nim-stew/stew/assign2.nim

70 lines
2.0 KiB
Nim

import
std/typetraits,
./shims/macros
when (NimMajor, NimMinor) < (1, 4):
{.push raises: [Defect].}
else:
{.push raises: [].}
func assign*[T](tgt: var seq[T], src: openArray[T]) {.gcsafe.}
func assign*[T](tgt: var openArray[T], src: openArray[T]) {.gcsafe.}
func assign*[T](tgt: var T, src: T) {.gcsafe.}
func assignImpl[T](tgt: var openArray[T], src: openArray[T]) =
mixin assign
when supportsCopyMem(T):
if tgt.len > 0:
moveMem(addr tgt[0], unsafeAddr src[0], sizeof(tgt[0]) * tgt.len)
else:
for i in 0..<tgt.len:
assign(tgt[i], src[i])
func assign*[T](tgt: var openArray[T], src: openArray[T]) =
mixin assign
if tgt.len != src.len:
raiseAssert "Target and source lengths don't match: " &
$tgt.len & " vs " & $src.len
assignImpl(tgt, src)
func assign*[T](tgt: var seq[T], src: openArray[T]) =
mixin assign
tgt.setLen(src.len)
assignImpl(tgt.toOpenArray(0, tgt.high), src)
func assign*(tgt: var string, src: string) =
tgt.setLen(src.len)
assignImpl(tgt.toOpenArrayByte(0, tgt.high), src.toOpenArrayByte(0, tgt.high))
macro unsupported(T: typed): untyped =
error "Assignment of the type " & humaneTypeName(T) & " is not supported"
func assign*[T](tgt: var T, src: T) =
# The default `genericAssignAux` that gets generated for assignments in nim
# is ridiculously slow. When syncing, the application was spending 50%+ CPU
# time in it - `assign`, in the same test, doesn't even show in the perf trace
mixin assign
when supportsCopyMem(T):
when sizeof(src) <= sizeof(int):
tgt = src
else:
moveMem(addr tgt, unsafeAddr src, sizeof(tgt))
elif T is object|tuple:
for t, s in fields(tgt, src):
when supportsCopyMem(type s) and sizeof(s) <= sizeof(int) * 2:
t = s # Shortcut
else:
assign(t, s)
elif T is seq:
assign(tgt, src.toOpenArray(0, src.high))
elif T is ref:
tgt = src
elif compiles(distinctBase(tgt)):
assign(distinctBase tgt, distinctBase src)
else:
unsupported T