Valentin Popov
842f4a8569
- Added `lzss_decompress_simple` function for LZSS decompression in `lzss.rs`. - Introduced `XorState` struct and `xor_stream` function for XOR decryption in `xor.rs`. - Updated `mod.rs` to include new LZSS and XOR modules. - Refactored `parse_library` function in `parse.rs` to utilize the new XOR decryption functionality. - Cleaned up and organized code in `lib.rs` by removing redundant functions and structures. - Added tests for new functionality in `tests.rs`.
80 lines
2.4 KiB
Rust
80 lines
2.4 KiB
Rust
use super::xor::XorState;
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use crate::error::Error;
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use crate::Result;
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/// Simple LZSS decompression with optional on-the-fly XOR decryption
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pub fn lzss_decompress_simple(
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data: &[u8],
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expected_size: usize,
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xor_key: Option<u16>,
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) -> Result<Vec<u8>> {
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let mut ring = [0x20u8; 0x1000];
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let mut ring_pos = 0xFEEusize;
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let mut out = Vec::with_capacity(expected_size);
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let mut in_pos = 0usize;
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let mut control = 0u8;
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let mut bits_left = 0u8;
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// XOR state for on-the-fly decryption
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let mut xor_state = xor_key.map(XorState::new);
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// Helper to read byte with optional XOR decryption
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let read_byte = |pos: usize, state: &mut Option<XorState>| -> Option<u8> {
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let encrypted = data.get(pos).copied()?;
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Some(if let Some(ref mut s) = state {
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s.decrypt_byte(encrypted)
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} else {
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encrypted
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})
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};
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while out.len() < expected_size {
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if bits_left == 0 {
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let byte = read_byte(in_pos, &mut xor_state)
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.ok_or(Error::DecompressionFailed("lzss-simple: unexpected EOF"))?;
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control = byte;
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in_pos += 1;
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bits_left = 8;
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}
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if (control & 1) != 0 {
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let byte = read_byte(in_pos, &mut xor_state)
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.ok_or(Error::DecompressionFailed("lzss-simple: unexpected EOF"))?;
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in_pos += 1;
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out.push(byte);
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ring[ring_pos] = byte;
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ring_pos = (ring_pos + 1) & 0x0FFF;
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} else {
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let low = read_byte(in_pos, &mut xor_state)
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.ok_or(Error::DecompressionFailed("lzss-simple: unexpected EOF"))?;
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let high = read_byte(in_pos + 1, &mut xor_state)
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.ok_or(Error::DecompressionFailed("lzss-simple: unexpected EOF"))?;
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in_pos += 2;
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let offset = usize::from(low) | (usize::from(high & 0xF0) << 4);
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let length = usize::from((high & 0x0F) + 3);
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for step in 0..length {
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let byte = ring[(offset + step) & 0x0FFF];
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out.push(byte);
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ring[ring_pos] = byte;
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ring_pos = (ring_pos + 1) & 0x0FFF;
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if out.len() >= expected_size {
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break;
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}
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}
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}
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control >>= 1;
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bits_left -= 1;
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}
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if out.len() != expected_size {
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return Err(Error::DecompressionFailed("lzss-simple"));
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}
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Ok(out)
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}
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