diff --git a/lrwn/src/applayer/fragmentation/v1.rs b/lrwn/src/applayer/fragmentation/v1.rs index e6036c26..671e9211 100644 --- a/lrwn/src/applayer/fragmentation/v1.rs +++ b/lrwn/src/applayer/fragmentation/v1.rs @@ -487,6 +487,65 @@ pub struct DataFragmentPayloadIndexAndN { pub frag_index: u8, } +// Encode the given slice of bytes to fragments including forward error correction. +// This is based on the proposed FEC code from the Fragmented Data Block Transport over +// LoRaWAN recommendation. +pub fn encode(payload: &[u8], fragment_size: usize, redundancy: usize) -> Result>> { + if payload.len() % fragment_size != 0 { + return Err(anyhow!("Payload size must be a multiple of fragment_size")); + } + + // fragment the data into rows + let mut data_rows: Vec> = payload.chunks(fragment_size).map(|v| v.to_vec()).collect(); + let w = data_rows.len(); + + for y in 0..redundancy { + let mut s = vec![0; fragment_size]; + let a = matrix_line(y + 1, w); + + for x in 0..w { + if a[x] == 1 { + for (m, s_val) in s.iter_mut().enumerate() { + *s_val ^= data_rows[x][m]; + } + } + } + + data_rows.push(s); + } + + Ok(data_rows) +} + +fn prbs23(x: usize) -> usize { + let b0 = x & 1; + let b1 = (x & 32) / 32; + (x / 2) + (b0 ^ b1) * (1 << 22) +} + +fn is_power_2(num: usize) -> bool { + num != 0 && (num & (num - 1)) == 0 +} + +fn matrix_line(n: usize, m: usize) -> Vec { + let mut line = vec![0; m]; + + let mm = if is_power_2(m) { 1 } else { 0 }; + + let mut x = 1 + (1001 * n); + + for _nb_coeff in 0..(m / 2) { + let mut r = 1 << 16; + while r >= m { + x = prbs23(x); + r = x % (m + mm); + } + line[r] = 1; + } + + line +} + #[cfg(test)] mod test { use super::*; @@ -759,6 +818,98 @@ mod test { run_tests_decode(&decode_tests); } + #[test] + fn test_encode() { + struct EncodeTest { + name: String, + data: Vec, + fragment_size: usize, + redundancy: usize, + expected_fragments: Vec>, + expected_error: Option, + } + + let mut data = vec![0; 100]; + for (i, v) in data.iter_mut().enumerate() { + *v = i as u8; + } + + let tests = [ + EncodeTest { + name: "invalid fragment size".into(), + data: vec![0; 5], + fragment_size: 10, + redundancy: 0, + expected_fragments: vec![], + expected_error: Some("Payload size must be a multiple of fragment_size".into()), + }, + EncodeTest { + name: "fragment size 10, redundancy 10".into(), + data: data.clone(), + fragment_size: 10, + redundancy: 10, + expected_fragments: vec![ + vec![0x0, 0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8, 0x9], + vec![0xa, 0xb, 0xc, 0xd, 0xe, 0xf, 0x10, 0x11, 0x12, 0x13], + vec![0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d], + vec![0x1e, 0x1f, 0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27], + vec![0x28, 0x29, 0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f, 0x30, 0x31], + vec![0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x3a, 0x3b], + vec![0x3c, 0x3d, 0x3e, 0x3f, 0x40, 0x41, 0x42, 0x43, 0x44, 0x45], + vec![0x46, 0x47, 0x48, 0x49, 0x4a, 0x4b, 0x4c, 0x4d, 0x4e, 0x4f], + vec![0x50, 0x51, 0x52, 0x53, 0x54, 0x55, 0x56, 0x57, 0x58, 0x59], + vec![0x5a, 0x5b, 0x5c, 0x5d, 0x5e, 0x5f, 0x60, 0x61, 0x62, 0x63], + vec![0x26, 0x26, 0x22, 0x22, 0x2e, 0x2e, 0x22, 0x22, 0x26, 0x26], + vec![0x54, 0x55, 0x56, 0x57, 0x58, 0x59, 0x6a, 0x6b, 0x7c, 0x7d], + vec![0x5c, 0x5d, 0x6e, 0x6f, 0x10, 0x11, 0x2, 0x3, 0x4, 0x5], + vec![0x36, 0x36, 0x32, 0x32, 0x3e, 0x3e, 0x22, 0x22, 0x36, 0x36], + vec![0x3a, 0x3a, 0xe, 0xe, 0xa, 0xa, 0x6, 0x6, 0xa, 0xa], + vec![0xe, 0xe, 0x32, 0x32, 0x36, 0x36, 0x22, 0x22, 0x3e, 0x3e], + vec![0x2, 0x2, 0xe, 0xe, 0x72, 0x72, 0x76, 0x76, 0x62, 0x62], + vec![0x1e, 0x1e, 0x1a, 0x1a, 0x66, 0x66, 0x5a, 0x5a, 0x4e, 0x4e], + vec![0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f, 0x30, 0x31, 0x22, 0x23], + vec![0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x18, 0x19, 0xa, 0xb], + ], + expected_error: None, + }, + EncodeTest { + name: "fragment size 10, redundancy 5".into(), + data: data.clone(), + fragment_size: 10, + redundancy: 5, + expected_fragments: vec![ + vec![0x0, 0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8, 0x9], + vec![0xa, 0xb, 0xc, 0xd, 0xe, 0xf, 0x10, 0x11, 0x12, 0x13], + vec![0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d], + vec![0x1e, 0x1f, 0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27], + vec![0x28, 0x29, 0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f, 0x30, 0x31], + vec![0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x3a, 0x3b], + vec![0x3c, 0x3d, 0x3e, 0x3f, 0x40, 0x41, 0x42, 0x43, 0x44, 0x45], + vec![0x46, 0x47, 0x48, 0x49, 0x4a, 0x4b, 0x4c, 0x4d, 0x4e, 0x4f], + vec![0x50, 0x51, 0x52, 0x53, 0x54, 0x55, 0x56, 0x57, 0x58, 0x59], + vec![0x5a, 0x5b, 0x5c, 0x5d, 0x5e, 0x5f, 0x60, 0x61, 0x62, 0x63], + vec![0x26, 0x26, 0x22, 0x22, 0x2e, 0x2e, 0x22, 0x22, 0x26, 0x26], + vec![0x54, 0x55, 0x56, 0x57, 0x58, 0x59, 0x6a, 0x6b, 0x7c, 0x7d], + vec![0x5c, 0x5d, 0x6e, 0x6f, 0x10, 0x11, 0x2, 0x3, 0x4, 0x5], + vec![0x36, 0x36, 0x32, 0x32, 0x3e, 0x3e, 0x22, 0x22, 0x36, 0x36], + vec![0x3a, 0x3a, 0xe, 0xe, 0xa, 0xa, 0x6, 0x6, 0xa, 0xa], + ], + expected_error: None, + }, + ]; + + for tst in &tests { + println!("> {}", tst.name); + + let res = encode(&tst.data, tst.fragment_size, tst.redundancy); + if let Some(e) = &tst.expected_error { + assert_eq!(e, &res.err().unwrap().to_string()); + } else { + assert_eq!(tst.expected_fragments, res.unwrap()); + } + } + } + fn run_tests_encode(tests: &[CommandTest]) { for tst in tests { println!("> {}", tst.name);