-int write_all(int fd, const char *buf, size_t *len);
-int file_exists(const char *);
-int para_select(int n, fd_set *readfds, fd_set *writefds,
- struct timeval *timeout_tv);
+int xrename(const char *oldpath, const char *newpath);
+int write_all(int fd, const char *buf, size_t len);
+__printf_2_3 int write_va_buffer(int fd, const char *fmt, ...);
+bool file_exists(const char *);
+int para_select(int n, fd_set *readfds, fd_set *writefds, int timeout);