nim-stew/stew/sequtils2.nim

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Nim
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import
std/typetraits,
./assign2
func write*[T](s: var seq[T], v: openArray[T]) =
# The Nim standard library is inefficient when copying simple types
# into a seq: it will first zero-init the new memory then copy the items
# one by one, when a copyMem would be sufficient - semantically, this
# function performs the same thing as `add`, but similar to faststreams, from
# where the `write` name comes from, it is much faster. Unfortunately, there's
# no easy way to avoid the zero-init, but a smart compiler might be able
# to elide it.
when nimvm:
s.add(v)
else:
if v.len > 0:
let start = s.len
s.setLen(start + v.len)
when supportsCopyMem(T): # shortcut
copyMem(addr s[start], unsafeAddr v[0], v.len * sizeof(T))
else:
assign(s.toOpenArray(start, s.high), v)