How to get bytes out of an UnsafeMutableRawPointer?

Question

How does one access bytes (or Int16\'s, floats, etc.) out of memory pointed to by an UnsafeMutableRawPointer (new in Swift 3) handed to a Swift function by a C API (Core Aud

Answer 1

Here's a Swift 4 example of converting a literal UInt8 array to an UnsafeMutableRawPointer and back to an UInt32 array

static func unsafePointerTest() {
    //let a : [UInt8] = [0,0,0,4,0,0,0,8,0,0,0,12]
    let a : [UInt8] = [0x04, 0x00, 0x00, 0x00,
                       0x08, 0x00, 0x00, 0x00,
                       0x0C, 0x00, 0x00, 0x00] //little endian
    //0xFF, 0xF0, 0xF0, 0x12]  //317780223 = 12F0F0FF
    let b:UnsafeMutableRawPointer = UnsafeMutableRawPointer(mutating:a)
    let bTypedPtr = b.bindMemory(to: UInt32.self, capacity: a.count/4)
    let UInt32Buffer = UnsafeBufferPointer(start: bTypedPtr, count: a.count/4)
    let output = Array(UInt32Buffer)
    print(output)
}