def ll_arraycopy(source, dest, source_start, dest_start, length):
    from pypy.rpython.lltypesystem.lloperation import llop
    from pypy.rlib.objectmodel import keepalive_until_here

    # supports non-overlapping copies only
    if not we_are_translated():
        if source == dest:
            assert (source_start + length <= dest_start or
                    dest_start + length <= source_start)

    TP = lltype.typeOf(source).TO
    assert TP == lltype.typeOf(dest).TO
    if isinstance(TP.OF, lltype.Ptr) and TP.OF.TO._gckind == 'gc':
        # perform a write barrier that copies necessary flags from
        # source to dest
        if not llop.gc_writebarrier_before_copy(lltype.Bool, source, dest):
            # if the write barrier is not supported, copy by hand
            for i in range(length):
                dest[i + dest_start] = source[i + source_start]
            return
    source_addr = llmemory.cast_ptr_to_adr(source)
    dest_addr   = llmemory.cast_ptr_to_adr(dest)
    cp_source_addr = (source_addr + llmemory.itemoffsetof(TP, 0) +
                      llmemory.sizeof(TP.OF) * source_start)
    cp_dest_addr = (dest_addr + llmemory.itemoffsetof(TP, 0) +
                    llmemory.sizeof(TP.OF) * dest_start)
    
    llmemory.raw_memcopy(cp_source_addr, cp_dest_addr,
                         llmemory.sizeof(TP.OF) * length)
    keepalive_until_here(source)
    keepalive_until_here(dest)

def ll_shrink_array(p, smallerlength):
    from pypy.rpython.lltypesystem.lloperation import llop
    from pypy.rlib.objectmodel import keepalive_until_here

    if llop.shrink_array(lltype.Bool, p, smallerlength):
        return p    # done by the GC
    # XXX we assume for now that the type of p is GcStruct containing a
    # variable array, with no further pointers anywhere, and exactly one
    # field in the fixed part -- like STR and UNICODE.

    TP = lltype.typeOf(p).TO
    newp = lltype.malloc(TP, smallerlength)

    assert len(TP._names) == 2
    field = getattr(p, TP._names[0])
    setattr(newp, TP._names[0], field)

    ARRAY = getattr(TP, TP._arrayfld)
    offset = (llmemory.offsetof(TP, TP._arrayfld) +
              llmemory.itemoffsetof(ARRAY, 0))
    source_addr = llmemory.cast_ptr_to_adr(p)    + offset
    dest_addr   = llmemory.cast_ptr_to_adr(newp) + offset
    llmemory.raw_memcopy(source_addr, dest_addr, 
                         llmemory.sizeof(ARRAY.OF) * smallerlength)

    keepalive_until_here(p)
    keepalive_until_here(newp)
    return newp

    def test_callback(self):
        slong = cast_type_to_ffitype(rffi.LONG)
        libc = self.get_libc()
        qsort = libc.getpointer("qsort", [ffi_type_pointer, slong, slong, ffi_type_pointer], ffi_type_void)

        def callback(ll_args, ll_res, stuff):
            p_a1 = rffi.cast(rffi.VOIDPP, ll_args[0])[0]
            p_a2 = rffi.cast(rffi.VOIDPP, ll_args[1])[0]
            a1 = rffi.cast(rffi.INTP, p_a1)[0]
            a2 = rffi.cast(rffi.INTP, p_a2)[0]
            res = rffi.cast(rffi.INTP, ll_res)
            if a1 > a2:
                res[0] = rffi.cast(rffi.INT, 1)
            else:
                res[0] = rffi.cast(rffi.INT, -1)

        ptr = CallbackFuncPtr([ffi_type_pointer, ffi_type_pointer], ffi_type_sint, callback)

        TP = rffi.CArray(rffi.INT)
        to_sort = lltype.malloc(TP, 4, flavor="raw")
        to_sort[0] = rffi.cast(rffi.INT, 4)
        to_sort[1] = rffi.cast(rffi.INT, 3)
        to_sort[2] = rffi.cast(rffi.INT, 1)
        to_sort[3] = rffi.cast(rffi.INT, 2)
        qsort.push_arg(rffi.cast(rffi.VOIDP, to_sort))
        qsort.push_arg(rffi.sizeof(rffi.INT))
        qsort.push_arg(4)
        qsort.push_arg(ptr.ll_closure)
        qsort.call(lltype.Void)
        assert [rffi.cast(lltype.Signed, to_sort[i]) for i in range(4)] == [1, 2, 3, 4]
        lltype.free(to_sort, flavor="raw")
        keepalive_until_here(ptr)  # <= this test is not translated, but don't

 def f(i):
     c = g()
     c.y
     if i:
         n = c.z1
     else:
         n = c.z2
     objectmodel.keepalive_until_here(c, n)

