| 1 | /* $NetBSD: container_of.h,v 1.1 2024/10/08 22:53:20 christos Exp $ */ |
| 2 | |
| 3 | /*- |
| 4 | * Copyright (c) 2024 The NetBSD Foundation, Inc. |
| 5 | * All rights reserved. |
| 6 | * |
| 7 | * Redistribution and use in source and binary forms, with or without |
| 8 | * modification, are permitted provided that the following conditions |
| 9 | * are met: |
| 10 | * 1. Redistributions of source code must retain the above copyright |
| 11 | * notice, this list of conditions and the following disclaimer. |
| 12 | * 2. Redistributions in binary form must reproduce the above copyright |
| 13 | * notice, this list of conditions and the following disclaimer in the |
| 14 | * documentation and/or other materials provided with the distribution. |
| 15 | * |
| 16 | * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS |
| 17 | * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED |
| 18 | * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR |
| 19 | * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS |
| 20 | * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR |
| 21 | * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF |
| 22 | * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS |
| 23 | * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN |
| 24 | * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) |
| 25 | * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE |
| 26 | * POSSIBILITY OF SUCH DAMAGE. |
| 27 | */ |
| 28 | |
| 29 | #ifndef _SYS_CONTAINER_OF_H_ |
| 30 | #define _SYS_CONTAINER_OF_H_ |
| 31 | |
| 32 | #include <sys/stddef.h> |
| 33 | |
| 34 | /* |
| 35 | * Return the container of an embedded struct. Given x = &c->f, |
| 36 | * container_of(x, T, f) yields c, where T is the type of c. Example: |
| 37 | * |
| 38 | * struct foo { ... }; |
| 39 | * struct bar { |
| 40 | * int b_x; |
| 41 | * struct foo b_foo; |
| 42 | * ... |
| 43 | * }; |
| 44 | * |
| 45 | * struct bar b; |
| 46 | * struct foo *fp = &b.b_foo; |
| 47 | * |
| 48 | * Now we can get at b from fp by: |
| 49 | * |
| 50 | * struct bar *bp = container_of(fp, struct bar, b_foo); |
| 51 | * |
| 52 | * The 0*sizeof((PTR) - ...) causes the compiler to warn if the type of |
| 53 | * *fp does not match the type of struct bar::b_foo. |
| 54 | * We skip the validation for coverity runs to avoid warnings. |
| 55 | */ |
| 56 | #if defined(__COVERITY__) || defined(__LGTM_BOT__) |
| 57 | #define __validate_container_of(PTR, TYPE, FIELD) 0 |
| 58 | #define __validate_const_container_of(PTR, TYPE, FIELD) 0 |
| 59 | #else |
| 60 | #define __validate_container_of(PTR, TYPE, FIELD) \ |
| 61 | (0 * sizeof((PTR) - &((TYPE *)(((char *)(PTR)) - \ |
| 62 | offsetof(TYPE, FIELD)))->FIELD)) |
| 63 | #define __validate_const_container_of(PTR, TYPE, FIELD) \ |
| 64 | (0 * sizeof((PTR) - &((const TYPE *)(((const char *)(PTR)) - \ |
| 65 | offsetof(TYPE, FIELD)))->FIELD)) |
| 66 | #endif |
| 67 | |
| 68 | #define container_of(PTR, TYPE, FIELD) \ |
| 69 | ((TYPE *)(((char *)(PTR)) - offsetof(TYPE, FIELD)) \ |
| 70 | + __validate_container_of(PTR, TYPE, FIELD)) |
| 71 | #define const_container_of(PTR, TYPE, FIELD) \ |
| 72 | ((const TYPE *)(((const char *)(PTR)) - offsetof(TYPE, FIELD)) \ |
| 73 | + __validate_const_container_of(PTR, TYPE, FIELD)) |
| 74 | |
| 75 | #endif /* !_SYS_CONTAINER_OF_H_ */ |