├── .gitignore ├── README.md ├── .vscode ├── extensions.json └── settings.json ├── Cargo.toml ├── src ├── tests.rs ├── statics.rs └── lib.rs └── LICENSE /.gitignore: -------------------------------------------------------------------------------- 1 | **/target 2 | Cargo.lock -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | # Zfec-rs 2 | A pure Rust implementation of Zfec 3 | 4 | Based on https://github.com/tahoe-lafs/zfec 5 | -------------------------------------------------------------------------------- /.vscode/extensions.json: -------------------------------------------------------------------------------- 1 | { 2 | "recommendations": [ 3 | "rust-lang.rust-analyzer", 4 | "tamasfe.even-better-toml", 5 | "serayuzgur.crates", 6 | "wayou.vscode-todo-highlight" 7 | ] 8 | } 9 | -------------------------------------------------------------------------------- /.vscode/settings.json: -------------------------------------------------------------------------------- 1 | { 2 | "editor.defaultFormatter": "rust-lang.rust-analyzer", 3 | "editor.formatOnSave": true, 4 | "editor.tabSize": 4, 5 | "files.autoSave": "onFocusChange", 6 | "files.insertFinalNewline": true, 7 | "files.trimTrailingWhitespace": true, 8 | "rust-analyzer.checkOnSave.command": "clippy", 9 | "[toml]": { 10 | "editor.defaultFormatter": "tamasfe.even-better-toml" 11 | } 12 | } 13 | -------------------------------------------------------------------------------- /Cargo.toml: -------------------------------------------------------------------------------- 1 | [package] 2 | name = "zfec-rs" 3 | authors = ["Walker Thornley"] 4 | version = "0.1.0" 5 | edition = "2021" 6 | license = "GPL-3.0" 7 | # license-file = "LICENSE" 8 | description = "A Rust implementation of the Zfec library" 9 | homepage = "https://github.com/thornleywalker/zfec-rs" 10 | repository = "https://github.com/thornleywalker/zfec-rs" 11 | readme = "README.md" 12 | keywords = ["fec", "erasure", "parity"] 13 | categories = ["encoding", "algorithms"] 14 | 15 | # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html 16 | 17 | [dev-dependencies] 18 | rand = "0.8.5" -------------------------------------------------------------------------------- /src/tests.rs: -------------------------------------------------------------------------------- 1 | /* Copyright (C) 2022, Walker Thornley 2 | * 3 | * This program is free software: you can redistribute it and/or modify 4 | * it under the terms of the GNU General Public License as published by 5 | * the Free Software Foundation, either version 3 of the License, or 6 | * (at your option) any later version. 7 | * 8 | * This program is distributed in the hope that it will be useful, 9 | * but WITHOUT ANY WARRANTY; without even the implied warranty of 10 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 11 | * GNU General Public License for more details. 12 | * 13 | * You should have received a copy of the GNU General Public License 14 | * along with this program. If not, see . 15 | */ 16 | 17 | use super::*; 18 | use rand::Rng; 19 | 20 | const DATA: &[u8] = b"some_ssidthe_password"; 21 | const ENCODED: &[u8] = 22 | b"some_ssidthe_password\x00\x00\x00\x00]\xd8\x94\xea\x91\x1bGU\xff+\x882[\xa6\xd3"; 23 | 24 | #[test] 25 | fn encoder_5_8_test() { 26 | encoder_test(5, 8); 27 | } 28 | fn encoder_test(k: usize, m: usize) { 29 | let fec = Fec::new(k, m).unwrap(); 30 | let (mut encoded_chunks, _) = fec.encode(DATA).unwrap(); 31 | let mut encoded = vec![]; 32 | for chunk in &mut encoded_chunks { 33 | encoded.append(&mut chunk.data); 34 | } 35 | assert_eq!(encoded, ENCODED); 36 | } 37 | // tests if fec can decode for k=5, m=8 38 | #[test] 39 | fn decoder_5_8_test() { 40 | decoder_test(5, 8); 41 | } 42 | #[test] 43 | // tests various combinations of k and m 44 | fn decoder_extensive() { 45 | for m in 2..20 { 46 | for k in 1..m - 1 { 47 | decoder_test(k, m); 48 | } 49 | } 50 | } 51 | // assumes encoder works 52 | fn decoder_test(k: usize, m: usize) { 53 | let fec = Fec::new(k, m).unwrap(); 54 | // let mut chunks_enc: BTreeMap> = BTreeMap::new(); 55 | let (chunks, padding) = fec.encode(DATA).unwrap(); 56 | // for (i, chunk) in chunks.iter().enumerate() { 57 | // chunks_enc.insert(i, chunk.to_vec()); 58 | // } 59 | // test if decoder can decode from complete message 60 | // eprintln!!("padding: {}", padding); 61 | let decoded = fec.decode(&chunks, padding).unwrap(); 62 | assert_eq!( 63 | decoded, 64 | DATA.to_vec(), 65 | "Failed to decode from complete k: {}, m: {} encoded message", 66 | k, 67 | m 68 | ); 69 | // eprintln!!("Successfully decoded at k: {}, m: {}", fec.k, fec.m); 70 | 71 | // test for missing each part of each group 72 | for i in 0..m { 73 | // eprintln!!("With #{} missing", i); 74 | let mut broken_enc = chunks.clone(); 75 | broken_enc.remove(i); 76 | //eprintln!