/
parser.rs
376 lines (336 loc) · 10.8 KB
/
parser.rs
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/*
* Copyright (c) Meta Platforms, Inc. and affiliates.
*
* This software may be used and distributed according to the terms of the
* GNU General Public License version 2.
*/
// Nom parser for Mercurial revlogs
use std::fmt::Debug;
use std::io::Read;
use bitflags::bitflags;
use flate2::read::ZlibDecoder;
use mercurial_types::bdiff::Delta;
use mercurial_types::HgNodeHash;
use nom::be_u16;
use nom::be_u32;
use nom::Err;
use nom::ErrorKind;
use nom::IResult;
use nom::Needed;
use nom::*;
use super::lz4;
use crate::revlog::revidx::RevIdx;
// #[derive(Copy, Clone, Debug, Eq, PartialEq)]
// pub enum Badness {
// IO,
// Version,
// Features,
// BadZlib,
// }
//
pub type Error = u32;
// hack until I work out how to propagate proper E type
#[allow(non_upper_case_globals, non_snake_case, dead_code)]
pub mod Badness {
use super::Error;
pub const IO: Error = 0;
pub const Version: Error = 1;
pub const Features: Error = 2;
pub const BadZlib: Error = 3;
pub const BadLZ4: Error = 4;
}
// `Revlog` features
bitflags! {
#[derive(PartialEq, Eq, PartialOrd, Ord, Hash, Debug, Clone, Copy)]
pub struct Features: u16 {
const INLINE = 1 << 0;
const GENERAL_DELTA = 1 << 1;
}
}
// Per-revision flags
bitflags! {
#[derive(PartialEq, Eq, PartialOrd, Ord, Hash, Debug, Clone, Copy)]
pub struct IdxFlags: u16 {
const OCTOPUS_MERGE = 1 << 12;
const EXTSTORED = 1 << 13;
const CENSORED = 1 << 15;
}
}
/// Revlog version number
#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub enum Version {
Revlog0 = 0,
RevlogNG = 1,
}
/// Revlog header
#[derive(Copy, Clone, Debug, Eq, PartialEq)]
pub struct Header {
pub version: Version,
pub features: Features,
}
/// Entry entry for a revision
#[derive(Copy, Clone, Debug)]
pub struct Entry {
pub offset: u64, // offset of content (delta/literal) in datafile (or inlined)
pub flags: IdxFlags, // unused?
pub compressed_len: u32, // compressed content size
pub len: Option<u32>, // size of final file (after applying deltas)
pub baserev: Option<RevIdx>, // base/previous rev for deltas (None if literal)
pub linkrev: RevIdx, // changeset id
pub p1: Option<RevIdx>, // parent p1
pub p2: Option<RevIdx>, // parent p2
pub nodeid: HgNodeHash, // nodeid
}
impl Entry {
pub fn nodeid(&self) -> HgNodeHash {
self.nodeid
}
}
// Parse the revlog header
named!(pub header<Header>,
do_parse!(
features: return_error!(ErrorKind::Custom(Badness::IO), be_u16) >>
version: return_error!(ErrorKind::Custom(Badness::IO), be_u16) >>
({
let vers = match version {
0 => Version::Revlog0,
1 => Version::RevlogNG,
_ => panic!("bad version"),
};
let features = match Features::from_bits(features) {
Some(f) => f,
None => panic!("bad features"),
};
Header {
version: vers,
features,
}
}))
);
pub fn indexng_size() -> usize {
6 + 2 + 4 + 4 + 4 + 4 + 4 + 4 + 32
}
// Parse an "NG" revlog entry
named!(pub indexng<Entry>,
do_parse!(
offset: return_error!(ErrorKind::Custom(Badness::IO), be_u48) >> // XXX if first, then only 2 bytes, implied 0 in top 4
flags: return_error!(ErrorKind::Custom(Badness::IO), be_u16) >> // ?
compressed_length: return_error!(ErrorKind::Custom(Badness::IO), be_u32) >>
uncompressed_length: return_error!(ErrorKind::Custom(Badness::IO), be_u32) >>
baserev: return_error!(ErrorKind::Custom(Badness::IO), be_u32) >>
linkrev: return_error!(ErrorKind::Custom(Badness::IO), be_u32) >>
p1: return_error!(ErrorKind::Custom(Badness::IO), be_u32) >>
p2: return_error!(ErrorKind::Custom(Badness::IO), be_u32) >>
hash: take!(32) >>
({
Entry {
offset,
flags: IdxFlags::from_bits(flags).expect("bad rev idx flags"),
compressed_len: compressed_length,
len: Some(uncompressed_length),
baserev: if baserev == !0 { None } else { Some(baserev.into()) },
linkrev: linkrev.into(),
p1: if p1 == !0 { None } else { Some(p1.into()) },
p2: if p2 == !0 { None } else { Some(p2.into()) },
nodeid: HgNodeHash::from_bytes(&hash[..20]).expect("bad bytes for sha"),
}
})
)
);
pub fn index0_size() -> usize {
4 + 4 + 4 + 4 + 4 + 4 + 4 + 20
}
// Parse an original revlog entry
named!(pub index0<Entry>,
do_parse!(
_header: header >>
offset: return_error!(ErrorKind::Custom(Badness::IO), be_u32) >>
compressed_length: return_error!(ErrorKind::Custom(Badness::IO), be_u32) >>
baserev: return_error!(ErrorKind::Custom(Badness::IO), be_u32) >>
linkrev: return_error!(ErrorKind::Custom(Badness::IO), be_u32) >>
p1: return_error!(ErrorKind::Custom(Badness::IO), be_u32) >>
p2: return_error!(ErrorKind::Custom(Badness::IO), be_u32) >>
hash: take!(20) >>
({
Entry {
offset: offset as u64,
flags: IdxFlags::empty(),
compressed_len: compressed_length,
len: None,
baserev: if baserev == !0 { None } else { Some(baserev.into()) },
linkrev: linkrev.into(),
p1: if p1 == !0 { None } else { Some(p1.into()) },
p2: if p2 == !0 { None } else { Some(p2.into()) },
nodeid: HgNodeHash::from_bytes(&hash[..20]).expect("bad bytes for sha"),
}
})
)
);
// Parse a single Delta
named!(pub delta<Delta>,
do_parse!(
start: be_u32 >>
end: be_u32 >>
content: length_bytes!(be_u32) >>
({
Delta {
start: start as usize,
end: end as usize,
content: content.into(),
}
})
)
);
// Parse 0 or more deltas
named!(deltas<Vec<Delta>>, many0!(delta));
// A chunk of data data that contains some Deltas; the caller defines the framing bytes
// bounding the input.
