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header.rs
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header.rs
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//! XZ header.
use crate::decode::util;
use crate::error;
use crate::xz::crc::CRC32;
use crate::xz::StreamFlags;
use byteorder::{BigEndian, LittleEndian, ReadBytesExt};
/// File format magic header signature, see sect. 2.1.1.1.
pub(crate) const XZ_MAGIC: &[u8] = &[0xFD, 0x37, 0x7A, 0x58, 0x5A, 0x00];
/// Stream Header, see sect. 2.1.1.
#[derive(Clone, Copy, Debug)]
pub(crate) struct StreamHeader {
pub(crate) stream_flags: StreamFlags,
}
impl StreamHeader {
/// Parse a Stream Header from a buffered reader.
pub(crate) fn parse<BR>(input: &mut BR) -> error::Result<Self>
where
BR: std::io::BufRead,
{
if !util::read_tag(input, XZ_MAGIC)? {
return Err(error::Error::XzError(format!(
"Invalid XZ magic, expected {:?}",
XZ_MAGIC
)));
}
let (flags, digested) = {
let mut digest = CRC32.digest();
let flags = {
let mut digest_rd = util::CrcDigestRead::new(input, &mut digest);
digest_rd.read_u16::<BigEndian>()?
};
(flags, digest.finalize())
};
let crc32 = input.read_u32::<LittleEndian>()?;
if crc32 != digested {
return Err(error::Error::XzError(format!(
"Invalid header CRC32: expected 0x{:08x} but got 0x{:08x}",
crc32, digested
)));
}
let stream_flags = StreamFlags::parse(flags)?;
let header = Self { stream_flags };
lzma_info!("XZ check method: {:?}", header.stream_flags.check_method);
Ok(header)
}
}