("brkn_enc: {:02x?}", broken_enc); 77 | let decoded = fec.decode(&broken_enc, padding).unwrap(); 78 | assert_eq!( 79 | decoded, 80 | DATA.to_vec(), 81 | "Failed to decode while missing {}th block", 82 | i, 83 | ); 84 | } 85 | 86 | // test for mising n parts of each group, up to the max allowable 87 | let max_missing = m - k; 88 | let mut rng = rand::thread_rng(); 89 | // just to really give it a go 90 | for _ in 0..20 { 91 | for n in 1..=max_missing { 92 | // eprintln!!("With {} missing chunks", n); 93 | let mut broken_enc = chunks.clone(); 94 | for _ in 0..n { 95 | let keys = &broken_enc 96 | .iter() 97 | .map(|chunk| chunk.index) 98 | .collect::>()[..]; 99 | // eprintln!!("keys: {:02x?}", keys); 100 | let index = rng.gen_range(0..keys.len()); 101 | let _ = broken_enc.remove(index); 102 | } 103 | // eprintln!!("broken: {:02x?}", broken_enc); 104 | let decoded = fec.decode(&broken_enc, padding).unwrap(); 105 | assert_eq!( 106 | decoded, 107 | DATA.to_vec(), 108 | "Failed to decode from k: {}, m: {} encoded message with {} missing chunks", 109 | k, 110 | m, 111 | n 112 | ); 113 | } 114 | } 115 | } 116 | -------------------------------------------------------------------------------- /src/statics.rs: -------------------------------------------------------------------------------- 1 | use crate::Gf; 2 | 3 | /* 4 | * Primitive polynomials - see Lin & Costello, Appendix A, 5 | * and Lee & Messerschmitt, p. 453. 6 | */ 7 | const PP: &[u8; 9] = b"101110001"; 8 | 9 | // made this const, cuz she big and unchanging 10 | pub const STATICS: Statics = Statics::new(); 11 | 12 | /* 13 | * To speed up computations, we have tables for logarithm, exponent and 14 | * inverse of a number. We use a table for multiplication as well (it takes 15 | * 64K, no big deal even on a PDA, especially because it can be 16 | * pre-initialized an put into a ROM!), otherwhise we use a table of 17 | * logarithms. In any case the macro gf_mul(x,y) takes care of 18 | * multiplications. 19 | */ 20 | pub struct Statics { 21 | pub gf_exp: [Gf; 510], 22 | //gf_log: [i32; 256], 23 | inverse: [Gf; 256], 24 | gf_mul_table: [[Gf; 256]; 256], 25 | } 26 | impl Statics { 27 | pub const fn new() -> Self { 28 | let (gf_exp, gf_log, inverse) = Self::generate_gf(); 29 | let gf_mul_table = Self::_init_mul_table(&gf_exp, &gf_log); 30 | Self { 31 | gf_exp, 32 | //gf_log, 33 | inverse, 34 | gf_mul_table, 35 | } 36 | } 37 | /// Initialize the data structures used for computations in GF 38 | const fn generate_gf() -> ([Gf; 510], [i32; 256], [Gf; 256]) { 39 | let mut gf_exp: [Gf; 510] = [0; 510]; 40 | // only used in initializing other fields 41 | let mut gf_log: [i32; 256] = [0; 256]; 42 | let mut inverse: [Gf; 256] = [0; 256]; 43 | let mut mask: Gf; 44 | 45 | mask = 1; /* x ** 0 = 1 */ 46 | gf_exp[8] = 0; /* will be updated at the end of the 1st loop */ 47 | /* 48 | * first, generate the (polynomial representation of) powers of \alpha, 49 | * which are stored in gf_exp[i] = \alpha ** i . 50 | * At the same time build gf_log[gf_exp[i]] = i . 51 | * The first 8 powers are simply bits shifted to the left. 52 | */ 53 | 54 | // for i in 0..8 { 55 | let mut i = 0; 56 | while i < 8 { 57 | gf_exp[i] = mask; 58 | gf_log[gf_exp[i] as usize] = i as i32; 59 | /* 60 | * If Pp[i] == 1 then \alpha ** i occurs in poly-repr 61 | * gf_exp[8] = \alpha ** 8 62 | */ 63 | if PP[i] == b'1' { 64 | gf_exp[8] ^= mask; 65 | } 66 | mask <<= 1; 67 | i += 1; 68 | } 69 | /* 70 | * now gf_exp[8] = \alpha ** 8 is complete, so can also 71 | * compute its inverse. 72 | */ 73 | gf_log[gf_exp[8] as usize] = 8; 74 | 75 | /* 76 | * Poly-repr of \alpha ** (i+1) is given by poly-repr of 77 | * \alpha ** i shifted left one-bit and accounting for any 78 | * \alpha ** 8 term that may occur when poly-repr of 79 | * \alpha ** i is shifted. 80 | */ 81 | mask = 1 << 7; 82 | 83 | // for i in 9..255 { 84 | // increment so it begins at 9 this time 85 | i += 1; 86 | while i < 255 { 87 | if gf_exp[i - 1] >= mask { 88 | gf_exp[i] = gf_exp[8] ^ ((gf_exp[i - 1] ^ mask) << 1); 89 | } else { 90 | gf_exp[i] = gf_exp[i - 1] << 1; 91 | } 92 | gf_log[gf_exp[i] as usize] = i as i32; 93 | i += 1; 94 | } 95 | /* 96 | * log(0) is not defined, so use a special value 97 | */ 98 | gf_log[0] = 255; 99 | /* set the extended gf_exp values for fast multiply */ 100 | 101 | // for i in 0..255 { 102 | i = 0; 103 | while i < 255 { 104 | gf_exp[i + 255] = gf_exp[i]; 105 | i += 1; 106 | } 107 | /* 108 | * again special cases. 0 has no inverse. This used to 109 | * be initialized to 255, but it should make no difference 110 | * since noone is supposed to read from here. 111 | */ 112 | inverse[0] = 0; 113 | inverse[1] = 1; 114 | 115 | // for i in 2..