| // Copyright 2022 The Fuchsia Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| use byteorder::{ByteOrder, LittleEndian}; |
| |
| /// For the foreseeable future, Fxfs will use 64-bit checksums. |
| pub type Checksum = u64; |
| |
| /// Generates a Fletcher64 checksum of |buf| seeded by |previous|. |
| /// |
| /// All logfile blocks are covered by a fletcher64 checksum as the last 8 bytes in a block. |
| /// |
| /// We also use this checksum for integrity validation of potentially out-of-order writes |
| /// during Journal replay. |
| pub fn fletcher64(buf: &[u8], previous: Checksum) -> Checksum { |
| assert!(buf.len() % 4 == 0); |
| let mut lo = previous as u32; |
| let mut hi = (previous >> 32) as u32; |
| for chunk in buf.chunks(4) { |
| lo = lo.wrapping_add(LittleEndian::read_u32(chunk)); |
| hi = hi.wrapping_add(lo); |
| } |
| (hi as u64) << 32 | lo as u64 |
| } |
