feat: add initial implementation of rsli crate

- Created Cargo.toml for the rsli crate with flate2 dependency.
- Implemented ResourceData enum for handling borrowed and owned byte slices.
- Added OutputBuffer trait and its Vec<u8> implementation for writing data.
- Defined a comprehensive Error enum for error handling in the library.
- Developed the Library struct to manage resource entries and provide methods for loading and unpacking resources.
- Implemented various packing methods and decompression algorithms, including LZSS and Deflate.
- Added tests for validating the functionality of the rsli library against sample data.

1 files changed, 1165 insertions, 0 deletions

diff --git a/crates/rsli/src/lib.rs b/crates/rsli/src/lib.rs
new file mode 100644
index 0000000..0c55b25
--- /dev/null
+++ b/crates/rsli/src/lib.rs
@@ -0,0 +1,1165 @@
+pub mod data;
+pub mod error;
+
+use crate::data::{OutputBuffer, ResourceData};
+use crate::error::Error;
+use flate2::read::{DeflateDecoder, ZlibDecoder};
+use std::cmp::Ordering;
+use std::fs;
+use std::io::Read;
+use std::path::Path;
+use std::sync::Arc;
+
+pub type Result<T> = core::result::Result<T, Error>;
+
+#[derive(Clone, Debug)]
+pub struct OpenOptions {
+    pub allow_ao_trailer: bool,
+    pub allow_deflate_eof_plus_one: bool,
+}
+
+impl Default for OpenOptions {
+    fn default() -> Self {
+        Self {
+            allow_ao_trailer: true,
+            allow_deflate_eof_plus_one: true,
+        }
+    }
+}
+
+pub struct Library {
+    bytes: Arc<[u8]>,
+    entries: Vec<EntryRecord>,
+    #[cfg(test)]
+    header_raw: [u8; 32],
+    #[cfg(test)]
+    table_plain_original: Vec<u8>,
+    #[cfg(test)]
+    xor_seed: u32,
+    #[cfg(test)]
+    source_size: usize,
+    #[cfg(test)]
+    trailer_raw: Option<[u8; 6]>,
+}
+
+#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
+pub struct EntryId(pub u32);
+
+#[derive(Clone, Debug)]
+pub struct EntryMeta {
+    pub name: String,
+    pub flags: i32,
+    pub method: PackMethod,
+    pub data_offset: u64,
+    pub packed_size: u32,
+    pub unpacked_size: u32,
+}
+
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub enum PackMethod {
+    None,
+    XorOnly,
+    Lzss,
+    XorLzss,
+    LzssHuffman,
+    XorLzssHuffman,
+    Deflate,
+    Unknown(u32),
+}
+
+#[derive(Copy, Clone, Debug)]
+pub struct EntryRef<'a> {
+    pub id: EntryId,
+    pub meta: &'a EntryMeta,
+}
+
+pub struct PackedResource {
+    pub meta: EntryMeta,
+    pub packed: Vec<u8>,
+}
+
+#[derive(Clone, Debug)]
+struct EntryRecord {
+    meta: EntryMeta,
+    name_raw: [u8; 12],
+    sort_to_original: i16,
+    key16: u16,
+    #[cfg(test)]
+    data_offset_raw: u32,
+    packed_size_declared: u32,
+    packed_size_available: usize,
+    effective_offset: usize,
+}
+
+impl Library {
+    pub fn open_path(path: impl AsRef<Path>) -> Result<Self> {
+        Self::open_path_with(path, OpenOptions::default())
+    }
+
+    pub fn open_path_with(path: impl AsRef<Path>, opts: OpenOptions) -> Result<Self> {
+        let bytes = fs::read(path.as_ref())?;
+        let arc: Arc<[u8]> = Arc::from(bytes.into_boxed_slice());
+        parse_library(arc, opts)
+    }
+
+    pub fn entry_count(&self) -> usize {
+        self.entries.len()
+    }
+
+    pub fn entries(&self) -> impl Iterator<Item = EntryRef<'_>> {
+        self.entries
+            .iter()
+            .enumerate()
+            .map(|(idx, entry)| EntryRef {
+                id: EntryId(idx as u32),
+                meta: &entry.meta,
+            })
+    }
+
+    pub fn find(&self, name: &str) -> Option<EntryId> {
+        if self.entries.is_empty() {
+            return None;
+        }
+
+        let query = name.to_ascii_uppercase();
+        let query_bytes = query.as_bytes();
+
+        let mut low = 0usize;
+        let mut high = self.entries.len();
+        while low < high {
+            let mid = low + (high - low) / 2;
+            let idx = self.entries[mid].sort_to_original;
+            if idx < 0 {
+                break;
+            }
+            let idx = usize::try_from(idx).ok()?;
+            if idx >= self.entries.len() {
+                break;
+            }
+
+            let cmp = cmp_c_string(query_bytes, c_name_bytes(&self.entries[idx].name_raw));
+            match cmp {
+                Ordering::Less => high = mid,
+                Ordering::Greater => low = mid + 1,
+                Ordering::Equal => return Some(EntryId(idx as u32)),
+            }
+        }
+
+        self.entries.iter().enumerate().find_map(|(idx, entry)| {
+            if cmp_c_string(query_bytes, c_name_bytes(&entry.name_raw)) == Ordering::Equal {
+                Some(EntryId(idx as u32))
+            } else {
+                None
+            }
+        })
+    }
+
+    pub fn get(&self, id: EntryId) -> Option<EntryRef<'_>> {
+        let idx = usize::try_from(id.0).ok()?;
+        let entry = self.entries.get(idx)?;
+        Some(EntryRef {
+            id,
+            meta: &entry.meta,
+        })
+    }
+