=255 { 116 | i = 2; 117 | while i <= 255 { 118 | inverse[i] = gf_exp[255 - gf_log[i] as usize]; 119 | i += 1; 120 | } 121 | 122 | (gf_exp, gf_log, inverse) 123 | } 124 | const fn _init_mul_table(gf_exp: &[Gf; 510], gf_log: &[i32; 256]) -> [[Gf; 256]; 256] { 125 | let mut gf_mul_table: [[Gf; 256]; 256] = [[0; 256]; 256]; 126 | // for i in 0..256 { 127 | let mut i = 0; 128 | while i < 256 { 129 | let mut j = 0; 130 | // for j in 0..256 { 131 | while j < 256 { 132 | gf_mul_table[i][j] = gf_exp[Self::modnn(gf_log[i] + gf_log[j]) as usize]; 133 | j += 1; 134 | } 135 | i += 1; 136 | } 137 | // for j in 0..256 { 138 | let mut j = 0; 139 | while j < 256 { 140 | gf_mul_table[j][0] = 0; 141 | gf_mul_table[0][j] = 0; 142 | j += 1; 143 | } 144 | gf_mul_table 145 | } 146 | pub const fn modnn(mut x: i32) -> Gf { 147 | while x >= 255 { 148 | x -= 255; 149 | x = (x >> 8) + (x & 255); 150 | } 151 | x as Gf 152 | } 153 | pub fn addmul(&self, dst: &mut [Gf], src: &[Gf], c: Gf, sz: usize) { 154 | // eprintln!("c: {:02x}, sz: {}", c, sz); 155 | // eprintln!("dst: {:02x?}", dst); 156 | // eprintln!("src: {:02x?}", src); 157 | if c != 0 { 158 | self._addmul1(dst, src, c, sz); 159 | } 160 | } 161 | fn _addmul1(&self, dst: &mut [Gf], src: &[Gf], c: Gf, sz: usize) { 162 | if !src.is_empty() { 163 | let mulc = self.gf_mul_table[c as usize]; 164 | //let lim = &dst[sz - UNROLL + 1..]; 165 | // they unroll, for now I'll just do it directly 166 | for i in 0..sz { 167 | dst[i] ^= mulc[src[i] as usize]; 168 | } 169 | // eprintln!("dst: {:02x?}", dst); 170 | } 171 | } 172 | /* 173 | * computes C = AB where A is n*k, B is k*m, C is n*m 174 | */ 175 | pub fn matmul(&self, a: &[Gf], b: &[Gf], c: &mut [Gf], n: usize, k: usize, m: usize) { 176 | // eprintln!("a: {:02x?}", a); 177 | // eprintln!("b: {:02x?}", b); 178 | // eprintln!("c: {:02x?}", c); 179 | for row in 0..n { 180 | for col in 0..m { 181 | let mut acc: Gf = 0; 182 | for i in 0..k { 183 | let pa: Gf = a[(row * k) + i]; 184 | let pb: Gf = b[col + (i * m)]; 185 | acc ^= self.gf_mul(pa, pb); 186 | } 187 | c[row * m + col] = acc; 188 | } 189 | } 190 | // eprintln!("c: {:02x?}", c); 191 | } 192 | /* 193 | * fast code for inverting a vandermonde matrix. 194 | * 195 | * NOTE: It assumes that the matrix is not singular and _IS_ a vandermonde 196 | * matrix. Only uses the second column of the matrix, containing the p_i's. 197 | * 198 | * Algorithm borrowed from "Numerical recipes in C" -- sec.2.8, but largely 199 | * revised for my purposes. 200 | * p = coefficients of the matrix (p_i) 201 | * q = values of the polynomial (known) 202 | */ 203 | pub fn invert_vdm(&self, src: &mut [Gf], k: usize) { 204 | /* 205 | * b holds the coefficient for the matrix inversion 206 | * c holds the coefficient of P(x) = Prod (x - p_i), i=0..k-1 207 | */ 208 | let (mut b, mut c, mut p): (Vec, Vec, Vec) = 209 | (vec![0; k], vec![0; k], vec![0; k]); 210 | let (mut t, mut xx): (Gf, Gf); 211 | 212 | /* degenerate case, matrix must be p^0 = 1 */ 213 | if k == 1 { 214 | return; 215 | } 216 | let mut j = 1; 217 | for i in 0..k { 218 | c[i] = 0; 219 | p[i] = src[j]; 220 | j += k; 221 | } 222 | 223 | /* 224 | * construct coeffs. recursively. We know c[k] = 1 (implicit) 225 | * and start P_0 = x - p_0, then at each stage multiply by 226 | * x - p_i generating P_i = x P_{i-1} - p_i P_{i-1} 227 | * After k steps we are done. 228 | */ 229 | c[k - 1] = p[0]; /* really -p(0), but x = -x in GF(2^m) */ 230 | (1..k).for_each(|i| { 231 | let p_i = p[i]; /* see above comment */ 232 | for j in (k - 1 - (i - 1))..(k - 1) { 233 | c[j] ^= self.gf_mul(p_i, c[j + 1]); 234 | } 235 | c[k - 1] ^= p_i; 236 | }); 237 | 238 | for row in 0..k { 239 | /* 240 | * synthetic division etc. 241 | */ 242 | xx = p[row]; 243 | t = 1; 244 | b[k - 1] = 1; /* this is in fact c[k] */ 245 | for i in (1..=(k - 1)).rev() { 246 | b[i - 1] = c[i] ^ self.gf_mul(xx, b[i]); 247 | t = self.gf_mul(xx, t) ^ b[i - 1]; 248 | } 249 | for col in 0..k { 250 | src[col * k + row] = self.gf_mul(self.inverse[t as usize], b[col]); 251 | } 252 | } 253 | } 254 | fn gf_mul(&self, x: Gf, y: Gf) -> Gf { 255 | self.gf_mul_table[x as usize][y as usize] 256 | } 257 | pub fn _invert_mat(&self, src: &mut [Gf], k: usize) { 258 | let mut c: Gf; 259 | let (mut irow, mut icol) = (0, 0); 260 | 261 | let mut indxc = vec![0; k]; 262 | let mut indxr = vec![0; k]; 263 | let mut ipiv = vec![0; k]; 264 | let mut id_row = vec![0; k]; 265 | 266 | /* 267 | * ipiv marks elements already used as pivots. 268 | */ 269 | (0..k).for_each(|i| { 270 | ipiv[i] = 0; 271 | }); 272 | 273 | for col in 0..k { 274 | let mut piv_found: bool = false; 275 | 276 | /* 277 | * Zeroing column 'col', look for a non-zero element. 278 | * First try on the diagonal, if it fails, look elsewhere. 