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swiftpointers
user965972
user965972

Reputation: 2587

Pointers in swift: purpose of UnsafeMutableBufferPointer

Currently looking into swift pointers.

UnsafePointer and UnsafeMutablePointer provide a pointer to a byte. By using pointer arithmetic, you can access the rest of the bytes.

Something similar can be done with a UnsafeMutableBufferPointer, which has an endIndex parameter. So what is the advantage/difference of using UnsafeMutableBufferPointer over UnsafeMutablePointer when accessing for example the bytes in NSData?

Upvotes: 6

Views: 1199

Answers (1)

Sergey Kalinichenko
Sergey Kalinichenko

Reputation: 726579

UnsafeMutablePointer<T> is designed for accessing a single element of type T. Its interface is designed for accessing a single scalar value.

UnsafeMutableBufferPointer<T>, on the other hand, is designed to access a group of elements of type T stored in a contiguous block of memory. Its interface is designed to access individual elements of the range, and also for treating the entire collection as a single unit (e.g. the generate method).

If you access bytes inside NSData, UnsafePointer alone is not sufficient, because you need to know the length of data. In contrast, a single UnsafeBufferPointer is sufficient to represent the data, because it provides both the initial location and the number of elements.

Upvotes: 2

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