+    pub fn load(&self, id: EntryId) -> Result<Vec<u8>> {
+        let entry = self.entry_by_id(id)?;
+        let packed = self.packed_slice(entry)?;
+        decode_payload(
+            packed,
+            entry.meta.method,
+            entry.key16,
+            entry.meta.unpacked_size,
+        )
+    }
+
+    pub fn load_into(&self, id: EntryId, out: &mut dyn OutputBuffer) -> Result<usize> {
+        let decoded = self.load(id)?;
+        out.write_exact(&decoded)?;
+        Ok(decoded.len())
+    }
+
+    pub fn load_packed(&self, id: EntryId) -> Result<PackedResource> {
+        let entry = self.entry_by_id(id)?;
+        let packed = self.packed_slice(entry)?.to_vec();
+        Ok(PackedResource {
+            meta: entry.meta.clone(),
+            packed,
+        })
+    }
+
+    pub fn unpack(&self, packed: &PackedResource) -> Result<Vec<u8>> {
+        let key16 = self.resolve_key_for_meta(&packed.meta).unwrap_or(0);
+
+        let method = packed.meta.method;
+        if needs_xor_key(method) && self.resolve_key_for_meta(&packed.meta).is_none() {
+            return Err(Error::CorruptEntryTable(
+                "cannot resolve XOR key for packed resource",
+            ));
+        }
+
+        decode_payload(&packed.packed, method, key16, packed.meta.unpacked_size)
+    }
+
+    pub fn load_fast(&self, id: EntryId) -> Result<ResourceData<'_>> {
+        let entry = self.entry_by_id(id)?;
+        if entry.meta.method == PackMethod::None {
+            let packed = self.packed_slice(entry)?;
+            let size =
+                usize::try_from(entry.meta.unpacked_size).map_err(|_| Error::IntegerOverflow)?;
+            if packed.len() < size {
+                return Err(Error::OutputSizeMismatch {
+                    expected: entry.meta.unpacked_size,
+                    got: u32::try_from(packed.len()).unwrap_or(u32::MAX),
+                });
+            }
+            return Ok(ResourceData::Borrowed(&packed[..size]));
+        }
+        Ok(ResourceData::Owned(self.load(id)?))
+    }
+
+    fn entry_by_id(&self, id: EntryId) -> Result<&EntryRecord> {
+        let idx = usize::try_from(id.0).map_err(|_| Error::IntegerOverflow)?;
+        self.entries
+            .get(idx)
+            .ok_or_else(|| Error::EntryIdOutOfRange {
+                id: id.0,
+                entry_count: self.entries.len().try_into().unwrap_or(u32::MAX),
+            })
+    }
+
+    fn packed_slice<'a>(&'a self, entry: &EntryRecord) -> Result<&'a [u8]> {
+        let start = entry.effective_offset;
+        let end = start
+            .checked_add(entry.packed_size_available)
+            .ok_or(Error::IntegerOverflow)?;
+        self.bytes
+            .get(start..end)
+            .ok_or(Error::EntryDataOutOfBounds {
+                id: 0,
+                offset: u64::try_from(start).unwrap_or(u64::MAX),
+                size: entry.packed_size_declared,
+                file_len: u64::try_from(self.bytes.len()).unwrap_or(u64::MAX),
+            })
+    }
+
+    fn resolve_key_for_meta(&self, meta: &EntryMeta) -> Option<u16> {
+        self.entries
+            .iter()
+            .find(|entry| {
+                entry.meta.name == meta.name
+                    && entry.meta.flags == meta.flags
+                    && entry.meta.data_offset == meta.data_offset
+                    && entry.meta.packed_size == meta.packed_size
+                    && entry.meta.unpacked_size == meta.unpacked_size
+                    && entry.meta.method == meta.method
+            })
+            .map(|entry| entry.key16)
+    }
+
+    #[cfg(test)]
+    fn rebuild_from_parsed_metadata(&self) -> Result<Vec<u8>> {
+        let trailer_len = usize::from(self.trailer_raw.is_some()) * 6;
+        let pre_trailer_size = self
+            .source_size
+            .checked_sub(trailer_len)
+            .ok_or(Error::IntegerOverflow)?;
+
+        let count = self.entries.len();
+        let table_len = count.checked_mul(32).ok_or(Error::IntegerOverflow)?;
+        let table_end = 32usize
+            .checked_add(table_len)
+            .ok_or(Error::IntegerOverflow)?;
+        if pre_trailer_size < table_end {
+            return Err(Error::EntryTableOutOfBounds {
+                table_offset: 32,
+                table_len: u64::try_from(table_len).map_err(|_| Error::IntegerOverflow)?,
+                file_len: u64::try_from(pre_trailer_size).map_err(|_| Error::IntegerOverflow)?,
+            });
+        }
+
+        let mut out = vec![0u8; pre_trailer_size];
+        out[0..32].copy_from_slice(&self.header_raw);
+        let encrypted_table =
+            xor_stream(&self.table_plain_original, (self.xor_seed & 0xFFFF) as u16);
+        out[32..table_end].copy_from_slice(&encrypted_table);
+
+        let mut occupied = vec![false; pre_trailer_size];
+        for byte in occupied.iter_mut().take(table_end) {
+            *byte = true;
+        }
+
+        for (idx, entry) in self.entries.iter().enumerate() {
+            let packed = self.load_packed(EntryId(idx as u32))?.packed;