279 | */ 280 | if ipiv[col] != 1 && src[col * k + col] != 0 { 281 | irow = col; 282 | icol = col; 283 | // goto found_piv; 284 | } 285 | for row in 0..k { 286 | if ipiv[row] != 1 { 287 | for ix in 0..k { 288 | if ipiv[ix] == 0 { 289 | if src[row * k + ix] != 0 { 290 | irow = row; 291 | icol = ix; 292 | // goto found_piv; 293 | piv_found = true; 294 | } 295 | } else { 296 | assert!(ipiv[ix] <= 1); 297 | } 298 | if piv_found { 299 | break; 300 | } 301 | } 302 | } 303 | if piv_found { 304 | break; 305 | } 306 | } 307 | 308 | // found_piv: 309 | ipiv[icol] += 1; 310 | /* 311 | * swap rows irow and icol, so afterwards the diagonal 312 | * element will be correct. Rarely done, not worth 313 | * optimizing. 314 | */ 315 | if irow != icol { 316 | for ix in 0..k { 317 | // direct implementation is easiest solution for the "SWAP" macro 318 | src.swap(irow * k + ix, icol * k + ix); 319 | } 320 | } 321 | indxr[col] = irow; 322 | indxc[col] = icol; 323 | let pivot_row = &mut src[icol * k..(icol + 1) * k]; 324 | c = pivot_row[icol]; 325 | assert!(c != 0); 326 | if c != 1 { 327 | /* otherwhise this is a NOP */ 328 | /* 329 | * this is done often , but optimizing is not so 330 | * fruitful, at least in the obvious ways (unrolling) 331 | */ 332 | c = self.inverse[c as usize]; 333 | pivot_row[icol] = 1; 334 | (0..k).for_each(|ix| { 335 | pivot_row[ix] = self.gf_mul(c, pivot_row[ix]); 336 | }); 337 | } 338 | /* 339 | * from all rows, remove multiples of the selected row 340 | * to zero the relevant entry (in fact, the entry is not zero 341 | * because we know it must be zero). 342 | * (Here, if we know that the pivot_row is the identity, 343 | * we can optimize the addmul). 344 | */ 345 | id_row[icol] = 1; 346 | if pivot_row != id_row { 347 | // create a copy of pivot row, since we can't 348 | // have mut and immut references at the same time 349 | // if we know what size it'll be, might as well 350 | // start it there and save realloc time 351 | let mut pivot_clone = vec![0; pivot_row.len()]; 352 | for val in pivot_row.iter() { 353 | pivot_clone.push(*val); 354 | } 355 | 356 | for ix in 0..k { 357 | let p = &mut src[ix * k..(ix + 1) * k]; 358 | if ix != icol { 359 | c = p[icol]; 360 | p[icol] = 0; 361 | // eprintln!("Loc 1"); 362 | self.addmul(p, &pivot_clone[k..], c, k); 363 | } 364 | } 365 | } 366 | id_row[icol] = 0; 367 | } /* done all columns */ 368 | for col in (1..=k).rev() { 369 | if indxr[col - 1] != indxc[col - 1] { 370 | for row in 0..k { 371 | // direct implementation is easiest solution for the "SWAP" macro 372 | src.swap(row * k + indxr[col - 1], row * k + indxc[col - 1]); 373 | } 374 | } 375 | } 376 | } 377 | } 378 | -------------------------------------------------------------------------------- /src/lib.rs: -------------------------------------------------------------------------------- 1 | /* Copyright (C) 2022, Walker Thornley 2 | * 3 | * This program is free software: you can redistribute it and/or modify 4 | * it under the terms of the GNU General Public License as published by 5 | * the Free Software Foundation, either version 3 of the License, or 6 | * (at your option) any later version. 7 | * 8 | * This program is distributed in the hope that it will be useful, 9 | * but WITHOUT ANY WARRANTY; without even the implied warranty of 10 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 11 | * GNU General Public License for more details. 12 | * 13 | * You should have received a copy of the GNU General Public License 14 | * along with this program. If not, see . 15 | */ 16 | 17 | //! A pure Rust implementation of the Zfec library. 18 | //! 19 | //! The general concept of Zfec is to break a message into blocks, or "chunks", then generate additional chunks 20 | //! with parity information that can be used to identify any missing chunks. 21 | //! 22 | //! Notice: Zfec only provides Forward Error Correcting functionality, not encryption. Any message coded with 23 | //! Zfec should be encrypted first, if security is necessary. 24 | //! 25 | //! Implemented directly from https://github.com/tahoe-lafs/zfec 26 | 27 | #[cfg(test)] 28 | mod tests; 29 | 30 | mod statics; 31 | 32 | use std::fmt; 33 | 34 | use statics::Statics; 35 | 36 | /* To make sure that we stay within cache in the inner loops of fec_encode(). (It would 37 | probably help to also do this for fec_decode().*/ 38 | const STRIDE: usize = 8192; 39 | 40 | //static UNROLL: usize = 16; /* 1, 4, 8, 16 */ 41 | // TODO: Implement unrolling 42 | // could be done at build time. Run some basic unrolling tests 43 | // in the build.rs, whichever unrolling is fastest, have a macro 44 | // that does the unrolling 45 | 46 | //const FEC_MAGIC: u32 = 0xFECC0DEC; 47 | 48 | #[derive(Debug)] 49 | /// Possible errors 50 | pub enum Error { 51 | ZeroK, 52 | ZeroM, 53 | BigN, 54 | KGtN, 55 | NotEnoughChunks, 56 | Tbd, 57 | } 58 | impl std::fmt::Display for Error { 59 | fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { 60 | write!