 def fn1(x, y):
     if x > 0:
         t = x+y, x-y
     else:
         t = x-y, x+y
     s, d = t
     keepalive_until_here(t)
     return s*d

 def copy_string_contents(src, dst, srcstart, dststart, length):
     assert srcstart >= 0
     assert dststart >= 0
     assert length >= 0
     src = llmemory.cast_ptr_to_adr(src) + _str_ofs(srcstart)
     dst = llmemory.cast_ptr_to_adr(dst) + _str_ofs(dststart)
     llmemory.raw_memcopy(src, dst, llmemory.sizeof(CHAR_TP) * length)
     keepalive_until_here(src)
     keepalive_until_here(dst)

 def start_all_threads():
     s = allocate_stuff()
     ident1 = new_thread()
     ident2 = new_thread()
     ident3 = new_thread()
     ident4 = new_thread()
     ident5 = new_thread()
     # wait for 4 more seconds, which should be plenty of time
     time.sleep(4)
     keepalive_until_here(s)

 def ll_function(flag):
     t = lltype.malloc(T)
     t.s.n = 3
     t.s1.n = 3
     if flag:
         s = t.s
     else:
         s = t.s1
     objectmodel.keepalive_until_here(t)
     return s, t

 def myfunc():
     b = B()
     b.keep = A()
     b.data = llmemory.cast_adr_to_ptr(b.keep.addr, PARRAY)
     b.data[0] = 42
     ptr = b.data
     # normally 'b' could go away as early as here, which would free
     # the memory held by the instance of A in b.keep...
     res = ptr[0]
     # ...so we explicitly keep 'b' alive until here
     objectmodel.keepalive_until_here(b)
     return res

    def _digest(self, space):
        copy = self.copy(space)
        ctx = copy.ctx
        digest_size = self._digest_size()
        digest = lltype.malloc(rffi.CCHARP.TO, digest_size, flavor='raw')

        try:
            ropenssl.EVP_DigestFinal(ctx, digest, None)
            return rffi.charpsize2str(digest, digest_size)
        finally:
            keepalive_until_here(copy)
            lltype.free(digest, flavor='raw')

 def f(n):
     states = []
     while n > 0:
         mydriver.jit_merge_point(n=n, states=states)
         state = State()
         states.append(state)
         x = X(state)
         do_stuff()
         state.num *= 1000
         do_stuff()
         keepalive_until_here(x)
         n -= 1
     return states

 def f():
     x = lltype.malloc(S)
     x.x = 10
     y = lltype.malloc(S)
     y.x = 20
     z = x
     llop.gc_x_become(lltype.Void,
                      llmemory.cast_ptr_to_adr(x),
                      llmemory.cast_ptr_to_adr(y))
     # keep 'y' alive until the x_become() is finished, because in
     # theory it could go away as soon as only its address is present
     objectmodel.keepalive_until_here(y)
     return z.x

def _ll_list_resize_really(l, newsize):
    """
    Ensure l.items has room for at least newsize elements, and set
    l.length to newsize.  Note that l.items may change, and even if
    newsize is less than l.length on entry.
    """
    allocated = len(l.items)

    # This over-allocates proportional to the list size, making room
    # for additional growth.  The over-allocation is mild, but is
    # enough to give linear-time amortized behavior over a long
    # sequence of appends() in the presence of a poorly-performing
    # system malloc().
    # The growth pattern is:  0, 4, 8, 16, 25, 35, 46, 58, 72, 88, ...
    if newsize <= 0:
        ll_assert(newsize == 0, "negative list length")
        l.length = 0
        l.items = _ll_new_empty_item_array(typeOf(l).TO)
        return
    else:
        if newsize < 9:
            some = 3
        else:
            some = 6
        some += newsize >> 3
        try:
            new_allocated = ovfcheck(newsize + some)
        except OverflowError:
            raise MemoryError
    # XXX consider to have a real realloc
    items = l.items
    newitems = malloc(typeOf(l).TO.items.TO, new_allocated)
    before_len = l.length
    if before_len < new_allocated:
        p = before_len - 1
    else:
        p = new_allocated - 1
    ITEM = typeOf(l).TO.ITEM
    if isinstance(ITEM, Ptr):
        while p >= 0:
            newitems[p] = items[p]
            items[p] = nullptr(ITEM.TO)
            p -= 1
    else:
        source = cast_ptr_to_adr(items) + itemoffsetof(typeOf(l.items).TO, 0)
        dest = cast_ptr_to_adr(newitems) + itemoffsetof(typeOf(l.items).TO, 0)
        s = p + 1
        raw_memcopy(source, dest, sizeof(ITEM) * s)
        keepalive_until_here(items)
    l.length = newsize
    l.items = newitems

