use simd_adler32::Adler32;
use std::{
convert::TryInto,
io::{self, Seek, SeekFrom, Write},
};
use crate::tables::{
BITMASKS, HUFFMAN_CODES, HUFFMAN_LENGTHS, LENGTH_TO_LEN_EXTRA, LENGTH_TO_SYMBOL,
};
/// Compressor that produces fdeflate compressed streams.
pub struct Compressor<W: Write> {
checksum: Adler32,
buffer: u64,
nbits: u8,
writer: W,
}
impl<W: Write> Compressor<W> {
fn write_bits(&mut self, bits: u64, nbits: u8) -> io::Result<()> {
debug_assert!(nbits <= 64);
self.buffer |= bits << self.nbits;
self.nbits += nbits;
if self.nbits >= 64 {
self.writer.write_all(&self.buffer.to_le_bytes())?;
self.nbits -= 64;
self.buffer = bits.checked_shr((nbits - self.nbits) as u32).unwrap_or(0);
}
debug_assert!(self.nbits < 64);
Ok(())
}
fn flush(&mut self) -> io::Result<()> {
if self.nbits % 8 != 0 {
self.write_bits(0, 8 - self.nbits % 8)?;
}
if self.nbits > 0 {
self.writer
.write_all(&self.buffer.to_le_bytes()[..self.nbits as usize / 8])
.unwrap();
self.buffer = 0;
self.nbits = 0;
}
Ok(())
}
fn write_run(&mut self, mut run: u32) -> io::Result<()> {
self.write_bits(HUFFMAN_CODES[0] as u64, HUFFMAN_LENGTHS[0])?;
run -= 1;
while run >= 258 {
self.write_bits(HUFFMAN_CODES[285] as u64, HUFFMAN_LENGTHS[285] + 1)?;
run -= 258;
}
if run > 4 {
let sym = LENGTH_TO_SYMBOL[run as usize - 3] as usize;
self.write_bits(HUFFMAN_CODES[sym] as u64, HUFFMAN_LENGTHS[sym])?;
let len_extra = LENGTH_TO_LEN_EXTRA[run as usize - 3];
let extra = ((run - 3) & BITMASKS[len_extra as usize]) as u64;
self.write_bits(extra, len_extra + 1)?;
} else {
debug_assert_eq!(HUFFMAN_CODES[0], 0);
self.write_bits(0, run as u8 * HUFFMAN_LENGTHS[0])?;
}
Ok(())
}
/// Create a new Compressor.
pub fn new(writer: W) -> io::Result<Self> {
let mut compressor = Self {
checksum: Adler32::new(),
buffer: 0,
nbits: 0,
writer,
};
compressor.write_headers()?;
Ok(compressor)
}
fn write_headers(&mut self) -> io::Result<()> {
self.write_bits(0x0178, 16)?; // zlib header
self.write_bits(0b1, 1)?; // BFINAL
self.write_bits(0b10, 2)?; // Dynamic Huffman block
self.write_bits((HUFFMAN_LENGTHS.len() - 257) as u64, 5)?; // # of length / literal codes
self.write_bits(0, 5)?; // 1 distance code
self.write_bits(15, 4)?; // 16 code length codes
// Write code lengths for code length alphabet
for _ in 0..3 {
self.write_bits(0, 3)?;
}
for _ in 0..16 {
self.write_bits(4, 3)?;
}
// Write code lengths for length/literal alphabet
for &len in &HUFFMAN_LENGTHS {
self.write_bits((len.reverse_bits() >> 4) as u64, 4)?;
}
// Write code lengths for distance alphabet
for _ in 0..1 {
self.write_bits(0b1000, 4)?;
}
Ok(())
}
/// Write data to the compressor.
pub fn write_data(&mut self, data: &[u8]) -> io::Result<()> {
self.checksum.write(data);
let mut run = 0;
let mut chunks = data.chunks_exact(8);
for chunk in &mut chunks {
let ichunk = u64::from_le_bytes(chunk.try_into().unwrap());
if ichunk == 0 {
run += 8;
continue;
} else if run > 0 {
let run_extra = ichunk.trailing_zeros() / 8;
self.write_run(run + run_extra)?;
run = 0;
if run_extra > 0 {
run = ichunk.leading_zeros() / 8;
for &b in &chunk[run_extra as usize..8 - run as usize] {
self.write_bits(
HUFFMAN_CODES[b as usize] as u64,
HUFFMAN_LENGTHS[b as usize],
)?;
}
continue;
}
}
let run_start = ichunk.leading_zeros() / 8;
if run_start > 0 {
for &b in &chunk[..8 - run_start as usize] {
self.write_bits(
HUFFMAN_CODES[b as usize] as u64,
HUFFMAN_LENGTHS[b as usize],
)?;
}
run = run_start;
continue;
}
let n0 = HUFFMAN_LENGTHS[chunk[0] as usize];
let n1 = HUFFMAN_LENGTHS[chunk[1] as usize];
let n2 = HUFFMAN_LENGTHS[chunk[2] as usize];
let n3 = HUFFMAN_LENGTHS[chunk[3] as usize];
let bits = HUFFMAN_CODES[chunk[0] as usize] as u64
| ((HUFFMAN_CODES[chunk[1] as usize] as u64) << n0)
| ((HUFFMAN_CODES[chunk[2] as usize] as u64) << (n0 + n1))
| ((HUFFMAN_CODES[chunk[3] as usize] as u64) << (n0 + n1 + n2));
self.write_bits(bits, n0 + n1 + n2 + n3)?;
let n4 = HUFFMAN_LENGTHS[chunk[4] as usize];
let n5 = HUFFMAN_LENGTHS[chunk[5] as usize];
let n6 = HUFFMAN_LENGTHS[chunk[6] as usize];
let n7 = HUFFMAN_LENGTHS[chunk[7] as usize];
let bits2 = HUFFMAN_CODES[chunk[4] as usize] as u64
| ((HUFFMAN_CODES[chunk[5] as usize] as u64) << n4)
| ((HUFFMAN_CODES[chunk[6] as usize] as u64) << (n4 + n5))
| ((HUFFMAN_CODES[chunk[7] as usize] as u64) << (n4 + n5 + n6));
self.write_bits(bits2, n4 + n5 + n6 + n7)?;
}
if run > 0 {
self.write_run(run)?;
}
for &b in chunks.remainder() {
self.write_bits(
HUFFMAN_CODES[b as usize] as u64,
HUFFMAN_LENGTHS[b as usize],
)?;
}
Ok(())
}
/// Write the remainder of the stream and return the inner writer.
