46 lines
1.1 KiB
Rust
46 lines
1.1 KiB
Rust
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use thiserror::Error;
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#[derive(Error, Debug)]
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pub enum XiamiError {
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#[error("header too small, require at least {0} bytes")]
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HeaderTooSmall(usize),
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#[error("not a xiami file")]
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NotXiamiFile,
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}
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pub struct XiamiFile {
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pub copy_len: usize,
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pub format: [u8; 4],
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key: u8,
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}
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impl XiamiFile {
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pub fn from_header(buffer: &[u8]) -> Result<Self, XiamiError> {
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if buffer.len() < 0x10 {
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Err(XiamiError::HeaderTooSmall(0x10))?;
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}
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let (format, copy_len, key) = match buffer[..0x10] {
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[b'i', b'f', b'm', b't', f1, f2, f3, f4, 0xfe, 0xfe, 0xfe, 0xfe, a, b, c, key] => {
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let copy_len = (a as usize) | ((b as usize) << 8) | ((c as usize) << 16);
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let format = [f1, f2, f3, f4];
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(format, copy_len, key.wrapping_sub(1))
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}
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_ => Err(XiamiError::NotXiamiFile)?,
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};
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Ok(Self {
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copy_len,
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format,
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key,
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})
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}
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pub fn decrypt(&self, buffer: &mut [u8]) {
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for b in buffer.iter_mut() {
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*b = self.key.wrapping_sub(*b);
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}
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}
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}
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