 def free_nonmovingbuffer(data, buf):
     """
     Either free a non-moving buffer or keep the original storage alive.
     """
     # We cannot rely on rgc.can_move(data) here, because its result
     # might have changed since get_nonmovingbuffer().  Instead we check
     # if 'buf' points inside 'data'.  This is only possible if we
     # followed the 2nd case in get_nonmovingbuffer(); in the first case,
     # 'buf' points to its own raw-malloced memory.
     data = llstrtype(data)
     data_start = cast_ptr_to_adr(data) + offsetof(STRTYPE, "chars") + itemoffsetof(STRTYPE.chars, 0)
     followed_2nd_path = buf == cast(TYPEP, data_start)
     keepalive_until_here(data)
     if not followed_2nd_path:
         lltype.free(buf, flavor="raw")

    def str_from_buffer(raw_buf, gc_buf, allocated_size, needed_size):
        """
        Converts from a pair returned by alloc_buffer to a high-level string.
        The returned string will be truncated to needed_size.
        """
        assert allocated_size >= needed_size

        if gc_buf and (allocated_size == needed_size):
            return hlstrtype(gc_buf)

        new_buf = lltype.malloc(STRTYPE, needed_size)
        str_chars_offset = offsetof(STRTYPE, "chars") + itemoffsetof(STRTYPE.chars, 0)
        if gc_buf:
            src = cast_ptr_to_adr(gc_buf) + str_chars_offset
        else:
            src = cast_ptr_to_adr(raw_buf) + itemoffsetof(TYPEP.TO, 0)
        dest = cast_ptr_to_adr(new_buf) + str_chars_offset
        raw_memcopy(src, dest, llmemory.sizeof(ll_char_type) * needed_size)
        keepalive_until_here(gc_buf)
        keepalive_until_here(new_buf)
        return hlstrtype(new_buf)

 def fn(n):
     keepalive = []
     weakrefs = []
     a = None
     for i in range(n):
         if i & 1 == 0:
             a = A()
             a.index = i
         assert a is not None
         weakrefs.append(weakref.ref(a))
         if i % 7 == 6:
             keepalive.append(a)
     rgc.collect()
     count_free = 0
     for i in range(n):
         a = weakrefs[i]()
         if i % 7 == 6:
             assert a is not None
         if a is not None:
             assert a.index == i & ~1
         else:
             count_free += 1
     keepalive_until_here(keepalive)
     return count_free

        def f():
            libc = CDLL(get_libc_name())
            qsort = libc.getpointer('qsort', [ffi_type_pointer, ffi_size_t,
                                              ffi_size_t, ffi_type_pointer],
                                    ffi_type_void)

            ptr = CallbackFuncPtr([ffi_type_pointer, ffi_type_pointer],
                                  ffi_type_sint, callback)

            TP = rffi.CArray(rffi.LONG)
            to_sort = lltype.malloc(TP, 4, flavor='raw')
            to_sort[0] = 4
            to_sort[1] = 3
            to_sort[2] = 1
            to_sort[3] = 2
            qsort.push_arg(rffi.cast(rffi.VOIDP, to_sort))
            qsort.push_arg(rffi.cast(rffi.SIZE_T, 4))
            qsort.push_arg(rffi.cast(rffi.SIZE_T, rffi.sizeof(rffi.LONG)))
            qsort.push_arg(rffi.cast(rffi.VOIDP, ptr.ll_closure))
            qsort.call(lltype.Void)
            result = [to_sort[i] for i in range(4)] == [1,2,3,4]
            lltype.free(to_sort, flavor='raw')
            keepalive_until_here(ptr)
            return int(result)

 def fn():
     s = lltype.malloc(S)
     s.u = lltype.malloc(U)
     s.u.next = lltype.malloc(U)
     s.u.next.next = lltype.malloc(U)
     a = lltype.malloc(A, 1000)
     s2 = lltype.malloc(S)
     #
     fd1 = os.open(filename1, os.O_WRONLY | os.O_CREAT, 0666)
     fd2 = os.open(filename2, os.O_WRONLY | os.O_CREAT, 0666)
     rgc.dump_rpy_heap(fd1)
     rgc.dump_rpy_heap(fd2)      # try twice in a row
     keepalive_until_here(s2)
     keepalive_until_here(s)
     keepalive_until_here(a)
     os.close(fd1)
     os.close(fd2)
     return 0

def virtual_ref_finish(vref, x):
    """See docstring in virtual_ref(x)"""
    keepalive_until_here(x)   # otherwise the whole function call is removed
    _virtual_ref_finish(vref, x)

def assert_green(value):
    """Very strong assert: checks that 'value' is a green
    (a JIT compile-time constant)."""
    keepalive_until_here(value)