pub fn finish(mut self) -> io::Result<W> {
// Write end of block
self.write_bits(HUFFMAN_CODES[256] as u64, HUFFMAN_LENGTHS[256])?;
self.flush()?;
// Write Adler32 checksum
let checksum: u32 = self.checksum.finish();
self.writer
.write_all(checksum.to_be_bytes().as_ref())
.unwrap();
Ok(self.writer)
}
}
/// Compressor that only writes the stored blocks.
///
/// This is useful for writing files that are not compressed, but still need to be wrapped in a
/// zlib stream.
pub struct StoredOnlyCompressor<W> {
writer: W,
checksum: Adler32,
block_bytes: u16,
}
impl<W: Write + Seek> StoredOnlyCompressor<W> {
/// Creates a new `StoredOnlyCompressor` that writes to the given writer.
pub fn new(mut writer: W) -> io::Result<Self> {
writer.write_all(&[0x78, 0x01])?; // zlib header
writer.write_all(&[0; 5])?; // placeholder stored block header
Ok(Self {
writer,
checksum: Adler32::new(),
block_bytes: 0,
})
}
fn set_block_header(&mut self, size: u16, last: bool) -> io::Result<()> {
self.writer.seek(SeekFrom::Current(-(size as i64 + 5)))?;
self.writer.write_all(&[
last as u8,
(size & 0xFF) as u8,
((size >> 8) & 0xFF) as u8,
(!size & 0xFF) as u8,
((!size >> 8) & 0xFF) as u8,
])?;
self.writer.seek(SeekFrom::Current(size as i64))?;
Ok(())
}
/// Writes the given data to the underlying writer.
pub fn write_data(&mut self, mut data: &[u8]) -> io::Result<()> {
self.checksum.write(data);
while !data.is_empty() {
if self.block_bytes == u16::MAX {
self.set_block_header(u16::MAX, false)?;
self.writer.write_all(&[0; 5])?; // placeholder stored block header
self.block_bytes = 0;
}
let prefix_bytes = data.len().min((u16::MAX - self.block_bytes) as usize);
self.writer.write_all(&data[..prefix_bytes])?;
self.block_bytes += prefix_bytes as u16;
data = &data[prefix_bytes..];
}
Ok(())
}
/// Finish writing the final block and return the underlying writer.
pub fn finish(mut self) -> io::Result<W> {
self.set_block_header(self.block_bytes, true)?;
// Write Adler32 checksum
let checksum: u32 = self.checksum.finish();
self.writer
.write_all(checksum.to_be_bytes().as_ref())
.unwrap();
Ok(self.writer)
}
}
impl<W> StoredOnlyCompressor<W> {
/// Return the number of bytes that will be written to the output stream
/// for the given input size. Because this compressor only writes stored blocks,
/// the output size is always slightly *larger* than the input size.
pub fn compressed_size(raw_size: usize) -> usize {
(raw_size.saturating_sub(1) / u16::MAX as usize) * (u16::MAX as usize + 5)
+ (raw_size % u16::MAX as usize + 5)
+ 6
}
}
/// Compresses the given data.
pub fn compress_to_vec(input: &[u8]) -> Vec<u8> {
let mut compressor = Compressor::new(Vec::with_capacity(input.len() / 4)).unwrap();
compressor.write_data(input).unwrap();
compressor.finish().unwrap()
}
#[cfg(test)]
mod tests {
use super::*;
use rand::Rng;
fn roundtrip(data: &[u8]) {
let compressed = compress_to_vec(data);
let decompressed = miniz_oxide::inflate::decompress_to_vec_zlib(&compressed).unwrap();
assert_eq!(&decompressed, data);
}
#[test]
fn it_works() {
roundtrip(b"Hello world!");
}
#[test]
fn constant() {
roundtrip(&vec![0; 2048]);
roundtrip(&vec![5; 2048]);
roundtrip(&vec![128; 2048]);
roundtrip(&vec![254; 2048]);
}
#[test]
fn random() {
let mut rng = rand::thread_rng();
let mut data = vec![0; 2048];
for _ in 0..10 {
for byte in &mut data {
*byte = rng.gen();
}
roundtrip(&data);
}
}
}
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