67 lines
1.6 KiB
Rust
67 lines
1.6 KiB
Rust
use anyhow::{anyhow, Result};
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use byteorder::{LittleEndian, ReadBytesExt, WriteBytesExt};
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use crc32c::crc32c;
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use std::io::Cursor;
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const BLOCK_SIZE: u64 = 4096;
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#[allow(dead_code)]
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const MAGIC: u64 = 0xa537a0aa6309ef77;
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const SUPERBLOCK_CSUM_XOR: u32 = 160774;
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const BITMAP_CSUM_XOR: u32 = 240779;
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const INDEX_CSUM_XOR: u32 = 160478;
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const BTREE_CSUM_XOR: u32 = 121107;
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fn checksum(buf: &[u8]) -> u32 {
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crc32c(&buf[4..]) ^ 0xffffffff
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}
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#[derive(Debug, PartialEq)]
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pub enum BT {
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SUPERBLOCK,
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NODE,
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INDEX,
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BITMAP,
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UNKNOWN,
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}
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pub fn metadata_block_type(buf: &[u8]) -> BT {
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if buf.len() != BLOCK_SIZE as usize {
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return BT::UNKNOWN;
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}
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// The checksum is always stored in the first u32 of the buffer.
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let mut rdr = Cursor::new(buf);
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let sum_on_disk = rdr.read_u32::<LittleEndian>().unwrap();
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let csum = checksum(buf);
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let btype = csum ^ sum_on_disk;
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match btype {
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SUPERBLOCK_CSUM_XOR => BT::SUPERBLOCK,
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BTREE_CSUM_XOR => BT::NODE,
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BITMAP_CSUM_XOR => BT::BITMAP,
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INDEX_CSUM_XOR => BT::INDEX,
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_ => BT::UNKNOWN,
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}
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}
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pub fn write_checksum(buf: &mut [u8], kind: BT) -> Result<()> {
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if buf.len() != BLOCK_SIZE as usize {
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return Err(anyhow!("block is wrong size"));
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}
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use BT::*;
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let salt = match kind {
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SUPERBLOCK => SUPERBLOCK_CSUM_XOR,
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NODE => BTREE_CSUM_XOR,
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BITMAP => BITMAP_CSUM_XOR,
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INDEX => INDEX_CSUM_XOR,
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UNKNOWN => {return Err(anyhow!("Invalid block type"));}
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};
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let csum = checksum(buf) ^ salt;
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let mut out = std::io::Cursor::new(buf);
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out.write_u32::<LittleEndian>(csum)?;
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Ok(())
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}
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