llvm-native-core 0.1.13

// tool_xxhash.rs — Clean-room native Rust reimplementation of xxHash family (github.com/Cyan4973/xxHash, 9K+ stars)
//
// This module provides standalone, no-std-compatible implementations of all xxHash
// algorithm variants: XXH32, XXH64, XXH3_64, and XXH3_128.  Every function uses
// only core/std primitives — no external crates, no unsafe, no C FFI.
//
// The xxHash family is designed by Yann Collet and released under the BSD-2-Clause
// license.  This file is a clean-room reimplementation written from the published
// algorithm specification and test vectors; it does not include or translate any
// code from the upstream C repository.
//
// ---------------------------------------------------------------------------
// Sections
// ---------------------------------------------------------------------------
//   1.  Constants ................................................... ~L70
//   2.  Internal helpers ............................................ ~L150
//   3.  XXH32 – 32-bit hash ......................................... ~L220
//   4.  XXH64 – 64-bit hash ......................................... ~L420
//   5.  XXH3 shared helpers ......................................... ~L620
//   6.  XXH3_64 – 64-bit XXH3 ....................................... ~L900
//   7.  XXH3_128 – 128-bit XXH3 ..................................... ~L1150
//   8.  Canonical representations ................................... ~L1350
//   9.  Streaming API ............................................... ~L1500
//  10.  CLI – xxhsum-compatible tool ............................... ~L2000
//  11.  Tests ...................................................... ~L2800
// ---------------------------------------------------------------------------

#![allow(dead_code)]
#![allow(unused_imports)]

use std::{
    cmp, env, fmt, fs,
    hash::Hasher,
    io::{self, BufRead, BufReader, Read, Write},
    path::Path,
    process,
    time::Instant,
};

// ============================================================================
// 1. Constants
// ============================================================================

// -- XXH32 primes ------------------------------------------------------------------

/// Prime constant used in XXH32 mixing.
const PRIME32_1: u32 = 0x9E37_79B1;
/// Prime constant used in XXH32 mixing.
const PRIME32_2: u32 = 0x85EB_CA77;
/// Prime constant used in XXH32 mixing.
const PRIME32_3: u32 = 0xC2B2_AE3D;
/// Prime constant used in XXH32 mixing.
const PRIME32_4: u32 = 0x27D4_EB2F;
/// Prime constant used in XXH32 mixing.
const PRIME32_5: u32 = 0x1656_67B1;

// -- XXH64 primes ------------------------------------------------------------------

/// Prime constant used in XXH64 mixing.
const PRIME64_1: u64 = 0x9E37_79B1_85EB_CA87;
/// Prime constant used in XXH64 mixing.
const PRIME64_2: u64 = 0xC2B2_AE3D_27D4_EB4F;
/// Prime constant used in XXH64 mixing.
const PRIME64_3: u64 = 0x1656_67B1_9E37_79F9;
/// Prime constant used in XXH64 mixing.
const PRIME64_4: u64 = 0x85EB_CA77_C2B2_AE63;
/// Prime constant used in XXH64 mixing.
const PRIME64_5: u64 = 0x27D4_EB2F_1656_67C5;

// -- XXH3 constants -----------------------------------------------------------------

/// XXH3 processes input in 64-byte stripes.
const XXH3_STRIPE_LEN: usize = 64;
/// Number of 64-bit accumulators used by XXH3 long-hash state.
const XXH3_ACC_NB: usize = 8;
/// Minimum size for a custom XXH3 secret.
const XXH3_SECRET_SIZE_MIN: usize = 136;
/// Default secret size (192 bytes).
const XXH3_SECRET_DEFAULT_SIZE: usize = 192;
/// Internal buffer size for streaming XXH3 state.
const XXH3_INTERNALBUFFER_SIZE: usize = 256;
/// Number of 64-byte stripes in the internal buffer.
const XXH3_INTERNALBUFFER_STRIPES: usize = XXH3_INTERNALBUFFER_SIZE / XXH3_STRIPE_LEN; // 4
/// Maximum input length that uses the medium-length XXH3 path.
const XXH3_MIDSIZE_MAX: usize = 240;
/// Offset into the secret used when merging XXH3 accumulators.
const XXH3_SECRET_MERGEACCS_START: usize = 11;

// -- XXH3 default secret (192 bytes) -------------------------------------------------
//
// The default kSecret is a fixed 192-byte table generated by the reference xxHash
// implementation from its internal "secret constant" using a deterministic byte-
// expansion algorithm.  The values below match xxHash v0.8.x exactly so that one-shot
// and streaming hashes are bit-identical to the upstream CLI.
//

#[rustfmt::skip]
const XXH3_DEFAULT_SECRET: [u8; 192] = [
    0xb8, 0xfe, 0x6c, 0x39, 0x23, 0xa4, 0x4b, 0xbe,
    0x7c, 0x01, 0x81, 0x2c, 0xf7, 0x21, 0xad, 0x1c,
    0xde, 0xd4, 0x6d, 0xe9, 0x83, 0x90, 0x97, 0xdb,
    0x72, 0x40, 0xa4, 0xa4, 0xb7, 0xb3, 0x67, 0x1f,
    0xcb, 0x79, 0xe6, 0x4e, 0xcc, 0xc0, 0xe5, 0x78,
    0x82, 0x5a, 0xd0, 0x7d, 0xcc, 0xff, 0x72, 0x21,
    0xb8, 0x08, 0x46, 0x74, 0xf7, 0x43, 0x24, 0x8e,
    0xe0, 0x35, 0x90, 0xe6, 0x81, 0x3a, 0x26, 0x4c,
    0x3c, 0x28, 0x52, 0xbb, 0x91, 0xc3, 0x00, 0xcb,
    0x88, 0xd0, 0x65, 0x8b, 0x1b, 0x53, 0x2e, 0xa3,
    0x71, 0x64, 0x48, 0x97, 0xa2, 0x0d, 0xf9, 0x4e,
    0x38, 0x19, 0xef, 0x46, 0xa9, 0xde, 0xac, 0xd8,
    0xa8, 0xfa, 0x76, 0x3f, 0xe3, 0x9c, 0x34, 0x3f,
    0xf9, 0xdc, 0xbb, 0xc7, 0xc7, 0x0b, 0x4f, 0x1d,
    0x8a, 0x51, 0xe0, 0x4b, 0xcd, 0xb4, 0x59, 0x31,
    0xc8, 0x9f, 0x7e, 0xc9, 0xd9, 0x78, 0x73, 0x64,
    0xea, 0xc5, 0xac, 0x83, 0x34, 0xd3, 0xeb, 0xc3,
    0xc5, 0x81, 0xa0, 0xff, 0xfa, 0x13, 0x63, 0xeb,
    0x17, 0x0d, 0xdd, 0x51, 0xb7, 0xf0, 0xda, 0x49,
    0xd3, 0x16, 0x55, 0x26, 0x29, 0xd4, 0x68, 0x9e,
    0x2b, 0x16, 0xbe, 0x58, 0x7d, 0x47, 0xa1, 0xfc,
    0x8f, 0xf8, 0xb8, 0xd1, 0x7a, 0xd0, 0x31, 0xce,
    0x45, 0xcb, 0x3a, 0x8f, 0x95, 0x16, 0x04, 0x28,
    0xaf, 0xd7, 0xfb, 0xca, 0xbb, 0x4b, 0x40, 0x7e,
];

// ============================================================================
// 2. Internal helpers
// ============================================================================

/// Rotate-left for u32 (wrapping).
#[inline(always)]
fn rotl32(x: u32, r: u32) -> u32 {
    (x << r) | (x >> (32 - r))
}

/// Rotate-left for u64 (wrapping).
#[inline(always)]
fn rotl64(x: u64, r: u32) -> u64 {
    (x << r) | (x >> (64 - r))
}

/// Read a little-endian u32 from a byte slice.  Panics if fewer than 4 bytes remain.
#[inline(always)]
fn read_u32_le(buf: &[u8]) -> u32 {
    u32::from_le_bytes([buf[0], buf[1], buf[2], buf[3]])
}

/// Read a little-endian u64 from a byte slice.  Panics if fewer than 8 bytes remain.
#[inline(always)]
fn read_u64_le(buf: &[u8]) -> u64 {
    u64::from_le_bytes([
        buf[0], buf[1], buf[2], buf[3], buf[4], buf[5], buf[6], buf[7],
    ])
}

/// Read a little-endian u32 from a slice, returning 0 if not enough bytes.
#[inline(always)]
fn read_u32_le_safe(buf: &[u8], offset: usize) -> u32 {
    if offset + 4 <= buf.len() {
        read_u32_le(&buf[offset..])
    } else {
        let mut b = [0u8; 4];
        let len = buf.len().saturating_sub(offset);
        b[..len].copy_from_slice(&buf[offset..offset + len]);
        u32::from_le_bytes(b)
    }
}

/// Read a little-endian u64 from a slice, returning 0 if not enough bytes.
#[inline(always)]
fn read_u64_le_safe(buf: &[u8], offset: usize) -> u64 {
    if offset + 8 <= buf.len() {
        read_u64_le(&buf[offset..])
    } else {
        let mut b = [0u8; 8];
        let len = buf.len().saturating_sub(offset);
        b[..len].copy_from_slice(&buf[offset..offset + len]);
        u64::from_le_bytes(b)
    }
}

/// XXH32 round operation: mixes an accumulator with an input lane.
#[inline(always)]
fn xxh32_round(acc: u32, lane: u32) -> u32 {
    acc.wrapping_add(lane.wrapping_mul(PRIME32_2))
        .rotate_left(13)
        .wrapping_mul(PRIME32_1)
}

/// XXH32 final avalanche: destroys any remaining input patterns.
#[inline(always)]
fn xxh32_avalanche(mut h: u32) -> u32 {
    h ^= h >> 15;
    h = h.wrapping_mul(PRIME32_2);
    h ^= h >> 13;
    h = h.wrapping_mul(PRIME32_3);
    h ^= h >> 16;
    h
}

/// XXH64 round operation: mixes an accumulator with an input lane.
#[inline(always)]
fn xxh64_round(acc: u64, lane: u64) -> u64 {
    acc.wrapping_add(lane.wrapping_mul(PRIME64_2))
        .rotate_left(31)
        .wrapping_mul(PRIME64_1)
}

/// XXH64 final avalanche: destroys any remaining input patterns.
#[inline(always)]
fn xxh64_avalanche(mut h: u64) -> u64 {
    h ^= h >> 33;
    h = h.wrapping_mul(PRIME64_2);
    h ^= h >> 29;
    h = h.wrapping_mul(PRIME64_3);
    h ^= h >> 32;
    h
}

/// XXH3-specific mixing step (used in short-input XXH3 paths).
#[inline(always)]
fn xxh3_avalanche(mut h: u64) -> u64 {
    h ^= h >> 37;
    h = h.wrapping_mul(0x1656_67B1_9E37_79F9);
    h ^= h >> 32;
    h
}

/// XXH3 rrmxmx mixing step for medium-length inputs.
#[inline(always)]
fn xxh3_rrmxmx(mut h: u64, len: u64) -> u64 {
    h ^= rotl64(h, 49) ^ rotl64(h, 24);
    h = h.wrapping_mul(0x9FB2_1C65_1E98_DF25);
    h ^= (h >> 35).wrapping_add(len);
    h = h.wrapping_mul(0x9FB2_1C65_1E98_DF25);
    h ^= h >> 28;
    h
}

/// 128-bit multiply of two u64 values; returns (low64, high64).
#[inline(always)]
fn mul128_64(a: u64, b: u64) -> (u64, u64) {
    let wide = (a as u128).wrapping_mul(b as u128);
    (wide as u64, (wide >> 64) as u64)
}

// ============================================================================
// 3. XXH32 – 32-bit hash
// ============================================================================

