함수 포인터
함수의 이름도 주소이다.
#include<stdio.h>
void Func1(int a) {
printf("Func1 %d\n", a);
}
int Func2() {
printf("Func2\n");
return 10;
}
int main() {
void (*p)(int);
p = Func1;
(*p)(10);
int (*q)();
q = Func2;
printf("%d", (*q)() + 100);
return 0;
}
구조체 내에서 함수 포인터를 사용하여 아래와 같이 사용한다.
struct file_operations {
struct module *owner;
loff_t (*llseek) (struct file *, loff_t, int);
ssize_t (*read) (struct file *, char __user *, size_t, loff_t *);
ssize_t (*write) (struct file *, const char __user *, size_t, loff_t *);
ssize_t (*read_iter) (struct kiocb *, struct iov_iter *);
ssize_t (*write_iter) (struct kiocb *, struct iov_iter *);
int (*iopoll)(struct kiocb *kiocb, struct io_comp_batch *,
unsigned int flags);
int (*iterate) (struct file *, struct dir_context *);
int (*iterate_shared) (struct file *, struct dir_context *);
__poll_t (*poll) (struct file *, struct poll_table_struct *);
long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long);
long (*compat_ioctl) (struct file *, unsigned int, unsigned long);
int (*mmap) (struct file *, struct vm_area_struct *);
unsigned long mmap_supported_flags;
int (*open) (struct inode *, struct file *);
int (*flush) (struct file *, fl_owner_t id);
int (*release) (struct inode *, struct file *);
int (*fsync) (struct file *, loff_t, loff_t, int datasync);
int (*fasync) (int, struct file *, int);
int (*lock) (struct file *, int, struct file_lock *);
ssize_t (*sendpage) (struct file *, struct page *, int, size_t, loff_t *, int);
unsigned long (*get_unmapped_area)(struct file *, unsigned long, unsigned long, unsigned long, unsigned long);
int (*check_flags)(int);
int (*flock) (struct file *, int, struct file_lock *);
ssize_t (*splice_write)(struct pipe_inode_info *, struct file *, loff_t *, size_t, unsigned int);
ssize_t (*splice_read)(struct file *, loff_t *, struct pipe_inode_info *, size_t, unsigned int);
void (*splice_eof)(struct file *file);
int (*setlease)(struct file *, long, struct file_lock **, void **);
long (*fallocate)(struct file *file, int mode, loff_t offset,
loff_t len);
void (*show_fdinfo)(struct seq_file *m, struct file *f);
#ifndef CONFIG_MMU
unsigned (*mmap_capabilities)(struct file *);
#endif
ssize_t (*copy_file_range)(struct file *, loff_t, struct file *,
loff_t, size_t, unsigned int);
loff_t (*remap_file_range)(struct file *file_in, loff_t pos_in,
struct file *file_out, loff_t pos_out,
loff_t len, unsigned int remap_flags);
int (*fadvise)(struct file *, loff_t, loff_t, int);
int (*uring_cmd)(struct io_uring_cmd *ioucmd, unsigned int issue_flags);
int (*uring_cmd_iopoll)(struct io_uring_cmd *, struct io_comp_batch *,
unsigned int poll_flags);
} __randomize_layout;
간단한 예제로 작성해보자
#include <stdio.h>
// 구조체 정의: 함수 포인터를 멤버로 가지는 구조체
struct Hyndrome_operation {
void (*act1)(int); // 함수 포인터 멤버
void (*act2)(int); // 함수 포인터 멤버
};
// 함수 선언
void Func1(int x) {
printf("Func1 : % d\n", x);
}
void Func2(int x) {
printf("Func2 : %d\n", x);
}
int main() {
// 구조체 변수 선언 및 선택적 초기화
struct Hyndrome_operation hyops = {
.act1 = Func1,
.act2 = Func2,
};
// 함수 포인터를 멤버로 갖는 구조체의 함수 호출
hyops.act1(10); // Func1 호출
hyops.act2(20); // Func2 호출
return 0;
}
