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// 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 atomic.Bool
// 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 getrandomUnsupported.Load() {
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 {
getrandomUnsupported.Store(true)
}
return 0, errno
}
return int(r1), nil
}
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