Usage of Withmemoryrebound with Apples Swift 3 Beta 6

Usage of withMemoryRebound with Apples Swift 3 beta 6

Pointer conversions are much more "verbose" now since Xcode 8 beta 6.
Here is a possible solution:

func binarytotype <T> (_ value: [UInt8], _: T.Type) -> T {
    return value.withUnsafeBufferPointer {
        UnsafeRawPointer($0.baseAddress!).load(as: T.self)
    }
}

func typetobinary<T>(_ value: T) -> [UInt8] {
    var data = [UInt8](repeating: 0, count: MemoryLayout<T>.size)
    data.withUnsafeMutableBufferPointer {
        UnsafeMutableRawPointer($0.baseAddress!).storeBytes(of: value, as: T.self)
    }
    return data
}

Example:

let d = typetobinary(UInt16(1000))
print(d) // [232, 3]
let i = binarytotype(d, UInt16.self)
print(i) // 1000

See SE-0107 UnsafeRawPointer API for
detailed information about the new raw pointer API.

Swift 3 UnsafePointer($0) no longer compile in Xcode 8 beta 6

From the Release Notes of Xcode 8 beta 6:

An Unsafe[Mutable]RawPointer type has been introduced, replacing Unsafe[Mutable]Pointer<Void>. Conversion from UnsafePointer<T> to
UnsafePointer<U> has been disallowed. Unsafe[Mutable]RawPointer
provides an API for untyped memory access, and an API for binding
memory to a type. Binding memory allows for safe conversion between
pointer types. See bindMemory(to:capacity:), assumingMemoryBound(to:),
and withMemoryRebound(to:capacity:). (SE-0107)

In your case, you may need to write something like this:

let defaultRouteReachability = withUnsafePointer(to: &zeroAddress) {
    $0.withMemoryRebound(to: sockaddr.self, capacity: 1) {zeroSockAddress in
        SCNetworkReachabilityCreateWithAddress(nil, zeroSockAddress)
    }
}

UnsafePointer no longer works in swift 3

You can try this:

let rawPointer = UnsafeRawPointer(array1)
let pointer = rawPointer.assumingMemoryBound(to: UInt32.self)
let value = pointer.pointee

Raw pointer is a pointer for accessing untype data.

assumingMemoryBound(to:) can convert from an UnsafeRawPointer to UnsafePointer<T>.

Reference :Swift 3.0 Unsafe World

Fatal error when using withMemoryRebound in iOS/Swift

Your original array arr is an array of Floats

var arr = Array<Float>(repeating: 0, count: 163840)

but you're trying to bind the pointer to a UInt16

arr_pointer.withMemoryRebound(to: UInt16.self)

Xcode 8 beta 6: main.swift won't compile

I write it this way:

UIApplicationMain(
    CommandLine.argc,
    UnsafeMutableRawPointer(CommandLine.unsafeArgv)
        .bindMemory(
            to: UnsafeMutablePointer<Int8>.self,
            capacity: Int(CommandLine.argc)),
    nil,
    NSStringFromClass(AppDelegate.self)
)

To change the UIApplication class, substitute NSStringFromClass(MobileUIApplication.self) for nil in that formulation.

However, if your only purpose here is to substitute a UIApplication subclass as the shared application instance, there's an easier way: in the Info.plist, add the "Principal class" key and set its value to the string name of your UIApplication subclass, and mark your declaration of that subclass with an @objc(...) attribute giving it the same Objective-C name.

EDIT This problem is now solved in Swift 4.2. CommandLine.unsafeArgv now has the correct signature, and one can call UIApplicationMain easily:

UIApplicationMain(
    CommandLine.argc, CommandLine.unsafeArgv, 
    nil, NSStringFromClass(AppDelegate.self)
)

SwiftData (SQLite wrapper) broken with Swift 3.0

sqlite3_column_int(statement, index) returns an Int32 and

sqlite3_column_int(statement, index) != 0

is a boolean value, so that makes no sense as the return value if
an (optional) AnyObject is expected. You can wrap the integer into
a NSNumber instead:

func getColumnValue(_ statement: OpaquePointer, index: Int32, type: String) -> AnyObject? {
    let val = sqlite3_column_int(statement, index)
    return NSNumber(value: val)
}

Another option would be

func getColumnValue(_ statement: OpaquePointer, index: Int32, type: String) -> AnyObject? {
    return sqlite3_column_int(statement, index) as AnyObject
}

because in Swift 3, anything can be converted to AnyObject.
The difference is that in the second solution, the object can only be
converted back to the original number type Int32, but not to
Int or any other integer type.

