// -*- coding: utf-8 -*- // // disktest - Hard drive tester // // Copyright 2020-2022 Michael Buesch // // This program is free software; you can redistribute it and/or modify // it under the terms of the GNU General Public License as published by // the Free Software Foundation; either version 2 of the License, or // (at your option) any later version. // // This program is distributed in the hope that it will be useful, // but WITHOUT ANY WARRANTY; without even the implied warranty of // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the // GNU General Public License for more details. // // You should have received a copy of the GNU General Public License along // with this program; if not, write to the Free Software Foundation, Inc., // 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. // use anyhow as ah; use crate::generator::NextRandom; use crate::util::fold; use crc::{crc64, Hasher64}; pub struct GeneratorCrc { crc: crc64::Digest, folded_seed: [u8; GeneratorCrc::FOLDED_SEED_SIZE], counter: u64, } impl GeneratorCrc { /// Size of the algorithm base output data. pub const BASE_SIZE: usize = 256 * GeneratorCrc::CRC_SIZE; /// Chunk size. Multiple of the generator base size. pub const CHUNK_FACTOR: usize = 1536; const CRC_SIZE: usize = 64 / 8; const FOLDED_SEED_SIZE: usize = 64 / 8; pub fn new(seed: &[u8]) -> GeneratorCrc { assert!(!seed.is_empty()); let crc = crc64::Digest::new(crc64::ECMA); let mut folded_seed = [0u8; GeneratorCrc::FOLDED_SEED_SIZE]; folded_seed.copy_from_slice(&fold(seed, GeneratorCrc::FOLDED_SEED_SIZE)); GeneratorCrc { crc, folded_seed, counter: 0, } } } impl NextRandom for GeneratorCrc { fn get_base_size(&self) -> usize { GeneratorCrc::BASE_SIZE } fn next(&mut self, buf: &mut [u8], count: usize) { debug_assert!(buf.len() == GeneratorCrc::BASE_SIZE * count); for i in 0..count { let chunk_offs = i * GeneratorCrc::BASE_SIZE; // Initialize CRC based on the seed and current counter. self.crc.reset(); self.crc.write(&self.folded_seed); self.crc.write(&self.counter.to_le_bytes()); self.counter += 1; // Fast inner loop: // Generate the next chunk with size = BASE_SIZE. for offs in 0..(GeneratorCrc::BASE_SIZE / GeneratorCrc::CRC_SIZE) { // Advance CRC state. debug_assert!(offs <= 0xFF); self.crc.write(&(offs as u8).to_le_bytes()); // Get CRC output. let crc = self.crc.sum64().to_le_bytes(); // Write CRC output to output buffer. let begin = chunk_offs + (offs * GeneratorCrc::CRC_SIZE); let end = chunk_offs + ((offs + 1) * GeneratorCrc::CRC_SIZE); buf[begin..end].copy_from_slice(&crc); } } } fn seek(&mut self, byte_offset: u64) -> ah::Result<()> { if byte_offset % GeneratorCrc::BASE_SIZE as u64 != 0 { return Err(ah::format_err!("CRC seek: Byte offset is not a \ multiple of the base size ({} bytes).", GeneratorCrc::BASE_SIZE)); } self.counter = byte_offset / GeneratorCrc::BASE_SIZE as u64; Ok(()) } } #[cfg(test)] mod tests { use super::*; #[test] fn test_cmp_result() { let mut a = GeneratorCrc::new(&vec![1,2,3]); fn reduce(acc: u32, (i, x): (usize, &u8)) -> u32 { acc.rotate_left(i as u32) ^ (*x as u32) } let mut buf = vec![0u8; GeneratorCrc::BASE_SIZE * 3]; a.next(&mut buf[0..GeneratorCrc::BASE_SIZE], 1); assert_eq!(buf.iter().enumerate().fold(0, reduce), 2183862535); a.next(&mut buf[0..GeneratorCrc::BASE_SIZE], 1); assert_eq!(buf.iter().enumerate().fold(0, reduce), 2200729683); a.next(&mut buf[0..GeneratorCrc::BASE_SIZE*2], 2); assert_eq!(buf.iter().enumerate().fold(0, reduce), 17260884); a.next(&mut buf[0..GeneratorCrc::BASE_SIZE*3], 3); assert_eq!(buf.iter().enumerate().fold(0, reduce), 581162875); } #[test] fn test_seed_equal() { let mut a = GeneratorCrc::new(&vec![1,2,3]); let mut b = GeneratorCrc::new(&vec![1,2,3]); let mut res_a: Vec> = vec![]; let mut res_b: Vec> = vec![]; for _ in 0..2 { let mut buf = vec![0u8; GeneratorCrc::BASE_SIZE]; a.next(&mut buf, 1); res_a.push(buf); let mut buf = vec![0u8; GeneratorCrc::BASE_SIZE]; b.next(&mut buf, 1); res_b.push(buf); } assert_eq!(res_a[0], res_b[0]); assert_eq!(res_a[1], res_b[1]); assert_ne!(res_a[0], res_a[1]); assert_ne!(res_b[0], res_b[1]); } #[test] fn test_seed_diff() { let mut a = GeneratorCrc::new(&vec![1,2,3]); let mut b = GeneratorCrc::new(&vec![1,2,4]); let mut res_a: Vec> = vec![]; let mut res_b: Vec> = vec![]; for _ in 0..2 { let mut buf = vec![0u8; GeneratorCrc::BASE_SIZE]; a.next(&mut buf, 1); res_a.push(buf); let mut buf = vec![0u8; GeneratorCrc::BASE_SIZE]; b.next(&mut buf, 1); res_b.push(buf); } assert_ne!(res_a[0], res_b[0]); assert_ne!(res_a[1], res_b[1]); assert_ne!(res_a[0], res_a[1]); assert_ne!(res_b[0], res_b[1]); } #[test] fn test_concat_equal() { let mut a = GeneratorCrc::new(&vec![1,2,3]); let mut b = GeneratorCrc::new(&vec![1,2,3]); let mut buf_a = vec![0u8; GeneratorCrc::BASE_SIZE * 2]; a.next(&mut buf_a[0..GeneratorCrc::BASE_SIZE], 1); a.next(&mut buf_a[GeneratorCrc::BASE_SIZE..GeneratorCrc::BASE_SIZE*2], 1); let mut buf_b = vec![0u8; GeneratorCrc::BASE_SIZE * 2]; b.next(&mut buf_b, 2); assert_eq!(buf_a, buf_b); } #[test] fn test_seek() { let mut a = GeneratorCrc::new(&vec![1,2,3]); let mut b = GeneratorCrc::new(&vec![1,2,3]); b.seek(GeneratorCrc::BASE_SIZE as u64 * 2).unwrap(); let mut bdata = vec![0u8; GeneratorCrc::BASE_SIZE]; b.next(&mut bdata, 1); let mut adata = vec![0u8; GeneratorCrc::BASE_SIZE]; a.next(&mut adata, 1); assert_ne!(adata, bdata); a.next(&mut adata, 1); assert_ne!(adata, bdata); a.next(&mut adata, 1); assert_eq!(adata, bdata); a.next(&mut adata, 1); assert_ne!(adata, bdata); } } // vim: ts=4 sw=4 expandtab