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Diffstat (limited to 'ccan/ccan/container_of/container_of.h')
| -rw-r--r-- | ccan/ccan/container_of/container_of.h | 145 |
1 files changed, 145 insertions, 0 deletions
diff --git a/ccan/ccan/container_of/container_of.h b/ccan/ccan/container_of/container_of.h new file mode 100644 index 0000000..47a34d8 --- /dev/null +++ b/ccan/ccan/container_of/container_of.h @@ -0,0 +1,145 @@ +/* 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_of_or_null - get pointer to enclosing structure, or NULL + * @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, unless it + * is given NULL, in which case it also returns NULL. + * + * Example: + * struct foo { + * int fielda, fieldb; + * // ... + * }; + * struct info { + * int some_other_field; + * struct foo my_foo; + * }; + * + * static struct info *foo_to_info_allowing_null(struct foo *foo) + * { + * return container_of_or_null(foo, struct info, my_foo); + * } + */ +static inline char *container_of_or_null_(void *member_ptr, size_t offset) +{ + return member_ptr ? (char *)member_ptr - offset : NULL; +} +#define container_of_or_null(member_ptr, containing_type, member) \ + ((containing_type *) \ + container_of_or_null_(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 */ |