initializeMemory(as:from:count:)

Declaration

@discardableResult func initializeMemory<T>(as type: T.Type, from source: UnsafePointer<T>, count: Int) -> UnsafeMutablePointer<T>

Parameters

• type:

  The type to bind this memory to.

• source:

  A pointer to the values to copy. The memory in the region source..<(source + count) must be initialized to type T and must not overlap the destination region.

• count:

  The number of copies of value to copy into memory. count must not be negative.

Return Value

A typed pointer to the memory referenced by this raw pointer.

Discussion

The memory referenced by this pointer must be uninitialized or initialized to a trivial type, and must be properly aligned for accessing T.

The following example allocates enough raw memory to hold four instances of Int8, and then uses the initializeMemory(as:from:count:) method to initialize the allocated memory.

let count = 4
let bytesPointer = UnsafeMutableRawPointer.allocate(
        byteCount: count * MemoryLayout<Int8>.stride,
        alignment: MemoryLayout<Int8>.alignment)
let values: [Int8] = [1, 2, 3, 4]
let int8Pointer = values.withUnsafeBufferPointer { buffer in
    return bytesPointer.initializeMemory(as: Int8.self,
              from: buffer.baseAddress!,
              count: buffer.count)
}
// int8Pointer.pointee == 1
// (int8Pointer + 3).pointee == 4

// After using 'int8Pointer':
int8Pointer.deallocate()

After calling this method on a raw pointer p, the region starting at p and continuing up to p + count * MemoryLayout<T>.stride is bound to type T and initialized. If T is a nontrivial type, you must eventually deinitialize or move from the values in this region to avoid leaks. The instances in the region source..<(source + count) are unaffected.