# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
# vim: set filetype=python:
# 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/.
from __future__ import absolute_import
from gdbpp import GeckoPrettyPrinter
# mfbt's LinkedList<T> is a doubly-linked list where the items in the list store
# the next/prev pointers as part of themselves rather than the list structure be
# its own independent data structure. This means:
# - Every item may belong to at most one LinkedList instance.
# - For our pretty printer, we only want to pretty-print the LinkedList object
# itself. We do not want to start printing every item in the list whenever
# we run into a LinkedListElement<T>.
def __init__(self, value):
self.value = value
# mfbt's LinkedList has the elements of the linked list subclass from
# LinkedListElement<T>. We want its pointer type for casting purposes.
# (We want to list pointers since we expect all of these objects to be
# complex enough that we don't want to automatically expand them. The
# LinkedListElement type itself isn't small.)
self.t_ptr_type = value.type.template_argument(0).pointer()
# Walk mNext until we loop back around to the sentinel. The sentinel
# item always exists and in the zero-length base-case mNext == sentinel,
# so extract that immediately and update it throughout the loop.
sentinel = self.value["sentinel"]
pSentinel = sentinel.address
pNext = sentinel["mNext"]
i = 0
while pSentinel != pNext:
list_elem = pNext.dereference()
list_value = pNext.cast(self.t_ptr_type)
yield ("%d" % i, list_value)
pNext = list_elem["mNext"]
i += 1