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use crate::dynamic::LzssDyn;
use crate::error::LzssError;
use crate::read_write::{Read, Write};
use core::convert::Infallible;
#[cfg(feature = "safe")]
use core::convert::TryInto;
mod compress;
mod compress_in_place;
mod decompress;
/// A zero-sized type, the const generics specify the parameters of the compression.
///
/// # Parameters
/// * `EI` - The number of bits in the offset, usually `10..13`
/// * `EJ` - The number of bits in the length, usually `4..5`
/// * `C` - The initial fill byte of the buffer, usually `0x20` (space)
/// * `N` - Equals `1 << EI`, the size of the buffer for [`Lzss::decompress`]
/// * `N2` - Equals `2 << EI` (`N * 2`), the size of the buffer for [`Lzss::compress`]
///
/// # Restrictions
/// * `EJ` must be larger than `0`
/// * `EI` must be larger than `EJ`
/// * `EI + EJ` must be at least 8
/// * `EI + EJ` must be 24 or less
/// * `N` must be equal to `1 << EI`
/// * `N2` must be equal to `2 << EI` (`N * 2`)
///
/// All parameters are checked at compile-time.
///
/// There is no runtime overhead since everything is checked during compile-time.
///
/// # Limitations
/// Since it's not possible to do const calculations on const generics all parameters
/// have to be set.
///
/// # Example
/// ```rust
/// # use lzss::{Lzss, SliceReader, SliceWriterExact};
/// type MyLzss = Lzss<10, 4, 0x20, { 1 << 10 }, { 2 << 10 }>;
/// let input = b"Example Data";
/// let mut output = [0; 14];
/// let result = MyLzss::compress_stack(
/// SliceReader::new(input),
/// SliceWriterExact::new(&mut output),
/// );
/// assert!(result.is_ok()); // the output is exactly 14 bytes long
/// ```
pub struct Lzss<const EI: usize, const EJ: usize, const C: u8, const N: usize, const N2: usize>(
Infallible,
);
impl<const EI: usize, const EJ: usize, const C: u8, const N: usize, const N2: usize>
Lzss<EI, EJ, C, N, N2>
{
/// Create a new [`LzssDyn`] with the parameter from this generic type.
///
/// This is mainly useful for creating const [`LzssDyn`].
///
/// ```rust
/// # use lzss::{Lzss, LzssDyn};
/// type MyLzss = Lzss<10, 4, 0x20, { 1 << 10 }, { 2 << 10 }>;
/// const MY_DYN1: LzssDyn = MyLzss::as_dyn();
/// // or
/// const MY_DYN2: LzssDyn = Lzss::<10, 4, 0x20, { 1 << 10 }, { 2 << 10 }>::as_dyn();
/// ```
#[must_use]
pub const fn as_dyn() -> LzssDyn {
let _: Result<(), ()> = Self::ASSERT_PARAMETERS; // This ensures that EI+EJ are "reasonable", 1<<EI == N and 2*N == N2
LzssDyn {
ei: EI,
ej: EJ,
c: C,
}
}
/// Compress the input data into the output.
///
/// The buffer, with `N2` bytes, is allocated on the stack.
#[inline(always)]
#[deprecated(since = "0.9.0", note = "renamed to compress_stack")]
pub fn compress<R: Read, W: Write>(
reader: R,
writer: W,
) -> Result<W::Output, LzssError<R::Error, W::Error>> {
Self::compress_stack(reader, writer)
}
/// Compress the input data into the output.
///
/// The buffer, with `N2` bytes, is allocated on the stack.
pub fn compress_stack<R: Read, W: Write>(
mut reader: R,
mut writer: W,
) -> Result<W::Output, LzssError<R::Error, W::Error>> {
let _: Result<(), ()> = Self::ASSERT_PARAMETERS; // This ensures that EI+EJ are "reasonable", 1<<EI == N and 2*N == N2
let mut buffer = [C; N2];
Self::compress_internal(&mut reader, &mut writer, &mut buffer)?;
writer.finish().map_err(LzssError::WriteError)
}
/// Compress the input data into the output.
///
/// The buffer, with `N2` bytes, is allocated on the heap.
