rapidhash 3.1.0

A rust port of rapidhash: an extremely fast, high quality, platform-independent hashing algorithm.
Documentation 
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/// Compare a Rust hash to the C implementation, and the COMPACT version.
macro_rules! compare_to_c {
    ($test:ident, $rust_fn:path, $compact_fn:path, $cc_fn:ident) => {
        #[test]
        fn $test() {
            use rand::Rng;
            use rapidhash_c::$cc_fn;

            // test zero-length input
            let rust_hash = $rust_fn(&[], &DEFAULT_RAPID_SECRETS);
            let compact_hash = $compact_fn(&[], &DEFAULT_RAPID_SECRETS);
            let c_hash = $cc_fn(&[], DEFAULT_SEED);
            assert_eq!(rust_hash, c_hash, "Mismatch with C on zero len input");
            assert_eq!(rust_hash, compact_hash, "Mismatch with COMPACT on zero len input");

            // test up to 512 bytes
            for len in 0..=512 {
                let mut data = std::vec![0; len];
                rand::rng().fill(&mut data[..]);

                for byte in 0..len {
                    for bit in 0..8 {
                        let mut data = data.clone();
                        data[byte] ^= 1 << bit;

                        let rust_hash = $rust_fn(&data, &DEFAULT_RAPID_SECRETS);
                        let compact_hash = $compact_fn(&data, &DEFAULT_RAPID_SECRETS);
                        let c_hash = $cc_fn(&data, DEFAULT_SEED);
                        assert_eq!(rust_hash, c_hash, "Mismatch with C on input {} byte {} bit {}", len, byte, bit);
                        assert_eq!(rust_hash, compact_hash, "Mismatch with COMPACT on input {} byte {} bit {}", len, byte, bit);
                    }
                }
            }
        }
    };
}

/// Check that flipping a single bit changes enough bits of output.
macro_rules! flip_bit_trial {
    ($test:ident, $hash:path) => {
        #[test]
        fn $test() {
            use rand::Rng;

            let mut flips = std::vec![];

            for len in 1..=256 {
                let mut data = std::vec![0; len];
                rand::rng().fill(&mut data[..]);

                let hash = $hash(&data, &DEFAULT_RAPID_SECRETS);
                for byte in 0..len {
                    for bit in 0..8 {
                        let mut data = data.clone();
                        data[byte] ^= 1 << bit;
                        let new_hash = $hash(&data, &DEFAULT_RAPID_SECRETS);
                        assert_ne!(hash, new_hash, "Flipping byte {} bit {} did not change hash for input len {}", byte, bit, len);
                        let xor = hash ^ new_hash;
                        let flipped = xor.count_ones() as u64;
                        assert!(xor.count_ones() >= 8, "Flipping bit {byte}:{bit} changed only {flipped} bits");

                        flips.push(flipped);
                    }
                }
            }

            let average = flips.iter().sum::<u64>() as f64 / flips.len() as f64;
            assert!(average > 31.95 && average < 32.05, "Did not flip an average of half the bits. average: {average}, expected: 32.0");
        }
    };
}

macro_rules! compare_rapidhash_file {
    ($test:ident, $hash:path, $file:path) => {
        #[test]
        fn $test() {
            use rand::RngCore;

            const LENGTH: usize = 1024;
            for len in 1..=LENGTH {
                let mut data = vec![0u8; len];
                rand::rng().fill_bytes(&mut data);

                let mut file = tempfile::tempfile().unwrap();
                file.write_all(&data).unwrap();
                file.seek(SeekFrom::Start(0)).unwrap();

                assert_eq!(
                    $hash(&data, &DEFAULT_RAPID_SECRETS),
                    $file(&mut file, &DEFAULT_RAPID_SECRETS).unwrap(),
                    "Mismatch for input len: {}", &data.len()
                );
            }
        }
    };
}

pub(crate) use compare_to_c;
pub(crate) use flip_bit_trial;
pub(crate) use compare_rapidhash_file;