named!(pub deltachunk<Vec<Delta> >,
map!(
many0!(
alt!(
do_parse!(tag!(b"u") >> d: deltas >> (d)) | // uncompressed with explicit 'u' header
do_parse!(peek!(tag!(b"\0")) >> d: deltas >> (d)) | // uncompressed with included initial 0x00
do_parse!(peek!(tag!(b"x")) >> d: apply!(zlib_decompress, deltas) >> (d)) | // compressed; 'x' part of the zlib stream
do_parse!(tag!(b"4") >> d: apply!(lz4::lz4_decompress, deltas) >> (d)) // compressed w/ lz4
)
),
|dv: Vec<_>| dv.into_iter().flatten().collect())
);
fn remains(i: &[u8]) -> IResult<&[u8], &[u8]> {
IResult::Done(&i[..0], i)
}
named!(remains_owned<Vec<u8>>, map!(remains, |x: &[u8]| x.into()));
// Parse some literal data, possibly compressed
named!(pub literal<Vec<u8> >,
alt!(
do_parse!(peek!(tag!(b"\0")) >> d: remains >> (d.into())) |
do_parse!(peek!(tag!(b"x")) >> d: apply!(zlib_decompress, remains_owned) >> (d)) |
do_parse!(tag!(b"4") >> d: apply!(lz4::lz4_decompress, remains_owned) >> (d)) |
do_parse!(tag!(b"u") >> d: remains >> (d.into()))
)
);
// Remap error to remove reference to `data`
pub fn detach_result<'inp, 'out, O: 'out, E: 'out>(
res: IResult<&'inp [u8], O, E>,
rest: &'out [u8],
) -> IResult<&'out [u8], O, E> {
match res {
IResult::Done(_, o) => IResult::Done(rest, o),
IResult::Incomplete(n) => IResult::Incomplete(n),
IResult::Error(Err::Code(e))
| IResult::Error(Err::Node(e, _))
| IResult::Error(Err::Position(e, _))
| IResult::Error(Err::NodePosition(e, ..)) => IResult::Error(Err::Code(e)),
}
}
/// Unpack a chunk of data and apply a parse function to the output.
fn zlib_decompress<'a, P, R: 'a, E: Debug + 'a>(i: &'a [u8], parse: P) -> IResult<&'a [u8], R, E>
where
for<'p> P: Fn(&'p [u8]) -> IResult<&'p [u8], R, E>,
{
let mut data = Vec::new();
let inused = {
let mut zdec = ZlibDecoder::new(i);
match zdec.read_to_end(&mut data) {
Ok(_) => zdec.total_in() as usize,
Err(err) => panic!("zdec failed {:?}", err),
}
};
let remains = &i[inused..];
detach_result(parse(&data[..]), remains)
}
/// Parse a 6 byte big-endian offset
#[inline]
#[allow(clippy::identity_op)]
fn be_u48(i: &[u8]) -> IResult<&[u8], u64> {
if i.len() < 6 {
IResult::Incomplete(Needed::Size(6))
} else {
let res = ((i[0] as u64) << 40)
+ ((i[1] as u64) << 32)
+ ((i[2] as u64) << 24)
+ ((i[3] as u64) << 16)
+ ((i[4] as u64) << 8)
+ ((i[5] as u64) << 0);
IResult::Done(&i[6..], res)
}
}
#[cfg(test)]
mod test {
use nom::IResult;
use super::header;
use super::Features;
use super::Header;
use super::Version;
#[test]
fn test_header_0() {
let d = [0x00, 0x00, 0x00, 0x00];
assert_eq!(
header(&d[..]),
IResult::Done(
&b""[..],
Header {
version: Version::Revlog0,
features: Features::empty(),
}
)
)
}
#[test]
fn test_header_1() {
let d = [0x00, 0x00, 0x00, 0x01];
assert_eq!(
header(&d[..]),
IResult::Done(
&b""[..],
Header {
version: Version::RevlogNG,
features: Features::empty(),
}
)
)
}
#[test]
fn test_header_feat_1() {
let d = [0x00, 0x01, 0x00, 0x01];
assert_eq!(
header(&d[..]),
IResult::Done(
&b""[..],
Header {
version: Version::RevlogNG,
features: Features::INLINE,
}
)
)
}
#[test]
fn test_header_feat_2() {
let d = [0x00, 0x02, 0x00, 0x01];
assert_eq!(
header(&d[..]),
IResult::Done(
&b""[..],
Header {
version: Version::RevlogNG,
features: Features::GENERAL_DELTA,
}
)
)
}
#[test]
fn test_header_feat_3() {
let d = [0x00, 0x03, 0x00, 0x01];
assert_eq!(
header(&d[..]),
IResult::Done(
&b""[..],
Header {
version: Version::RevlogNG,
features: Features::INLINE | Features::GENERAL_DELTA,
}
)
)
}
}