AudioToolbox/AudioUnits (AudioFileWriteBytes) unavailable in Swift? - xcode

Question

Apple's documentation :
AudioToolbox Framework Reference > Audio File Services Reference > Reading and Writing Audio Files > AudioFileWriteBytes
Declaration Swift func AudioFileWriteBytes(_ inAudioFile: AudioFileID,
_ inUseCache: Boolean,
_ inStartingByte: Int64,
_ ioNumBytes: UnsafeMutablePointer<UInt32>,
_ inBuffer: UnsafePointer<Void>) -> OSStatus
Code in XCode Version 7.0 beta 4 (7A165t)
audioErr = AudioFileWriteBytes(audioFile, false, Int64(sampleCount * 2), bytesToWriteMem, sampleMem as! UnsafePointer<Void>)
XCode's reponse :
Cannot invoke 'AudioFileWriteBytes' with an argument list of type '(AudioFileID, Bool, Int64, UnsafeMutablePointer<UInt32>, UnsafePointer<Void>)'
Any idea ?
EDIT :
Thanks Martin R for your response, here is my full code and i don't understand why the AudioFileWriteBytes call returns an error ... :
import Foundation
import AudioToolbox
import Darwin
import AudioUnit
import CoreFoundation
extension Int {
func format (f:String) -> String {
return NSString(format:"%\(f)d", self) as String
}
}
let SAMPLE_RATE:Float64 = 44100 // 1
let DURATION = 0.1 // 2
// #define FILENAME_FORMAT #"%0.3f-square.aif" 3 skipped
if (Process.arguments.count < 2) {
print("Usage: CAToneFileGenerator n\n(where n is tone in Hz)")
exit(0)
}
var hz:Double = atof(Process.arguments[1]) // 4 (atof convert ASCII string to double)
assert(hz > 0)
print("generating \(hz) tone")
var fileName:String = String(format:"%d-square.aif", hz) // 5
var filePath:String = NSFileManager.defaultManager().currentDirectoryPath.stringByAppendingPathComponent(fileName)
var fileURL:NSURL = NSURL.fileURLWithPath(filePath) // the Audio File Services functions take URLs, not file paths
// Prepare the format
var asbd = AudioStreamBasicDescription() // 6
memset(&asbd, 0, sizeof(AudioStreamBasicDescription)) // 7
asbd.mSampleRate = SAMPLE_RATE // 8
asbd.mFormatID = AudioFormatID(kAudioFormatLinearPCM)
asbd.mFormatFlags = AudioFormatFlags(kAudioFormatFlagIsBigEndian | kAudioFormatFlagIsSignedInteger | kAudioFormatFlagIsPacked)
asbd.mBitsPerChannel = 16
asbd.mChannelsPerFrame = 1
asbd.mFramesPerPacket = 1
asbd.mBytesPerFrame = 2
asbd.mBytesPerPacket = 2
// Set up the file
var audioFile:AudioFileID = AudioFileID()
var audioErr:OSStatus = noErr
audioErr = AudioFileCreateWithURL(fileURL, // 9
AudioFileTypeID(kAudioFileAIFFType),
&asbd,
.EraseFile,
&audioFile)
// 1 -> AudioFileFlags(kAudioFileFlags_EraseFile)
assert(audioErr == noErr)
// Start writing samples
var maxSampleCount:CLong = CLong(SAMPLE_RATE * DURATION) // 10
var sampleCount:CLong = 0
var bytesToWrite:UInt32 = 2
/*
var bytesToWriteMem = UnsafeMutablePointer<UInt32>.alloc(1)
bytesToWriteMem.initialize(bytesToWrite)
*/
var wavelengthInSamples:Double = SAMPLE_RATE / hz // 11
var sample:UInt16
//var sampleMem = UnsafeMutablePointer<UInt16>.alloc(1)
//sampleMem.initialize(sample)
while sampleCount < maxSampleCount {
for i in 0..<Int(wavelengthInSamples) {
// Square wave
if ( i < Int(wavelengthInSamples/2)) { // 12
sample = UInt16.max // 13
} else {
sample = UInt16.min
}
//let bytesToWrite2 = bytesToWrite
audioErr = AudioFileWriteBytes(audioFile, // 14
false,
Int64(sampleCount * 2),
&bytesToWrite, //UnsafeMutablePointer<UInt32>
&sample) //UnsafePointer<Void>
assert(audioErr == noErr)
sampleCount++ // 15
}
}
/*
bytesToWriteMem.destroy()
bytesToWriteMem.dealloc(1)
sampleMem.destroy()
sampleMem.dealloc(1)
*/
audioErr = AudioFileClose(audioFile) // 16
assert(audioErr == noErr)
print("wrote \(sampleCount) samples")

Answer 1

That was tricky to find, because the error message does not help at all.
The problem is that the type of the second parameter of AudioFileWriteBytes() is Boolean, not Bool:
audioErr = AudioFileWriteBytes(audioFile,
Boolean(0), // <--- HERE
Int64(sampleCount * 2),
&bytesToWrite,
&sample)
For more information about the difference between Boolean and Bool
see for example Type 'Boolean' does not conform to protocol 'BooleanType'.
Update: As of Swift 2/Xcode 7, the Mac type Boolean is mapped
to the Swift Bool, so you have to pass false or true now:
audioErr = AudioFileWriteBytes(audioFile,
false, // <--- HERE
Int64(sampleCount * 2),
&bytesToWrite,
&sample)