1#include <unistd.h> 2#include <fcntl.h> 3#include <errno.h> 4#include "libc.h" 5 6int lockf(int fd, int op, off_t size) 7{ 8 struct flock l = { 9 .l_type = F_WRLCK, 10 .l_whence = SEEK_CUR, 11 .l_len = size, 12 }; 13 switch (op) { 14 case F_TEST: 15 l.l_type = F_RDLCK; 16 if (fcntl(fd, F_GETLK, &l) < 0) 17 return -1; 18 if (l.l_type == F_UNLCK || l.l_pid == getpid()) 19 return 0; 20 errno = EACCES; 21 return -1; 22 case F_ULOCK: 23 l.l_type = F_UNLCK; 24 case F_TLOCK: 25 return fcntl(fd, F_SETLK, &l); 26 case F_LOCK: 27 return fcntl(fd, F_SETLKW, &l); 28 } 29 errno = EINVAL; 30 return -1; 31} 32 33LFS64(lockf); 34