# This Source Code Form is subject to the terms of the Mozilla Public
# License, v. 2.0. If a copy of the MPL was not distributed with this file,
# You can obtain one at http://mozilla.org/MPL/2.0/.

import gdb


def get_header_ptr(value, ptr_t):
    # Return the pointer stored in Cell::header_ for subclasses of
    # TenuredCellWithNonGCPointer and CellWithTenuredGCPointer.
    return value["header_"]["mValue"].cast(ptr_t)


def get_header_length_and_flags(value, cache):
    # Return the length and flags values for subclasses of
    # CellWithLengthAndFlags.
    flags = value["header_"]["mValue"].cast(cache.uintptr_t)
    try:
        length = value["length_"]
    except gdb.error:
        # If we couldn't fetch the length directly, it must be stored
        # within `flags`.
        length = flags >> 32
        flags = flags % 2 ** 32
    return length, flags