+            let start =
+                usize::try_from(entry.data_offset_raw).map_err(|_| Error::IntegerOverflow)?;
+            for (offset, byte) in packed.iter().copied().enumerate() {
+                let pos = start.checked_add(offset).ok_or(Error::IntegerOverflow)?;
+                if pos >= out.len() {
+                    return Err(Error::PackedSizePastEof {
+                        id: idx as u32,
+                        offset: u64::from(entry.data_offset_raw),
+                        packed_size: entry.packed_size_declared,
+                        file_len: u64::try_from(out.len()).map_err(|_| Error::IntegerOverflow)?,
+                    });
+                }
+                if occupied[pos] && out[pos] != byte {
+                    return Err(Error::CorruptEntryTable("packed payload overlap conflict"));
+                }
+                out[pos] = byte;
+                occupied[pos] = true;
+            }
+        }
+
+        if let Some(trailer) = self.trailer_raw {
+            out.extend_from_slice(&trailer);
+        }
+        Ok(out)
+    }
+}
+
+fn parse_library(bytes: Arc<[u8]>, opts: OpenOptions) -> Result<Library> {
+    if bytes.len() < 32 {
+        return Err(Error::EntryTableOutOfBounds {
+            table_offset: 32,
+            table_len: 0,
+            file_len: u64::try_from(bytes.len()).map_err(|_| Error::IntegerOverflow)?,
+        });
+    }
+
+    let mut header_raw = [0u8; 32];
+    header_raw.copy_from_slice(&bytes[0..32]);
+
+    if &bytes[0..2] != b"NL" {
+        let mut got = [0u8; 2];
+        got.copy_from_slice(&bytes[0..2]);
+        return Err(Error::InvalidMagic { got });
+    }
+    if bytes[3] != 0x01 {
+        return Err(Error::UnsupportedVersion { got: bytes[3] });
+    }
+
+    let entry_count = i16::from_le_bytes([bytes[4], bytes[5]]);
+    if entry_count < 0 {
+        return Err(Error::InvalidEntryCount { got: entry_count });
+    }
+    let count = usize::try_from(entry_count).map_err(|_| Error::IntegerOverflow)?;
+
+    let xor_seed = u32::from_le_bytes([bytes[20], bytes[21], bytes[22], bytes[23]]);
+
+    let table_len = count.checked_mul(32).ok_or(Error::IntegerOverflow)?;
+    let table_offset = 32usize;
+    let table_end = table_offset
+        .checked_add(table_len)
+        .ok_or(Error::IntegerOverflow)?;
+    if table_end > bytes.len() {
+        return Err(Error::EntryTableOutOfBounds {
+            table_offset: u64::try_from(table_offset).map_err(|_| Error::IntegerOverflow)?,
+            table_len: u64::try_from(table_len).map_err(|_| Error::IntegerOverflow)?,
+            file_len: u64::try_from(bytes.len()).map_err(|_| Error::IntegerOverflow)?,
+        });
+    }
+
+    let table_enc = &bytes[table_offset..table_end];
+    let table_plain_original = xor_stream(table_enc, (xor_seed & 0xFFFF) as u16);
+    if table_plain_original.len() != table_len {
+        return Err(Error::EntryTableDecryptFailed);
+    }
+
+    let (overlay, trailer_raw) = parse_ao_trailer(&bytes, opts.allow_ao_trailer)?;
+    #[cfg(not(test))]
+    let _ = trailer_raw;
+
+    let mut entries = Vec::with_capacity(count);
+    for idx in 0..count {
+        let row = &table_plain_original[idx * 32..(idx + 1) * 32];
+
+        let mut name_raw = [0u8; 12];
+        name_raw.copy_from_slice(&row[0..12]);
+
+        let flags_signed = i16::from_le_bytes([row[16], row[17]]);
+        let sort_to_original = i16::from_le_bytes([row[18], row[19]]);
+        let unpacked_size = u32::from_le_bytes([row[20], row[21], row[22], row[23]]);
+        let data_offset_raw = u32::from_le_bytes([row[24], row[25], row[26], row[27]]);
+        let packed_size_declared = u32::from_le_bytes([row[28], row[29], row[30], row[31]]);
+
+        let method_raw = (flags_signed as u16 as u32) & 0x1E0;
+        let method = parse_method(method_raw);
+
+        let effective_offset_u64 = u64::from(data_offset_raw)
+            .checked_add(u64::from(overlay))
+            .ok_or(Error::IntegerOverflow)?;
+        let effective_offset =
+            usize::try_from(effective_offset_u64).map_err(|_| Error::IntegerOverflow)?;
+
+        let packed_size_usize =
+            usize::try_from(packed_size_declared).map_err(|_| Error::IntegerOverflow)?;
+        let mut packed_size_available = packed_size_usize;
+
+        let end = effective_offset_u64
+            .checked_add(u64::from(packed_size_declared))
+            .ok_or(Error::IntegerOverflow)?;
+        let file_len_u64 = u64::try_from(bytes.len()).map_err(|_| Error::IntegerOverflow)?;
+
+        if end > file_len_u64 {
+            if method_raw == 0x100 && end == file_len_u64 + 1 {
+                if opts.allow_deflate_eof_plus_one {
+                    packed_size_available = packed_size_available
+                        .checked_sub(1)
+                        .ok_or(Error::IntegerOverflow)?;
+                } else {
+                    return Err(Error::DeflateEofPlusOneQuirkRejected { id: idx as u32 });
+                }
+            } else {
