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use std::{io, io::BufRead};
use flate2::{Decompress, FlushDecompress, Status};
/// The boxed variant is faster for what we do (moving the decompressor in and out a lot)
pub struct ReadBoxed<R> {
/// The reader from which bytes should be decompressed.
pub inner: R,
/// The decompressor doing all the work.
pub decompressor: Box<Decompress>,
}
impl<R> io::Read for ReadBoxed<R>
where
R: BufRead,
{
fn read(&mut self, into: &mut [u8]) -> io::Result<usize> {
read(&mut self.inner, &mut self.decompressor, into)
}
}
/// Read bytes from `rd` and decompress them using `state` into a pre-allocated fitting buffer `dst`, returning the amount of bytes written.
pub fn read(rd: &mut impl BufRead, state: &mut Decompress, mut dst: &mut [u8]) -> io::Result<usize> {
let mut total_written = 0;
loop {
let (written, consumed, ret, eof);
{
let input = rd.fill_buf()?;
eof = input.is_empty();
let before_out = state.total_out();
let before_in = state.total_in();
let flush = if eof {
FlushDecompress::Finish
} else {
FlushDecompress::None
};
ret = state.decompress(input, dst, flush);
written = (state.total_out() - before_out) as usize;
total_written += written;
dst = &mut dst[written..];
consumed = (state.total_in() - before_in) as usize;
}
rd.consume(consumed);
match ret {
// The stream has officially ended, nothing more to do here.
Ok(Status::StreamEnd) => return Ok(total_written),
// Either input our output are depleted even though the stream is not depleted yet.
Ok(Status::Ok | Status::BufError) if eof || dst.is_empty() => return Ok(total_written),
// Some progress was made in both the input and the output, it must continue to reach the end.
Ok(Status::Ok | Status::BufError) if consumed != 0 || written != 0 => continue,
// A strange state, where zlib makes no progress but isn't done either. Call it out.
Ok(Status::Ok | Status::BufError) => unreachable!("Definitely a bug somewhere"),
Err(..) => return Err(io::Error::new(io::ErrorKind::InvalidInput, "corrupt deflate stream")),
}
}
}
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