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util: introduce container_of() macro

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This macro comes from kernel and it's useful for unwrapping structs
inside another one. The generated code is actually the same to the one
where this logic is used in udev, but using this macro is much cleaner
and less error prone.
This commit is contained in:
Lucas De Marchi 2012-04-26 13:36:01 -03:00 committed by Kay Sievers
parent c8f8394a93
commit c4326aa4af
1 changed files with 11 additions and 0 deletions
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11
src/shared/util.h
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@ -59,6 +59,17 @@ typedef struct dual_timestamp {
#define USEC_PER_MONTH (2629800ULL*USEC_PER_SEC)
#define USEC_PER_YEAR (31557600ULL*USEC_PER_SEC)
/*
* container_of - cast a member of a structure out to the containing structure
* @ptr: the pointer to the member.
* @type: the type of the container struct this is embedded in.
* @member: the name of the member within the struct.
*
*/
#define container_of(ptr, type, member) ({ \
const typeof( ((type *)0)->member ) *__mptr = (ptr); \
(type *)( (char *)__mptr - offsetof(type,member) );})
/* What is interpreted as whitespace? */
#define WHITESPACE " \t\n\r"
#define NEWLINE "\n\r"