FunctionSwift

withUnsafeTemporaryAllocation(of:capacity:_:)

Provides scoped access to a buffer pointer to memory of the specified type and with the specified capacity.

func withUnsafeTemporaryAllocation<T, R>(of type: T.Type, capacity: Int, _ body: (UnsafeMutableBufferPointer<T>) throws -> R) rethrows -> R

Parameters

type

The type of the elements in the buffer being temporarily allocated.

capacity

The capacity of the buffer pointer being temporarily allocated.

body

A closure to invoke and to which the allocated buffer pointer should be passed.

Returns

Whatever is returned by body.

Overview

This function is useful for cheaply allocating storage for a sequence of values for a brief duration. Storage may be allocated on the heap or on the stack, depending on the required size and alignment.

When body is called, the contents of the buffer pointer passed to it are in an unspecified, uninitialized state. body is responsible for initializing the buffer pointer before it is used and for deinitializing it before returning, but deallocation is automatic.

The implementation may allocate a larger buffer pointer than is strictly necessary to contain capacity values of type type. The behavior of a program that attempts to access any such additional storage is undefined.

The buffer pointer passed to body (as well as any pointers to elements in the buffer) must not escape. It will be deallocated when body returns and cannot be used afterward.