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use {Status, ok, sys};
/// Draw random bytes from the kernel's CPRNG to fill the given buffer. Returns the actual number of
/// bytes drawn, which may sometimes be less than the size of the buffer provided.
///
/// The buffer must have length less than `ZX_CPRNG_DRAW_MAX_LEN`.
///
/// Wraps the
/// syscall.
pub fn cprng_draw(buffer: &mut [u8]) -> Result<usize, Status> {
let mut actual = 0;
let status = unsafe { sys::zx_cprng_draw(buffer.as_mut_ptr(), buffer.len(), &mut actual) };
ok(status).map(|()| actual)
}
/// Mix the given entropy into the kernel CPRNG.
///
/// The buffer must have length less than `ZX_CPRNG_ADD_ENTROPY_MAX_LEN`.
///
/// Wraps the
/// [zx_cprng_add_entropy](https://fuchsia.googlesource.com/zircon/+/HEAD/docs/syscalls/cprng_add_entropy.md)
/// syscall.
pub fn cprng_add_entropy(buffer: &[u8]) -> Result<(), Status> {
let status = unsafe { sys::zx_cprng_add_entropy(buffer.as_ptr(), buffer.len()) };
ok(status)
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn cprng() {
let mut buffer = [0; 20];
assert_eq!(cprng_draw(&mut buffer), Ok(20));
let mut first_zero = 0;
let mut last_zero = 0;
for _ in 0..30 {
let mut buffer = [0; 20];
assert_eq!(cprng_draw(&mut buffer), Ok(20));
if buffer[0] == 0 {
first_zero += 1;
}
if buffer[19] == 0 {
last_zero += 1;
}
}
assert_ne!(first_zero, 30);
assert_ne!(last_zero, 30);
}
#[test]
fn cprng_too_large() {
let mut buffer = [0; sys::ZX_CPRNG_DRAW_MAX_LEN + 1];
assert_eq!(cprng_draw(&mut buffer), Err(Status::INVALID_ARGS));
for mut s in buffer.chunks_mut(sys::ZX_CPRNG_DRAW_MAX_LEN) {
assert_eq!(cprng_draw(&mut s), Ok(s.len()));
}
}
#[test]
fn cprng_add() {
let buffer = [0, 1, 2];
assert_eq!(cprng_add_entropy(&buffer), Ok(()));
}
}