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move List.prepend to zig

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Folkert 2021-08-14 12:28:05 +02:00
parent 6741d93517
commit 225c97aae3
5 changed files with 59 additions and 63 deletions
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24
compiler/builtins/bitcode/src/list.zig
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@ -733,6 +733,30 @@ pub fn listAppend(list: RocList, alignment: u32, element: Opaque, element_width:
return output;
}
pub fn listPrepend(list: RocList, alignment: u32, element: Opaque, element_width: usize) callconv(.C) RocList {
const old_length = list.len();
var output = list.reallocate(alignment, old_length + 1, element_width);
// can't use one memcpy here because source and target overlap
if (output.bytes) |target| {
var i: usize = old_length;
while (i > 0) {
i -= 1;
// move the ith element to the (i + 1)th position
@memcpy(target + (i + 1) * element_width, target + i * element_width, element_width);
}
// finally copy in the new first element
if (element) |source| {
@memcpy(target, source, element_width);
}
}
return output;
}
pub fn listSwap(
list: RocList,
alignment: u32,