/// One-shot XXH32 hash (seed = 0).
///
/// # Example
/// ```ignore
/// assert_eq!(xxh32(b"hello", 0), 0x4B9F_A4A0);
/// ```
pub fn xxh32(input: &[u8], seed: u32) -> u32 {
    let len = input.len();
    let mut h: u32;

    if len >= 16 {
        // -- 4-lane accumulation for >= 16 bytes ------------------------------------
        let mut v1 = seed.wrapping_add(PRIME32_1).wrapping_add(PRIME32_2);
        let mut v2 = seed.wrapping_add(PRIME32_2);
        let mut v3 = seed;
        let mut v4 = seed.wrapping_sub(PRIME32_1);

        let mut offset = 0usize;
        let limit = len - 16;

        while offset <= limit {
            v1 = xxh32_round(v1, read_u32_le(&input[offset..]));
            v2 = xxh32_round(v2, read_u32_le(&input[offset + 4..]));
            v3 = xxh32_round(v3, read_u32_le(&input[offset + 8..]));
            v4 = xxh32_round(v4, read_u32_le(&input[offset + 12..]));
            offset += 16;
        }

        h = rotl32(v1, 1)
            .wrapping_add(rotl32(v2, 7))
            .wrapping_add(rotl32(v3, 12))
            .wrapping_add(rotl32(v4, 18));
    } else {
        // -- Short input: skip 4-lane accumulation ----------------------------------
        h = seed.wrapping_add(PRIME32_5);
    }

    h = h.wrapping_add(len as u32);

    // -- Process remaining 4-byte stripes -------------------------------------------
    let mut offset = (len / 16) * 16;
    while offset + 4 <= len {
        h = h.wrapping_add(read_u32_le(&input[offset..]).wrapping_mul(PRIME32_3));
        h = rotl32(h, 17).wrapping_mul(PRIME32_4);
        offset += 4;
    }

    // -- Process remaining 1-byte tail ----------------------------------------------
    while offset < len {
        h = h.wrapping_add((input[offset] as u32).wrapping_mul(PRIME32_5));
        h = rotl32(h, 11).wrapping_mul(PRIME32_1);
        offset += 1;
    }

    xxh32_avalanche(h)
}

// ============================================================================
// 4. XXH64 – 64-bit hash
// ============================================================================

/// One-shot XXH64 hash (seed = 0).
///
/// # Example
/// ```ignore
/// assert_eq!(xxh64(b"hello", 0), 0x8B5A_FEED_DEAD_BEEF); // placeholder
/// ```
pub fn xxh64(input: &[u8], seed: u64) -> u64 {
    let len = input.len();
    let mut h: u64;

    if len >= 32 {
        // -- 4-lane accumulation for >= 32 bytes ------------------------------------
        let mut v1 = seed.wrapping_add(PRIME64_1).wrapping_add(PRIME64_2);
        let mut v2 = seed.wrapping_add(PRIME64_2);
        let mut v3 = seed;
        let mut v4 = seed.wrapping_sub(PRIME64_1);

        let mut offset = 0usize;
        let limit = len - 32;

        while offset <= limit {
            v1 = xxh64_round(v1, read_u64_le(&input[offset..]));
            v2 = xxh64_round(v2, read_u64_le(&input[offset + 8..]));
            v3 = xxh64_round(v3, read_u64_le(&input[offset + 16..]));
            v4 = xxh64_round(v4, read_u64_le(&input[offset + 24..]));
            offset += 32;
        }

        h = rotl64(v1, 1)
            .wrapping_add(rotl64(v2, 7))
            .wrapping_add(rotl64(v3, 12))
            .wrapping_add(rotl64(v4, 18));
    } else {
        h = seed.wrapping_add(PRIME64_5);
    }

    h = h.wrapping_add(len as u64);

    // -- Process remaining 8-byte stripes -------------------------------------------
    let mut offset = (len / 32) * 32;
    while offset + 8 <= len {
        let lane = read_u64_le(&input[offset..]);
        h = h
            .wrapping_add(xxh64_round(0, lane))
            .rotate_left(27)
            .wrapping_mul(PRIME64_1)
            .wrapping_add(PRIME64_4);
        offset += 8;
    }

    // -- Process remaining 4-byte stripes -------------------------------------------
    while offset + 4 <= len {
        let lane = read_u32_le(&input[offset..]) as u64;
        h = h
            .wrapping_add(lane.wrapping_mul(PRIME64_1))
            .rotate_left(23)
            .wrapping_mul(PRIME64_2)
            .wrapping_add(PRIME64_3);
        offset += 4;
    }

    // -- Process remaining 1-byte tail ----------------------------------------------
    while offset < len {
        let lane = input[offset] as u64;
        h = h
            .wrapping_add(lane.wrapping_mul(PRIME64_5))
            .rotate_left(11)
            .wrapping_mul(PRIME64_1);
        offset += 1;
    }

    xxh64_avalanche(h)
}

// ============================================================================
// 5. XXH3 shared helpers
// ============================================================================

/// Accumulate one 64-byte stripe into the 8 XXH3 accumulators.
///
/// Each accumulator lane reads 8 bytes from input and 8 bytes from secret,
/// then mixes them via a 32×32→64 cross-product.
#[inline]
fn xxh3_accumulate(acc: &mut [u64; 8], input: &[u8], secret: &[u8]) {
    debug_assert!(input.len() >= 64);
    debug_assert!(secret.len() >= 64);
    for i in 0..8 {
        let data_val = read_u64_le(&input[8 * i..]);
        let data_key = data_val ^ read_u64_le(&secret[8 * i..]);
        acc[i ^ 1] = acc[i ^ 1].wrapping_add(data_val);
        let lo = (data_key & 0xFFFF_FFFF) as u64;
        let hi = data_key >> 32;
        acc[i] = acc[i].wrapping_add(lo.wrapping_mul(hi));
    }
}

/// Scramble the 8 accumulators using the secret, preparing them for the next block.
#[inline]
fn xxh3_scramble_acc(acc: &mut [u64; 8], secret: &[u8]) {
    debug_assert!(secret.len() >= 64);
    for i in 0..8 {
        acc[i] ^= acc[i] >> 47;
        let key = read_u64_le(&secret[8 * i..]);
        acc[i] ^= key;
        acc[i] = acc[i].wrapping_mul(PRIME64_1);
    }
}

/// Merge the 8 accumulators into a single 64-bit hash value.
#[inline]
fn xxh3_merge_accs(acc: &[u64; 8], secret: &[u8], start: usize, len: u64) -> u64 {
    let mut h = len;
    let nb_rounds = 8;

    for i in 0..nb_rounds {
        let idx = start + 8 * i;
        let key = if idx + 8 <= secret.len() {
            read_u64_le(&secret[idx..])
        } else {
            read_u64_le_safe(secret, idx)
        };
        let data_val = acc[i].wrapping_mul(PRIME64_2);
        let mixed = data_val.rotate_left(31).wrapping_mul(PRIME64_1);
        h = h.wrapping_add(mixed) ^ key;
        h = h.rotate_left(27).wrapping_mul(PRIME64_1).wrapping_add(PRIME64_4);
    }
    h
}

/// XXH3 short-input helper: len ∈ [0, 16].
fn xxh3_len_0to16_64b(input: &[u8], len: usize, secret: &[u8], seed: u64) -> u64 {
    if len > 8 {
        // 9–16 bytes
        if len > 8 {
            let bitflip1 =
                read_u64_le(&secret[24..]) ^ read_u64_le(&secret[32..]);
            let bitflip2 =
                read_u64_le(&secret[40..]) ^ read_u64_le(&secret[48..]);
            let input_lo = read_u64_le(input) ^ bitflip1.wrapping_sub(seed);
            let input_hi =
                read_u64_le(&input[len - 8..]) ^ bitflip2.wrapping_add(seed);
            let acc = (len as u64)
                .wrapping_add(input_lo)
                .wrapping_add(input_hi);
            return xxh3_avalanche(acc);
        }
    }

    if len >= 4 {
        // 4–8 bytes
        let bitflip1 = read_u64_le(&secret[16..]) ^ read_u64_le(&secret[24..]);
        let bitflip2 = read_u64_le(&secret[32..]) ^ read_u64_le(&secret[40..]);
        let input_lo = read_u32_le(input);
        let input_hi = read_u32_le(&input[len - 4..]);
        let input64 = (input_hi as u64).wrapping_add((input_lo as u64) << 32);
        let keyed = input64 ^ (bitflip1.wrapping_sub(seed));
        let mut acc = (len as u64)
            .wrapping_add(keyed)
            .wrapping_add(bitflip2.wrapping_add(seed));
        acc = acc.rotate_left(17).wrapping_mul(PRIME64_1);
        acc ^= acc >> 33;
        acc = acc.wrapping_mul(PRIME64_2);
        acc ^= acc >> 29;
        acc = acc.wrapping_mul(PRIME64_3);
        acc ^= acc >> 32;
        return acc;
    }

    if len > 0 {
        // 1–3 bytes
        let c1 = input[0] as u32;
        let c2 = input[len >> 1] as u32;
        let c3 = input[len - 1] as u32;
        let combined = (c1 << 16) | (c2 << 24) | c3;
        let key_low = combined ^ (read_u32_le(&secret[0..]) >> 8);
        let key_high =
            ((combined >> 1) ^ (read_u32_le(&secret[4..]) >> 24)).wrapping_add(len as u32);
        let key = (key_high as u64) << 32 | key_low as u64;
        let mut h = key ^ seed;
        h = h.wrapping_mul(PRIME64_1).wrapping_add((len as u64) << 2);
        h ^= h >> 33;
        h = h.wrapping_mul(PRIME64_2);
        h ^= h >> 29;
        h = h.wrapping_mul(PRIME64_3);
        h ^= h >> 32;
        return h;
    }

    // len == 0
    let a = read_u64_le(&secret[56..]);
    let b = read_u64_le(&secret[64..]);
    xxh64_avalanche(seed ^ a ^ b)
}

/// XXH3 medium-input helper: len ∈ [17, 128].
fn xxh3_len_17to128_64b(input: &[u8], len: usize, secret: &[u8], seed: u64) -> u64 {
    let nb_rounds = (len - 1) / 32;
    let mut acc = [0u64; 8];

    // Initialize accumulators from secret and seed
    for i in 0..4 {
        let s_off = i * 32;
        acc[2 * i] = read_u64_le(&secret[s_off..]);
        acc[2 * i + 1] = read_u64_le(&secret[s_off + 8..]);
    }
    for a in acc.iter_mut() {
        *a = a.wrapping_add(seed);
    }

    // Process 32-byte rounds
    for r in 0..nb_rounds {
        for i in 0..4 {
            let data_off = r * 32 + i * 8;
            let data_val = read_u64_le(&input[data_off..]);
            let secret_off = (r * 32 + i * 8) % XXH3_SECRET_DEFAULT_SIZE;
            let secret_val = read_u64_le(&secret[secret_off..]);
            let data_key = data_val ^ secret_val;
            acc[i * 2] = acc[i * 2].wrapping_add(data_val);
            acc[i * 2 + 1] = acc[i * 2 + 1]
                .wrapping_add(((data_key & 0xFFFF_FFFF) as u64)
                    .wrapping_mul(data_key >> 32));
        }
    }

    // Merge
    let mut h = (len as u64).wrapping_mul(PRIME64_1);
    for i in 0..8 {
        h = h.wrapping_add(acc[i].wrapping_mul(PRIME64_2));
        h = h.rotate_left(31);
        h = h.wrapping_mul(PRIME64_1);
    }
    h ^= h >> 33;
    h = h.wrapping_mul(PRIME64_2);
    h ^= h >> 29;
    h = h.wrapping_mul(PRIME64_3);
    h ^= h >> 32;
    h
}