#[cfg_attr(docsrs, doc(cfg(any(feature = "alloc", feature = "std"))))]
#[cfg(feature = "alloc")]
pub fn compress_heap<R: Read, W: Write>(
mut reader: R,
mut writer: W,
) -> Result<W::Output, LzssError<R::Error, W::Error>> {
let _: Result<(), ()> = Self::ASSERT_PARAMETERS; // This ensures that EI+EJ are "reasonable", 1<<EI == N and 2*N == N2
let mut buffer = vec![C; N2];
#[cfg(not(feature = "safe"))]
let buffer = unsafe { &mut *(buffer.as_mut_ptr().cast::<[u8; N2]>()) };
#[cfg(feature = "safe")]
let buffer: &mut [u8; N2] = (&mut buffer[..]).try_into().unwrap();
Self::compress_internal(&mut reader, &mut writer, buffer)?;
writer.finish().map_err(LzssError::WriteError)
}
/// Compress the input data into the output.
pub fn compress_with_buffer<R: Read, W: Write>(
mut reader: R,
mut writer: W,
buffer: &mut [u8; N2],
) -> Result<W::Output, LzssError<R::Error, W::Error>> {
let _: Result<(), ()> = Self::ASSERT_PARAMETERS; // This ensures that EI+EJ are "reasonable", 1<<EI == N and 2*N == N2
buffer[..N - Self::F].fill(C);
Self::compress_internal(&mut reader, &mut writer, buffer)?;
writer.finish().map_err(LzssError::WriteError)
}
/// Decompress the input data into the output.
///
/// The buffer, with `N` bytes, is allocated on the stack.
#[inline(always)]
#[deprecated(since = "0.9.0", note = "renamed to decompress_stack")]
pub fn decompress<R: Read, W: Write>(
reader: R,
writer: W,
) -> Result<W::Output, LzssError<R::Error, W::Error>> {
Self::decompress_stack(reader, writer)
}
/// Decompress the input data into the output.
///
/// The buffer, with `N` bytes, is allocated on the stack.
pub fn decompress_stack<R: Read, W: Write>(
mut reader: R,
mut writer: W,
) -> Result<W::Output, LzssError<R::Error, W::Error>> {
let _: Result<(), ()> = Self::ASSERT_PARAMETERS; // This ensures that EI+EJ are "reasonable", 1<<EI == N and 2*N == N2
let mut buffer: [u8; N] = [C; N];
Self::decompress_internal(&mut reader, &mut writer, &mut buffer)?;
writer.finish().map_err(LzssError::WriteError)
}
/// Decompress the input data into the output.
///
/// The buffer, with `N` bytes, is allocated on the heap.
#[cfg_attr(docsrs, doc(cfg(any(feature = "alloc", feature = "std"))))]
#[cfg(feature = "alloc")]
pub fn decompress_heap<R: Read, W: Write>(
mut reader: R,
mut writer: W,
) -> Result<W::Output, LzssError<R::Error, W::Error>> {
let _: Result<(), ()> = Self::ASSERT_PARAMETERS; // This ensures that EI+EJ are "reasonable", 1<<EI == N and 2*N == N2
let mut buffer = vec![C; N];
#[cfg(not(feature = "safe"))]
let buffer = unsafe { &mut *(buffer.as_mut_ptr().cast::<[u8; N]>()) };
#[cfg(feature = "safe")]
let buffer: &mut [u8; N] = (&mut buffer[..]).try_into().unwrap();
Self::decompress_internal(&mut reader, &mut writer, buffer)?;
writer.finish().map_err(LzssError::WriteError)
}
/// Decompress the input data into the output.
pub fn decompress_with_buffer<R: Read, W: Write>(
mut reader: R,
mut writer: W,
buffer: &mut [u8; N],
) -> Result<W::Output, LzssError<R::Error, W::Error>> {
let _: Result<(), ()> = Self::ASSERT_PARAMETERS; // This ensures that EI+EJ are "reasonable", 1<<EI == N and 2*N == N2
buffer[..N].fill(C);
Self::decompress_internal(&mut reader, &mut writer, buffer)?;
writer.finish().map_err(LzssError::WriteError)
}
/// Compress, the input and output is in the same slice.
///
/// The input is located at `io[offset..]`.
/// When there is enough space in the slice then the result will be `(size, None)`.
/// And the output is located at `io[0..size]`.
///
/// If there is not enough space in the slice, i.e. the output (or buffer) would overwrite
/// the input, then the result will be `(size, Some(new_offset))`, the already compressed
/// data is in `io[0..size]` and the not yet compressed data is in `io[new_offset..]`.
///
/// Even when the compression fails due to space the data is recoverable.
///
/// The minimum offset is [`Lzss::MIN_OFFSET`], though if the offset is `Lzss::MIN_OFFSET + input_size/8`
/// then the compression can't fail.
pub fn compress_in_place(io: &mut [u8], offset: usize) -> (usize, Option<usize>) {
let _: Result<(), ()> = Self::ASSERT_PARAMETERS; // This ensures that EI+EJ are "reasonable", 1<<EI == N and 2*N == N2
Self::compress_in_place_internal(io, offset)
}
/// The minimal offset when using `compress_in_place`.
