fix: initialise/deinitialise of (boxed) array data#8
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| public protocol ArrayData { | ||
| associatedtype Buffer | ||
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| static func initialise(_ arrayData: Buffer, at: Int, to value: Self) |
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Let's add a comment here that describes what these are expected to do
JaapWijnen
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Storage is variable sized (depending on the element type) so having the count and context pointer fields at the start of the object gives a fixed a offset to (the start of) all fields.
This also drops the inout qualifier on the Buffer parameter, which is not needed (the buffer contents may change, but not the pointer to the buffer itself).
This is required for any class-based types (e.g. String) that we are storing via Box. When first writing to the raw buffer we must initialise the memory (retaining as strong reference to the value that is not owned by us) and ensure that memory is deinitialised when the containing MultiArray is deallocated (releasing said strong reference). Previously we were not doing the latter, and when modifying elements (subscript write) re-initialising that slot. Both of these would cause memory leaks.
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Summary
This is required for any class-based types (e.g. String) that we are storing via
Box. When first writing to the raw buffer we must initialise the memory (retaining as strong reference to the value that is not owned by us) and ensure that memory is deinitialised when the containing MultiArray is deallocated (releasing said strong reference). Previously we were not doing the latter, and when modifying elements (subscript write) re-initialising that slot. Both of these would cause memory leaks.