For the other problems, see

Issue with UnsafePointer<Uint8> in SQLite project in Swift
Error in for loop CGFloat

Getting memory usage Live/Dirty Bytes in iOS app programmatically (not Resident/Real Bytes)

I found something else, but it seems to work on the device that the previous method didn't work and not work on the device that the previous method did work :-(
Now I need to figure out how to know which one to use. One device is iPhone 5s with iOS 9 and another is iPhone 5s with iOS 11.
I guess I need to test on more veriaty of devices...

I found it here:

https://opensource.apple.com/source/WebKit/WebKit-7603.1.30.1.33/ios/Misc/MemoryMeasure.mm.auto.html

This translated to something like this in Objective-C:

task_vm_info_data_t vmInfo;
mach_msg_type_number_t count = TASK_VM_INFO_COUNT;
kern_return_t err = task_info(mach_task_self(), TASK_VM_INFO, (task_info_t) &vmInfo, &count);
if (err != KERN_SUCCESS)
    return 0;

NSLog(@"Memory in use vmInfo.internal (in bytes): %u", vmInfo.internal);

return vmInfo.internal;

I think if I add vmInfo.internal and vmInfo.compressed then I'll get the right result (matching what Xcode Debug navigator is showing)

It looks right for these two devices so far, and 2 other devices I tested.

So my final code looks like this:

task_vm_info_data_t info;
mach_msg_type_number_t size = TASK_VM_INFO_COUNT;
kern_return_t kerr = task_info(mach_task_self(),
                               TASK_VM_INFO,
                               (task_info_t)&info,
                               &size);
if( kerr == KERN_SUCCESS ) {
    mach_vm_size_t totalSize = info.internal + info.compressed;
    NSLog(@"Memory in use (in bytes): %u", totalSize);
    return totalSize;
} else {
    NSLog(@"Error with task_info(): %s", mach_error_string(kerr));
}

How to use SCNetworkReachability in Swift

(This answer was extended repeatedly due to changes in the Swift language, which made it a bit confusing. I have now rewritten it and removed everything which refers to Swift 1.x. The older code can
be found in the edit history if somebody needs it.)

This is how you would do it in Swift 2.0 (Xcode 7):

import SystemConfiguration

func connectedToNetwork() -> Bool {

    var zeroAddress = sockaddr_in()
    zeroAddress.sin_len = UInt8(sizeofValue(zeroAddress))
    zeroAddress.sin_family = sa_family_t(AF_INET)

    guard let defaultRouteReachability = withUnsafePointer(&zeroAddress, {
        SCNetworkReachabilityCreateWithAddress(nil, UnsafePointer($0))
    }) else {
        return false
    }

    var flags : SCNetworkReachabilityFlags = []
    if !SCNetworkReachabilityGetFlags(defaultRouteReachability, &flags) {
        return false
    }

    let isReachable = flags.contains(.Reachable)
    let needsConnection = flags.contains(.ConnectionRequired)

    return (isReachable && !needsConnection)
}

Explanations:

As of Swift 1.2 (Xcode 6.3), imported C structs have a default initializer in Swift, which initializes all of the struct's fields to zero, so the socket address structure can be initialized with
```
var zeroAddress = sockaddr_in()
```
sizeofValue() gives the size of this structure, this has
to be converted to UInt8 for sin_len:
```
zeroAddress.sin_len = UInt8(sizeofValue(zeroAddress))
```
AF_INET is an Int32, this has to be converted to the correct type for sin_family:
```
zeroAddress.sin_family = sa_family_t(AF_INET)
```
withUnsafePointer(&zeroAddress) { ... } passes the address of the
structure to the closure where it is used as argument for
SCNetworkReachabilityCreateWithAddress(). The UnsafePointer($0)
conversion is needed because that function expects a pointer to
sockaddr, not sockaddr_in.
The value returned from withUnsafePointer() is the return value
from SCNetworkReachabilityCreateWithAddress() and that has the
type SCNetworkReachability?, i.e. it is an optional.
The guard let statement (a new feature in Swift 2.0) assigns the unwrapped value to the defaultRouteReachability variable if it is
not nil. Otherwise the else block is executed and the function
returns.
As of Swift 2, SCNetworkReachabilityCreateWithAddress() returns
a managed object. You don't have to release it explicitly.
As of Swift 2, SCNetworkReachabilityFlags conforms to
OptionSetType which has a set-like interface. You create an
empty flags variable with
```
var flags : SCNetworkReachabilityFlags = []
```
and check for flags with
```
let isReachable = flags.contains(.Reachable)
let needsConnection = flags.contains(.ConnectionRequired)
```
The second parameter of SCNetworkReachabilityGetFlags has the type
UnsafeMutablePointer<SCNetworkReachabilityFlags>, which means that you have to
pass the address of the flags variable.