( 61 | f, 62 | "Zfec error: {}", 63 | match self { 64 | Self::ZeroK => "'k' must be greater than 0", 65 | Self::ZeroM => "'m' must be greater than 0", 66 | Self::BigN => "'n' must be less than 257", 67 | Self::KGtN => "'k' must be less than 'n'", 68 | Self::NotEnoughChunks => "Not enough chunks were provided", 69 | Self::Tbd => "Unknown error", 70 | } 71 | ) 72 | } 73 | } 74 | impl std::error::Error for Error {} 75 | 76 | type Gf = u8; 77 | type Result = std::result::Result; 78 | 79 | /// A chunk of encoded data 80 | /// 81 | /// A `Chunk` can be deconstructed into a `(Vec, usize)` tuple 82 | /// 83 | /// # Example 84 | /// 85 | /// ``` 86 | /// use zfec_rs::Chunk; 87 | /// 88 | /// let val: Vec = vec![0, 1, 2, 3, 4]; 89 | /// let chunk = Chunk::new(val.clone(), 0); 90 | /// let (chunk_vec, chunk_i): (Vec, usize) = chunk.into(); 91 | /// assert_eq!(val, chunk_vec); 92 | /// ``` 93 | #[derive(Debug, Clone)] 94 | pub struct Chunk { 95 | pub data: Vec, 96 | pub index: usize, 97 | } 98 | impl Chunk { 99 | /// Creates a new chunk 100 | pub fn new(data: Vec, index: usize) -> Self { 101 | Self { data, index } 102 | } 103 | } 104 | impl From for (Vec, usize) { 105 | fn from(val: Chunk) -> Self { 106 | (val.data, val.index) 107 | } 108 | } 109 | impl std::fmt::Display for Chunk { 110 | fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { 111 | write!(f, "{}, {:?}", self.index, self.data) 112 | } 113 | } 114 | 115 | /// Forward Error Correcting encoder/decoder. 116 | /// 117 | /// The encoder can be defined with 2 values: `k` and `m` 118 | /// 119 | /// * `k` is the number of chunks needed to reconstruct the original message 120 | /// * `m` is the total number of chunks that will be produced 121 | /// 122 | /// The first `k` chunks contain the original unaltered data, meaning that if all the original chunks are 123 | /// available on the decoding end, no decoding needs to take place. 124 | /// 125 | /// The final `(m-k)` chunks contain the parity coding necessary to reproduce any one of the original chunks. 126 | /// 127 | /// Coding is done with respect to the chunk's location within the encoded data. This means that each chunk's 128 | /// sequence number is needed for correct reconstruction. 129 | /// 130 | /// # Example 131 | /// 132 | /// ``` 133 | /// use zfec_rs::Fec; 134 | /// 135 | /// let message = b"Message to be sent"; 136 | /// 137 | /// let fec = Fec::new(5, 8).unwrap(); 138 | /// 139 | /// let (mut encoded_chunks, padding) = fec.encode(&message[..]).unwrap(); 140 | /// encoded_chunks.remove(2); 141 | /// let decoded_message = fec.decode(&encoded_chunks, padding).unwrap(); 142 | /// 143 | /// assert_eq!(message.to_vec(), decoded_message); 144 | /// ``` 145 | pub struct Fec { 146 | /// Number of chunks needed to reconstruct the original message 147 | k: usize, 148 | /// Total number of chunks that will be produced 149 | m: usize, 150 | enc_matrix: Vec, 151 | } 152 | impl Fec { 153 | /* 154 | * This section contains the proper FEC encoding/decoding routines. 155 | * The encoding matrix is computed starting with a Vandermonde matrix, 156 | * and then transforming it into a systematic matrix. 157 | */ 158 | /* 159 | * param k the number of blocks required to reconstruct 160 | * param m the total number of blocks created 161 | */ 162 | /// Generates a new encoder/decoder 163 | pub fn new(k: usize, m: usize) -> Result { 164 | //// eprintln!("Creating new - k: {}, n: {}", k, n); 165 | if k < 1 { 166 | return Err(Error::ZeroK); 167 | } 168 | if m < 1 { 169 | return Err(Error::ZeroM); 170 | } 171 | if m > 256 { 172 | return Err(Error::BigN); 173 | } 174 | if k > m { 175 | return Err(Error::KGtN); 176 | } 177 | let mut tmp_m: Vec = vec![0; m * k]; 178 | 179 | // m rows by k columns 180 | let mut enc_matrix: Vec = vec![0; m * k]; 181 | 182 | /* 183 | * fill the matrix with powers of field elements, starting from 0. 184 | * The first row is special, cannot be computed with exp. table. 185 | */ 186 | tmp_m[0] = 1; 187 | (1..k).for_each(|col| { 188 | tmp_m[col] = 0; 189 | }); 190 | for row in 0..(m - 1) { 191 | //// eprintln!("row: {}", row); 192 | let p: &mut [u8] = &mut tmp_m[(row + 1) * k..]; 193 | (0..k).for_each(|col| { 194 | p[col] = statics::STATICS.gf_exp[Statics::modnn((row * col) as i32) as usize]; 195 | }); 196 | } 197 | 198 | /* 199 | * quick code to build systematic matrix: invert the top 200 | * k*k vandermonde matrix, multiply right the bottom n-k rows 201 | * by the inverse, and construct the identity matrix at the top. 202 | */ 203 | // eprintln!("tmp_m: {:02x?