diff options
Diffstat (limited to 'ccan/ccan/container_of')
| l--------- | ccan/ccan/container_of/LICENSE | 1 | ||||
| -rw-r--r-- | ccan/ccan/container_of/_info | 65 | ||||
| -rw-r--r-- | ccan/ccan/container_of/container_of.h | 145 |
3 files changed, 211 insertions, 0 deletions
diff --git a/ccan/ccan/container_of/LICENSE b/ccan/ccan/container_of/LICENSE new file mode 120000 index 0000000..b7951da --- /dev/null +++ b/ccan/ccan/container_of/LICENSE @@ -0,0 +1 @@ +../../licenses/CC0
\ No newline at end of file diff --git a/ccan/ccan/container_of/_info b/ccan/ccan/container_of/_info new file mode 100644 index 0000000..b116052 --- /dev/null +++ b/ccan/ccan/container_of/_info @@ -0,0 +1,65 @@ +#include "config.h" +#include <stdio.h> +#include <string.h> + +/** + * container_of - routine for upcasting + * + * It is often convenient to create code where the caller registers a pointer + * to a generic structure and a callback. The callback might know that the + * pointer points to within a larger structure, and container_of gives a + * convenient and fairly type-safe way of returning to the enclosing structure. + * + * This idiom is an alternative to providing a void * pointer for every + * callback. + * + * Example: + * #include <stdio.h> + * #include <ccan/container_of/container_of.h> + * + * struct timer { + * void *members; + * }; + * + * struct info { + * int my_stuff; + * struct timer timer; + * }; + * + * static void my_timer_callback(struct timer *timer) + * { + * struct info *info = container_of(timer, struct info, timer); + * printf("my_stuff is %u\n", info->my_stuff); + * } + * + * static void register_timer(struct timer *timer) + * { + * (void)timer; + * (void)my_timer_callback; + * //... + * } + * + * int main(void) + * { + * struct info info = { .my_stuff = 1 }; + * + * register_timer(&info.timer); + * // ... + * return 0; + * } + * + * License: CC0 (Public domain) + * Author: Rusty Russell <rusty@rustcorp.com.au> + */ +int main(int argc, char *argv[]) +{ + if (argc != 2) + return 1; + + if (strcmp(argv[1], "depends") == 0) { + printf("ccan/check_type\n"); + return 0; + } + + return 1; +} 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 */ |