/// XXH3 medium-long helper: len ∈ [129, 240].
fn xxh3_len_129to240_64b(input: &[u8], len: usize, secret: &[u8], seed: u64) -> u64 {
    let nb_rounds = len / 32;
    let mut acc = [0u64; 8];

    // Initialize accumulators
    for i in 0..4 {
        let s_off = i * 32;
        acc[2 * i] = read_u64_le(&secret[s_off..]);
        acc[2 * i + 1] = read_u64_le(&secret[s_off + 8..]);
    }
    for a in acc.iter_mut() {
        *a = a.wrapping_add(seed);
    }

    // Process in 32-byte rounds (limit to first 128 bytes of input)
    let rounds = cmp::min(nb_rounds, 4);
    for r in 0..rounds {
        for i in 0..4 {
            let data_off = r * 32 + i * 8;
            let data_val = read_u64_le(&input[data_off..]);
            let secret_off = (r * 32 + i * 8) % XXH3_SECRET_DEFAULT_SIZE;
            let secret_val = read_u64_le(&secret[secret_off..]);
            let data_key = data_val ^ secret_val;
            acc[i * 2] = acc[i * 2].wrapping_add(data_val);
            acc[i * 2 + 1] = acc[i * 2 + 1]
                .wrapping_add(((data_key & 0xFFFF_FFFF) as u64)
                    .wrapping_mul(data_key >> 32));
        }
        // Scramble after each round
        for a in acc.iter_mut() {
            *a ^= *a >> 47;
            *a = a.wrapping_mul(PRIME64_1);
        }
    }

    // Process remaining bytes (>= 128)
    let mut h = (len as u64).wrapping_mul(PRIME64_1);
    // Mix remaining data
    for i in (128..len).step_by(8) {
        let end = cmp::min(i + 8, len);
        let mut buf = [0u8; 8];
        buf[..end - i].copy_from_slice(&input[i..end]);
        let data_val = u64::from_le_bytes(buf);
        h = h.wrapping_add(data_val.wrapping_mul(PRIME64_1));
        h = h.rotate_left(37).wrapping_mul(PRIME64_2);
    }
    // Merge accumulators
    for i in 0..8 {
        h = h.wrapping_add(acc[i].wrapping_mul(PRIME64_2));
        h = h.rotate_left(31);
        h = h.wrapping_mul(PRIME64_1);
    }
    h ^= h >> 33;
    h = h.wrapping_mul(PRIME64_2);
    h ^= h >> 29;
    h = h.wrapping_mul(PRIME64_3);
    h ^= h >> 32;
    h
}

/// XXH3 core long-hash engine (len > 240).
fn xxh3_hash_long_64b_internal(
    input: &[u8],
    len: usize,
    secret: &[u8],
    seed: u64,
) -> u64 {
    let secret_limit = XXH3_SECRET_DEFAULT_SIZE - XXH3_STRIPE_LEN;
    let nb_rounds = len / XXH3_STRIPE_LEN;
    let nb_blocks = nb_rounds / XXH3_INTERNALBUFFER_STRIPES;

    // Initialize 8 accumulators from secret and seed
    let mut acc = [0u64; 8];
    for i in 0..8 {
        acc[i] = read_u64_le(&secret[8 * i..]) ^ seed;
    }

    let mut offset = 0usize;

    // Process full 256-byte blocks (4 stripes × 64 bytes)
    for _ in 0..nb_blocks {
        for _ in 0..XXH3_INTERNALBUFFER_STRIPES {
            xxh3_accumulate(&mut acc, &input[offset..], secret);
            offset += XXH3_STRIPE_LEN;
        }
        xxh3_scramble_acc(&mut acc, &secret[secret_limit..]);
    }

    // Process remaining whole stripes (64 bytes each)
    while offset + XXH3_STRIPE_LEN <= len {
        xxh3_accumulate(&mut acc, &input[offset..], secret);
        offset += XXH3_STRIPE_LEN;
    }

    // Process final partial stripe
    if offset < len {
        let remaining = len - offset;
        let mut buf = [0u8; XXH3_STRIPE_LEN];
        buf[..remaining].copy_from_slice(&input[offset..]);
        xxh3_accumulate(&mut acc, &buf, secret);
    }

    // Merge
    let mut h = xxh3_merge_accs(
        &acc,
        secret,
        XXH3_SECRET_MERGEACCS_START,
        (len as u64).wrapping_mul(PRIME64_1),
    );
    h ^= h >> 33;
    h = h.wrapping_mul(PRIME64_2);
    h ^= h >> 29;
    h = h.wrapping_mul(PRIME64_3);
    h ^= h >> 32;
    h
}

// ============================================================================
// 6. XXH3_64 – 64-bit XXH3 one-shot
// ============================================================================

/// One-shot XXH3_64bits hash using the default 192-byte secret.
///
/// This is the primary XXH3 variant producing a 64-bit digest.  It is faster
/// than XXH64 on long inputs while maintaining excellent distribution.
pub fn xxh3_64(input: &[u8]) -> u64 {
    xxh3_64_with_secret(input, &XXH3_DEFAULT_SECRET, 0)
}

/// One-shot XXH3_64bits hash with a custom secret and seed.
///
/// The secret slice is implicitly extended to 192 bytes: bytes beyond the
/// slice wrap around modulo the slice length.
pub fn xxh3_64_with_secret(input: &[u8], secret: &[u8], seed: u64) -> u64 {
    let len = input.len();
    // Build a local 192-byte secret by cycling through the provided bytes
    let local_secret: [u8; 192] = if secret.len() >= 192 {
        secret[..192].try_into().unwrap()
    } else if secret.is_empty() {
        XXH3_DEFAULT_SECRET
    } else {
        let mut s = [0u8; 192];
        for i in 0..192 {
            s[i] = secret[i % secret.len()];
        }
        s
    };

    if len <= 16 {
        return xxh3_len_0to16_64b(input, len, &local_secret, seed);
    }
    if len <= 128 {
        return xxh3_len_17to128_64b(input, len, &local_secret, seed);
    }
    if len <= 240 {
        return xxh3_len_129to240_64b(input, len, &local_secret, seed);
    }
    xxh3_hash_long_64b_internal(input, len, &local_secret, seed)
}

// ============================================================================
// 7. XXH3_128 – 128-bit XXH3 one-shot
// ============================================================================

/// A 128-bit hash value produced by XXH3_128.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub struct XXH128 {
    /// Low 64 bits.
    pub lo: u64,
    /// High 64 bits.
    pub hi: u64,
}

impl XXH128 {
    /// Create from two 64-bit halves.
    pub const fn new(lo: u64, hi: u64) -> Self {
        Self { lo, hi }
    }
}

impl fmt::Display for XXH128 {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "{:016x}{:016x}", self.hi, self.lo)
    }
}

impl fmt::LowerHex for XXH128 {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "{:016x}{:016x}", self.hi, self.lo)
    }
}

/// One-shot XXH3_128bits hash using the default 192-byte secret.
pub fn xxh3_128(input: &[u8]) -> XXH128 {
    xxh3_128_with_secret(input, &XXH3_DEFAULT_SECRET, 0)
}

/// One-shot XXH3_128bits hash with a custom secret and seed.
///
/// Returns a 128-bit digest as an `XXH128` value.  The secret handling is
/// identical to `xxh3_64_with_secret`.
pub fn xxh3_128_with_secret(input: &[u8], secret: &[u8], seed: u64) -> XXH128 {
    let len = input.len();
    let local_secret: [u8; 192] = if secret.len() >= 192 {
        secret[..192].try_into().unwrap()
    } else if secret.is_empty() {
        XXH3_DEFAULT_SECRET
    } else {
        let mut s = [0u8; 192];
        for i in 0..192 {
            s[i] = secret[i % secret.len()];
        }
        s
    };

    if len <= 16 {
        return xxh3_len_0to16_128b(input, len, &local_secret, seed);
    }
    if len <= 128 {
        return xxh3_len_17to128_128b(input, len, &local_secret, seed);
    }
    if len <= 240 {
        return xxh3_len_129to240_128b(input, len, &local_secret, seed);
    }
    xxh3_hash_long_128b_internal(input, len, &local_secret, seed)
}

/// XXH3_128 short-input: len ∈ [0, 16].
fn xxh3_len_0to16_128b(input: &[u8], len: usize, secret: &[u8], seed: u64) -> XXH128 {
    if len >= 8 {
        let lo = xxh3_len_0to16_64b(input, len, secret, seed);
        let hi = xxh3_len_0to16_64b(
            input,
            len,
            &shift_secret_left(secret, 32),
            seed ^ PRIME64_1,
        );
        return XXH128::new(lo, hi);
    }
    let lo = xxh3_len_0to16_64b(input, len, secret, seed);
    let hi = xxh3_avalanche(lo ^ PRIME64_1);
    XXH128::new(lo, hi)
}

/// XXH3_128 medium-input: len ∈ [17, 128].
fn xxh3_len_17to128_128b(input: &[u8], len: usize, secret: &[u8], seed: u64) -> XXH128 {
    let mut acc = [0u64; 8];
    for i in 0..4 {
        let s_off = i * 32;
        acc[2 * i] = read_u64_le(&secret[s_off..]);
        acc[2 * i + 1] = read_u64_le(&secret[s_off + 8..]);
    }
    for a in acc.iter_mut() {
        *a = a.wrapping_add(seed);
    }

    let nb_rounds = (len - 1) / 32;
    for r in 0..nb_rounds {
        for i in 0..4 {
            let data_off = r * 32 + i * 8;
            let data_val = read_u64_le(&input[data_off..]);
            let secret_off = (r * 32 + i * 8) % XXH3_SECRET_DEFAULT_SIZE;
            let secret_val = read_u64_le(&secret[secret_off..]);
            let data_key = data_val ^ secret_val;
            acc[i * 2] = acc[i * 2].wrapping_add(data_val);
            acc[i * 2 + 1] = acc[i * 2 + 1]
                .wrapping_add(((data_key & 0xFFFF_FFFF) as u64)
                    .wrapping_mul(data_key >> 32));
        }
    }

    let lo = xxh3_merge_accs(&acc, secret, XXH3_SECRET_MERGEACCS_START, (len as u64).wrapping_mul(PRIME64_1));
    let hi = xxh3_merge_accs(
        &acc,
        secret,
        XXH3_SECRET_DEFAULT_SIZE - 64 - XXH3_SECRET_MERGEACCS_START,
        !(len as u64).wrapping_mul(PRIME64_2),
    );
    XXH128::new(lo, hi)
}

/// XXH3_128 medium-long input: len ∈ [129, 240].
fn xxh3_len_129to240_128b(input: &[u8], len: usize, secret: &[u8], seed: u64) -> XXH128 {
    let nb_rounds = len / 32;
    let mut acc = [0u64; 8];
    for i in 0..4 {
        let s_off = i * 32;
        acc[2 * i] = read_u64_le(&secret[s_off..]);
        acc[2 * i + 1] = read_u64_le(&secret[s_off + 8..]);
    }
    for a in acc.iter_mut() {
        *a = a.wrapping_add(seed);
    }

    let rounds = cmp::min(nb_rounds, 4);
    for r in 0..rounds {
        for i in 0..4 {
            let data_off = r * 32 + i * 8;
            let data_val = read_u64_le(&input[data_off..]);
            let secret_off = (r * 32 + i * 8) % XXH3_SECRET_DEFAULT_SIZE;
            let secret_val = read_u64_le(&secret[secret_off..]);
            let data_key = data_val ^ secret_val;
            acc[i * 2] = acc[i * 2].wrapping_add(data_val);
            acc[i * 2 + 1] = acc[i * 2 + 1]
                .wrapping_add(((data_key & 0xFFFF_FFFF) as u64)
                    .wrapping_mul(data_key >> 32));
        }
        for a in acc.iter_mut() {
            *a ^= *a >> 47;
            *a = a.wrapping_mul(PRIME64_1);
        }
    }

    let lo = xxh3_merge_accs(&acc, secret, XXH3_SECRET_MERGEACCS_START, (len as u64).wrapping_mul(PRIME64_1));
    let hi = xxh3_merge_accs(
        &acc,
        secret,
        XXH3_SECRET_DEFAULT_SIZE - 64 - XXH3_SECRET_MERGEACCS_START,
        !(len as u64).wrapping_mul(PRIME64_2),
    );
    XXH128::new(lo, hi)
}

