spl_tool 0.2.0

Port of StarFive's C spl_tool with default support for VisionFive2
Documentation 
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// SPDX-License-Identifier: GPL-2.0+

/// Default CRC-32 initialization vector used by StarFive.
pub const DEF_CRC32_IV: u32 = !0;
/// Default CRC-32 state vector used by StarFive.
pub const DEF_CRC32_SV: u32 = 0x04c1_1db7;

/// Reverses the bits in the CRC-32 calculation.
///
/// From the `spl_tool` C implementation: <https://github.com/starfive-tech/Tools/blob/master/spl_tool/crc32.c>
pub const fn crc32_reverse(mut x: u32) -> u32 {
    x = ((x & 0x55555555) << 1) | ((x >> 1) & 0x55555555);
    x = ((x & 0x33333333) << 2) | ((x >> 2) & 0x33333333);
    x = ((x & 0x0F0F0F0F) << 4) | ((x >> 4) & 0x0F0F0F0F);
    (x << 24) | ((x & 0xFF00) << 8) | ((x >> 8) & 0xFF00) | (x >> 24)
}

/// Calculate the CRC-32 value over the provided data buffer.
///
/// Parameters:
///
/// - `iv`: initialization vector for the CRC-32 polynomial.
/// - `sv`: state vector for the CRC-32 polynomial.
/// - `data`: byte buffer to calculate the checksum.
///
/// From the `spl_tool` C implementation: <https://github.com/starfive-tech/Tools/blob/master/spl_tool/crc32.c>
pub fn crc32(iv: u32, sv: u32, data: &[u8]) -> u32 {
    let mut crc = iv;

    data.iter().for_each(|&byte| {
        let mut sum = crc32_reverse(byte as u32);
        (0..8).for_each(|_| {
            crc = if ((crc ^ sum) & 0x8000_0000) != 0 {
                (crc << 1) ^ sv
            } else {
                crc << 1
            };
            sum <<= 1;
        })
    });

    crc
}

/// Performs the final round of the CRC-32 calculation.
///
/// From the `spl_tool` C implementation: <https://github.com/starfive-tech/Tools/blob/master/spl_tool/crc32.c>
pub const fn crc32_final(iv: u32) -> u32 {
    crc32_reverse(iv ^ !0u32)
}