+                return Err(Error::PackedSizePastEof {
+                    id: idx as u32,
+                    offset: effective_offset_u64,
+                    packed_size: packed_size_declared,
+                    file_len: file_len_u64,
+                });
+            }
+        }
+
+        let available_end = effective_offset
+            .checked_add(packed_size_available)
+            .ok_or(Error::IntegerOverflow)?;
+        if available_end > bytes.len() {
+            return Err(Error::EntryDataOutOfBounds {
+                id: idx as u32,
+                offset: effective_offset_u64,
+                size: packed_size_declared,
+                file_len: file_len_u64,
+            });
+        }
+
+        let name = decode_name(c_name_bytes(&name_raw));
+
+        entries.push(EntryRecord {
+            meta: EntryMeta {
+                name,
+                flags: i32::from(flags_signed),
+                method,
+                data_offset: effective_offset_u64,
+                packed_size: packed_size_declared,
+                unpacked_size,
+            },
+            name_raw,
+            sort_to_original,
+            key16: sort_to_original as u16,
+            #[cfg(test)]
+            data_offset_raw,
+            packed_size_declared,
+            packed_size_available,
+            effective_offset,
+        });
+    }
+
+    let presorted_flag = u16::from_le_bytes([bytes[14], bytes[15]]);
+    if presorted_flag == 0xABBA {
+        for entry in &entries {
+            let idx = i32::from(entry.sort_to_original);
+            if idx < 0 || usize::try_from(idx).map_err(|_| Error::IntegerOverflow)? >= count {
+                return Err(Error::CorruptEntryTable(
+                    "sort_to_original is not a valid permutation index",
+                ));
+            }
+        }
+    } else {
+        let mut sorted: Vec<usize> = (0..count).collect();
+        sorted.sort_by(|a, b| {
+            cmp_c_string(
+                c_name_bytes(&entries[*a].name_raw),
+                c_name_bytes(&entries[*b].name_raw),
+            )
+        });
+        for (idx, entry) in entries.iter_mut().enumerate() {
+            entry.sort_to_original =
+                i16::try_from(sorted[idx]).map_err(|_| Error::IntegerOverflow)?;
+            entry.key16 = entry.sort_to_original as u16;
+        }
+    }
+
+    #[cfg(test)]
+    let source_size = bytes.len();
+
+    Ok(Library {
+        bytes,
+        entries,
+        #[cfg(test)]
+        header_raw,
+        #[cfg(test)]
+        table_plain_original,
+        #[cfg(test)]
+        xor_seed,
+        #[cfg(test)]
+        source_size,
+        #[cfg(test)]
+        trailer_raw,
+    })
+}
+
+fn parse_ao_trailer(bytes: &[u8], allow: bool) -> Result<(u32, Option<[u8; 6]>)> {
+    if !allow || bytes.len() < 6 {
+        return Ok((0, None));
+    }
+
+    if &bytes[bytes.len() - 6..bytes.len() - 4] != b"AO" {
+        return Ok((0, None));
+    }
+
+    let mut trailer = [0u8; 6];
+    trailer.copy_from_slice(&bytes[bytes.len() - 6..]);
+    let overlay = u32::from_le_bytes([trailer[2], trailer[3], trailer[4], trailer[5]]);
+
+    if u64::from(overlay) > u64::try_from(bytes.len()).map_err(|_| Error::IntegerOverflow)? {
+        return Err(Error::MediaOverlayOutOfBounds {
+            overlay,
+            file_len: u64::try_from(bytes.len()).map_err(|_| Error::IntegerOverflow)?,
+        });
+    }
+
+    Ok((overlay, Some(trailer)))
+}
+
+fn parse_method(raw: u32) -> PackMethod {
+    match raw {
+        0x000 => PackMethod::None,
+        0x020 => PackMethod::XorOnly,
+        0x040 => PackMethod::Lzss,
+        0x060 => PackMethod::XorLzss,
+        0x080 => PackMethod::LzssHuffman,
+        0x0A0 => PackMethod::XorLzssHuffman,
+        0x100 => PackMethod::Deflate,
+        other => PackMethod::Unknown(other),
+    }
+}
+
+fn decode_payload(
+    packed: &[u8],
+    method: PackMethod,
+    key16: u16,
+    unpacked_size: u32,
+) -> Result<Vec<u8>> {
+    let expected = usize::try_from(unpacked_size).map_err(|_| Error::IntegerOverflow)?;
+
+    let out = match method {
+        PackMethod::None => {
+            if packed.len() < expected {
+                return Err(Error::OutputSizeMismatch {
+                    expected: unpacked_size,
+                    got: u32::try_from(packed.len()).unwrap_or(u32::MAX),
+                });
+            }
+            packed[..expected].to_vec()
+        }
+        PackMethod::XorOnly => {
+            if packed.len() < expected {
+                return Err(Error::OutputSizeMismatch {
+                    expected: unpacked_size,
+                    got: u32::try_from(packed.len()).unwrap_or(u32::MAX),
+                });
+            }
+            xor_stream(&packed[..expected], key16)
+        }
+        PackMethod::Lzss => lzss_decompress_simple(packed, expected)?,
+        PackMethod::XorLzss => {
+            let decrypted = xor_stream(packed, key16);
+            lzss_decompress_simple(&decrypted, expected)?
