forked from M-Labs/ionpak-thermostat
45 lines
1.1 KiB
Rust
45 lines
1.1 KiB
Rust
#[derive(Clone, Copy, PartialEq)]
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#[repr(u8)]
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pub enum ChecksumMode {
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Off = 0b00,
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/// Seems much less reliable than `Crc`
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Xor = 0b01,
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Crc = 0b10,
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}
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pub struct Checksum {
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mode: ChecksumMode,
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state: u8,
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}
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impl Checksum {
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pub fn new(mode: ChecksumMode) -> Self {
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Checksum { mode, state: 0 }
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}
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pub fn feed(&mut self, input: u8) {
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match self.mode {
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ChecksumMode::Off => {},
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ChecksumMode::Xor => self.state ^= input,
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ChecksumMode::Crc => {
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for i in 0..8 {
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let input_mask = 0x80 >> i;
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self.state = (self.state << 1) ^
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if ((self.state & 0x80) != 0) != ((input & input_mask) != 0) {
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0x07 /* x8 + x2 + x + 1 */
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} else {
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0
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};
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}
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}
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}
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}
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pub fn result(&self) -> Option<u8> {
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match self.mode {
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ChecksumMode::Off => None,
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_ => Some(self.state)
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}
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}
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}
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