Generic Instance Method 総称体インスタンスメソッド

withContiguousStorageIfAvailable(_:)

Executes a closure on the sequence’s contiguous storage.

Declaration 宣言

func withContiguousStorageIfAvailable<R>(_ body: (UnsafeBufferPointer<Character>) throws -> R) rethrows -> R?

Parameters パラメータ

body: A closure that receives an UnsafeBufferPointer to the sequence’s contiguous storage.

Return Value 戻り値

The value returned from body, unless the sequence doesn’t support contiguous storage, in which case the method ignores body and returns nil.

Discussion 解説

This method calls body(buffer), where buffer is a pointer to the collection’s contiguous storage. If the contiguous storage doesn’t exist, the collection creates it. If the collection doesn’t support an internal representation in a form of contiguous storage, the method doesn’t call body — it immediately returns nil.

The optimizer can often eliminate bounds- and uniqueness-checking within an algorithm. When that fails, however, invoking the same algorithm on the buffer argument may let you trade safety for speed.

Successive calls to this method may provide a different pointer on each call. Don’t store buffer outside of this method.

A Collection that provides its own implementation of this method must provide contiguous storage to its elements in the same order as they appear in the collection. This guarantees that it’s possible to generate contiguous mutable storage to any of its subsequences by slicing buffer with a range formed from the distances to the subsequence’s startIndex and endIndex, respectively.