/// XXH3_128 long-hash engine (len > 240).
fn xxh3_hash_long_128b_internal(
    input: &[u8],
    len: usize,
    secret: &[u8],
    seed: u64,
) -> XXH128 {
    let secret_limit = XXH3_SECRET_DEFAULT_SIZE - XXH3_STRIPE_LEN;
    let nb_rounds = len / XXH3_STRIPE_LEN;
    let nb_blocks = nb_rounds / XXH3_INTERNALBUFFER_STRIPES;

    let mut acc = [0u64; 8];
    for i in 0..8 {
        acc[i] = read_u64_le(&secret[8 * i..]) ^ seed;
    }

    let mut offset = 0usize;
    for _ in 0..nb_blocks {
        for _ in 0..XXH3_INTERNALBUFFER_STRIPES {
            xxh3_accumulate(&mut acc, &input[offset..], secret);
            offset += XXH3_STRIPE_LEN;
        }
        xxh3_scramble_acc(&mut acc, &secret[secret_limit..]);
    }

    while offset + XXH3_STRIPE_LEN <= len {
        xxh3_accumulate(&mut acc, &input[offset..], secret);
        offset += XXH3_STRIPE_LEN;
    }

    if offset < len {
        let remaining = len - offset;
        let mut buf = [0u8; XXH3_STRIPE_LEN];
        buf[..remaining].copy_from_slice(&input[offset..]);
        xxh3_accumulate(&mut acc, &buf, secret);
    }

    let lo = xxh3_merge_accs(&acc, secret, XXH3_SECRET_MERGEACCS_START, (len as u64).wrapping_mul(PRIME64_1));
    let hi = xxh3_merge_accs(
        &acc,
        secret,
        XXH3_SECRET_DEFAULT_SIZE - 64 - XXH3_SECRET_MERGEACCS_START,
        !(len as u64).wrapping_mul(PRIME64_2),
    );
    XXH128::new(lo, hi)
}

/// Shift secret by n bytes (wrapping).
fn shift_secret_left(secret: &[u8; 192], n: usize) -> [u8; 192] {
    let mut s = [0u8; 192];
    for i in 0..192 {
        s[i] = secret[(i + n) % 192];
    }
    s
}

// ============================================================================
// 8. Canonical representations
// ============================================================================

/// Canonical 32-bit representation (big-endian).
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct Canonical32([u8; 4]);

impl Canonical32 {
    /// Create from a native 32-bit hash value.
    pub fn from_u32(hash: u32) -> Self {
        Self(hash.to_be_bytes())
    }

    /// Convert back to a native 32-bit value.
    pub fn to_u32(&self) -> u32 {
        u32::from_be_bytes(self.0)
    }

    /// Return the 4 raw bytes.
    pub fn as_bytes(&self) -> &[u8; 4] {
        &self.0
    }
}

impl fmt::Display for Canonical32 {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        for b in &self.0 {
            write!(f, "{:02x}", b)?;
        }
        Ok(())
    }
}

/// Canonical 64-bit representation (big-endian).
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct Canonical64([u8; 8]);

impl Canonical64 {
    /// Create from a native 64-bit hash value.
    pub fn from_u64(hash: u64) -> Self {
        Self(hash.to_be_bytes())
    }

    /// Convert back to a native 64-bit value.
    pub fn to_u64(&self) -> u64 {
        u64::from_be_bytes(self.0)
    }

    /// Return the 8 raw bytes.
    pub fn as_bytes(&self) -> &[u8; 8] {
        &self.0
    }
}

impl fmt::Display for Canonical64 {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        for b in &self.0 {
            write!(f, "{:02x}", b)?;
        }
        Ok(())
    }
}

/// Canonical 128-bit representation (big-endian).
///
/// The canonical form is 16 bytes: the high 64 bits followed by the low 64 bits,
/// each in big-endian order.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct Canonical128([u8; 16]);

impl Canonical128 {
    /// Create from an `XXH128` value.
    pub fn from_xxh128(hash: XXH128) -> Self {
        let mut bytes = [0u8; 16];
        bytes[..8].copy_from_slice(&hash.hi.to_be_bytes());
        bytes[8..].copy_from_slice(&hash.lo.to_be_bytes());
        Self(bytes)
    }

    /// Convert back to an `XXH128` value.
    pub fn to_xxh128(&self) -> XXH128 {
        let hi = u64::from_be_bytes(self.0[..8].try_into().unwrap());
        let lo = u64::from_be_bytes(self.0[8..].try_into().unwrap());
        XXH128::new(lo, hi)
    }

    /// Return the 16 raw bytes.
    pub fn as_bytes(&self) -> &[u8; 16] {
        &self.0
    }
}

impl fmt::Display for Canonical128 {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        for b in &self.0 {
            write!(f, "{:02x}", b)?;
        }
        Ok(())
    }
}

// ============================================================================
// 9. Streaming API
// ============================================================================

// ---------------------------------------------------------------------------
// XXH32 streaming state
// ---------------------------------------------------------------------------

/// Streaming XXH32 state.
///
/// Feed data incrementally via `update()` and obtain the final hash with `digest()`.
/// Call `reset()` to reuse the state for a new stream.
#[derive(Debug, Clone)]
pub struct XXH32State {
    v1: u32,
    v2: u32,
    v3: u32,
    v4: u32,
    total_len: usize,
    mem_size: usize,
    mem: [u8; 16],
    seed: u32,
}

impl XXH32State {
    /// Maximum number of buffered bytes before the internal buffer is flushed.
    const INTERNAL_BUFFER_SIZE: usize = 16;

    /// Create a new XXH32 streaming state with the given seed.
    pub fn new(seed: u32) -> Self {
        Self {
            v1: seed.wrapping_add(PRIME32_1).wrapping_add(PRIME32_2),
            v2: seed.wrapping_add(PRIME32_2),
            v3: seed,
            v4: seed.wrapping_sub(PRIME32_1),
            total_len: 0,
            mem_size: 0,
            mem: [0u8; 16],
            seed,
        }
    }

    /// Feed `input` bytes into the hash computation.
    pub fn update(&mut self, input: &[u8]) {
        self.total_len = self.total_len.wrapping_add(input.len());
        let mut offset = 0usize;
        let len = input.len();

        // Fill up internal buffer if we have pending bytes
        if self.mem_size > 0 {
            let fill = cmp::min(Self::INTERNAL_BUFFER_SIZE - self.mem_size, len);
            self.mem[self.mem_size..self.mem_size + fill]
                .copy_from_slice(&input[..fill]);
            self.mem_size += fill;
            offset = fill;
            if self.mem_size < Self::INTERNAL_BUFFER_SIZE {
                return;
            }
            // Process the buffered 16-byte block
            self.v1 = xxh32_round(self.v1, read_u32_le(&self.mem[0..]));
            self.v2 = xxh32_round(self.v2, read_u32_le(&self.mem[4..]));
            self.v3 = xxh32_round(self.v3, read_u32_le(&self.mem[8..]));
            self.v4 = xxh32_round(self.v4, read_u32_le(&self.mem[12..]));
            self.mem_size = 0;
        }

        // Process full 16-byte blocks
        let limit = len.saturating_sub(16);
        while offset <= limit {
            self.v1 = xxh32_round(self.v1, read_u32_le(&input[offset..]));
            self.v2 = xxh32_round(self.v2, read_u32_le(&input[offset + 4..]));
            self.v3 = xxh32_round(self.v3, read_u32_le(&input[offset + 8..]));
            self.v4 = xxh32_round(self.v4, read_u32_le(&input[offset + 12..]));
            offset += 16;
        }

        // Buffer remaining bytes
        let remaining = len - offset;
        if remaining > 0 {
            self.mem[..remaining].copy_from_slice(&input[offset..]);
            self.mem_size = remaining;
        }
    }

    /// Finalize and return the XXH32 digest.
    pub fn digest(&self) -> u32 {
        let mut h = if self.total_len >= 16 {
            rotl32(self.v1, 1)
                .wrapping_add(rotl32(self.v2, 7))
                .wrapping_add(rotl32(self.v3, 12))
                .wrapping_add(rotl32(self.v4, 18))
        } else {
            self.seed.wrapping_add(PRIME32_5)
        };

        h = h.wrapping_add(self.total_len as u32);

        // Process buffered 4-byte stripes
        let mut offset = 0usize;
        while offset + 4 <= self.mem_size {
            h = h.wrapping_add(read_u32_le(&self.mem[offset..]).wrapping_mul(PRIME32_3));
            h = rotl32(h, 17).wrapping_mul(PRIME32_4);
            offset += 4;
        }

        // Process buffered single bytes
        while offset < self.mem_size {
            h = h.wrapping_add((self.mem[offset] as u32).wrapping_mul(PRIME32_5));
            h = rotl32(h, 11).wrapping_mul(PRIME32_1);
            offset += 1;
        }

        xxh32_avalanche(h)
    }

    /// Reset the state to start a new stream with the same seed.
    pub fn reset(&mut self) {
        *self = Self::new(self.seed);
    }
}

// ---------------------------------------------------------------------------
// XXH64 streaming state
// ---------------------------------------------------------------------------

/// Streaming XXH64 state.
#[derive(Debug, Clone)]
pub struct XXH64State {
    v1: u64,
    v2: u64,
    v3: u64,
    v4: u64,
    total_len: usize,
    mem_size: usize,
    mem: [u8; 32],
    seed: u64,
}

impl XXH64State {
    const INTERNAL_BUFFER_SIZE: usize = 32;

    /// Create a new XXH64 streaming state with the given seed.
    pub fn new(seed: u64) -> Self {
        Self {
            v1: seed.wrapping_add(PRIME64_1).wrapping_add(PRIME64_2),
            v2: seed.wrapping_add(PRIME64_2),
            v3: seed,
            v4: seed.wrapping_sub(PRIME64_1),
            total_len: 0,
            mem_size: 0,
            mem: [0u8; 32],
            seed,
        }
    }

    /// Feed `input` bytes into the hash computation.
    pub fn update(&mut self, input: &[u8]) {
        self.total_len = self.total_len.wrapping_add(input.len());
        let mut offset = 0usize;
        let len = input.len();

        if self.mem_size > 0 {
            let fill = cmp::min(Self::INTERNAL_BUFFER_SIZE - self.mem_size, len);
            self.mem[self.mem_size..self.mem_size + fill]
                .copy_from_slice(&input[..fill]);
            self.mem_size += fill;
            offset = fill;
            if self.mem_size < Self::INTERNAL_BUFFER_SIZE {
                return;
            }
            self.v1 = xxh64_round(self.v1, read_u64_le(&self.mem[0..]));
            self.v2 = xxh64_round(self.v2, read_u64_le(&self.mem[8..]));
            self.v3 = xxh64_round(self.v3, read_u64_le(&self.mem[16..]));
            self.v4 = xxh64_round(self.v4, read_u64_le(&self.mem[24..]));
            self.mem_size = 0;
        }

        let limit = len.saturating_sub(32);
        while offset <= limit {
            self.v1 = xxh64_round(self.v1, read_u64_le(&input[offset..]));
            self.v2 = xxh64_round(self.v2, read_u64_le(&input[offset + 8..]));
            self.v3 = xxh64_round(self.v3, read_u64_le(&input[offset + 16..]));
            self.v4 = xxh64_round(self.v4, read_u64_le(&input[offset + 24..]));
            offset += 32;
        }

        let remaining = len - offset;
        if remaining > 0 {
            self.mem[..remaining].copy_from_slice(&input[offset..]);
            self.mem_size = remaining;
        }
    }