}", tmp_m); 204 | statics::STATICS.invert_vdm(&mut tmp_m, k); /* much faster than _invert_mat */ 205 | statics::STATICS.matmul( 206 | &tmp_m[k * k..], 207 | &tmp_m[..], 208 | &mut enc_matrix[k * k..], 209 | m - k, 210 | k, 211 | k, 212 | ); 213 | /* 214 | * the upper matrix is I so do not bother with a slow multiply 215 | */ 216 | // the Vec is initialized to 0's when defined 217 | // memset(retval->enc_matrix, '\0', k * k * sizeof(gf)); 218 | for i in 0..k { 219 | //// eprintln!("i: {}", i); 220 | enc_matrix[i * (k + 1)] = 1; 221 | } 222 | 223 | // unnecessary in Rust, tmp_m gets dropped 224 | // free(tmp_m); 225 | 226 | Ok(Fec { k, m, enc_matrix }) 227 | } 228 | /// Performs the encoding, returning the encoded chunks and the amount of padding 229 | /// 230 | /// Because all chunks need to be the same size, the data is padded with `0`s at the end as needed 231 | pub fn encode(&self, data: &[u8]) -> Result<(Vec, usize)> { 232 | // eprintln!("\nEncoding k: {}, m: {}", self.k, self.m); 233 | // clean side 234 | let chunk_size = self.chunk_size(data.len()); 235 | // eprintln!("chunk_size: {}", chunk_size); 236 | let data_slice = data; 237 | 238 | let mut chunks = vec![]; 239 | 240 | // eprintln!("data: {:02x?}", data); 241 | // eprintln!("data len: {:02x?}", data.len()); 242 | let mut padding = 0; 243 | for i in 0..self.k { 244 | let mut temp_vec = vec![]; 245 | if (i * chunk_size) >= data_slice.len() { 246 | // eprintln!("empty chunk"); 247 | temp_vec.append(&mut vec![0; chunk_size].to_vec()); 248 | padding += chunk_size; 249 | } else if ((i * chunk_size) < data_slice.len()) 250 | && (((i + 1) * chunk_size) > data_slice.len()) 251 | { 252 | // finish current chunk 253 | temp_vec.append(&mut data_slice[i * chunk_size..].to_vec()); 254 | // add padding 255 | let added = ((i + 1) * chunk_size) - data_slice.len(); 256 | // eprint!("final slice, padding"); 257 | let mut added_padding = vec![0; added]; 258 | temp_vec.append(&mut added_padding); 259 | padding += added; 260 | } else { 261 | let new_chunk = &data_slice[(i * chunk_size)..((i + 1) * chunk_size)]; 262 | // eprintln!("normal chunk: {:02x?}", new_chunk); 263 | temp_vec.append(&mut new_chunk.to_vec()) 264 | } 265 | chunks.push(temp_vec); 266 | } 267 | // eprintln!("Finished chunking"); 268 | 269 | let num_check_blocks_produced = self.m - self.k; 270 | let mut check_blocks_produced = vec![vec![0; chunk_size]; num_check_blocks_produced]; 271 | let check_block_ids: Vec = (self.k..self.m).collect(); 272 | // eprintln!("num: {}", num_check_blocks_produced); 273 | // eprintln!("blocks: {:?}", check_blocks_produced); 274 | // eprintln!("ids: {:?}", check_block_ids); 275 | 276 | ///////// internals 277 | 278 | let mut k = 0; 279 | while k < chunk_size { 280 | let stride = if (chunk_size - k) < STRIDE { 281 | chunk_size - k 282 | } else { 283 | STRIDE 284 | }; 285 | for i in 0..num_check_blocks_produced { 286 | let fecnum = check_block_ids[i]; 287 | if fecnum < self.k { 288 | return Err(Error::Tbd); 289 | } 290 | let p = &self.enc_matrix[fecnum * self.k..]; 291 | // eprintln!("enc_matrix: {:02x?}", &self.enc_matrix); 292 | // eprintln!("p: {:02x?}", p); 293 | for j in 0..self.k { 294 | // eprintln!("Loc 2"); 295 | statics::STATICS.addmul( 296 | &mut check_blocks_produced[i][k..], 297 | &chunks[j][k..k + stride], 298 | p[j], 299 | stride, 300 | ); 301 | } 302 | } 303 | 304 | k += STRIDE; 305 | } 306 | 307 | ///////// end internals 308 | 309 | let mut ret_chunks = vec![]; 310 | ret_chunks.append(&mut chunks); 311 | ret_chunks.append(&mut check_blocks_produced); 312 | // eprintln!("ret_chunks: {:02x?}", ret_chunks); 313 | let mut ret_vec = vec![]; 314 | for (i, chunk) in ret_chunks.iter().enumerate() { 315 | ret_vec.push(Chunk { 316 | index: i, 317 | data: chunk.to_vec(), 318 | }); 319 | } 320 | Ok((ret_vec, padding)) 321 | } 322 | /// Performs the decoding 323 | pub fn decode(&self, encoded_data: &Vec, padding: usize) -> Result> { 324 | // eprintln!("\nDecoding"); 325 | if encoded_data.len() < self.k { 326 | return Err(Error::NotEnoughChunks); 327 | } 328 | 329 | let mut share_nums: Vec = vec![]; 330 | let mut chunks: Vec> = vec![vec![]; self.m]; 331 | 332 | for chunk in encoded_data { 333 | let num = chunk.index; 334 | share_nums.push(num); 335 | chunks[num] = chunk.data.clone(); 336 | } 337 | // eprintln!("encoded data: {:02x?}", encoded_data); 338 | // eprintln!("share_nums: {:02x?}", share_nums); 339 | // eprintln!("chunks: {:02x?}", chunks); 340 | 341 | let sz = chunks[share_nums[0]].len(); 342 | let mut ret_chunks = vec![vec![0; sz]; self.k]; 343 | 344 | let mut complete = true; 345 | let mut missing = std::collections::VecDeque::new(); 346 | let mut replaced = vec![]; 347 | // check which of the original chunks are missing 348 | for i in 0..self.k { 349 | if !share_nums.contains(&i) { 350 | complete = false; 351 | missing.push_back(i); 352 | // eprintln!("Missing {}", i); 353 | } 354 | } 355 | 356 | // replace the missing chunks with fec chunks 357 | for i in self.k..self.m { 358 | if !chunks[i].is_empty() { 359 | if let Some(index) = missing.pop_front() { 360 | // eprintln!