Constant GRND_NONBLOCK 

pub const GRND_NONBLOCK: u32 = 1;

Fill a buffer with random bytes from the kernel entropy pool.

Arguments

• buf - Mutable byte buffer to fill
• flags - GRND_NONBLOCK (1) to return EAGAIN if pool not ready, GRND_RANDOM (2) for /dev/random quality (same pool)

Returns

• Number of bytes written on success
• Err(Error::Again) if GRND_NONBLOCK and entropy not yet ready