thin-provisioning-tools/src/checksum.rs

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use anyhow::{anyhow, Result};
use byteorder::{LittleEndian, ReadBytesExt, WriteBytesExt};
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use crc32c::crc32c;
use std::io::Cursor;
const BLOCK_SIZE: u64 = 4096;
#[allow(dead_code)]
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const SUPERBLOCK_CSUM_XOR: u32 = 160774;
const BITMAP_CSUM_XOR: u32 = 240779;
const INDEX_CSUM_XOR: u32 = 160478;
const BTREE_CSUM_XOR: u32 = 121107;
fn checksum(buf: &[u8]) -> u32 {
crc32c(&buf[4..]) ^ 0xffffffff
}
#[derive(Debug, PartialEq)]
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pub enum BT {
SUPERBLOCK,
NODE,
INDEX,
BITMAP,
UNKNOWN,
}
pub fn metadata_block_type(buf: &[u8]) -> BT {
if buf.len() != BLOCK_SIZE as usize {
return BT::UNKNOWN;
}
// The checksum is always stored in the first u32 of the buffer.
let mut rdr = Cursor::new(buf);
let sum_on_disk = rdr.read_u32::<LittleEndian>().unwrap();
let csum = checksum(buf);
let btype = csum ^ sum_on_disk;
match btype {
SUPERBLOCK_CSUM_XOR => BT::SUPERBLOCK,
BTREE_CSUM_XOR => BT::NODE,
BITMAP_CSUM_XOR => BT::BITMAP,
INDEX_CSUM_XOR => BT::INDEX,
_ => BT::UNKNOWN,
}
}
pub fn write_checksum(buf: &mut [u8], kind: BT) -> Result<()> {
if buf.len() != BLOCK_SIZE as usize {
return Err(anyhow!("block is wrong size"));
}
use BT::*;
let salt = match kind {
SUPERBLOCK => SUPERBLOCK_CSUM_XOR,
NODE => BTREE_CSUM_XOR,
BITMAP => BITMAP_CSUM_XOR,
INDEX => INDEX_CSUM_XOR,
UNKNOWN => {return Err(anyhow!("Invalid block type"));}
};
let csum = checksum(buf) ^ salt;
let mut out = std::io::Cursor::new(buf);
out.write_u32::<LittleEndian>(csum)?;
Ok(())
}