golang getrandom 代码
文件路径：/src/internal/syscall/unix/getrandom.go
/ Copyright 2021 The Go Authors. All rights reserved.
/ Use of this source code is governed by a BSD-style
/ license that can be found in the LICENSE file.
/go:build dragonfly || freebsd || linux
package unix
import (
"sync/atomic"
"syscall"
"unsafe"
)
var getrandomUnsupported int32 / atomic
/ GetRandomFlag is a flag supported by the getrandom system call.
type GetRandomFlag uintptr
/ GetRandom calls the getrandom system call.
func GetRandom(p []byte, flags GetRandomFlag) (n int, err error) {
if len(p) == 0 {
return 0, nil
}
if atomic.LoadInt32(&getrandomUnsupported) != 0 {
return 0, syscall.ENOSYS
}
r1, _, errno := syscall.Syscall(getrandomTrap,
uintptr(unsafe.Pointer(&p[0])),
uintptr(len(p)),
uintptr(flags))
if errno != 0 {
if errno == syscall.ENOSYS {
atomic.StoreInt32(&getrandomUnsupported, 1)
}
return 0, errno
}
return int(r1), nil
}