truncate
#define truncate(p) ((p)->wt = (p)->rd)
#define truncate truncate64
#define truncate truncate64
truncate(const char *path, off_t len)
#define truncate(x) ((x) <= 2 ? (x) : (1 << (highbit(x) - 1)))
#define truncate(x) ((x) <= 2 ? (x) : (1 << (highbit(x) - 1)))