1 files changed, 48 insertions, 0 deletions
diff --git a/python/gdbpp/gdbpp/linkedlist.py b/python/gdbpp/gdbpp/linkedlist.py
new file mode 100644
index 0000000000..1ba25a1cf0
--- /dev/null
+++ b/python/gdbpp/gdbpp/linkedlist.py
@@ -0,0 +1,48 @@
+# -*- 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"