1 #![no_std] 2 3 #[rustfmt::skip] 4 pub mod algorithm; 5 pub mod poly; 6 pub use algorithm::*; 7 8 pub trait Width: Sized + 'static {} 9 impl Width for u8 {} 10 impl Width for u16 {} 11 impl Width for u32 {} 12 impl Width for u64 {} 13 impl Width for u128 {} 14 15 /// This struct describes a CRC algorithm using the fields specified by the [Catalogue of 16 /// parametrised CRC algorithms](https://reveng.sourceforge.io/crc-catalogue/all.htm). 17 pub struct Algorithm<W: Width> { 18 /// The number of bit cells in the linear feedback shift register; the degree of the generator 19 /// polynomial, minus one. 20 pub width: u8, 21 /// The generator polynomial that sets the feedback tap positions of the shift register. The 22 /// least significant bit corresponds to the inward end of the shift register, and is always 23 /// set. The highest-order term is omitted. 24 pub poly: W, 25 /// The settings of the bit cells at the start of each calculation, before reading the first 26 /// message bit. The least significant bit corresponds to the inward end of the shift register. 27 pub init: W, 28 /// If equal to `false`, specifies that the characters of the message are read bit-by-bit, most 29 /// significant bit (MSB) first; if equal to `true`, the characters are read bit-by-bit, least 30 /// significant bit (LSB) first. Each sampled message bit is then XORed with the bit being 31 /// simultaneously shifted out of the register at the most significant end, and the result is 32 /// passed to the feedback taps. 33 pub refin: bool, 34 /// If equal to `false`, specifies that the contents of the register after reading the last 35 /// message bit are unreflected before presentation; if equal to `true`, it specifies that they 36 /// are reflected, character-by-character, before presentation. For the purpose of this 37 /// definition, the reflection is performed by swapping the content of each cell with that of 38 /// the cell an equal distance from the opposite end of the register; the characters of the CRC 39 /// are then true images of parts of the reflected register, the character containing the 40 /// original MSB always appearing first. 41 pub refout: bool, 42 /// The XOR value applied to the contents of the register after the last message bit has been 43 /// read and after the optional reflection. It has the same endianness as the CRC such that its 44 /// true image appears in the characters of the CRC. 45 pub xorout: W, 46 /// The contents of the register after initialising, reading the UTF-8 string `"123456789"` (as 47 /// 8-bit characters), optionally reflecting, and applying the final XOR. 48 pub check: W, 49 /// The contents of the register after initialising, reading an error-free codeword and 50 /// optionally reflecting the register (if [`refout`](Algorithm::refout)=`true`), but not 51 /// applying the final XOR. This is mathematically equivalent to initialising the register with 52 /// the xorout parameter, reflecting it as described (if [`refout`](Algorithm::refout)=`true`), 53 /// reading as many zero bits as there are cells in the register, and reflecting the result (if 54 /// [`refin`](Algorithm::refin)=`true`). The residue of a crossed-endian model is calculated 55 /// assuming that the characters of the received CRC are specially reflected before submitting 56 /// the codeword. 57 pub residue: W, 58 } 59