12 messages in net.java.dev.jna.usersRe: [jna-users] Structure
FromSent OnAttachments
Paul LoyJan 10, 2008 8:29 am.java
Paul LoyJan 10, 2008 9:31 am.java
Paul LoyJan 10, 2008 9:47 am.java
Timothy WallJan 14, 2008 5:08 am 
Timothy WallJan 14, 2008 5:23 am 
Paul LoyJan 14, 2008 5:46 am 
Paul LoyJan 14, 2008 8:56 am 
Paul LoyJan 14, 2008 9:21 am 
Timothy WallJan 14, 2008 9:57 am 
Timothy WallJan 14, 2008 11:32 am 
Paul LoyJan 15, 2008 2:05 am 
Timothy WallJan 15, 2008 5:41 am 
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Subject:Re: [jna-users] StructureActions...
From:Paul Loy (kete@gmail.com)
Date:Jan 15, 2008 2:05:54 am
List:net.java.dev.jna.users

Hi Tim,

the calls I want to make are:

extern OSStatus AudioFormatGetProperty( AudioFormatPropertyID inPropertyID, UInt32 inSpecifierSize, void* inSpecifier, UInt32* ioPropertyDataSize, void* outPropertyData );

OSErr QTSetTrackProperty ( Track inTrack, QTPropertyClass inPropClass, QTPropertyID inPropID, ByteCount inPropValueSize, ConstQTPropertyValuePtr inPropValueAddress );

defined in AudioFormat.h in the QuickTime framework (MacOSX). Below is a native example of use:

AudioChannelLayout* layout = nil; int channels = 4;

UInt32 size = ((size_t) &((AudioChannelLayout *) 0)->mChannelDescriptions[channels]); layout = (AudioChannelLayout*)calloc(size);

(*layout).mChannelLayoutTag = kAudioChannelLayoutTag_UseChannelDescriptions; (*layout).mChannelBitmap = 0; (*layout).mNumberChannelDescriptions = channels;

int i; for (i = 0; i < channels; i++) { if (channelBitmap & (1 << i)) { (*layout).mChannelDescriptions[i].mChannelLabel = (0 == i % 2) ? kAudioChannelLabel_Left : kAudioChannelLabel_Right; } else { (*layout).mChannelDescriptions[i].mChannelLabel = kAudioChannelLabel_Unused; } } // see if this layout can be made into a tag if ((*layout).mChannelLayoutTag == kAudioChannelLayoutTag_UseChannelDescriptions) { UInt32 tag; UInt32 propSize = sizeof(tag); if (noErr == AudioFormatGetProperty( kAudioFormatProperty_TagForChannelLayout, size, layout, &propSize, &tag)) { (*layout).mChannelLayoutTag = tag; } } error = QTSetTrackProperty(track, kQTPropertyClass_Audio,kQTAudioPropertyID_ChannelLayout,size,layout);

I am going to try using the latest drop you committed last night to see if I can do this using Structure or keep using Memory.

Paul.

On Jan 14, 2008 7:32 PM, Timothy Wall <twal@dev.java.net> wrote:

What OSX headers hold the TrackProperty and ChannelDescription definitions?

On Jan 14, 2008, at 11:56 AM, Paul Loy wrote:

Hi Tim,

I built the latest code from SVN and this allows me to call TrackProperty.size() without a NPE if both the TrackProperty and ChannelDescription are ByReference.

By calling TrackProperty.size(), for 2 channels I get 12 when the actual size of this struct is 36 (2xChannelDescription+4). This makes the native call fail. If I botch it and send the 'correct' size, the call passes, although I guess I can't be sure it's writing to the correct memory. If I set ChannelDescription to be ByValue, I get a "Cannot inline ChannelDescription" exception.

Nested structures are by value by default, as are nested structure arrays. Your struct def should look something like this:

public class TrackProperty extends Structure { public ChannelDescription[] channels = new ChannelDescription[1]; public TrackProperty(int count) { // only required if you need to tweak the structures before a
call; otherwise // the array elements are auto-generated channels = (ChannelDescription[])new
ChannelDescription().toArray (count); } }

I think the .toArray version may fail, since the array's memory is not properly synched to the enclosing struct's memory.

So I think that we need a way to inline the memory for the ChannelDescriptions inside the TrackProperty as this is what the Native API is expecting.

Paul.

PS: I think JNA is great BTW. I've been using it for a couple of months now, and for everything up to this point it has worked perfectly first-time. JNA has drastically simplified our build and enables us to try things out much much more quickly. Thank you!

Thanks for the feedback!

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--------------------------------------------- Paul Loy pa@keteracel.com http://www.keteracel.com/paul