CFBitVector is part of Core Foundation (CF). CF is a supported API on Apple platforms but on other platforms it’s considered an implementation detail of Foundation. As Foundation doesn’t need CFBitVector, that part of CF never made it across.
See this post and this post by @millenomi.
If I were in your shoes I’d implement my own bit vector as a simple value type, using an array of Bool as the underlying storage. Later on, once you’ve got the rest of your code up and running, you can fix your type to store the data compactly.
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Quinn “The Eskimo!” @ DTS @ Apple