework "CoreAudio" def getAvailableFormats(stream, channel)

pSize = Pointer.new("I") ret = AudioStreamGetPropertyInfo( stream , channel, KAudioStreamPropertyAvailableVirtualFormats, pRequiredSize, nil) requiredSize = pSize[0]

howmany = ??? # how to get reqired length of array? in C: howmany = requiredSize / sizeof( AudioStreamRangedDescription ) pAudioStreamRangedDescription = Pointer.new("{AudioStreamRangedDescription={AudioStreamBasicDescription=dIIIIIIII}{AudioValueRange=dd}}", howmany)

ret = AudioStreamGetProperty(stream, channel, KAudioStreamPropertyAvailableVirtualFormats, pRequiredSize, pAudioStreamRangedDescription) ... end

Of course I could calculate sizeof( AudioStreamRangedDescription) manually but it's annoying. Is there any convenient way? _______________________________________________ MacRuby-devel mailing list MacRuby-devel@lists.macosforge.org http://lists.macosforge.org/mailman/listinfo.cgi/macruby-devel