sgx_tstd/src/sys/rand.rs

// Copyright (c) 2017 Baidu, Inc. All Rights Reserved.
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use core::mem;

pub use self::imp::SgxRng;

fn next_u32(fill_buf: &mut FnMut(&mut [u8])) -> u32 {
    let mut buf: [u8; 4] = [0; 4];
    fill_buf(&mut buf);
    unsafe { mem::transmute::<[u8; 4], u32>(buf) }
}

fn next_u64(fill_buf: &mut FnMut(&mut [u8])) -> u64 {
    let mut buf: [u8; 8] = [0; 8];
    fill_buf(&mut buf);
    unsafe { mem::transmute::<[u8; 8], u64>(buf) }
}

mod imp {

    use sgx_types::*;
    use sgx_trts::rsgx_read_rand;

    use super::{next_u32, next_u64};
    use io;
    use core_rand::Rng;

    fn getrandom(buf: &mut [u8]) -> SgxError {
        rsgx_read_rand(buf)
    }

    fn getrandom_fill_bytes(v: &mut [u8]) {
        getrandom(v).expect("unexpected getrandom error");
    }

    #[allow(dead_code)] 
    fn is_getrandom_available() -> bool { true }

    pub struct SgxRng;
   
    impl SgxRng {
        /// Create a new `SgxRng`.
        pub fn new() -> io::Result<SgxRng> {
            Ok(SgxRng)
        }
    }

    impl Rng for SgxRng {
        fn next_u32(&mut self) -> u32 {
            next_u32(&mut getrandom_fill_bytes)
        }
        fn next_u64(&mut self) -> u64 {
            next_u64(&mut getrandom_fill_bytes)
        }
        fn fill_bytes(&mut self, v: &mut [u8]) {
            getrandom_fill_bytes(v)
        }
    }
}