+        }
+        PackMethod::LzssHuffman => lzss_huffman_decompress(packed, expected)?,
+        PackMethod::XorLzssHuffman => {
+            let decrypted = xor_stream(packed, key16);
+            lzss_huffman_decompress(&decrypted, expected)?
+        }
+        PackMethod::Deflate => decode_deflate(packed)?,
+        PackMethod::Unknown(raw) => return Err(Error::UnsupportedMethod { raw }),
+    };
+
+    if out.len() != expected {
+        return Err(Error::OutputSizeMismatch {
+            expected: unpacked_size,
+            got: u32::try_from(out.len()).unwrap_or(u32::MAX),
+        });
+    }
+
+    Ok(out)
+}
+
+fn decode_deflate(packed: &[u8]) -> Result<Vec<u8>> {
+    let mut out = Vec::new();
+    let mut decoder = DeflateDecoder::new(packed);
+    if decoder.read_to_end(&mut out).is_ok() {
+        return Ok(out);
+    }
+
+    out.clear();
+    let mut zlib = ZlibDecoder::new(packed);
+    zlib.read_to_end(&mut out)
+        .map_err(|_| Error::DecompressionFailed("deflate"))?;
+    Ok(out)
+}
+
+fn xor_stream(data: &[u8], key16: u16) -> Vec<u8> {
+    let mut lo = (key16 & 0xFF) as u8;
+    let mut hi = ((key16 >> 8) & 0xFF) as u8;
+
+    let mut out = Vec::with_capacity(data.len());
+    for value in data {
+        lo = hi ^ lo.wrapping_shl(1);
+        out.push(value ^ lo);
+        hi = lo ^ (hi >> 1);
+    }
+    out
+}
+
+fn lzss_decompress_simple(data: &[u8], expected_size: usize) -> Result<Vec<u8>> {
+    let mut ring = [0x20u8; 0x1000];
+    let mut ring_pos = 0xFEEusize;
+    let mut out = Vec::with_capacity(expected_size);
+    let mut in_pos = 0usize;
+
+    let mut control = 0u8;
+    let mut bits_left = 0u8;
+
+    while out.len() < expected_size {
+        if bits_left == 0 {
+            let Some(byte) = data.get(in_pos).copied() else {
+                break;
+            };
+            control = byte;
+            in_pos += 1;
+            bits_left = 8;
+        }
+
+        if (control & 1) != 0 {
+            let Some(byte) = data.get(in_pos).copied() else {
+                break;
+            };
+            in_pos += 1;
+
+            out.push(byte);
+            ring[ring_pos] = byte;
+            ring_pos = (ring_pos + 1) & 0x0FFF;
+        } else {
+            let (Some(low), Some(high)) =
+                (data.get(in_pos).copied(), data.get(in_pos + 1).copied())
+            else {
+                break;
+            };
+            in_pos += 2;
+
+            let offset = usize::from(low) | (usize::from(high & 0xF0) << 4);
+            let length = usize::from((high & 0x0F) + 3);
+
+            for step in 0..length {
+                let byte = ring[(offset + step) & 0x0FFF];
+                out.push(byte);
+                ring[ring_pos] = byte;
+                ring_pos = (ring_pos + 1) & 0x0FFF;
+                if out.len() >= expected_size {
+                    break;
+                }
+            }
+        }
+
+        control >>= 1;
+        bits_left -= 1;
+    }
+
+    if out.len() != expected_size {
+        return Err(Error::DecompressionFailed("lzss-simple"));
+    }
+
+    Ok(out)
+}
+
+const LZH_N: usize = 4096;
+const LZH_F: usize = 60;
+const LZH_THRESHOLD: usize = 2;
+const LZH_N_CHAR: usize = 256 - LZH_THRESHOLD + LZH_F;
+const LZH_T: usize = LZH_N_CHAR * 2 - 1;
+const LZH_R: usize = LZH_T - 1;
+const LZH_MAX_FREQ: u16 = 0x8000;
+
+fn lzss_huffman_decompress(data: &[u8], expected_size: usize) -> Result<Vec<u8>> {
+    let mut decoder = LzhDecoder::new(data);
+    decoder.decode(expected_size)
+}
+
+struct LzhDecoder<'a> {
+    bit_reader: BitReader<'a>,
+    text: [u8; LZH_N],
+    freq: [u16; LZH_T + 1],
+    parent: [usize; LZH_T + LZH_N_CHAR],
+    son: [usize; LZH_T],
+    d_code: [u8; 256],
+    d_len: [u8; 256],
+    ring_pos: usize,
+}
+
+impl<'a> LzhDecoder<'a> {
+    fn new(data: &'a [u8]) -> Self {
+        let mut decoder = Self {
+            bit_reader: BitReader::new(data),
+            text: [0x20u8; LZH_N],
+            freq: [0u16; LZH_T + 1],
+            parent: [0usize; LZH_T + LZH_N_CHAR],
+            son: [0usize; LZH_T],
+            d_code: [0u8; 256],
+            d_len: [0u8; 256],
+            ring_pos: LZH_N - LZH_F,
+        };
