Branch data     Line data    Source code

       1                 :            : /* CC0 (Public domain) - see LICENSE file for details */
       2                 :            : #ifndef CCAN_CONTAINER_OF_H
       3                 :            : #define CCAN_CONTAINER_OF_H
       4                 :            : #include <stddef.h>
       5                 :            : 
       6                 :            : #include "config.h"
       7                 :            : #include <ccan/check_type/check_type.h>
       8                 :            : 
       9                 :            : /**
      10                 :            :  * container_of - get pointer to enclosing structure
      11                 :            :  * @member_ptr: pointer to the structure member
      12                 :            :  * @containing_type: the type this member is within
      13                 :            :  * @member: the name of this member within the structure.
      14                 :            :  *
      15                 :            :  * Given a pointer to a member of a structure, this macro does pointer
      16                 :            :  * subtraction to return the pointer to the enclosing type.
      17                 :            :  *
      18                 :            :  * Example:
      19                 :            :  *      struct foo {
      20                 :            :  *              int fielda, fieldb;
      21                 :            :  *              // ...
      22                 :            :  *      };
      23                 :            :  *      struct info {
      24                 :            :  *              int some_other_field;
      25                 :            :  *              struct foo my_foo;
      26                 :            :  *      };
      27                 :            :  *
      28                 :            :  *      static struct info *foo_to_info(struct foo *foo)
      29                 :            :  *      {
      30                 :            :  *              return container_of(foo, struct info, my_foo);
      31                 :            :  *      }
      32                 :            :  */
      33                 :            : #define container_of(member_ptr, containing_type, member)               \
      34                 :            :          ((containing_type *)                                           \
      35                 :            :           ((char *)(member_ptr)                                         \
      36                 :            :            - container_off(containing_type, member))                    \
      37                 :            :           + check_types_match(*(member_ptr), ((containing_type *)0)->member))
      38                 :            : 
      39                 :            : 
      40                 :            : /**
      41                 :            :  * container_of_or_null - get pointer to enclosing structure, or NULL
      42                 :            :  * @member_ptr: pointer to the structure member
      43                 :            :  * @containing_type: the type this member is within
      44                 :            :  * @member: the name of this member within the structure.
      45                 :            :  *
      46                 :            :  * Given a pointer to a member of a structure, this macro does pointer
      47                 :            :  * subtraction to return the pointer to the enclosing type, unless it
      48                 :            :  * is given NULL, in which case it also returns NULL.
      49                 :            :  *
      50                 :            :  * Example:
      51                 :            :  *      struct foo {
      52                 :            :  *              int fielda, fieldb;
      53                 :            :  *              // ...
      54                 :            :  *      };
      55                 :            :  *      struct info {
      56                 :            :  *              int some_other_field;
      57                 :            :  *              struct foo my_foo;
      58                 :            :  *      };
      59                 :            :  *
      60                 :            :  *      static struct info *foo_to_info_allowing_null(struct foo *foo)
      61                 :            :  *      {
      62                 :            :  *              return container_of_or_null(foo, struct info, my_foo);
      63                 :            :  *      }
      64                 :            :  */
      65                 :          8 : static inline char *container_of_or_null_(void *member_ptr, size_t offset)
      66                 :            : {
      67                 :          8 :         return member_ptr ? (char *)member_ptr - offset : NULL;
      68                 :            : }
      69                 :            : #define container_of_or_null(member_ptr, containing_type, member)       \
      70                 :            :         ((containing_type *)                                            \
      71                 :            :          container_of_or_null_(member_ptr,                              \
      72                 :            :                                container_off(containing_type, member))  \
      73                 :            :          + check_types_match(*(member_ptr), ((containing_type *)0)->member))
      74                 :            : 
      75                 :            : /**
      76                 :            :  * container_off - get offset to enclosing structure
      77                 :            :  * @containing_type: the type this member is within
      78                 :            :  * @member: the name of this member within the structure.
      79                 :            :  *
      80                 :            :  * Given a pointer to a member of a structure, this macro does
      81                 :            :  * typechecking and figures out the offset to the enclosing type.
      82                 :            :  *
      83                 :            :  * Example:
      84                 :            :  *      struct foo {
      85                 :            :  *              int fielda, fieldb;
      86                 :            :  *              // ...
      87                 :            :  *      };
      88                 :            :  *      struct info {
      89                 :            :  *              int some_other_field;
      90                 :            :  *              struct foo my_foo;
      91                 :            :  *      };
      92                 :            :  *
      93                 :            :  *      static struct info *foo_to_info(struct foo *foo)
      94                 :            :  *      {
      95                 :            :  *              size_t off = container_off(struct info, my_foo);
      96                 :            :  *              return (void *)((char *)foo - off);
      97                 :            :  *      }
      98                 :            :  */
      99                 :            : #define container_off(containing_type, member)  \
     100                 :            :         offsetof(containing_type, member)
     101                 :            : 
     102                 :            : /**
     103                 :            :  * container_of_var - get pointer to enclosing structure using a variable
     104                 :            :  * @member_ptr: pointer to the structure member
     105                 :            :  * @container_var: a pointer of same type as this member's container
     106                 :            :  * @member: the name of this member within the structure.
     107                 :            :  *
     108                 :            :  * Given a pointer to a member of a structure, this macro does pointer
     109                 :            :  * subtraction to return the pointer to the enclosing type.
     110                 :            :  *
     111                 :            :  * Example:
     112                 :            :  *      static struct info *foo_to_i(struct foo *foo)
     113                 :            :  *      {
     114                 :            :  *              struct info *i = container_of_var(foo, i, my_foo);
     115                 :            :  *              return i;
     116                 :            :  *      }
     117                 :            :  */
     118                 :            : #if HAVE_TYPEOF
     119                 :            : #define container_of_var(member_ptr, container_var, member) \
     120                 :            :         container_of(member_ptr, typeof(*container_var), member)
     121                 :            : #else
     122                 :            : #define container_of_var(member_ptr, container_var, member)     \
     123                 :            :         ((void *)((char *)(member_ptr)  -                       \
     124                 :            :                   container_off_var(container_var, member)))
     125                 :            : #endif
     126                 :            : 
     127                 :            : /**
     128                 :            :  * container_off_var - get offset of a field in enclosing structure
     129                 :            :  * @container_var: a pointer to a container structure
     130                 :            :  * @member: the name of a member within the structure.
     131                 :            :  *
     132                 :            :  * Given (any) pointer to a structure and a its member name, this
     133                 :            :  * macro does pointer subtraction to return offset of member in a
     134                 :            :  * structure memory layout.
     135                 :            :  *
     136                 :            :  */
     137                 :            : #if HAVE_TYPEOF
     138                 :            : #define container_off_var(var, member)          \
     139                 :            :         container_off(typeof(*var), member)
     140                 :            : #else
     141                 :            : #define container_off_var(var, member)                  \
     142                 :            :         ((const char *)&(var)->member - (const char *)(var))
     143                 :            : #endif
     144                 :            : 
     145                 :            : #endif /* CCAN_CONTAINER_OF_H */