Unsafe abstractions for pony data

Unsafe.pony

primitive Unsafe
  fun gc() =>
    @pony_triggergc[None](@pony_ctx[USize]())

  fun usize[T](value: T): USize =>
    Unsafe.ptr[T](consume value).usize()

  fun ptr[T](value: T): Pointer[T] =>
    @memcpy[Pointer[T]](value, USize(0), USize(0))

  fun deref[T](pointer: USize): T^ =>
    @memcpy[T^](pointer, USize(0), USize(0))
    
  fun offset[T, R](value: T, offs: USize = 0): R^ =>
    Unsafe.deref[R](Unsafe.usize[T](consume value) + offs)
    
  fun alloc[T](size: USize): T^ =>
    @pony_alloc[T^](@pony_ctx[USize](), size)
    
  fun realloc[T](pointer: USize, size: USize): T^ =>
    @pony_realloc[T^](@pony_ctx[USize](), pointer, size)

  fun istype2[T, T1, T2](): Bool =>
    Unsafe.istype[T, T1]() or Unsafe.istype[T, T2]()

  fun istype[T1, T2](): Bool =>
    iftype T1 <: T2
    then true
    else false
    end
  
  fun sizeof[T](): USize =>
    if     Unsafe.istype2[T, U8, I8]() then 1
    elseif Unsafe.istype2[T, U16, I16]() then 2
    elseif Unsafe.istype2[T, U32, I32]() then 4
    elseif Unsafe.istype2[T, U64, I64]() then 8
    elseif Unsafe.istype2[T, U128, I128]() then 16
    elseif Unsafe.istype2[T, ULong, ILong]() then
      ifdef ilp32 or llp64 then 4 else 8 end
    else
      USize.max_value().bitwidth() >> 3
    end