Harald Welte | aae69be | 2004-08-29 23:32:14 +0000 | [diff] [blame^] | 1 | #ifndef _LINUX_STDDEF_H |
| 2 | #define _LINUX_STDDEF_H |
| 3 | |
| 4 | #undef NULL |
| 5 | #if defined(__cplusplus) |
| 6 | #define NULL 0 |
| 7 | #else |
| 8 | #define NULL ((void *)0) |
| 9 | #endif |
| 10 | |
| 11 | #undef offsetof |
| 12 | #define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER) |
| 13 | |
| 14 | |
| 15 | /** |
| 16 | * container_of - cast a member of a structure out to the containing structure |
| 17 | * |
| 18 | * @ptr: the pointer to the member. |
| 19 | * @type: the type of the container struct this is embedded in. |
| 20 | * @member: the name of the member within the struct. |
| 21 | * |
| 22 | */ |
| 23 | #define container_of(ptr, type, member) ({ \ |
| 24 | const typeof( ((type *)0)->member ) *__mptr = (ptr); \ |
| 25 | (type *)( (char *)__mptr - offsetof(type,member) );}) |
| 26 | |
| 27 | /* |
| 28 | * Check at compile time that something is of a particular type. |
| 29 | * Always evaluates to 1 so you may use it easily in comparisons. |
| 30 | */ |
| 31 | #define typecheck(type,x) \ |
| 32 | ({ type __dummy; \ |
| 33 | typeof(x) __dummy2; \ |
| 34 | (void)(&__dummy == &__dummy2); \ |
| 35 | 1; \ |
| 36 | }) |
| 37 | |
| 38 | |
| 39 | #endif |