#![feature(test)]

extern crate num_bigint;
extern crate num_traits;
extern crate test;

use num_bigint::{BigInt, BigUint};
use num_traits::ToPrimitive;

use std::u32;

fn truncate_biguint_to_u32(a: &BigUint) -> u32 {
    use std::u32;
    let mask = BigUint::from(u32::MAX);
    (a & mask).to_u32().unwrap()
}

fn truncate_bigint_to_u32(a: &BigInt) -> u32 {
    use num_traits::Signed;

    let was_negative = a.is_negative();
    let abs = a.abs().to_biguint().unwrap();
    let mut truncated = truncate_biguint_to_u32(&abs);
    if was_negative {
        truncated = (!truncated).wrapping_add(1);
    }
    truncated
}

#[bench]
fn bench_truncate_biguint(bencher: &mut test::Bencher) {
    let b = BigUint::parse_bytes(b"423445324324324324234324", 10).unwrap();
    let c = BigUint::parse_bytes(b"76543210fedcba98", 16).unwrap();
    let d = BigUint::parse_bytes(&vec![b'8'; 1000], 36).unwrap();
    let e = (BigUint::from(1u32) << d.bits()) - &d;
    bencher.iter(|| {
        assert_eq!(truncate_biguint_to_u32(&b), 43078740);
        assert_eq!(truncate_biguint_to_u32(&c), 0xfedcba98);
        assert_eq!(truncate_biguint_to_u32(&d), 2822407080);
        assert_eq!(truncate_biguint_to_u32(&e), 1472560216);
    });
    bencher.bytes = (b.bits() + c.bits() + d.bits() + e.bits()) as u64 / 8;
}

#[bench]
fn bench_truncate_bigint(bencher: &mut test::Bencher) {
    let b = BigInt::parse_bytes(b"423445324324324324234324", 10).unwrap();
    let c = BigInt::parse_bytes(b"76543210fedcba98", 16).unwrap();
    let d = BigInt::parse_bytes(&vec![b'8'; 1000], 36).unwrap();
    let e = -&d;
    bencher.iter(|| {
        assert_eq!(truncate_bigint_to_u32(&b), 43078740);
        assert_eq!(truncate_bigint_to_u32(&c), 0xfedcba98);
        assert_eq!(truncate_bigint_to_u32(&d), 2822407080);
        assert_eq!(truncate_bigint_to_u32(&e), 1472560216);
    });
    bencher.bytes = (b.bits() + c.bits() + d.bits() + e.bits()) as u64 / 8;
}

#[test] fn test() {}