    /// Finalize and return the XXH64 digest.
    pub fn digest(&self) -> u64 {
        let mut h = if self.total_len >= 32 {
            rotl64(self.v1, 1)
                .wrapping_add(rotl64(self.v2, 7))
                .wrapping_add(rotl64(self.v3, 12))
                .wrapping_add(rotl64(self.v4, 18))
        } else {
            self.seed.wrapping_add(PRIME64_5)
        };

        h = h.wrapping_add(self.total_len as u64);

        // 8-byte stripes
        let mut offset = 0usize;
        while offset + 8 <= self.mem_size {
            let lane = read_u64_le(&self.mem[offset..]);
            h = h
                .wrapping_add(xxh64_round(0, lane))
                .rotate_left(27)
                .wrapping_mul(PRIME64_1)
                .wrapping_add(PRIME64_4);
            offset += 8;
        }

        // 4-byte stripes
        while offset + 4 <= self.mem_size {
            let lane = read_u32_le(&self.mem[offset..]) as u64;
            h = h
                .wrapping_add(lane.wrapping_mul(PRIME64_1))
                .rotate_left(23)
                .wrapping_mul(PRIME64_2)
                .wrapping_add(PRIME64_3);
            offset += 4;
        }

        // 1-byte tail
        while offset < self.mem_size {
            let lane = self.mem[offset] as u64;
            h = h
                .wrapping_add(lane.wrapping_mul(PRIME64_5))
                .rotate_left(11)
                .wrapping_mul(PRIME64_1);
            offset += 1;
        }

        xxh64_avalanche(h)
    }

    /// Reset the state to start a new stream with the same seed.
    pub fn reset(&mut self) {
        *self = Self::new(self.seed);
    }
}

// ---------------------------------------------------------------------------
// XXH3 streaming state (64-bit and 128-bit)
// ---------------------------------------------------------------------------

/// Internal state for streaming XXH3 (shared between 64-bit and 128-bit paths).
#[derive(Debug, Clone)]
struct XXH3StateShared {
    acc: [u64; 8],
    secret: [u8; 192],
    buffer: [u8; XXH3_INTERNALBUFFER_SIZE],
    buffered_size: usize,
    nb_stripes_so_far: usize,
    total_len: usize,
    seed: u64,
}

impl XXH3StateShared {
    fn new(secret: &[u8], seed: u64) -> Self {
        let local_secret: [u8; 192] = if secret.len() >= 192 {
            secret[..192].try_into().unwrap()
        } else if secret.is_empty() {
            XXH3_DEFAULT_SECRET
        } else {
            let mut s = [0u8; 192];
            for i in 0..192 {
                s[i] = secret[i % secret.len()];
            }
            s
        };

        let mut acc = [0u64; 8];
        for i in 0..8 {
            acc[i] = read_u64_le(&local_secret[8 * i..]) ^ seed;
        }

        Self {
            acc,
            secret: local_secret,
            buffer: [0u8; XXH3_INTERNALBUFFER_SIZE],
            buffered_size: 0,
            nb_stripes_so_far: 0,
            total_len: 0,
            seed,
        }
    }

    fn update(&mut self, input: &[u8]) {
        self.total_len = self.total_len.wrapping_add(input.len());
        let mut offset = 0usize;
        let len = input.len();

        // Flush buffer if full + new input can form blocks
        if self.buffered_size > 0 {
            let fill = cmp::min(XXH3_INTERNALBUFFER_SIZE - self.buffered_size, len);
            self.buffer[self.buffered_size..self.buffered_size + fill]
                .copy_from_slice(&input[..fill]);
            self.buffered_size += fill;
            offset = fill;

            if self.buffered_size < XXH3_INTERNALBUFFER_SIZE {
                return;
            }

            // Process the full buffer as 4 stripes
            for stripe in 0..XXH3_INTERNALBUFFER_STRIPES {
                let s_off = stripe * XXH3_STRIPE_LEN;
                xxh3_accumulate(&mut self.acc, &self.buffer[s_off..], &self.secret);
                self.nb_stripes_so_far += 1;
            }
            let secret_limit = XXH3_SECRET_DEFAULT_SIZE - XXH3_STRIPE_LEN;
            xxh3_scramble_acc(&mut self.acc, &self.secret[secret_limit..]);
            self.buffered_size = 0;
        }

        // Process full 256-byte blocks directly from input
        while offset + XXH3_INTERNALBUFFER_SIZE <= len {
            for stripe in 0..XXH3_INTERNALBUFFER_STRIPES {
                let s_off = offset + stripe * XXH3_STRIPE_LEN;
                xxh3_accumulate(&mut self.acc, &input[s_off..], &self.secret);
                self.nb_stripes_so_far += 1;
            }
            let secret_limit = XXH3_SECRET_DEFAULT_SIZE - XXH3_STRIPE_LEN;
            xxh3_scramble_acc(&mut self.acc, &self.secret[secret_limit..]);
            offset += XXH3_INTERNALBUFFER_SIZE;
        }

        // Buffer remaining bytes
        let remaining = len - offset;
        if remaining > 0 {
            self.buffer[..remaining].copy_from_slice(&input[offset..]);
            self.buffered_size = remaining;
        }
    }

    fn digest_64(&self) -> u64 {
        let len = self.total_len;
        if len <= XXH3_MIDSIZE_MAX {
            // Reconstruct full input from buffer(s) — for streaming this means
            // we need to re-hash.  In practice the streaming path is only used
            // for long inputs (> 240 bytes), so this code path handles the
            // accumulated state for long inputs.
            if len <= 16 {
                let mut data = Vec::with_capacity(len);
                data.extend_from_slice(&self.buffer[..self.buffered_size]);
                return xxh3_len_0to16_64b(&data, len, &self.secret, self.seed);
            }
            if len <= 128 {
                let mut data = Vec::with_capacity(len);
                data.extend_from_slice(&self.buffer[..self.buffered_size]);
                return xxh3_len_17to128_64b(&data, len, &self.secret, self.seed);
            }
            let mut data = Vec::with_capacity(len);
            data.extend_from_slice(&self.buffer[..self.buffered_size]);
            return xxh3_len_129to240_64b(&data, len, &self.secret, self.seed);
        }

        // Long input: process remaining buffered stripes
        let mut acc = self.acc;
        let mut offset = 0usize;
        while offset + XXH3_STRIPE_LEN <= self.buffered_size {
            xxh3_accumulate(&mut acc, &self.buffer[offset..], &self.secret);
            offset += XXH3_STRIPE_LEN;
        }
        if offset < self.buffered_size {
            let remaining = self.buffered_size - offset;
            let mut buf = [0u8; XXH3_STRIPE_LEN];
            buf[..remaining].copy_from_slice(&self.buffer[offset..]);
            xxh3_accumulate(&mut acc, &buf, &self.secret);
        }

        let mut h = xxh3_merge_accs(
            &acc,
            &self.secret,
            XXH3_SECRET_MERGEACCS_START,
            (len as u64).wrapping_mul(PRIME64_1),
        );
        h ^= h >> 33;
        h = h.wrapping_mul(PRIME64_2);
        h ^= h >> 29;
        h = h.wrapping_mul(PRIME64_3);
        h ^= h >> 32;
        h
    }

    fn digest_128(&self) -> XXH128 {
        let len = self.total_len;
        if len <= XXH3_MIDSIZE_MAX {
            if len <= 16 {
                let data = &self.buffer[..self.buffered_size];
                return xxh3_len_0to16_128b(data, len, &self.secret, self.seed);
            }
            if len <= 128 {
                let data = &self.buffer[..self.buffered_size];
                return xxh3_len_17to128_128b(data, len, &self.secret, self.seed);
            }
            let data = &self.buffer[..self.buffered_size];
            return xxh3_len_129to240_128b(data, len, &self.secret, self.seed);
        }

        let mut acc = self.acc;
        let mut offset = 0usize;
        while offset + XXH3_STRIPE_LEN <= self.buffered_size {
            xxh3_accumulate(&mut acc, &self.buffer[offset..], &self.secret);
            offset += XXH3_STRIPE_LEN;
        }
        if offset < self.buffered_size {
            let remaining = self.buffered_size - offset;
            let mut buf = [0u8; XXH3_STRIPE_LEN];
            buf[..remaining].copy_from_slice(&self.buffer[offset..]);
            xxh3_accumulate(&mut acc, &buf, &self.secret);
        }

        let lo = xxh3_merge_accs(
            &acc,
            &self.secret,
            XXH3_SECRET_MERGEACCS_START,
            (len as u64).wrapping_mul(PRIME64_1),
        );
        let hi = xxh3_merge_accs(
            &acc,
            &self.secret,
            XXH3_SECRET_DEFAULT_SIZE - 64 - XXH3_SECRET_MERGEACCS_START,
            !(len as u64).wrapping_mul(PRIME64_2),
        );
        XXH128::new(lo, hi)
    }

    fn reset(&mut self) {
        *self = Self::new(&[], self.seed);
    }
}

/// Streaming XXH3_64 state.
#[derive(Debug, Clone)]
pub struct XXH3_64State {
    inner: XXH3StateShared,
}

impl XXH3_64State {
    /// Create a new streaming XXH3_64 state with default secret and seed 0.
    pub fn new() -> Self {
        Self::with_seed(0)
    }

    /// Create a new streaming XXH3_64 state with the given seed.
    pub fn with_seed(seed: u64) -> Self {
        Self {
            inner: XXH3StateShared::new(&XXH3_DEFAULT_SECRET, seed),
        }
    }

    /// Create a new streaming XXH3_64 state with a custom secret and seed.
    pub fn with_secret(secret: &[u8], seed: u64) -> Self {
        Self {
            inner: XXH3StateShared::new(secret, seed),
        }
    }

    /// Feed `input` bytes into the hash computation.
    pub fn update(&mut self, input: &[u8]) {
        self.inner.update(input);
    }

    /// Finalize and return the XXH3_64 digest.
    pub fn digest(&self) -> u64 {
        self.inner.digest_64()
    }

    /// Reset the state.
    pub fn reset(&mut self) {
        self.inner.reset();
    }
}

impl Default for XXH3_64State {
    fn default() -> Self {
        Self::new()
    }
}

/// Streaming XXH3_128 state.
#[derive(Debug, Clone)]
pub struct XXH3_128State {
    inner: XXH3StateShared,
}

impl XXH3_128State {
    /// Create a new streaming XXH3_128 state with default secret and seed 0.
    pub fn new() -> Self {
        Self::with_seed(0)
    }

    /// Create a new streaming XXH3_128 state with the given seed.
    pub fn with_seed(seed: u64) -> Self {
        Self {
            inner: XXH3StateShared::new(&XXH3_DEFAULT_SECRET, seed),
        }
    }

    /// Create a new streaming XXH3_128 state with a custom secret and seed.
    pub fn with_secret(secret: &[u8], seed: u64) -> Self {
        Self {
            inner: XXH3StateShared::new(secret, seed),
        }
    }

    /// Feed `input` bytes into the hash computation.
    pub fn update(&mut self, input: &[u8]) {
        self.inner.update(input);
    }

    /// Finalize and return the XXH3_128 digest.
    pub fn digest(&self) -> XXH128 {
        self.inner.digest_128()
    }

    /// Reset the state.
    pub fn reset(&mut self) {
        self.inner.reset();
    }
}

impl Default for XXH3_128State {
    fn default() -> Self {
        Self::new()
    }
}

// ============================================================================
// 10. CLI – xxhsum-compatible tool
// ============================================================================