+        decoder.init_tables();
+        decoder.start_huff();
+        decoder
+    }
+
+    fn decode(&mut self, expected_size: usize) -> Result<Vec<u8>> {
+        let mut out = Vec::with_capacity(expected_size);
+
+        while out.len() < expected_size {
+            let c = self.decode_char();
+            if c < 256 {
+                let byte = c as u8;
+                out.push(byte);
+                self.text[self.ring_pos] = byte;
+                self.ring_pos = (self.ring_pos + 1) & (LZH_N - 1);
+            } else {
+                let mut offset = self.decode_position();
+                offset = (self.ring_pos.wrapping_sub(offset).wrapping_sub(1)) & (LZH_N - 1);
+                let mut length = c.saturating_sub(253);
+
+                while length > 0 && out.len() < expected_size {
+                    let byte = self.text[offset];
+                    out.push(byte);
+                    self.text[self.ring_pos] = byte;
+                    self.ring_pos = (self.ring_pos + 1) & (LZH_N - 1);
+                    offset = (offset + 1) & (LZH_N - 1);
+                    length -= 1;
+                }
+            }
+        }
+
+        if out.len() != expected_size {
+            return Err(Error::DecompressionFailed("lzss-huffman"));
+        }
+        Ok(out)
+    }
+
+    fn init_tables(&mut self) {
+        let d_code_group_counts = [1usize, 3, 8, 12, 24, 16];
+        let d_len_group_counts = [32usize, 48, 64, 48, 48, 16];
+
+        let mut group_index = 0u8;
+        let mut idx = 0usize;
+        let mut run = 32usize;
+        for count in d_code_group_counts {
+            for _ in 0..count {
+                for _ in 0..run {
+                    self.d_code[idx] = group_index;
+                    idx += 1;
+                }
+                group_index = group_index.wrapping_add(1);
+            }
+            run >>= 1;
+        }
+
+        let mut len = 3u8;
+        idx = 0;
+        for count in d_len_group_counts {
+            for _ in 0..count {
+                self.d_len[idx] = len;
+                idx += 1;
+            }
+            len = len.saturating_add(1);
+        }
+    }
+
+    fn start_huff(&mut self) {
+        for i in 0..LZH_N_CHAR {
+            self.freq[i] = 1;
+            self.son[i] = i + LZH_T;
+            self.parent[i + LZH_T] = i;
+        }
+
+        let mut i = 0usize;
+        let mut j = LZH_N_CHAR;
+        while j <= LZH_R {
+            self.freq[j] = self.freq[i].saturating_add(self.freq[i + 1]);
+            self.son[j] = i;
+            self.parent[i] = j;
+            self.parent[i + 1] = j;
+            i += 2;
+            j += 1;
+        }
+
+        self.freq[LZH_T] = u16::MAX;
+        self.parent[LZH_R] = 0;
+    }
+
+    fn decode_char(&mut self) -> usize {
+        let mut node = self.son[LZH_R];
+        while node < LZH_T {
+            let bit = usize::from(self.bit_reader.read_bit_or_zero());
+            node = self.son[node + bit];
+        }
+
+        let c = node - LZH_T;
+        self.update(c);
+        c
+    }
+
+    fn decode_position(&mut self) -> usize {
+        let i = self.bit_reader.read_bits_or_zero(8) as usize;
+        let mut c = usize::from(self.d_code[i]) << 6;
+        let mut j = usize::from(self.d_len[i]).saturating_sub(2);
+
+        while j > 0 {
+            j -= 1;
+            c |= usize::from(self.bit_reader.read_bit_or_zero()) << j;
+        }
+
+        c | (i & 0x3F)
+    }
+
+    fn update(&mut self, c: usize) {
+        if self.freq[LZH_R] == LZH_MAX_FREQ {
+            self.reconstruct();
+        }
+
+        let mut current = self.parent[c + LZH_T];
+        loop {
+            self.freq[current] = self.freq[current].saturating_add(1);
+            let freq = self.freq[current];
+
+            if current + 1 < self.freq.len() && freq > self.freq[current + 1] {
+                let mut swap_idx = current + 1;
+                while swap_idx + 1 < self.freq.len() && freq > self.freq[swap_idx + 1] {
+                    swap_idx += 1;
+                }
+
+                self.freq.swap(current, swap_idx);
+
+                let left = self.son[current];
+                let right = self.son[swap_idx];
