github.com/afumu/libc@v0.0.6/musl/src/select/select.c (about)

     1  #include <sys/select.h>
     2  #include <signal.h>
     3  #include <stdint.h>
     4  #include <errno.h>
     5  #include "syscall.h"
     6  
     7  #define IS32BIT(x) !((x)+0x80000000ULL>>32)
     8  #define CLAMP(x) (int)(IS32BIT(x) ? (x) : 0x7fffffffU+((0ULL+(x))>>63))
     9  
    10  int select(int n, fd_set *restrict rfds, fd_set *restrict wfds, fd_set *restrict efds, struct timeval *restrict tv)
    11  {
    12  	time_t s = tv ? tv->tv_sec : 0;
    13  	suseconds_t us = tv ? tv->tv_usec : 0;
    14  	long ns;
    15  	const time_t max_time = (1ULL<<8*sizeof(time_t)-1)-1;
    16  
    17  	if (s<0 || us<0) return __syscall_ret(-EINVAL);
    18  	if (us/1000000 > max_time - s) {
    19  		s = max_time;
    20  		us = 999999;
    21  		ns = 999999999;
    22  	} else {
    23  		s += us/1000000;
    24  		us %= 1000000;
    25  		ns = us*1000;
    26  	}
    27  
    28  #ifdef SYS_pselect6_time64
    29  	int r = -ENOSYS;
    30  	if (SYS_pselect6 == SYS_pselect6_time64 || !IS32BIT(s))
    31  		r = __syscall_cp(SYS_pselect6_time64, n, rfds, wfds, efds,
    32  			tv ? ((long long[]){s, ns}) : 0,
    33  			((syscall_arg_t[]){ 0, _NSIG/8 }));
    34  	if (SYS_pselect6 == SYS_pselect6_time64 || r!=-ENOSYS)
    35  		return __syscall_ret(r);
    36  #endif
    37  #ifdef SYS_select
    38  	return syscall_cp(SYS_select, n, rfds, wfds, efds,
    39  		tv ? ((long[]){s, us}) : 0);
    40  #else
    41  	return syscall_cp(SYS_pselect6, n, rfds, wfds, efds,
    42  		tv ? ((long[]){s, ns}) : 0, ((syscall_arg_t[]){ 0, _NSIG/8 }));
    43  #endif
    44  }