linkedlist.py - mozsearch

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# -*- 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 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>.

@GeckoPrettyPrinter("mozilla::LinkedList", "^mozilla::LinkedList<.*>$")

class linkedlist_printer(object):

    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()

    def children(self):

        # 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

    def to_string(self):

        return str(self.value.type)

    def display_hint(self):

        return "array"