Hi Kelvin,
> On 8 Nov 2017, at 4:54 pm, Kelvin Ma via swift-users <swift-users@swift.org>
> wrote:
>
> According to the docs, the load(fromByteOffset:as:) method requires the
> instance to be “properly aligned” Does that mean if I have raw data meant to
> be interpreted as
>
> 0 1 2 3 4 5 6
> [ Int8 | Int16 | Int16 | Int8 | Int8 ]
>
>
> i can’t just load the Int16 from byte offset 1?
you can't just dereference that pointer as an Int16 (in any language) without
causing UB but it's not really an issue, just do this (assuming `ptr` is the
pointer into your data and `index` is the index to where your Int16 lives):
var value: Int16 = 0
withUnsafeMutableBytes(of: &value) { valuePtr in
valuePtr.copyBytes(from: UnsafeRawBufferPointer(start:
ptr.baseAddress!.advanced(by: index),
count:
MemoryLayout<Int16>.size))
}
you can have the whole thing generic too for <T: FixedWidthInteger>
var value: T = 0
withUnsafeMutableBytes(of: &value) { valuePtr in
valuePtr.copyBytes(from: UnsafeRawBufferPointer(start:
ptr.baseAddress!.advanced(by: index),
count:
MemoryLayout<T>.size))
}
-- Johannes
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