| 1 | //===-- Intrusive queue implementation. -------------------------*- C++ -*-===// |
|---|---|
| 2 | // |
| 3 | // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| 4 | // See https://llvm.org/LICENSE.txt for license information. |
| 5 | // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| 6 | // |
| 7 | //===----------------------------------------------------------------------===// |
| 8 | // |
| 9 | // An intrusive list that implements the insque and remque semantics. |
| 10 | // |
| 11 | //===----------------------------------------------------------------------===// |
| 12 | |
| 13 | #ifndef LLVM_LIBC_SRC___SUPPORT_INTRUSIVE_LIST_H |
| 14 | #define LLVM_LIBC_SRC___SUPPORT_INTRUSIVE_LIST_H |
| 15 | |
| 16 | #include "common.h" |
| 17 | |
| 18 | namespace LIBC_NAMESPACE { |
| 19 | namespace internal { |
| 20 | |
| 21 | class IntrusiveList { |
| 22 | struct IntrusiveNodeHeader { |
| 23 | IntrusiveNodeHeader *next; |
| 24 | IntrusiveNodeHeader *prev; |
| 25 | }; |
| 26 | |
| 27 | public: |
| 28 | LIBC_INLINE static void insert(void *elem, void *prev) { |
| 29 | auto elem_header = static_cast<IntrusiveNodeHeader *>(elem); |
| 30 | auto prev_header = static_cast<IntrusiveNodeHeader *>(prev); |
| 31 | |
| 32 | if (!prev_header) { |
| 33 | // The list is linear and elem will be the only element. |
| 34 | elem_header->next = nullptr; |
| 35 | elem_header->prev = nullptr; |
| 36 | return; |
| 37 | } |
| 38 | |
| 39 | auto next = prev_header->next; |
| 40 | |
| 41 | elem_header->next = next; |
| 42 | elem_header->prev = prev_header; |
| 43 | |
| 44 | prev_header->next = elem_header; |
| 45 | if (next) |
| 46 | next->prev = elem_header; |
| 47 | } |
| 48 | |
| 49 | LIBC_INLINE static void remove(void *elem) { |
| 50 | auto elem_header = static_cast<IntrusiveNodeHeader *>(elem); |
| 51 | |
| 52 | auto prev = elem_header->prev; |
| 53 | auto next = elem_header->next; |
| 54 | |
| 55 | if (prev) |
| 56 | prev->next = next; |
| 57 | if (next) |
| 58 | next->prev = prev; |
| 59 | } |
| 60 | }; |
| 61 | |
| 62 | } // namespace internal |
| 63 | } // namespace LIBC_NAMESPACE |
| 64 | |
| 65 | #endif // LLVM_LIBC_SRC___SUPPORT_INTRUSIVE_LIST_H |
| 66 |