如何访问字节(或Int16、浮点数等)由C应用程序接口(核心音频等)传递给Swift函数的UnsafeMutableRawPointer ( Swift 3中的新功能)指向的内存不足
发布于 2018-03-03 08:44:39
下面是一个将文字UInt8数组转换为UnsafeMutableRawPointer数组然后再转换回UInt32数组的Swift 4示例
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)
}
发布于 2016-11-03 04:26:22
下面是UnsafeMutableRawPointer到T/UnsafeMutablePointer转换的接口文档:
/// Binds the allocated memory to type `T` and returns an
/// `UnsafePointer<T>` to the bound memory at `self`.
///
/// - Precondition: The memory is uninitialized.
/// - Postcondition: The memory is bound to 'T' starting at `self` continuing
/// through `self` + `count` * `MemoryLayout<T>.stride`
/// - Warning: Binding memory to a type is potentially undefined if the
/// memory is ever accessed as an unrelated type.
public func bindMemory<T>(to type: T.Type, capacity count: Int) -> UnsafePointer<T>
/// Converts from an `UnsafeRawPointer` to UnsafePointer<T> given that
/// the region of memory starting at `self` is already bound to type `T`.
///
/// - Precondition: The memory is bound to 'T' starting at `self` for some
/// unspecified capacity.
///
/// - Warning: Accessing memory via the returned pointer is undefined if the
/// if the memory has not been bound to `T`.
public func assumingMemoryBound<T>(to: T.Type) -> UnsafePointer<T>
/// Reads raw bytes from memory at `self + offset` and constructs a
/// value of type `T`.
///
/// - Precondition: The underlying pointer plus `offset` is properly
/// aligned for accessing `T`.
///
/// - Precondition: The memory is initialized to a value of some type, `U`,
/// such that `T` is layout compatible with `U`.
public func load<T>(fromByteOffset offset: Int = default, as type: T.Type) -> T
然后可以使用pointee
和move
apis将Unsafe[MutablePointer]<T>
转换为T
/// Accesses the `Pointee` instance referenced by `self`.
///
/// - Precondition: the pointee has been initialized with an instance of
/// type `Pointee`.
public var pointee: Pointee { get }
/// Retrieves the `pointee`, returning the referenced memory to an
/// uninitialized state.
///
/// Equivalent to `{ defer { deinitialize() }; return pointee }()`, but
/// more efficient.
///
/// - Precondition: The pointee is initialized.
///
/// - Postcondition: The memory is uninitialized.
public func move() -> Pointee
https://stackoverflow.com/questions/38983277
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