Builder package:proto-lens

Builders denote sequences of bytes. They are Monoids where mempty is the zero-length sequence and mappend is concatenation, which runs in O(1).
Loop over the elements of a vector and concatenate the resulting Builders. This function has been hand-tuned to perform better than a naive implementation using, e.g., Vector.foldr or a manual loop.
Constructs a strict ByteString from the given Builder.