+                self.son[current] = right;
+                self.son[swap_idx] = left;
+
+                self.parent[left] = swap_idx;
+                if left < LZH_T {
+                    self.parent[left + 1] = swap_idx;
+                }
+
+                self.parent[right] = current;
+                if right < LZH_T {
+                    self.parent[right + 1] = current;
+                }
+
+                current = swap_idx;
+            }
+
+            current = self.parent[current];
+            if current == 0 {
+                break;
+            }
+        }
+    }
+
+    fn reconstruct(&mut self) {
+        let mut j = 0usize;
+        for i in 0..LZH_T {
+            if self.son[i] >= LZH_T {
+                self.freq[j] = (self.freq[i].saturating_add(1)) / 2;
+                self.son[j] = self.son[i];
+                j += 1;
+            }
+        }
+
+        let mut i = 0usize;
+        let mut current = LZH_N_CHAR;
+        while current < LZH_T {
+            let sum = self.freq[i].saturating_add(self.freq[i + 1]);
+            self.freq[current] = sum;
+
+            let mut insert_at = current;
+            while insert_at > 0 && sum < self.freq[insert_at - 1] {
+                insert_at -= 1;
+            }
+
+            for move_idx in (insert_at..current).rev() {
+                self.freq[move_idx + 1] = self.freq[move_idx];
+                self.son[move_idx + 1] = self.son[move_idx];
+            }
+
+            self.freq[insert_at] = sum;
+            self.son[insert_at] = i;
+
+            i += 2;
+            current += 1;
+        }
+
+        for idx in 0..LZH_T {
+            let node = self.son[idx];
+            self.parent[node] = idx;
+            if node < LZH_T {
+                self.parent[node + 1] = idx;
+            }
+        }
+
+        self.freq[LZH_T] = u16::MAX;
+        self.parent[LZH_R] = 0;
+    }
+}
+
+struct BitReader<'a> {
+    data: &'a [u8],
+    byte_pos: usize,
+    bit_mask: u8,
+}
+
+impl<'a> BitReader<'a> {
+    fn new(data: &'a [u8]) -> Self {
+        Self {
+            data,
+            byte_pos: 0,
+            bit_mask: 0x80,
+        }
+    }
+
+    fn read_bit_or_zero(&mut self) -> u8 {
+        let Some(byte) = self.data.get(self.byte_pos).copied() else {
+            return 0;
+        };
+
+        let bit = if (byte & self.bit_mask) != 0 { 1 } else { 0 };
+        self.bit_mask >>= 1;
+        if self.bit_mask == 0 {
+            self.bit_mask = 0x80;
+            self.byte_pos = self.byte_pos.saturating_add(1);
+        }
+        bit
+    }
+
+    fn read_bits_or_zero(&mut self, bits: usize) -> u32 {
+        let mut value = 0u32;
+        for _ in 0..bits {
+            value = (value << 1) | u32::from(self.read_bit_or_zero());
+        }
+        value
+    }
+}
+
+fn decode_name(name: &[u8]) -> String {
+    name.iter().map(|b| char::from(*b)).collect()
+}
+
+fn c_name_bytes(raw: &[u8; 12]) -> &[u8] {
+    let len = raw.iter().position(|&b| b == 0).unwrap_or(raw.len());
+    &raw[..len]
+}
+
+fn cmp_c_string(a: &[u8], b: &[u8]) -> Ordering {
+    let min_len = a.len().min(b.len());
+    let mut idx = 0usize;
+    while idx < min_len {
+        if a[idx] != b[idx] {
+            return a[idx].cmp(&b[idx]);
+        }
+        idx += 1;
+    }
+    a.len().cmp(&b.len())
+}
+
+fn needs_xor_key(method: PackMethod) -> bool {
+    matches!(
+        method,
+        PackMethod::XorOnly | PackMethod::XorLzss | PackMethod::XorLzssHuffman
+    )
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::any::Any;
+    use std::panic::{catch_unwind, AssertUnwindSafe};
+    use std::path::PathBuf;
+
+    fn collect_files_recursive(root: &Path, out: &mut Vec<PathBuf>) {
+        let Ok(entries) = fs::read_dir(root) else {
+            return;
+        };
+        for entry in entries.flatten() {
+            let path = entry.path();
+            if path.is_dir() {
+                collect_files_recursive(&path, out);
+            } else if path.is_file() {
+                out.push(path);
+            }
+        }
+    }
+
+    fn rsli_test_files() -> Vec<PathBuf> {
+        let root = Path::new(env!("CARGO_MANIFEST_DIR"))
+            .join("..")
