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use std::io::Read;
use crate::{
internal::ppmd7::{PPMd7, RangeDecoder7a},
Error, PPMD7_MAX_MEM_SIZE, PPMD7_MAX_ORDER, PPMD7_MIN_MEM_SIZE, PPMD7_MIN_ORDER, SYM_END,
};
/// A decoder to decompress data using PPMd7 (PPMdH) with the carryless range coder (PPMd7a).
pub struct Ppmd7aDecoder<R: Read> {
ppmd: PPMd7<RangeDecoder7a<R>>,
finished: bool,
}
impl<R: Read> Ppmd7aDecoder<R> {
/// Creates a new [`Ppmd7aDecoder`] which provides a reader over the uncompressed data.
///
/// The given `order` must be between [`PPMD7_MIN_ORDER`] and [`PPMD7_MAX_ORDER`]
/// The given `mem_size` must be between [`PPMD7_MIN_MEM_SIZE`] and [`PPMD7_MAX_MEM_SIZE`]
pub fn new(reader: R, order: u32, mem_size: u32) -> crate::Result<Self> {
if !(PPMD7_MIN_ORDER..=PPMD7_MAX_ORDER).contains(&order)
|| !(PPMD7_MIN_MEM_SIZE..=PPMD7_MAX_MEM_SIZE).contains(&mem_size)
{
return Err(Error::InvalidParameter);
}
let ppmd = PPMd7::new_decoder_7a(reader, order, mem_size)?;
Ok(Self {
ppmd,
finished: false,
})
}
/// Gets a reference to the underlying reader.
pub fn get_ref(&self) -> &R {
self.ppmd.get_ref()
}
/// Gets a mutable reference to the underlying reader.
///
/// Note that mutation of the stream may result in surprising results if
/// this decoder is continued to be used.
pub fn get_mut(&mut self) -> &mut R {
self.ppmd.get_mut()
}
/// Returns the inner reader.
pub fn into_inner(self) -> R {
self.ppmd.into_inner()
}
}
impl<R: Read> Read for Ppmd7aDecoder<R> {
fn read(&mut self, buf: &mut [u8]) -> std::io::Result<usize> {
if self.finished {
return Ok(0);
}
if buf.is_empty() {
return Ok(0);
}
let mut sym = 0;
let mut decoded = 0;
for byte in buf.iter_mut() {
match self.ppmd.decode_symbol() {
Ok(symbol) => sym = symbol,
Err(err) => {
if err.kind() == std::io::ErrorKind::UnexpectedEof {
self.finished = true;
return Ok(decoded);
}
return Err(err);
}
}
if sym < 0 {
break;
}
*byte = sym as u8;
decoded += 1;
}
let code = self.ppmd.range_decoder_code();
if sym >= 0 {
return Ok(decoded);
}
self.finished = true;
if sym != SYM_END || code != 0 {
return Err(std::io::Error::new(
std::io::ErrorKind::InvalidData,
"Error during PPMd decoding",
));
}
// END_MARKER detected
Ok(decoded)
}
}