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use byteorder::ReadBytesExt;
use std::io::{Read, Seek, SeekFrom};
use crate::header::Yaz0Header;
use crate::Error;
/// Wraps a reader of Yaz0 data, providing decompression methods.
#[derive(Debug)]
pub struct Yaz0Archive<R>
where
R: Read + Seek,
{
reader: R,
data_start: usize,
header: Yaz0Header,
}
impl<R> Yaz0Archive<R>
where
R: Read + Seek,
{
/// Creates a new `Yaz0` from a reader.
pub fn new(mut reader: R) -> Result<Yaz0Archive<R>, Error> {
// Parses header and advances reader to start of data
let header = Yaz0Header::parse(&mut reader)?;
let data_start = reader.seek(SeekFrom::Current(0))?;
Ok(Yaz0Archive {
reader,
header,
data_start: data_start as usize,
})
}
/// Get the expected size of inflated data from parsed `Yaz0Header`.
pub fn expected_size(&self) -> usize {
self.header.expected_size
}
/// Decompresses the Yaz0 file, producing a `Vec<u8>` of the decompressed data.
pub fn decompress(&mut self) -> Result<Vec<u8>, Error> {
let mut dest: Vec<u8> = Vec::with_capacity(self.header.expected_size);
dest.resize(self.header.expected_size, 0x00);
self.decompress_into(&mut dest)?;
Ok(dest)
}
/// Decompresses the Yaz0 file into a destination buffer.
///
/// # Invariants
/// `dest` must have a length of at least the required size to decompress successfully (consider using [`Yaz0Archive::expected_size`] to determine this)
pub fn decompress_into(&mut self, dest: &mut [u8]) -> Result<(), Error> {
assert!(dest.len() >= self.expected_size());
let mut dest_pos: usize = 0;
let mut ops_left: u8 = 0;
let mut code_byte: u8 = 0;
while dest_pos < self.header.expected_size {
if ops_left == 0 {
code_byte = self.reader.read_u8()?;
ops_left = 8;
}
if code_byte & 0x80 != 0 {
dest[dest_pos] = self.reader.read_u8()?;
dest_pos += 1;
} else {
let byte1: u8 = self.reader.read_u8()?;
let byte2: u8 = self.reader.read_u8()?;
// Calculate where the copy should start
let dist = (((byte1 & 0xf) as usize) << 8) | (byte2 as usize);
let run_base = dest_pos - (dist + 1);
// Figure out how many bytes we have to copy
let copy_len: usize = match byte1 >> 4 {
0 => self.reader.read_u8()? as usize + 0x12, // read the next input byte and add 0x12
// to get the length to copy
n => n as usize + 2 // otherwise, just take the upper nybble of byte1 and add 2 to get the length
};
for i in 0..copy_len {
dest[dest_pos] = dest[run_base + i];
dest_pos += 1;
}
}
// use next operation bit from the code byte
code_byte <<= 1;
ops_left -= 1;
}
Ok(())
}
}
#[cfg(test)]
mod tests {
use super::*;
use std::io::Cursor;
use pretty_assertions::assert_eq;
/// Deflate a test .szs file encoded by yaz0enc, and compare to the decompressed file produced by yaz0dec.
#[test]
fn test_deflate_bianco() {
let data: &[u8] = include_bytes!("../data/test.yaz0");
let reference_decompressed: &[u8] = include_bytes!("../data/test");
let reader = Cursor::new(data);
let mut f = Yaz0Archive::new(reader).unwrap();
let deflated = f.decompress().unwrap();
println!("{} :: {}", deflated.len(), reference_decompressed.len());
assert!(deflated == reference_decompressed, "deflated bianco0 did not match reference deflation!");
}
/// Test loading a small constructed Yaz0 file containing random data.
/// Note: this file will almost certainly error if decompression is attempted.
#[test]
fn test_load() {
let data: &[u8] = &[
// 'Yaz0'
0x59, 0x61, 0x7a, 0x30,
// 13371337 bytes, when deflated
0x00, 0xcc, 0x07, 0xc9,
// 8 bytes of zeros
0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00,
// 20 bytes of (random) data
0x69, 0x95, 0xa4, 0xa3,
0x5f, 0xfd, 0xf6, 0x8c,
0x7d, 0xee, 0x93, 0xc5,
0x4a, 0x1f, 0xd3, 0x19,
0xdc, 0x78, 0xfd, 0x3f,
];
let cursor = Cursor::new(&data);
let f = Yaz0Archive::new(cursor).unwrap();
assert_eq!(f.header.expected_size, 13371337);
}
/// Check that the Yaz0 header parsing fails when provided with a file not starting with the Yaz0 magic.
#[test]
fn test_bad_magic() {
let data: &[u8] = &[
// 'Foo0'
0x46, 0x6f, 0x6f, 0x30,
// 13371337 bytes, when deflated
0x00, 0xcc, 0x07, 0xc9,
// 8 bytes of zeros
0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00,
];
let cursor = Cursor::new(&data);
let result = Yaz0Archive::new(cursor);
assert!(result.is_err());
}
}