diff options
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/system/seqs_v2.nim | 24 |
1 files changed, 24 insertions, 0 deletions
diff --git a/lib/system/seqs_v2.nim b/lib/system/seqs_v2.nim index c4e3e3e6b..7ce8de054 100644 --- a/lib/system/seqs_v2.nim +++ b/lib/system/seqs_v2.nim @@ -195,5 +195,29 @@ func capacity*[T](self: seq[T]): int {.inline.} = let sek = cast[ptr NimSeqV2[T]](unsafeAddr self) result = if sek.p != nil: sek.p.cap and not strlitFlag else: 0 +func setLenUninit*[T](s: var seq[T], newlen: Natural) {.nodestroy.} = + ## Sets the length of seq `s` to `newlen`. `T` may be any sequence type. + ## New slots will not be initialized. + ## + ## If the current length is greater than the new length, + ## `s` will be truncated. + ## ```nim + ## var x = @[10, 20] + ## x.setLenUninit(5) + ## x[4] = 50 + ## assert x[4] == 50 + ## x.setLenUninit(1) + ## assert x == @[10] + ## ``` + {.noSideEffect.}: + if newlen < s.len: + shrink(s, newlen) + else: + let oldLen = s.len + if newlen <= oldLen: return + var xu = cast[ptr NimSeqV2[T]](addr s) + if xu.p == nil or (xu.p.cap and not strlitFlag) < newlen: + xu.p = cast[typeof(xu.p)](prepareSeqAddUninit(oldLen, xu.p, newlen - oldLen, sizeof(T), alignof(T))) + xu.len = newlen {.pop.} # See https://github.com/nim-lang/Nim/issues/21401 |