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    // Copyright 2018 Developers of the Rand project.
    //
    // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
    // https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
    // <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
    // option. This file may not be copied, modified, or distributed
    // except according to those terms.

    //! Implementation for Linux / Android
    use crate::{
        util::LazyBool,
        util_libc::{last_os_error, sys_fill_exact},
        {use_file, Error},
    };

    pub fn getrandom_inner(dest: &mut [u8]) -> Result<(), Error> {
        // getrandom(2) was introduced in Linux 3.17
        static HAS_GETRANDOM: LazyBool = LazyBool::new();
        if HAS_GETRANDOM.unsync_init(is_getrandom_available) {
            sys_fill_exact(dest, |buf| unsafe {
                getrandom(buf.as_mut_ptr() as *mut libc::c_void, buf.len(), 0)
            })
        } else {
            use_file::getrandom_inner(dest)
        }
    }

    fn is_getrandom_available() -> bool {
        let res = unsafe { getrandom(core::ptr::null_mut(), 0, libc::GRND_NONBLOCK) };
        if res < 0 {
            match last_os_error().raw_os_error() {
                Some(libc::ENOSYS) => false, // No kernel support
                Some(libc::EPERM) => false,  // Blocked by seccomp
                _ => true,
            }
        } else {
            true
        }
    }

    unsafe fn getrandom(
        buf: *mut libc::c_void,
        buflen: libc::size_t,
        flags: libc::c_uint,
    ) -> libc::ssize_t {
        libc::syscall(libc::SYS_getrandom, buf, buflen, flags) as libc::ssize_t
    }