in src/main/kotlin/jsitter/impl/SubtreeAccess.kt [64:73]
fun childAt(subtree: Ptr, i: Int): Ptr {
if (subtree == 0L) {
throw NullPointerException()
}
if (isInline(subtree)) {
throw AssertionError()
}
val children_ptr = unsafe.getAddress(subtree + children)
return unsafe.getAddress(children_ptr + i * 8)
}