Note also that registering a notifier callback is possible as of
Swift 2, compare Working with C APIs from Swift and Swift 2 - UnsafeMutablePointer<Void> to object.

Update for Swift 3/4:

Unsafe pointers cannot be simply be converted to a pointer of a
different type anymore (see - SE-0107 UnsafeRawPointer API). Here the updated code:

import SystemConfiguration

func connectedToNetwork() -> Bool {

    var zeroAddress = sockaddr_in()
    zeroAddress.sin_len = UInt8(MemoryLayout<sockaddr_in>.size)
    zeroAddress.sin_family = sa_family_t(AF_INET)

    guard let defaultRouteReachability = withUnsafePointer(to: &zeroAddress, {
        $0.withMemoryRebound(to: sockaddr.self, capacity: 1) {
            SCNetworkReachabilityCreateWithAddress(nil, $0)
        }
    }) else {
        return false
    }

    var flags: SCNetworkReachabilityFlags = []
    if !SCNetworkReachabilityGetFlags(defaultRouteReachability, &flags) {
        return false
    }

    let isReachable = flags.contains(.reachable)
    let needsConnection = flags.contains(.connectionRequired)

    return (isReachable && !needsConnection)
}

Trying to stream audio from microphone to another phone via multipeer connectivity

Your AVAudioPCMBuffer serialisation/deserialisation is wrong.

Swift3's casting has changed a lot & seems to require more copying than Swift2.

Here's how you can convert between [UInt8] and AVAudioPCMBuffers:

N.B: this code assumes mono float data at 44.1kHz.

You might want to change that.

func copyAudioBufferBytes(_ audioBuffer: AVAudioPCMBuffer) -> [UInt8] {
    let srcLeft = audioBuffer.floatChannelData![0]
    let bytesPerFrame = audioBuffer.format.streamDescription.pointee.mBytesPerFrame
    let numBytes = Int(bytesPerFrame * audioBuffer.frameLength)

    // initialize bytes to 0 (how to avoid?)
    var audioByteArray = [UInt8](repeating: 0, count: numBytes)

    // copy data from buffer
    srcLeft.withMemoryRebound(to: UInt8.self, capacity: numBytes) { srcByteData in
        audioByteArray.withUnsafeMutableBufferPointer {
            $0.baseAddress!.initialize(from: srcByteData, count: numBytes)
        }
    }

    return audioByteArray
}

func bytesToAudioBuffer(_ buf: [UInt8]) -> AVAudioPCMBuffer {
    // format assumption! make this part of your protocol?
    let fmt = AVAudioFormat(commonFormat: .pcmFormatFloat32, sampleRate: 44100, channels: 1, interleaved: true)
    let frameLength = UInt32(buf.count) / fmt.streamDescription.pointee.mBytesPerFrame

    let audioBuffer = AVAudioPCMBuffer(pcmFormat: fmt, frameCapacity: frameLength)
    audioBuffer.frameLength = frameLength

    let dstLeft = audioBuffer.floatChannelData![0]
    // for stereo
    // let dstRight = audioBuffer.floatChannelData![1]

    buf.withUnsafeBufferPointer {
        let src = UnsafeRawPointer($0.baseAddress!).bindMemory(to: Float.self, capacity: Int(frameLength))
        dstLeft.initialize(from: src, count: Int(frameLength))
    }

    return audioBuffer
}

Usage of Withmemoryrebound with Apples Swift 3 Beta 6