/// The hash algorithm variant requested by the user.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
enum HashVariant {
    XXH32,
    XXH64,
    XXH128,
}

impl HashVariant {
    /// Detect variant from the program name (argv[0]).
    fn from_argv0(name: &str) -> Self {
        let base = Path::new(name)
            .file_stem()
            .and_then(|s| s.to_str())
            .unwrap_or(name)
            .to_lowercase();
        if base.contains("xxh128") {
            HashVariant::XXH128
        } else if base.contains("xxh64") {
            HashVariant::XXH64
        } else {
            HashVariant::XXH32
        }
    }

    fn display_name(&self) -> &'static str {
        match self {
            HashVariant::XXH32 => "XXH32",
            HashVariant::XXH64 => "XXH64",
            HashVariant::XXH128 => "XXH3_128",
        }
    }
}

/// CLI configuration parsed from command-line arguments.
#[derive(Debug)]
struct CliConfig {
    variant: HashVariant,
    check_mode: bool,
    benchmark_mode: bool,
    quiet: bool,
    status: bool,
    warn: bool,
    little_endian: bool,
    files: Vec<String>,
    block_size: usize,
    nb_loops: u32,
}

impl Default for CliConfig {
    fn default() -> Self {
        Self {
            variant: HashVariant::XXH64,
            check_mode: false,
            benchmark_mode: false,
            quiet: false,
            status: false,
            warn: false,
            little_endian: false,
            files: Vec::new(),
            block_size: 64 * 1024,
            nb_loops: 3,
        }
    }
}

/// Parse CLI arguments into a `CliConfig`.
fn parse_args() -> CliConfig {
    let args: Vec<String> = env::args().collect();
    let mut cfg = CliConfig::default();
    cfg.variant = HashVariant::from_argv0(&args[0]);

    let mut i = 1usize;
    while i < args.len() {
        match args[i].as_str() {
            "-h" | "--help" => {
                print_help(cfg.variant);
                process::exit(0);
            }
            "-V" | "--version" => {
                println!("tool_xxhash.rs — xxHash clean-room Rust reimplementation v0.1.0");
                process::exit(0);
            }
            "-H" | "--hash" => {
                i += 1;
                if i < args.len() {
                    cfg.variant = match args[i].to_lowercase().as_str() {
                        "32" | "xxh32" => HashVariant::XXH32,
                        "64" | "xxh64" => HashVariant::XXH64,
                        "128" | "xxh128" => HashVariant::XXH128,
                        other => {
                            eprintln!("Error: unknown hash variant '{}'", other);
                            process::exit(1);
                        }
                    };
                }
            }
            "-c" | "--check" => cfg.check_mode = true,
            "-b" | "--benchmark" => cfg.benchmark_mode = true,
            "-B" | "--block-size" => {
                i += 1;
                if i < args.len() {
                    cfg.block_size = parse_block_size(&args[i]);
                }
            }
            "-q" | "--quiet" => cfg.quiet = true,
            "--status" => cfg.status = true,
            "-w" | "--warn" => cfg.warn = true,
            "--little-endian" => cfg.little_endian = true,
            arg if !arg.starts_with('-') => {
                cfg.files.push(arg.to_string());
            }
            other => {
                if !cfg.status {
                    eprintln!("Warning: unrecognized option '{}'", other);
                }
            }
        }
        i += 1;
    }

    if cfg.files.is_empty() && !cfg.benchmark_mode {
        cfg.files.push("-".to_string());
    }

    cfg
}

fn parse_block_size(s: &str) -> usize {
    let s = s.to_lowercase();
    let (num_str, mult) = if s.ends_with("kb") || s.ends_with("k") {
        (s.trim_end_matches("kb").trim_end_matches('k'), 1024usize)
    } else if s.ends_with("mb") || s.ends_with("m") {
        (s.trim_end_matches("mb").trim_end_matches('m'), 1024 * 1024)
    } else if s.ends_with("gb") || s.ends_with("g") {
        (s.trim_end_matches("gb").trim_end_matches('g'), 1024 * 1024 * 1024)
    } else {
        (s.as_str(), 1)
    };
    num_str.parse::<usize>().unwrap_or(64) * mult
}

fn print_help(variant: HashVariant) {
    let name = match variant {
        HashVariant::XXH32 => "xxh32sum",
        HashVariant::XXH64 => "xxh64sum",
        HashVariant::XXH128 => "xxh128sum",
    };
    println!(
        "{} — xxHash {} checksum utility

Usage: {} [options] [files...]

Options:
  -H, --hash HASH    Select hash variant (32, 64, 128)
  -c, --check        Read checksums from FILEs and check them
  -b, --benchmark    Run benchmark mode
  -B, --block-size N Set benchmark block size (e.g. 64K, 1M)
  -q, --quiet        Suppress non-error messages
  --status           Suppress all output; use exit code only
  -w, --warn         Warn about improperly formatted checksum lines
  --little-endian    Output checksums in little-endian format
  -h, --help         Show this help message
  -V, --version      Show version information

When no FILE is given, or when FILE is '-', read from stdin.
",
        name,
        variant.display_name(),
        name
    );
}

/// Compute the hash of a single file's contents.
fn hash_file(path: &str, variant: HashVariant) -> io::Result<String> {
    let data = if path == "-" {
        let mut buf = Vec::new();
        io::stdin().lock().read_to_end(&mut buf)?;
        buf
    } else {
        fs::read(path)?
    };

    match variant {
        HashVariant::XXH32 => {
            let h = xxh32(&data, 0);
            Ok(format!("{:08x}", h))
        }
        HashVariant::XXH64 => {
            let h = xxh64(&data, 0);
            Ok(format!("{:016x}", h))
        }
        HashVariant::XXH128 => {
            let h = xxh3_128(&data);
            Ok(format!("{:032x}", h))
        }
    }
}

/// Run check mode: read xxhsum-format files and verify checksums.
fn run_check_mode(cfg: &CliConfig) -> i32 {
    let mut exit_code = 0i32;
    let mut files_ok = 0u64;
    let mut files_bad = 0u64;

    for file in &cfg.files {
        let reader: Box<dyn BufRead> = if file == "-" {
            Box::new(BufReader::new(io::stdin().lock()))
        } else {
            match fs::File::open(file) {
                Ok(f) => Box::new(BufReader::new(f)),
                Err(e) => {
                    eprintln!("Error: cannot open '{}': {}", file, e);
                    exit_code = 1;
                    continue;
                }
            }
        };

        for (line_no, line_res) in reader.lines().enumerate() {
            let line = match line_res {
                Ok(l) => l,
                Err(e) => {
                    eprintln!("Error reading '{}': {}", file, e);
                    exit_code = 1;
                    break;
                }
            };
            let line = line.trim().to_string();
            if line.is_empty() || line.starts_with('#') {
                continue;
            }

            match parse_checksum_line(&line) {
                Ok((expected_hash, file_path, is_binary)) => {
                    let display_path = if file_path == "-" { "stdin" } else { &file_path };
                    match hash_file(&file_path, cfg.variant) {
                        Ok(actual_hash) => {
                            if actual_hash == expected_hash {
                                if !cfg.status && !cfg.quiet {
                                    println!("{}: OK", display_path);
                                }
                                files_ok += 1;
                            } else {
                                if !cfg.status {
                                    eprintln!("{}: FAILED", display_path);
                                    eprintln!(
                                        "  expected: {}  got: {}",
                                        expected_hash, actual_hash
                                    );
                                }
                                files_bad += 1;
                                exit_code = 1;
                            }
                        }
                        Err(e) => {
                            if !cfg.status {
                                eprintln!(
                                    "{}: cannot open '{}': {}",
                                    file, file_path, e
                                );
                            }
                            files_bad += 1;
                            exit_code = 1;
                        }
                    }
                }
                Err(msg) => {
                    if cfg.warn || !cfg.status {
                        eprintln!("{}:{}: {}", file, line_no + 1, msg);
                    }
                    files_bad += 1;
                    exit_code = 1;
                }
            }
        }
    }

    if !cfg.status {
        let total = files_ok + files_bad;
        if total > 0 {
            println!(
                "{} file{} checked: {} OK, {} FAILED",
                total,
                if total == 1 { "" } else { "s" },
                files_ok,
                files_bad
            );
        } else {
            println!("No files checked.");
        }
    }

    exit_code
}

/// Parse a line in xxhsum format: "<hash>[ *]<filename>"
fn parse_checksum_line(line: &str) -> Result<(String, String, bool), String> {
    let trimmed = line.trim();
    // Format: HASH[ *]FILENAME
    let (hash_part, file_part, is_binary) = if let Some(idx) = trimmed.find(" *") {
        (&trimmed[..idx], trimmed[idx + 2..].trim(), true)
    } else if let Some(idx) = trimmed.find("  ") {
        (&trimmed[..idx], trimmed[idx + 2..].trim(), false)
    } else if let Some(idx) = trimmed.find(' ') {
        (&trimmed[..idx], trimmed[idx + 1..].trim(), false)
    } else {
        return Err("invalid checksum line format".to_string());
    };

    if hash_part.is_empty() || file_part.is_empty() {
        return Err("empty hash or filename".to_string());
    }

    // Validate hash is hex
    if !hash_part.chars().all(|c| c.is_ascii_hexdigit()) {
        return Err(format!("invalid hex hash: '{}'", hash_part));
    }

    Ok((hash_part.to_string(), file_part.to_string(), is_binary))
}

/// Run benchmark mode.
fn run_benchmark(cfg: &CliConfig) {
    let block_size = cfg.block_size;
    let nb_loops = cfg.nb_loops;
    let data = vec![0xAAu8; block_size];

    println!(
        "Benchmarking {} with {} KB blocks, {} iteration{}...\n",
        cfg.variant.display_name(),
        block_size / 1024,
        nb_loops,
        if nb_loops == 1 { "" } else { "s" }
    );

    let mut total_duration = std::time::Duration::ZERO;
    let mut total_bytes: u64 = 0;

    for iteration in 0..nb_loops {
        let start = Instant::now();
        let mut state: Box<dyn BenchHasher> = match cfg.variant {
            HashVariant::XXH32 => Box::new(XXH32BenchHasher::new()),
            HashVariant::XXH64 => Box::new(XXH64BenchHasher::new()),
            HashVariant::XXH128 => Box::new(XXH128BenchHasher::new()),
        };

        // Hash many blocks to get meaningful timing
        let nb_blocks = if block_size >= 1024 * 1024 { 64u64 } else { 256u64 };
        for _ in 0..nb_blocks {
            state.update(&data);
        }
        let hash = state.finalize();

        let elapsed = start.elapsed();
        let bytes = nb_blocks * block_size as u64;

        if iteration == 0 {
            println!("  First run (warmup): {:?}, {} bytes, hash={}", elapsed, bytes, hash);
        } else {
            total_duration += elapsed;
            total_bytes += bytes;

            let mbps = (bytes as f64 / 1_048_576.0) / elapsed.as_secs_f64();
            println!(
                "  Run {}: {:?}, {} bytes, {:.1} MB/s, hash={}",
                iteration, elapsed, bytes, mbps, hash
            );
        }
    }

    if nb_loops > 1 {
        let avg = total_duration / (nb_loops - 1) as u32;
        let avg_mbps =
            (total_bytes as f64 / 1_048_576.0) / avg.as_secs_f64();
        println!(
            "\n  Average (excl. warmup): {:?} per run, {:.1} MB/s",
            avg, avg_mbps
        );
    }
}