+            .join("..")
+            .join("testdata")
+            .join("rsli");
+        let mut files = Vec::new();
+        collect_files_recursive(&root, &mut files);
+        files.sort();
+        files
+            .into_iter()
+            .filter(|path| {
+                fs::read(path)
+                    .map(|data| data.get(0..4) == Some(b"NL\0\x01"))
+                    .unwrap_or(false)
+            })
+            .collect()
+    }
+
+    fn panic_message(payload: Box<dyn Any + Send>) -> String {
+        let any = payload.as_ref();
+        if let Some(message) = any.downcast_ref::<String>() {
+            return message.clone();
+        }
+        if let Some(message) = any.downcast_ref::<&str>() {
+            return (*message).to_string();
+        }
+        String::from("panic without message")
+    }
+
+    #[test]
+    fn rsli_read_unpack_and_repack_all_files() {
+        let files = rsli_test_files();
+        assert!(!files.is_empty(), "testdata/rsli contains no RsLi archives");
+
+        let checked = files.len();
+        let mut success = 0usize;
+        let mut failures = Vec::new();
+
+        for path in files {
+            let display_path = path.display().to_string();
+            let result = catch_unwind(AssertUnwindSafe(|| {
+                let original = fs::read(&path).expect("failed to read archive");
+                let library = Library::open_path(&path)
+                    .unwrap_or_else(|err| panic!("failed to open {}: {err}", path.display()));
+
+                let count = library.entry_count();
+                assert_eq!(
+                    count,
+                    library.entries().count(),
+                    "entry count mismatch: {}",
+                    path.display()
+                );
+
+                for idx in 0..count {
+                    let id = EntryId(idx as u32);
+                    let meta_ref = library
+                        .get(id)
+                        .unwrap_or_else(|| panic!("missing entry #{idx} in {}", path.display()));
+
+                    let loaded = library.load(id).unwrap_or_else(|err| {
+                        panic!("load failed for {} entry #{idx}: {err}", path.display())
+                    });
+
+                    let packed = library.load_packed(id).unwrap_or_else(|err| {
+                        panic!(
+                            "load_packed failed for {} entry #{idx}: {err}",
+                            path.display()
+                        )
+                    });
+                    let unpacked = library.unpack(&packed).unwrap_or_else(|err| {
+                        panic!("unpack failed for {} entry #{idx}: {err}", path.display())
+                    });
+                    assert_eq!(
+                        loaded,
+                        unpacked,
+                        "load != unpack in {} entry #{idx}",
+                        path.display()
+                    );
+
+                    let mut out = Vec::new();
+                    let written = library.load_into(id, &mut out).unwrap_or_else(|err| {
+                        panic!(
+                            "load_into failed for {} entry #{idx}: {err}",
+                            path.display()
+                        )
+                    });
+                    assert_eq!(
+                        written,
+                        loaded.len(),
+                        "load_into size mismatch in {} entry #{idx}",
+                        path.display()
+                    );
+                    assert_eq!(
+                        out,
+                        loaded,
+                        "load_into payload mismatch in {} entry #{idx}",
+                        path.display()
+                    );
+
+                    let fast = library.load_fast(id).unwrap_or_else(|err| {
+                        panic!(
+                            "load_fast failed for {} entry #{idx}: {err}",
+                            path.display()
+                        )
+                    });
+                    assert_eq!(
+                        fast.as_slice(),
+                        loaded.as_slice(),
+                        "load_fast mismatch in {} entry #{idx}",
+                        path.display()
+                    );
+
+                    let found = library.find(&meta_ref.meta.name).unwrap_or_else(|| {
+                        panic!(
+                            "find failed for '{}' in {}",
+                            meta_ref.meta.name,
+                            path.display()
+                        )
+                    });
+                    let found_meta = library.get(found).expect("find returned invalid entry id");
+                    assert_eq!(
+                        found_meta.meta.name,
+                        meta_ref.meta.name,
+                        "find returned a different entry in {}",
+                        path.display()
+                    );
+                }
+
+                let rebuilt = library
+                    .rebuild_from_parsed_metadata()
+                    .unwrap_or_else(|err| panic!("rebuild failed for {}: {err}", path.display()));
+                assert_eq!(
+                    rebuilt,
+                    original,
+                    "byte-to-byte roundtrip mismatch for {}",
+                    path.display()
+                );
+            }));
+
+            match result {
+                Ok(()) => success += 1,
+                Err(payload) => {
+                    failures.push(format!("{}: {}", display_path, panic_message(payload)));
+                }
+            }
+        }
+
+        let failed = failures.len();
+        eprintln!(
+            "RsLi summary: checked={}, success={}, failed={}",
+            checked, success, failed
+        );
+        if !failures.is_empty() {
+            panic!(
+                "RsLi validation failed.\nsummary: checked={}, success={}, failed={}\n{}",
+                checked,
+                success,
+                failed,
+                failures.join("\n")
+            );
+        }
+    }
+}