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//! Returns `OsRng` with `getrandom`, or a `CryptoRng` which panics without `getrandom`.

#![no_std]

/// Re-export rand_core types to simplify dependences
pub use rand_core::{self,RngCore,CryptoRng,CryptoRngCore,SeedableRng};


#[cfg(all( feature = "getrandom", not(feature = "std") ))]
pub fn getrandom_or_panic() -> impl RngCore+CryptoRng {
    rand_core::OsRng
}

#[cfg(all( feature = "getrandom", feature = "std" ))]
pub fn getrandom_or_panic() -> impl RngCore+CryptoRng {
    rand::thread_rng()
}

#[cfg(not(feature = "getrandom"))]
pub fn getrandom_or_panic() -> impl RngCore+CryptoRng {
    const PRM: &'static str = "Attempted to use functionality that requires system randomness!!";

    // Should we panic when invoked or when used?

    struct PanicRng;
    impl rand_core::RngCore for PanicRng {
        fn next_u32(&mut self) -> u32 {  panic!("{}", PRM)  }
        fn next_u64(&mut self) -> u64 {  panic!("{}", PRM)  }
        fn fill_bytes(&mut self, _dest: &mut [u8]) {  panic!("{}", PRM)  }
        fn try_fill_bytes(&mut self, _dest: &mut [u8]) -> Result<(), rand_core::Error> {  panic!("{}", PRM)  }
    }
    impl rand_core::CryptoRng for PanicRng {}

    PanicRng
}