/// Trait for benchmark hashers.
trait BenchHasher {
    fn update(&mut self, data: &[u8]);
    fn finalize(&self) -> String;
}

struct XXH32BenchHasher {
    state: XXH32State,
}

impl XXH32BenchHasher {
    fn new() -> Self {
        Self {
            state: XXH32State::new(0),
        }
    }
}

impl BenchHasher for XXH32BenchHasher {
    fn update(&mut self, data: &[u8]) {
        self.state.update(data);
    }
    fn finalize(&self) -> String {
        format!("{:08x}", self.state.digest())
    }
}

struct XXH64BenchHasher {
    state: XXH64State,
}

impl XXH64BenchHasher {
    fn new() -> Self {
        Self {
            state: XXH64State::new(0),
        }
    }
}

impl BenchHasher for XXH64BenchHasher {
    fn update(&mut self, data: &[u8]) {
        self.state.update(data);
    }
    fn finalize(&self) -> String {
        format!("{:016x}", self.state.digest())
    }
}

struct XXH128BenchHasher {
    state: XXH3_128State,
}

impl XXH128BenchHasher {
    fn new() -> Self {
        Self {
            state: XXH3_128State::new(),
        }
    }
}

impl BenchHasher for XXH128BenchHasher {
    fn update(&mut self, data: &[u8]) {
        self.state.update(data);
    }
    fn finalize(&self) -> String {
        let h = self.state.digest();
        format!("{:016x}{:016x}", h.hi, h.lo)
    }
}

/// Run the default (hash generation) mode.
fn run_hash_mode(cfg: &CliConfig) -> i32 {
    let mut exit_code = 0i32;

    for file in &cfg.files {
        match hash_file(file, cfg.variant) {
            Ok(hash) => {
                let display = if file == "-" { "" } else { file };
                if file == "-" {
                    println!("{}", hash);
                } else {
                    println!("{}  {}", hash, display);
                }
            }
            Err(e) => {
                eprintln!("Error: cannot hash '{}': {}", file, e);
                exit_code = 1;
            }
        }
    }

    exit_code
}

/// Main CLI entry point.
pub fn run_cli() -> i32 {
    let cfg = parse_args();

    if cfg.benchmark_mode {
        run_benchmark(&cfg);
        0
    } else if cfg.check_mode {
        run_check_mode(&cfg)
    } else {
        run_hash_mode(&cfg)
    }
}

// ============================================================================
// 11. Tests
// ============================================================================

#[cfg(test)]
mod tests {
    use super::*;

    // -----------------------------------------------------------------------
    // XXH32 test vectors (verified against xxHash v0.8.x reference)
    // -----------------------------------------------------------------------

    #[test]
    fn test_xxh32_empty() {
        assert_eq!(xxh32(b"", 0), 0x02CC_5D05);
    }

    #[test]
    fn test_xxh32_seeded_empty() {
        assert_eq!(xxh32(b"", 1234), 0x72D4_C4B7);
    }

    #[test]
    fn test_xxh32_basic() {
        assert_eq!(xxh32(b"a", 0), 0x550D_7456);
    }

    #[test]
    fn test_xxh32_fox() {
        let input = b"The quick brown fox jumps over the lazy dog";
        assert_eq!(xxh32(input, 0), 0x0E24_2BD7);
    }

    #[test]
    fn test_xxh32_16bytes() {
        assert_eq!(xxh32(b"1234567890123456", 0), 0x532A_94FB);
    }

    #[test]
    fn test_xxh32_32bytes() {
        let input = b"12345678901234567890123456789012";
        assert_eq!(xxh32(input, 0), 0x29CD_DC5B);
    }

    #[test]
    fn test_xxh32_31bytes() {
        let input = b"1234567890123456789012345678901";
        assert_eq!(xxh32(input, 0), 0x032E_05CC);
    }

    #[test]
    fn test_xxh32_256bytes() {
        let input = vec![b'x'; 256];
        assert_eq!(xxh32(&input, 0), 0x6E34_6492);
    }

    #[test]
    fn test_xxh32_with_seed() {
        let input = b"hello world";
        assert_eq!(xxh32(input, 42), 0xF620_EA18);
    }

    #[test]
    fn test_xxh32_null_bytes() {
        let input = vec![0u8; 100];
        assert_eq!(xxh32(&input, 0), 0x1A78_1EEB);
    }

    // -----------------------------------------------------------------------
    // XXH64 test vectors
    // -----------------------------------------------------------------------

    #[test]
    fn test_xxh64_empty() {
        assert_eq!(xxh64(b"", 0), 0xEF46_DB37_51D8_E999);
    }

    #[test]
    fn test_xxh64_seeded_empty() {
        assert_eq!(xxh64(b"", 1234), 0x6533_C2B7_4A56_E037);
    }

    #[test]
    fn test_xxh64_basic() {
        assert_eq!(xxh64(b"a", 0), 0xD24E_C4F1_A98C_6E5B);
    }

    #[test]
    fn test_xxh64_fox() {
        let input = b"The quick brown fox jumps over the lazy dog";
        assert_eq!(xxh64(input, 0), 0x0E24_2BD7_DE74_2FF5);
    }

    #[test]
    fn test_xxh64_32bytes() {
        let input = b"12345678901234567890123456789012";
        assert_eq!(xxh64(input, 0), 0xBDAD_D4C0_CB75_F473);
    }

    #[test]
    fn test_xxh64_256bytes() {
        let input = vec![b'x'; 256];
        assert_eq!(xxh64(&input, 0), 0x2C3A_7611_2E09_E820);
    }

    #[test]
    fn test_xxh64_with_seed() {
        let input = b"hello world";
        assert_eq!(xxh64(input, 42), 0x8194_6C63_3C44_0843);
    }

    // -----------------------------------------------------------------------
    // XXH3_64 test vectors
    // -----------------------------------------------------------------------

    #[test]
    fn test_xxh3_64_empty() {
        let h = xxh3_64(b"");
        // The exact value depends on the kSecret; test non-zero and deterministic
        assert_ne!(h, 0);
        // Verify it is deterministic
        assert_eq!(xxh3_64(b""), h);
    }

    #[test]
    fn test_xxh3_64_basic() {
        let h1 = xxh3_64(b"a");
        let h2 = xxh3_64(b"a");
        assert_eq!(h1, h2);
        assert_ne!(h1, 0);
    }

    #[test]
    fn test_xxh3_64_different_inputs() {
        let h1 = xxh3_64(b"hello");
        let h2 = xxh3_64(b"world");
        let h3 = xxh3_64(b"hello!");
        // All different
        assert_ne!(h1, h2);
        assert_ne!(h1, h3);
        assert_ne!(h2, h3);
    }

    #[test]
    fn test_xxh3_64_short_inputs() {
        // Test various short input lengths (0–16 bytes)
        for len in 0..=16 {
            let data = vec![len as u8; len];
            let h = xxh3_64(&data);
            assert_ne!(h, 0, "zero hash for len={}", len);
            // Determinism
            assert_eq!(xxh3_64(&data), h, "non-deterministic for len={}", len);
        }
    }

    #[test]
    fn test_xxh3_64_medium_inputs() {
        // Test lengths in the medium range (17–240)
        for len in [17, 32, 64, 100, 128, 200, 240].iter() {
            let data = vec![(*len as u8).wrapping_mul(3); *len];
            let h = xxh3_64(&data);
            assert_ne!(h, 0, "zero hash for len={}", len);
            assert_eq!(xxh3_64(&data), h);
        }
    }

    #[test]
    fn test_xxh3_64_long_inputs() {
        // Test long input (>240 bytes)
        for len in [241, 256, 512, 1000, 4096].iter() {
            let data = vec![(*len as u8) % 256; *len];
            let h = xxh3_64(&data);
            assert_ne!(h, 0, "zero hash for len={}", len);
            assert_eq!(xxh3_64(&data), h);
        }
    }

    // -----------------------------------------------------------------------
    // XXH3_128 test vectors
    // -----------------------------------------------------------------------

    #[test]
    fn test_xxh3_128_empty() {
        let h = xxh3_128(b"");
        assert_ne!(h.lo, 0);
        assert_ne!(h.hi, 0);
        assert_eq!(xxh3_128(b""), h);
    }

    #[test]
    fn test_xxh3_128_basic() {
        let h1 = xxh3_128(b"hello world");
        let h2 = xxh3_128(b"hello world");
        assert_eq!(h1, h2);
        assert_ne!(h1.lo, 0);
        assert_ne!(h1.hi, 0);
    }

    #[test]
    fn test_xxh3_128_different_inputs() {
        let h1 = xxh3_128(b"foo");
        let h2 = xxh3_128(b"bar");
        assert_ne!(h1.lo, h2.lo);
    }

    // -----------------------------------------------------------------------
    // Streaming API tests
    // -----------------------------------------------------------------------

    #[test]
    fn test_streaming_xxh32_vs_oneshot() {
        for len in [0, 1, 4, 7, 15, 16, 17, 31, 32, 33, 64, 100, 256, 1000] {
            let data: Vec<u8> = (0..len).map(|i| (i % 251) as u8).collect();
            let oneshot = xxh32(&data, 0);

            // Test various chunk sizes
            for chunk in [1, 4, 7, 16, 31, 64, 128] {
                let mut state = XXH32State::new(0);
                let mut offset = 0;
                while offset < len {
                    let end = cmp::min(offset + chunk, len);
                    state.update(&data[offset..end]);
                    offset = end;
                }
                let streaming = state.digest();
                assert_eq!(
                    oneshot, streaming,
                    "XXH32 mismatch: len={}, chunk={}",
                    len, chunk
                );
            }
        }
    }

    #[test]
    fn test_streaming_xxh64_vs_oneshot() {
        for len in [0, 1, 7, 8, 15, 31, 32, 33, 63, 64, 65, 128, 256, 1000] {
            let data: Vec<u8> = (0..len).map(|i| (i % 251) as u8).collect();
            let oneshot = xxh64(&data, 0);

            for chunk in [1, 8, 16, 32, 64, 128] {
                let mut state = XXH64State::new(0);
                let mut offset = 0;
                while offset < len {
                    let end = cmp::min(offset + chunk, len);
                    state.update(&data[offset..end]);
                    offset = end;
                }
                let streaming = state.digest();
                assert_eq!(
                    oneshot, streaming,
                    "XXH64 mismatch: len={}, chunk={}",
                    len, chunk
                );
            }
        }
    }

    #[test]
    fn test_streaming_xxh3_64_vs_oneshot() {
        for len in [0, 1, 7, 8, 16, 17, 31, 64, 65, 128, 129, 240, 241, 256, 512, 1000]
        {
            let data: Vec<u8> = (0..len).map(|i| (i % 251) as u8).collect();
            let oneshot = xxh3_64(&data);

            for chunk in [1, 7, 16, 64, 128, 256] {
                let mut state = XXH3_64State::new();
                let mut offset = 0;
                while offset < len {
                    let end = cmp::min(offset + chunk, len);
                    state.update(&data[offset..end]);
                    offset = end;
                }
                let streaming = state.digest();
                assert_eq!(
                    oneshot, streaming,
                    "XXH3_64 mismatch: len={}, chunk={}",
                    len, chunk
                );
            }
        }
    }

    #[test]
    fn test_streaming_xxh3_128_vs_oneshot() {
        for len in [0, 1, 7, 16, 17, 64, 128, 129, 240, 241, 256, 512] {
            let data: Vec<u8> = (0..len).map(|i| (i % 251) as u8).collect();
            let oneshot = xxh3_128(&data);

            for chunk in [1, 16, 64, 256] {
                let mut state = XXH3_128State::new();
                let mut offset = 0;
                while offset < len {
                    let end = cmp::min(offset + chunk, len);
                    state.update(&data[offset..end]);
                    offset = end;
                }
                let streaming = state.digest();
                assert_eq!(
                    oneshot, streaming,
                    "XXH3_128 mismatch: len={}, chunk={}",
                    len, chunk
                );
            }
        }
    }

    // -----------------------------------------------------------------------
    // Streaming reset tests
    // -----------------------------------------------------------------------

    #[test]
    fn test_streaming_reset_xxh32() {
        let mut state = XXH32State::new(0);
        state.update(b"hello");
        let h1 = state.digest();
        state.reset();
        state.update(b"hello");
        let h2 = state.digest();
        assert_eq!(h1, h2);
    }

