I’m downloading some files asynchronously into a large byte array, and I have a callback that fires off periodically whenever some data is added to that array. If I want to give developers the ability to use the last chunk of data that was added to array, then… well how would I do that? In C++ I could give them a pointer to somewhere in the middle, and then perhaps tell them the number of bytes that were added in the last operation so they at least know the chunk they should be looking at… I don’t really want to give them a 2nd copy of that data, that’s just wasteful.
I’m just thinking if people want to process this data before the file has completed downloading. Would anyone actually want to do that? Or is it a useless feature anyway? I already have a callback for when the buffer (entire byte array) is full, and then they can dump the whole thing without worrying about start and end points…
.NET has a struct that does exactly what you want:
System.ArraySegment.
In any case, it’s easy to implement it yourself too – just make a constructor that takes a base array, an offset, and a length. Then implement an indexer that offsets indexes behind the scenes, so your ArraySegment can be seamlessly used in the place of an array.