#
core/stdarch/crates/core_arch/src/x86_64/
rdrand.rs

    1//! RDRAND and RDSEED instructions for returning random numbers from an Intel
    2//! on-chip hardware random number generator which has been seeded by an
    3//! on-chip entropy source.
    4
    5#![allow(clippy::module_name_repetitions)]
    6
    7#[allow(improper_ctypes)]
    8unsafe extern "unadjusted" {
    9    #[link_name = "llvm.x86.rdrand.64"]
    10    fn x86_rdrand64_step() -> (u64, i32);
    11    #[link_name = "llvm.x86.rdseed.64"]
    12    fn x86_rdseed64_step() -> (u64, i32);
    13}
    14
    15#[cfg(test)]
    16use stdarch_test::assert_instr;
    17
    18/// Read a hardware generated 64-bit random value and store the result in val.
    19/// Returns 1 if a random value was generated, and 0 otherwise.
    20///
    21/// [Intel's documentation](https://www.intel.com/content/www/us/en/docs/intrinsics-guide/index.html#text=_rdrand64_step)
    22#[inline]
    23#[target_feature(enable = "rdrand")]
    24#[cfg_attr(test, assert_instr(rdrand))]
    25#[stable(feature = "simd_x86", since = "1.27.0")]
    26pub unsafe fn _rdrand64_step(val: &mut u64) -> i32 {
    27    let (v, flag) = x86_rdrand64_step();
    28    *val = v;
    29    flag
    30}
    31
    32/// Read a 64-bit NIST SP800-90B and SP800-90C compliant random value and store
    33/// in val. Return 1 if a random value was generated, and 0 otherwise.
    34///
    35/// [Intel's documentation](https://www.intel.com/content/www/us/en/docs/intrinsics-guide/index.html#text=_rdseed64_step)
    36#[inline]
    37#[target_feature(enable = "rdseed")]
    38#[cfg_attr(test, assert_instr(rdseed))]
    39#[stable(feature = "simd_x86", since = "1.27.0")]
    40pub unsafe fn _rdseed64_step(val: &mut u64) -> i32 {
    41    let (v, flag) = x86_rdseed64_step();
    42    *val = v;
    43    flag
    44}