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lowlevel isUnique

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J.Teeuwissen 2023-04-26 17:23:10 +02:00
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16
crates/compiler/builtins/bitcode/src/utils.zig
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@ -231,6 +231,22 @@ inline fn decref_ptr_to_refcount(
}
}
pub export fn isUnique(
bytes_or_null: ?[*]u8,
) bool {
var bytes = bytes_or_null orelse return true;
const ptr = @ptrToInt(bytes);
const tag_mask: usize = if (@sizeOf(usize) == 8) 0b111 else 0b11;
const masked_ptr = ptr & ~tag_mask;
const isizes: [*]isize = @intToPtr([*]isize, masked_ptr);
const refcount = (isizes - 1)[0];
return refcount == REFCOUNT_ONE_ISIZE;
}
// We follow roughly the [fbvector](https://github.com/facebook/folly/blob/main/folly/docs/FBVector.md) when it comes to growing a RocList.
// Here is [their growth strategy](https://github.com/facebook/folly/blob/3e0525988fd444201b19b76b390a5927c15cb697/folly/FBVector.h#L1128) for push_back:
//