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1/* Copyright (c) Facebook, Inc. and its affiliates. (http://www.facebook.com) */
2#pragma once
3
4namespace py {
5
6struct ListEntry {
7 ListEntry* prev;
8 ListEntry* next;
9};
10
11// Inserts an entry into the linked list as the new root
12bool listEntryInsert(ListEntry* entry, ListEntry** root);
13
14// Removes an entry from the linked list
15bool listEntryRemove(ListEntry* entry, ListEntry** root);
16
17inline bool listEntryInsert(ListEntry* entry, ListEntry** root) {
18 // If already tracked, do nothing.
19 if (entry->prev != nullptr || entry->next != nullptr || entry == *root) {
20 return false;
21 }
22 entry->prev = nullptr;
23 entry->next = *root;
24 if (*root != nullptr) {
25 (*root)->prev = entry;
26 }
27 *root = entry;
28 return true;
29}
30
31inline bool listEntryRemove(ListEntry* entry, ListEntry** root) {
32 // The node is the first node of the list.
33 if (*root == entry) {
34 *root = entry->next;
35 } else if (entry->prev == nullptr && entry->next == nullptr) {
36 // This is an already untracked object.
37 return false;
38 }
39 if (entry->prev != nullptr) {
40 entry->prev->next = entry->next;
41 }
42 if (entry->next != nullptr) {
43 entry->next->prev = entry->prev;
44 }
45 entry->prev = nullptr;
46 entry->next = nullptr;
47 return true;
48}
49
50} // namespace py