//! XZ header.

use crate::decode::util;

use crate::error;

use crate::xz::StreamFlags;

use byteorder::{BigEndian, LittleEndian, ReadBytesExt};

use crc::crc32::{self, Hasher32};

/// 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::new(crc32::IEEE);

            let mut digest_rd = util::HasherRead::new(input, &mut digest);

            let value = digest_rd.read_u16::<BigEndian>()?;

            (value, digest.sum32())

        };

        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)

    }

}