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| author | Zachary T Welch <zw@superlucidity.net> | 2009-11-16 02:29:09 -0800 |
|---|---|---|
| committer | Zachary T Welch <zw@superlucidity.net> | 2009-11-16 09:57:59 -0800 |
| commit | f0ce88b3af9a6090ac986160950d66317de5087e (patch) | |
| tree | 5f652f85f5d6ab9109692049990dc676af00dfe3 /src/helper/types.h | |
| parent | cbc05783727122f0052fe6f3be40635eb73ec5bc (diff) | |
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move container_of to types.h
The container_of macro is useful as a general solution. It belongs
in types.h, rather than target.h where it was introduced. Requires
the offsetof macro, which comes from <stddef.h> (moved as well).
Diffstat (limited to 'src/helper/types.h')
| -rw-r--r-- | src/helper/types.h | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/src/helper/types.h b/src/helper/types.h index 79eac13a..a8753c5f 100644 --- a/src/helper/types.h +++ b/src/helper/types.h @@ -23,6 +23,7 @@ #ifndef TYPES_H #define TYPES_H +#include <stddef.h> #ifdef HAVE_SYS_TYPES_H #include <sys/types.h> #endif @@ -58,6 +59,20 @@ typedef bool _Bool; #define stringify(s) __stringify(s) #define __stringify(s) #s + +/** + * Cast a member of a structure out to the containing structure. + * @param ptr The pointer to the member. + * @param type The type of the container struct this is embedded in. + * @param member The name of the member within the struct. + * + * This is a mechanism which is used throughout the Linux kernel. + */ +#define container_of(ptr, type, member) ({ \ + const typeof( ((type *)0)->member ) *__mptr = (ptr); \ + (type *)( (char *)__mptr - offsetof(type,member) );}) + + /* DANGER!!!! here be dragons! * * Leave these fn's as byte accesses because it is safe |