///
/// It's a little less than `N`.
pub const MIN_OFFSET: usize = (N - Self::F) + Self::MIN_GAP_SIZE;
// non-public helpers
pub(crate) const P: usize = (1 + EI + EJ) / 9; /* If match length <= P then output one character */
pub(crate) const F: usize = (1 << EJ) + Self::P; /* lookahead buffer size */
pub(crate) const MIN_GAP_SIZE: usize = Self::P + 4;
const ASSERT_PARAMETERS: Result<(), ()> = {
if EJ == 0 {
panic!("LZSS: Invalid EJ, must be larger than 0")
}
if EJ >= EI {
panic!("LZSS: Invalid EI, must be larger than EJ")
}
if EI + EJ < 8 {
panic!("LZSS: Invalid EI, EJ, both together must be 8 or more")
}
if EI + EJ > 24 {
panic!("LZSS: Invalid EI, EJ, both together must be 24 or less")
}
// check if buffer size < usize
if (EI as u32) + 1 >= usize::BITS {
panic!("LZSS: Invalid EI, too large for usize")
}
if N != 1usize << EI {
panic!("LZSS: Invalid N, must be exactly 1<<EI")
}
if N2 != 2 * N {
panic!("LZSS: Invalid N2, must be exactly 2*N")
}
Ok(())
};
}
#[cfg(test)]
mod tests {
use crate::generic::Lzss;
use crate::slice::SliceReader;
use crate::vec::VecWriter;
use crate::void::ResultLzssErrorVoidExt;
type TestLZSS = Lzss<10, 4, 0x20, { 1 << 10 }, { 2 << 10 }>;
const TEST_DATA: &[u8; 27] = b"Sample Data 11221233123";
const COMPRESSED_DATA: [u8; 26] = [
169, 216, 109, 183, 11, 101, 149, 246, 13, 18, 195, 116, 176, 191, 81, 152, 204, 102, 83,
32, 0, 19, 57, 152, 3, 16,
];
#[test]
fn test_decompress() {
let output = TestLZSS::decompress_stack(
SliceReader::new(&COMPRESSED_DATA),
VecWriter::with_capacity(TEST_DATA.len()),
)
.void_unwrap();
assert_eq!(output.as_slice(), TEST_DATA);
}
#[test]
fn test_decompress_with_buffer() {
let mut buffer = [123; 1024];
let output = TestLZSS::decompress_with_buffer(
SliceReader::new(&COMPRESSED_DATA),
VecWriter::with_capacity(TEST_DATA.len()),
&mut buffer,
)
.void_unwrap();
assert_eq!(output.as_slice(), TEST_DATA);
}
#[test]
fn test_compress() {
let output = TestLZSS::compress_stack(
SliceReader::new(TEST_DATA),
VecWriter::with_capacity(COMPRESSED_DATA.len()),
)
.void_unwrap();
assert_eq!(output.as_slice(), COMPRESSED_DATA);
}
#[test]
fn test_compress_with_buffer() {
let mut buffer = [123; 2048];
let output = TestLZSS::compress_with_buffer(
SliceReader::new(TEST_DATA),
VecWriter::with_capacity(COMPRESSED_DATA.len()),
&mut buffer,
)
.void_unwrap();
assert_eq!(output.as_slice(), COMPRESSED_DATA);
}
#[test]
fn test_compress_in_place() {
const OFFSET: usize = TestLZSS::MIN_OFFSET + TEST_DATA.len() / 8;
let mut io = [0u8; OFFSET + TEST_DATA.len()];
io[OFFSET..].copy_from_slice(TEST_DATA);
let (c, u) = TestLZSS::compress_in_place(&mut io, OFFSET);
assert_eq!(c, COMPRESSED_DATA.len());
assert_eq!(u, None);
assert_eq!(io[0..c], COMPRESSED_DATA);
}
#[test]
fn test_compress_big() {
let big_test_data = include_bytes!("mod.rs");
// compress
let output1 = TestLZSS::compress_stack(
SliceReader::new(big_test_data),
VecWriter::with_capacity(big_test_data.len()),
)
.void_unwrap();
// compress_in_place
let offset: usize = TestLZSS::MIN_OFFSET + big_test_data.len() / 8;
let mut io = Vec::new();
io.resize(offset + big_test_data.len(), 0);
let io = io.as_mut_slice();
io[offset..].copy_from_slice(big_test_data);
let (c, u) = TestLZSS::compress_in_place(io, offset);
assert_eq!(u, None);
// compare both
assert_eq!(output1.as_slice(), &io[0..c]);
// decompress
let output2 = TestLZSS::decompress_stack(
SliceReader::new(&io[0..c]),
VecWriter::with_capacity(big_test_data.len()),
)
.void_unwrap();
assert_eq!(output2.as_slice(), big_test_data);
}
}