pub fn from_lsb0_bytes(offset: u32, bytes: &[u8]) -> RoaringBitmap

use roaring::RoaringBitmap;

let bytes = [0b00000101, 0b00000010, 0b00000000, 0b10000000];
//             ^^^^^^^^    ^^^^^^^^    ^^^^^^^^    ^^^^^^^^
//             76543210          98
let rb = RoaringBitmap::from_lsb0_bytes(0, &bytes);
assert!(rb.contains(0));
assert!(!rb.contains(1));
assert!(rb.contains(2));
assert!(rb.contains(9));
assert!(rb.contains(31));

let rb = RoaringBitmap::from_lsb0_bytes(8, &bytes);
assert!(rb.contains(8));
assert!(!rb.contains(9));
assert!(rb.contains(10));
assert!(rb.contains(17));
assert!(rb.contains(39));

use std::arch::x86_64::*;

#[target_feature(enable = "avx2")]
unsafe fn compare_u8_avx2(a: &[u8], b: &[u8]) -> u32 {
    assert!(
        a.len() == 32 && b.len() == 32,
        "Inputs must have a length of 32."
    );

    // Load the data into 256-bit AVX2 registers
    let a_vec = _mm256_loadu_si256(a.as_ptr() as *const __m256i);
    let b_vec = _mm256_loadu_si256(b.as_ptr() as *const __m256i);

    // Perform comparison (a == b)
    let cmp_result = _mm256_cmpeq_epi8(a_vec, b_vec);

    // Extract the comparison result as a bitmask
    let mask = _mm256_movemask_epi8(cmp_result);

    mask as u32
}

fn main() {
    let a: [u8; 32] = [
        1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,
        26, 27, 28, 29, 30, 31, 32,
    ];
    let b: [u8; 32] = [
        1, 0, 3, 4, 5, 6, 7, 8, 0, 10, 11, 12, 13, 0, 15, 16, 0, 18, 19, 20, 21, 0, 23, 24, 0, 26,
        27, 0, 29, 0, 31, 32,
    ];

    let mask = unsafe {
        compare_u8_avx2(&a, &b)
    };
    println!("Bitmask: {:#034b}", mask);
    // Bitmask: 0b11010110110111101101111011111101
    print!("Bitmask (little endian u8): ");
    for b in mask.to_le_bytes() {
        print!("{:08b} ", b);
    }
    println!();
    // Bitmask (little endian u8): 11111101 11011110 11011110 11010110 
    
    let n = 2;
    println!("Bitmask at {n}: {}", mask & (1 << n) != 0);
    // Bitmask at 2: true
}