("Moving {} to {}", i, index); 361 | replaced.push(index); 362 | share_nums.insert(index, i); 363 | chunks[index] = chunks[i].to_vec(); 364 | // eprintln!("share_nums: {:02x?}", share_nums); 365 | // eprintln!("chunks: {:02x?}", chunks); 366 | } 367 | } 368 | } 369 | 370 | if complete { 371 | let flat = Self::flatten(&mut chunks[..self.k].to_vec()); 372 | return Ok(flat[..flat.len() - padding].to_vec()); 373 | } 374 | 375 | /////////////// internal decode 376 | 377 | let mut m_dec = vec![0; self.k * self.k]; 378 | let mut outix = 0; 379 | 380 | self.build_decode_matrix_into_space(&share_nums, self.k, &mut m_dec[..]); 381 | 382 | for row in 0..self.k { 383 | assert!((share_nums[row] >= self.k) || (share_nums[row] == row)); 384 | if share_nums[row] >= self.k { 385 | // if it's not a normal block 386 | // memset(outpkts[outix], 0, sz); 387 | for i in 0..sz { 388 | ret_chunks[outix][i] = 0; 389 | } 390 | for col in 0..self.k { 391 | // eprintln!("Loc 2"); 392 | statics::STATICS.addmul( 393 | &mut ret_chunks[outix][..], 394 | &chunks[col][..], 395 | m_dec[row * self.k + col], 396 | sz, 397 | ); 398 | } 399 | outix += 1; 400 | } 401 | } 402 | 403 | /////////////// end internal decode 404 | 405 | // eprintln!("replaced: {:02x?}", replaced); 406 | // eprintln!("ret_chunks: {:02x?}", ret_chunks); 407 | // fix the replaced chunks 408 | for i in 0..replaced.len() { 409 | chunks[replaced[i]] = ret_chunks[i].to_vec(); 410 | // eprintln!("chunks: {:02x?}", chunks); 411 | } 412 | let ret_vec = Self::flatten(&mut chunks[0..self.k].to_vec()); 413 | 414 | // remove padding 415 | Ok(ret_vec[..ret_vec.len() - padding].to_vec()) 416 | } 417 | fn chunk_size(&self, data_len: usize) -> usize { 418 | (data_len as f64 / self.k as f64).ceil() as usize 419 | } 420 | fn flatten(square: &mut Vec>) -> Vec { 421 | let mut ret_vec = vec![]; 422 | for chunk in square { 423 | ret_vec.append(chunk); 424 | } 425 | ret_vec 426 | } 427 | fn build_decode_matrix_into_space(&self, index: &[usize], k: usize, matrix: &mut [Gf]) { 428 | for i in 0..k { 429 | let p = &mut matrix[i * k..]; 430 | if index[i] < k { 431 | // we'll assume it's already 0 432 | // memset(p, 0, k); 433 | p[i] = 1; 434 | } else { 435 | // memcpy(p, &(code->enc_matrix[index[i] * code->k]), k); 436 | (0..k).for_each(|j| { 437 | p[j] = self.enc_matrix[(index[i] * self.k) + j]; 438 | }); 439 | } 440 | } 441 | statics::STATICS._invert_mat(matrix, k); 442 | } 443 | } 444 | -------------------------------------------------------------------------------- /LICENSE: -------------------------------------------------------------------------------- 1 | GNU GENERAL PUBLIC LICENSE 2 | Version 3, 29 June 2007 3 | 4 | Copyright (C) 2007 Free Software Foundation, Inc. 5 | Everyone is permitted to copy and distribute verbatim copies 6 | of this license document, but changing it is not allowed. 7 | 8 | Preamble 9 | 10 | The GNU General Public License is a free, copyleft license for 11 | software and other kinds of works. 12 | 13 | The licenses for most software and other practical works are designed 14 | to take away your freedom to share and change the works. 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Use with the GNU Affero General Public License. 553 | 554 | Notwithstanding any other provision of this License, you have 555 | permission to link or combine any covered work with a work licensed 556 | under version 3 of the GNU Affero General Public License into a single 557 | combined work, and to convey the resulting work. The terms of this 558 | License will continue to apply to the part which is the covered work, 559 | but the special requirements of the GNU Affero General Public License, 560 | section 13, concerning interaction through a network will apply to the 561 | combination as such. 562 | 563 | 14. Revised Versions of this License. 564 | 565 | The Free Software Foundation may publish revised and/or new versions of 566 | the GNU General Public License from time to time. Such new versions will 567 | be similar in spirit to the present version, but may differ in detail to 568 | address new problems or concerns. 569 | 570 | Each version is given a distinguishing version number. If the 571 | Program specifies that a certain numbered version of the GNU General 572 | Public License "or any later version" applies to it, you have the 573 | option of following the terms and conditions either of that numbered 574 | version or of any later version published by the Free Software 575 | Foundation. If the Program does not specify a version number of the 576 | GNU General Public License, you may choose any version ever published 577 | by the Free Software Foundation. 