A new version of Allegro.pas was released yesterday. Allegro.pas is a wrapper to allow Pascal compilers (such as Free Pascal) to use the Allegro library in games or multimedia programs.

This version introduces new functions that allows to create, write and read files using the LZSS compression algorithm.

Also I've created a public mailing list, but it needs some hours to be active so be patient if you find an error page.

That's all today. Don't forget to download and test it.

http://allegro-pas.sourceforge.net/

Hi all,

I've been playing with audio unit framework on Mac OSX 10.4, and trying to make a sample from Xcode (PlayAudioFileLite) running on Lazarus 0.9.25/rev 15279 with FPC 2.2.0.

I'm nearly done, and I'm only getting an error -50 (error in user parameter list) on the last API call from the callback process.

I don't have the sufficient experience with C/C++ vs. Pascal calling conventions, but I've been lucky with other API calls, except for the last one. I'm hoping one of you can help translate this call, which btw the way works fine in Xcode - the sample is playing an audio file.

The API call is in the AudioFile.h:

Extern OSStatus
AudioFileReadPackets ( AudioFileID inAudioFile, Boolean inUseCache,
UInt32 *outNumBytes,
AudioStreamPacketDescription
*outPacketDescriptions,
SInt64 inStartingPacket,
UInt32 *ioNumPacket,
void *outBuffer)
AVAILABLE_MAC_OS_X_VERSION_10_2_AND_LATER;

I've translated this to:

function AudioFileReadPacket(inAudioFile: AudioFileID;
                             inUseCache: Boolean;
                             var outNumBytes: UInt32;
                             var outPacketDescriptions:
AudioStreamPacketDescription; //also tried Pointer
                             inStartingPacket: SInt64;
                             var ioNumPacket: UInt32;
                             var outBuffer: Pointer): OSStatus; external
name '_AudioFileReadPackets'; mwpascal;

I've tried to change the types of parameters in various combination, but yet it didn't give me a clue on which of the parameters is in a wrong type.

I'm sorry if this off topic, but I'll be happy if one of you can tell me what I'm translating wrong.

Best regards,
Normann

I think it should be (no var for the pointer):
function AudioFileReadPacket(inAudioFile: AudioFileID;
                              inUseCache: Boolean;
                              var outNumBytes: UInt32;
                              var outPacketDescriptions:
AudioStreamPacketDescription; //also tried Pointer
                              inStartingPacket: SInt64;
                              var ioNumPacket: UInt32;
                              outBuffer: Pointer): OSStatus; external
name '_AudioFileReadPackets'; mwpascal;

Vincent

In our previous episode, Vincent Snijders said:

I think it should be (no var for the pointer):

... and if ObjC's concept of a boolean is the same as FPC's. Maybe longbool ?

I tried, and same result.

Could a Mac OSX API call return -50 even though the types are correct, but the contents of them are not what it expected?

I would assume -50 is only after a check for types in the parameter list, and check is done before even calling the API.

Thanks,
Normann

I did thought the boolean type could have a different size, and I did make a sizeof in Xcode and in FPC, and the both returned a size of 1. This don't mean, there's an alignment issue?

Thanks,
Normann

External functions have no idea what the declaration of the function in your source code is. A couple of the parameters your are passing (inAudioFile a outPacketDescriptions) however are pointers to opaque structures, and the called function is probably performing some sanity checks on those structures to ensure that they are valid.

Jonas

Or alternatively, one of the other parameters could be invalid as well (either on their own or in combination with the other parame