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Move gzip header parsing out of bufread module #346

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merged 1 commit into from
May 7, 2023
Merged

Move gzip header parsing out of bufread module #346

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227 changes: 5 additions & 222 deletions src/gz/bufread.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -3,9 +3,12 @@ use std::io;
use std::io::prelude::*;
use std::mem;

use super::corrupt;
use super::read_gz_header_part;
use super::Buffer;
use super::GzHeaderPartial;
use super::{GzBuilder, GzHeader};
use super::{FCOMMENT, FEXTRA, FHCRC, FNAME};
use crate::crc::{Crc, CrcReader};
use crate::crc::CrcReader;
use crate::deflate;
use crate::Compression;

Expand All @@ -18,112 +21,6 @@ fn copy(into: &mut [u8], from: &[u8], pos: &mut usize) -> usize {
min
}

pub(crate) fn corrupt() -> io::Error {
io::Error::new(
io::ErrorKind::InvalidInput,
"corrupt gzip stream does not have a matching checksum",
)
}

fn bad_header() -> io::Error {
io::Error::new(io::ErrorKind::InvalidInput, "invalid gzip header")
}

fn read_le_u16<R: Read>(r: &mut Buffer<R>) -> io::Result<u16> {
let mut b = [0; 2];
r.read_and_forget(&mut b)?;
Ok((b[0] as u16) | ((b[1] as u16) << 8))
}

fn read_gz_header_part<'a, R: Read>(r: &'a mut Buffer<'a, R>) -> io::Result<()> {
loop {
match r.part.state {
GzHeaderParsingState::Start => {
let mut header = [0; 10];
r.read_and_forget(&mut header)?;

if header[0] != 0x1f || header[1] != 0x8b {
return Err(bad_header());
}
if header[2] != 8 {
return Err(bad_header());
}

r.part.flg = header[3];
r.part.header.mtime = ((header[4] as u32) << 0)
| ((header[5] as u32) << 8)
| ((header[6] as u32) << 16)
| ((header[7] as u32) << 24);
let _xfl = header[8];
r.part.header.operating_system = header[9];
r.part.state = GzHeaderParsingState::Xlen;
}
GzHeaderParsingState::Xlen => {
if r.part.flg & FEXTRA != 0 {
r.part.xlen = read_le_u16(r)?;
}
r.part.state = GzHeaderParsingState::Extra;
}
GzHeaderParsingState::Extra => {
if r.part.flg & FEXTRA != 0 {
let mut extra = vec![0; r.part.xlen as usize];
r.read_and_forget(&mut extra)?;
r.part.header.extra = Some(extra);
}
r.part.state = GzHeaderParsingState::Filename;
}
GzHeaderParsingState::Filename => {
if r.part.flg & FNAME != 0 {
if r.part.header.filename.is_none() {
r.part.header.filename = Some(Vec::new());
};
for byte in r.bytes() {
let byte = byte?;
if byte == 0 {
break;
}
}
}
r.part.state = GzHeaderParsingState::Comment;
}
GzHeaderParsingState::Comment => {
if r.part.flg & FCOMMENT != 0 {
if r.part.header.comment.is_none() {
r.part.header.comment = Some(Vec::new());
};
for byte in r.bytes() {
let byte = byte?;
if byte == 0 {
break;
}
}
}
r.part.state = GzHeaderParsingState::Crc;
}
GzHeaderParsingState::Crc => {
if r.part.flg & FHCRC != 0 {
let stored_crc = read_le_u16(r)?;
let calced_crc = r.part.crc.sum() as u16;
if stored_crc != calced_crc {
return Err(corrupt());
}
}
return Ok(());
}
}
}
}

pub(crate) fn read_gz_header<R: Read>(r: &mut R) -> io::Result<GzHeader> {
let mut part = GzHeaderPartial::new();

let result = {
let mut reader = Buffer::new(&mut part, r);
read_gz_header_part(&mut reader)
};
result.map(|()| part.take_header())
}

/// A gzip streaming encoder
///
/// This structure exposes a [`BufRead`] interface that will read uncompressed data
Expand Down Expand Up @@ -311,49 +208,6 @@ pub struct GzDecoder<R> {
multi: bool,
}

#[derive(Debug)]
pub enum GzHeaderParsingState {
Start,
Xlen,
Extra,
Filename,
Comment,
Crc,
}

#[derive(Debug)]
pub struct GzHeaderPartial {
buf: Vec<u8>,
state: GzHeaderParsingState,
flg: u8,
xlen: u16,
crc: Crc,
header: GzHeader,
}

impl GzHeaderPartial {
fn new() -> GzHeaderPartial {
GzHeaderPartial {
buf: Vec::with_capacity(10), // minimum header length
state: GzHeaderParsingState::Start,
flg: 0,
xlen: 0,
crc: Crc::new(),
header: GzHeader {
extra: None,
filename: None,
comment: None,
operating_system: 0,
mtime: 0,
},
}
}

pub fn take_header(self) -> GzHeader {
self.header
}
}

#[derive(Debug)]
enum GzState {
Header(GzHeaderPartial),
Expand All @@ -363,77 +217,6 @@ enum GzState {
End,
}

/// A small adapter which reads data originally from `buf` and then reads all
/// further data from `reader`. This will also buffer all data read from
/// `reader` into `buf` for reuse on a further call.
struct Buffer<'a, T: 'a> {
part: &'a mut GzHeaderPartial,
buf_cur: usize,
buf_max: usize,
reader: &'a mut T,
}

impl<'a, T> Buffer<'a, T> {
fn new(part: &'a mut GzHeaderPartial, reader: &'a mut T) -> Buffer<'a, T> {
Buffer {
reader,
buf_cur: 0,
buf_max: part.buf.len(),
part,
}
}
}

impl<'a, T: Read> Read for Buffer<'a, T> {
fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
let mut bufref = match self.part.state {
GzHeaderParsingState::Filename => self.part.header.filename.as_mut(),
GzHeaderParsingState::Comment => self.part.header.comment.as_mut(),
_ => None,
};
if let Some(ref mut b) = bufref {
// we have a direct reference to a buffer where to write
let len = self.reader.read(buf)?;
if len > 0 && buf[len - 1] == 0 {
// we do not append the final 0
b.extend_from_slice(&buf[..len - 1]);
} else {
b.extend_from_slice(&buf[..len]);
}
self.part.crc.update(&buf[..len]);
Ok(len)
} else if self.buf_cur == self.buf_max {
// we read new bytes and also save them in self.part.buf
let len = self.reader.read(buf)?;
self.part.buf.extend_from_slice(&buf[..len]);
self.part.crc.update(&buf[..len]);
Ok(len)
} else {
// we first read the previously saved bytes
let len = (&self.part.buf[self.buf_cur..self.buf_max]).read(buf)?;
self.buf_cur += len;
Ok(len)
}
}
}

impl<'a, T> Buffer<'a, T>
where
T: std::io::Read,
{
// If we manage to read all the bytes, we reset the buffer
fn read_and_forget(&mut self, buf: &mut [u8]) -> io::Result<usize> {
self.read_exact(buf)?;
// we managed to read the whole buf
// we will no longer need the previously saved bytes in self.part.buf
let rlen = buf.len();
self.part.buf.truncate(0);
self.buf_cur = 0;
self.buf_max = 0;
Ok(rlen)
}
}

impl<R: BufRead> GzDecoder<R> {
/// Creates a new decoder from the given reader, immediately parsing the
/// gzip header.
Expand Down
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