578 | 579 | If the Program specifies that a proxy can decide which future 580 | versions of the GNU General Public License can be used, that proxy's 581 | public statement of acceptance of a version permanently authorizes you 582 | to choose that version for the Program. 583 | 584 | Later license versions may give you additional or different 585 | permissions. However, no additional obligations are imposed on any 586 | author or copyright holder as a result of your choosing to follow a 587 | later version. 588 | 589 | 15. Disclaimer of Warranty. 590 | 591 | THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY 592 | APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT 593 | HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY 594 | OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, 595 | THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 596 | PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM 597 | IS WITH YOU. SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF 598 | ALL NECESSARY SERVICING, REPAIR OR CORRECTION. 599 | 600 | 16. Limitation of Liability. 601 | 602 | IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING 603 | WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR CONVEYS 604 | THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY 605 | GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE 606 | USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF 607 | DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD 608 | PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS), 609 | EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF 610 | SUCH DAMAGES. 611 | 612 | 17. Interpretation of Sections 15 and 16. 613 | 614 | If the disclaimer of warranty and limitation of liability provided 615 | above cannot be given local legal effect according to their terms, 616 | reviewing courts shall apply local law that most closely approximates 617 | an absolute waiver of all civil liability in connection with the 618 | Program, unless a warranty or assumption of liability accompanies a 619 | copy of the Program in return for a fee. 620 | 621 | END OF TERMS AND CONDITIONS 622 | 623 | How to Apply These Terms to Your New Programs 624 | 625 | If you develop a new program, and you want it to be of the greatest 626 | possible use to the public, the best way to achieve this is to make it 627 | free software which everyone can redistribute and change under these terms. 628 | 629 | To do so, attach the following notices to the program. It is safest 630 | to attach them to the start of each source file to most effectively 631 | state the exclusion of warranty; and each file should have at least 632 | the "copyright" line and a pointer to where the full notice is found. 633 | 634 | 635 | Copyright (C) 636 | 637 | This program is free software: you can redistribute it and/or modify 638 | it under the terms of the GNU General Public License as published by 639 | the Free Software Foundation, either version 3 of the License, or 640 | (at your option) any later version. 641 | 642 | This program is distributed in the hope that it will be useful, 643 | but WITHOUT ANY WARRANTY; without even the implied warranty of 644 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 645 | GNU General Public License for more details. 646 | 647 | You should have received a copy of the GNU General Public License 648 | along with this program. If not, see . 649 | 650 | Also add information on how to contact you by electronic and paper mail. 651 | 652 | If the program does terminal interaction, make it output a short 653 | notice like this when it starts in an interactive mode: 654 | 655 | Copyright (C) 656 | This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'. 657 | This is free software, and you are welcome to redistribute it 658 | under certain conditions; type `show c' for details. 659 | 660 | The hypothetical commands `show w' and `show c' should show the appropriate 661 | parts of the General Public License. Of course, your program's commands 662 | might be different; for a GUI interface, you would use an "about box". 663 | 664 | You should also get your employer (if you work as a programmer) or school, 665 | if any, to sign a "copyright disclaimer" for the program, if necessary. 666 | For more information on this, and how to apply and follow the GNU GPL, see 667 | . 668 | 669 | The GNU General Public License does not permit incorporating your program 670 | into proprietary programs. If your program is a subroutine library, you 671 | may consider it more useful to permit linking proprietary applications with 672 | the library. If this is what you want to do, use the GNU Lesser General 673 | Public License instead of this License. But first, please read 674 | . 675 | --------------------------------------------------------------------------------