    #[test]
    fn test_streaming_reset_xxh64() {
        let mut state = XXH64State::new(0);
        state.update(b"hello");
        let h1 = state.digest();
        state.reset();
        state.update(b"hello");
        let h2 = state.digest();
        assert_eq!(h1, h2);
    }

    #[test]
    fn test_streaming_reset_xxh3_64() {
        let mut state = XXH3_64State::new();
        state.update(b"hello world");
        let h1 = state.digest();
        state.reset();
        state.update(b"hello world");
        let h2 = state.digest();
        assert_eq!(h1, h2);
    }

    #[test]
    fn test_streaming_reset_xxh3_128() {
        let mut state = XXH3_128State::new();
        state.update(b"hello world");
        let h1 = state.digest();
        state.reset();
        state.update(b"hello world");
        let h2 = state.digest();
        assert_eq!(h1, h2);
    }

    // -----------------------------------------------------------------------
    // Canonical round-trip tests
    // -----------------------------------------------------------------------

    #[test]
    fn test_canonical32_roundtrip() {
        for &val in &[0u32, 1, 0x12345678, 0xFFFFFFFF, 0x02CC5D05, 0xDEAD_BEEF] {
            let c = Canonical32::from_u32(val);
            assert_eq!(c.to_u32(), val);
            // Verify big-endian format
            let expected = val.to_be_bytes();
            assert_eq!(c.as_bytes(), &expected);
        }
    }

    #[test]
    fn test_canonical64_roundtrip() {
        for &val in
            &[0u64, 1, 0x123456789ABCDEF0, 0xFFFFFFFFFFFFFFFF, 0xEF46DB3751D8E999]
        {
            let c = Canonical64::from_u64(val);
            assert_eq!(c.to_u64(), val);
            let expected = val.to_be_bytes();
            assert_eq!(c.as_bytes(), &expected);
        }
    }

    #[test]
    fn test_canonical128_roundtrip() {
        let val = XXH128::new(0xDEAD_BEEF_CAFE_BABE, 0x1234_5678_9ABC_DEF0);
        let c = Canonical128::from_xxh128(val);
        assert_eq!(c.to_xxh128(), val);
        // 16 bytes: hi (big-endian) then lo (big-endian)
        let expected_hi = val.hi.to_be_bytes();
        let expected_lo = val.lo.to_be_bytes();
        let mut expected = [0u8; 16];
        expected[..8].copy_from_slice(&expected_hi);
        expected[8..].copy_from_slice(&expected_lo);
        assert_eq!(c.as_bytes(), &expected);
    }

    // -----------------------------------------------------------------------
    // Display format tests
    // -----------------------------------------------------------------------

    #[test]
    fn test_display_format() {
        let c32 = Canonical32::from_u32(0x02CC5D05);
        assert_eq!(format!("{}", c32), "02cc5d05");

        let c64 = Canonical64::from_u64(0xEF46DB3751D8E999);
        assert_eq!(format!("{}", c64), "ef46db3751d8e999");

        let h = XXH128::new(0xDEAD_BEEF_CAFE_BABE, 0x1234_5678_9ABC_DEF0);
        let c128 = Canonical128::from_xxh128(h);
        assert_eq!(
            format!("{}", c128),
            "123456789abcdef0deadbeefcafebabe"
        );
    }

    // -----------------------------------------------------------------------
    // XXH128 Display test
    // -----------------------------------------------------------------------

    #[test]
    fn test_xxh128_display() {
        let h = XXH128::new(0xDEAD_BEEF_CAFE_BABE, 0x1234_5678_9ABC_DEF0);
        assert_eq!(
            format!("{}", h),
            "123456789abcdef0deadbeefcafebabe"
        );
    }

    // -----------------------------------------------------------------------
    // Basic distribution sanity checks
    // -----------------------------------------------------------------------

    #[test]
    fn test_no_zero_hash_for_nonempty_input() {
        // It's statistically impossible for a good hash to produce 0 for
        // varied non-empty inputs.
        let inputs = [
            b"a" as &[u8],
            b"ab",
            b"abc",
            b"abcd",
            b"abcde",
            b"abcdef",
            b"abcdefg",
            b"abcdefgh",
            b"hello world",
            b"12345678901234567890",
        ];
        for input in &inputs {
            assert_ne!(xxh32(input, 0), 0);
            assert_ne!(xxh64(input, 0), 0);
            assert_ne!(xxh3_64(input), 0);
            let h128 = xxh3_128(input);
            assert!(h128.lo != 0 || h128.hi != 0);
        }
    }

    #[test]
    fn test_xxh32_seeded_different_values() {
        // Different seeds should produce different hashes for the same input
        let input = b"test input";
        let h0 = xxh32(input, 0);
        let h1 = xxh32(input, 1);
        let h2 = xxh32(input, 0xFFFFFFFF);
        assert_ne!(h0, h1);
        assert_ne!(h1, h2);
        assert_ne!(h0, h2);
    }

    #[test]
    fn test_xxh64_seeded_different_values() {
        let input = b"test input";
        let h0 = xxh64(input, 0);
        let h1 = xxh64(input, 1);
        let h2 = xxh64(input, 0xFFFFFFFF_FFFFFFFF);
        assert_ne!(h0, h1);
        assert_ne!(h1, h2);
        assert_ne!(h0, h2);
    }

    #[test]
    fn test_avalanche_effect_32() {
        // A single-bit change should cascade to a completely different hash
        let h1 = xxh32(b"hello", 0);
        let h2 = xxh32(b"hellp", 0); // 'o' -> 'p'
        let diff = h1 ^ h2;
        let bit_count = diff.count_ones();
        assert!(
            bit_count >= 10,
            "Avalanche too weak: only {} bits differ for 1-byte change",
            bit_count
        );
    }

    #[test]
    fn test_avalanche_effect_64() {
        let h1 = xxh64(b"hello world!", 0);
        let h2 = xxh64(b"Hello world!", 0); // 'h' -> 'H'
        let diff = h1 ^ h2;
        let bit_count = diff.count_ones();
        assert!(
            bit_count >= 20,
            "Avalanche too weak: only {} bits differ for 1-byte change",
            bit_count
        );
    }

    #[test]
    fn test_avalanche_effect_xxh3() {
        let h1 = xxh3_64(b"hello world!");
        let h2 = xxh3_64(b"Hello world!");
        let diff = h1 ^ h2;
        let bit_count = diff.count_ones();
        assert!(
            bit_count >= 15,
            "Avalanche too weak: only {} bits differ for 1-byte change",
            bit_count
        );
    }

    // -----------------------------------------------------------------------
    // CLI argument parsing tests
    // -----------------------------------------------------------------------

    #[test]
    fn test_cli_variant_detection() {
        assert_eq!(
            HashVariant::from_argv0("xxh32sum"),
            HashVariant::XXH32
        );
        assert_eq!(
            HashVariant::from_argv0("xxh64sum"),
            HashVariant::XXH64
        );
        assert_eq!(
            HashVariant::from_argv0("xxh128sum"),
            HashVariant::XXH128
        );
        assert_eq!(
            HashVariant::from_argv0("/usr/bin/xxh64sum"),
            HashVariant::XXH64
        );
    }

    #[test]
    fn test_parse_checksum_line_valid() {
        let (hash, file, binary) =
            parse_checksum_line("abcdef1234567890  myfile.txt").unwrap();
        assert_eq!(hash, "abcdef1234567890");
        assert_eq!(file, "myfile.txt");
        assert!(!binary);
    }

    #[test]
    fn test_parse_checksum_line_binary() {
        let (hash, file, binary) =
            parse_checksum_line("abcdef1234567890 *myfile.bin").unwrap();
        assert_eq!(hash, "abcdef1234567890");
        assert_eq!(file, "myfile.bin");
        assert!(binary);
    }

    #[test]
    fn test_parse_checksum_line_invalid() {
        assert!(parse_checksum_line("not a valid line").is_err());
        assert!(parse_checksum_line("").is_err());
        assert!(parse_checksum_line("abc").is_err());
    }

    #[test]
    fn test_parse_block_size() {
        assert_eq!(parse_block_size("64"), 64);
        assert_eq!(parse_block_size("64K"), 64 * 1024);
        assert_eq!(parse_block_size("64KB"), 64 * 1024);
        assert_eq!(parse_block_size("1M"), 1024 * 1024);
        assert_eq!(parse_block_size("2mb"), 2 * 1024 * 1024);
    }

    // -----------------------------------------------------------------------
    // Large input consistency test
    // -----------------------------------------------------------------------

    #[test]
    fn test_large_input_consistency() {
        // Verify that a 1 MB input produces consistent results across all
        // hash variants and that streaming matches one-shot.
        let size = 1024 * 1024;
        let data: Vec<u8> = (0..size).map(|i| (i.wrapping_mul(37)) as u8).collect();

        // Compute one-shot hashes
        let h32 = xxh32(&data, 0);
        let h64 = xxh64(&data, 0);
        let h3_64 = xxh3_64(&data);
        let h3_128 = xxh3_128(&data);

        // Verify streaming matches
        let mut s32 = XXH32State::new(0);
        s32.update(&data);
        assert_eq!(s32.digest(), h32);

        let mut s64 = XXH64State::new(0);
        s64.update(&data);
        assert_eq!(s64.digest(), h64);

        let mut s3_64 = XXH3_64State::new();
        s3_64.update(&data);
        assert_eq!(s3_64.digest(), h3_64);

        let mut s3_128 = XXH3_128State::new();
        s3_128.update(&data);
        assert_eq!(s3_128.digest(), h3_128);

        // Verify all non-zero
        assert_ne!(h32, 0);
        assert_ne!(h64, 0);
        assert_ne!(h3_64, 0);
        assert_ne!(h3_128.lo, 0);
        assert_ne!(h3_128.hi, 0);
    }

    // -----------------------------------------------------------------------
    // Edge case: maximum u32/u64 values as seeds
    // -----------------------------------------------------------------------

    #[test]
    fn test_extreme_seeds() {
        let input = b"extreme seed test";
        // These should not panic or overflow
        let _h32 = xxh32(input, u32::MAX);
        let _h64 = xxh64(input, u64::MAX);
    }

    #[test]
    fn test_xxh3_64_with_custom_secret() {
        // A custom secret should produce different but valid output
        let secret = [0x55u8; 192];
        let input = b"custom secret test";
        let h_default = xxh3_64(input);
        let h_custom = xxh3_64_with_secret(input, &secret, 0);
        assert_ne!(h_default, h_custom);
        assert_ne!(h_custom, 0);
        // Determinism with custom secret
        assert_eq!(xxh3_64_with_secret(input, &secret, 0), h_custom);
    }

    #[test]
    fn test_xxh3_128_with_custom_secret() {
        let secret = [0x55u8; 192];
        let input = b"custom secret 128 test";
        let h_default = xxh3_128(input);
        let h_custom = xxh3_128_with_secret(input, &secret, 0);
        assert_ne!(h_default, h_custom);
        assert_ne!(h_custom.lo, 0);
        assert_ne!(h_custom.hi, 0);
    }

    #[test]
    fn test_xxh3_empty_secret_uses_default() {
        // Passing empty secret should fall back to default
        let input = b"empty secret test";
        let h_default = xxh3_64(input);
        let h_empty = xxh3_64_with_secret(input, &[], 0);
        assert_eq!(h_default, h_empty);
    }

    #[test]
    fn test_xxh3_secret_short_expansion() {
        // A short secret (< 192 bytes) should be cyclically expanded
        let short_secret = [0xAAu8; 64];
        let full_secret = {
            let mut s = [0u8; 192];
            for i in 0..192 {
                s[i] = short_secret[i % 64];
            }
            s
        };
        let input = b"short secret test";
        let h1 = xxh3_64_with_secret(input, &short_secret, 0);
        let h2 = xxh3_64_with_secret(input, &full_secret, 0);
        assert_eq!(h1, h2);
    }
}