> On May 26, 2016, at 9:59 AM, Adrian Zubarev via swift-users > <swift-users@swift.org> wrote: > > I’ve got one more questions about Unsafe(Mutable)Pointer. I know that I’m > able to access memory that might not belong to me. > > My question is: > > Can I trust these functions that they will return a pointer to some memory > when I allocate more than one object AND when I’m moving only inside that > range? > > Yes. > public func successor() -> UnsafeMutablePointer<Memory> > public func predecessor() -> UnsafeMutablePointer<Memory> > public func advancedBy(n: Int) -> UnsafeMutablePointer<Memory> > UnsafeMutablePointer<Int>.alloc(4) when I advance only in range of [0,1,2,3] > am I safe or could I get a pointer to memory that does not belong to me? > > UnsafeMutablePointer<T>.alloc(N) creates a single object in memory that holds N consecutive T values. Each value resides at index*strideof(T.self) bytes beyond the allocated pointer where index is valid in the range 0..<N.
-Andy > Example: > > // imagine this is some memory portion, > // where x is memory that does not belong to me > // and 0 is moemory free to use > > […, x, 0, 0, 0 x, 0, x, …] > > // now I want to allocate 4 objects > // variant A: > > […, x, MY1, MY2, MY3, x, MY4, x, …] > > // my pointer will sit at `MY1` and if I advance by 2 I'll get `x` > // can this happen to me? > > // variant B: > // Unsafe(Mutable)Pointer will ensure that I always get memory tied together > // (or the above functions will skip memory that doesn't belong to me??): > > > […, x, MY1, MY2, MY3, MY4 x, …] > So which is right? > > > > > -- > Adrian Zubarev > Sent with Airmail > > _______________________________________________ > swift-users mailing list > swift-users@swift.org <mailto:swift-users@swift.org> > https://lists.swift.org/mailman/listinfo/swift-users > <https://lists.swift.org/mailman/listinfo/swift-users>
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