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/* CC0 (Public domain) - see LICENSE file for details */
#ifndef CCAN_CONTAINER_OF_H
#define CCAN_CONTAINER_OF_H
#include <stddef.h>
#include "config.h"
#include <ccan/check_type/check_type.h>
/**
* container_of - get pointer to enclosing structure
* @member_ptr: pointer to the structure member
* @containing_type: the type this member is within
* @member: the name of this member within the structure.
*
* Given a pointer to a member of a structure, this macro does pointer
* subtraction to return the pointer to the enclosing type.
*
* Example:
* struct foo {
* int fielda, fieldb;
* // ...
* };
* struct info {
* int some_other_field;
* struct foo my_foo;
* };
*
* static struct info *foo_to_info(struct foo *foo)
* {
* return container_of(foo, struct info, my_foo);
* }
*/
#define container_of(member_ptr, containing_type, member) \
((containing_type *) \
((char *)(member_ptr) \
- container_off(containing_type, member)) \
+ check_types_match(*(member_ptr), ((containing_type *)0)->member))
/**
* container_off - get offset to enclosing structure
* @containing_type: the type this member is within
* @member: the name of this member within the structure.
*
* Given a pointer to a member of a structure, this macro does
* typechecking and figures out the offset to the enclosing type.
*
* Example:
* struct foo {
* int fielda, fieldb;
* // ...
* };
* struct info {
* int some_other_field;
* struct foo my_foo;
* };
*
* static struct info *foo_to_info(struct foo *foo)
* {
* size_t off = container_off(struct info, my_foo);
* return (void *)((char *)foo - off);
* }
*/
#define container_off(containing_type, member) \
offsetof(containing_type, member)
/**
* container_of_var - get pointer to enclosing structure using a variable
* @member_ptr: pointer to the structure member
* @container_var: a pointer of same type as this member's container
* @member: the name of this member within the structure.
*
* Given a pointer to a member of a structure, this macro does pointer
* subtraction to return the pointer to the enclosing type.
*
* Example:
* static struct info *foo_to_i(struct foo *foo)
* {
* struct info *i = container_of_var(foo, i, my_foo);
* return i;
* }
*/
#if HAVE_TYPEOF
#define container_of_var(member_ptr, container_var, member) \
container_of(member_ptr, typeof(*container_var), member)
#else
#define container_of_var(member_ptr, container_var, member) \
((void *)((char *)(member_ptr) - \
container_off_var(container_var, member)))
#endif
/**
* container_off_var - get offset of a field in enclosing structure
* @container_var: a pointer to a container structure
* @member: the name of a member within the structure.
*
* Given (any) pointer to a structure and a its member name, this
* macro does pointer subtraction to return offset of member in a
* structure memory layout.
*
*/
#if HAVE_TYPEOF
#define container_off_var(var, member) \
container_off(typeof(*var), member)
#else
#define container_off_var(var, member) \
((const char *)&(var)->member - (const char *)(var))
#endif
#endif /* CCAN_CONTAINER_OF_H */