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// Copyright (C) 2020 Jordan Petridis <jordan@centricular.com>
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Library General Public
// License as published by the Free Software Foundation; either
// version 2 of the License, or (at your option) any later version.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// Library General Public License for more details.
//
// You should have received a copy of the GNU Library General Public
// License along with this library; if not, write to the
// Free Software Foundation, Inc., 51 Franklin Street, Suite 500,
// Boston, MA 02110-1335, USA.
use byteorder::{BigEndian, WriteBytesExt};
use crc::crc32;
use nom::{
self, bytes::complete::take, combinator::map_res, multi::many0, number::complete::be_u16,
number::complete::be_u32, number::complete::be_u8, sequence::tuple, IResult,
};
use std::borrow::Cow;
use std::io::{self, Write};
#[derive(Debug)]
struct Prelude {
total_bytes: u32,
header_bytes: u32,
prelude_crc: u32,
}
#[derive(Debug)]
pub struct Header {
pub name: Cow<'static, str>,
pub value_type: u8,
pub value: Cow<'static, str>,
}
#[derive(Debug)]
pub struct Packet<'a> {
prelude: Prelude,
headers: Vec<Header>,
pub payload: &'a [u8],
msg_crc: u32,
}
fn write_header<W: Write>(w: &mut W, header: &Header) -> Result<(), io::Error> {
w.write_u8(header.name.len() as u8)?;
w.write_all(header.name.as_bytes())?;
w.write_u8(header.value_type)?;
w.write_u16::<BigEndian>(header.value.len() as u16)?;
w.write_all(header.value.as_bytes())?;
Ok(())
}
fn write_headers<W: Write>(w: &mut W, headers: &[Header]) -> Result<(), io::Error> {
for header in headers {
write_header(w, header)?;
}
Ok(())
}
pub fn encode_packet(payload: &[u8], headers: &[Header]) -> Result<Vec<u8>, io::Error> {
let mut res = Vec::with_capacity(1024);
// Total length
res.write_u32::<BigEndian>(0)?;
// Header length
res.write_u32::<BigEndian>(0)?;
// Prelude CRC32 placeholder
res.write_u32::<BigEndian>(0)?;
// Write all headers
write_headers(&mut res, headers)?;
// Rewrite header length
let header_length = res.len() - 12;
(&mut res[4..8]).write_u32::<BigEndian>(header_length as u32)?;
// Write payload
res.write_all(payload)?;
// Rewrite total length
let total_length = res.len() + 4;
(&mut res[0..4]).write_u32::<BigEndian>(total_length as u32)?;
// Rewrite the prelude crc since we replaced the lengths
let prelude_crc = crc32::checksum_ieee(&res[0..8]);
(&mut res[8..12]).write_u32::<BigEndian>(prelude_crc)?;
// Message CRC
let message_crc = crc32::checksum_ieee(&res);
res.write_u32::<BigEndian>(message_crc)?;
Ok(res)
}
fn parse_prelude(input: &[u8]) -> IResult<&[u8], Prelude> {
map_res(
tuple((be_u32, be_u32, be_u32)),
|(total_bytes, header_bytes, prelude_crc)| {
let sum = crc32::checksum_ieee(&input[0..8]);
if prelude_crc != sum {
return Err(nom::Err::Error((
"Prelude CRC doesn't match",
nom::error::ErrorKind::MapRes,
)));
}
Ok(Prelude {
total_bytes,
header_bytes,
prelude_crc,
})
},
)(input)
}
fn parse_header(input: &[u8]) -> IResult<&[u8], Header> {
let (input, header_length) = be_u8(input)?;
let (input, name) = map_res(take(header_length), std::str::from_utf8)(input)?;
let (input, value_type) = be_u8(input)?;
let (input, value_length) = be_u16(input)?;
let (input, value) = map_res(take(value_length), std::str::from_utf8)(input)?;
let header = Header {
name: name.to_string().into(),
value_type,
value: value.to_string().into(),
};
Ok((input, header))
}
pub fn packet_is_exception(packet: &Packet) -> bool {
for header in &packet.headers {
if header.name == ":message-type" && header.value == "exception" {
return true;
}
}
false
}
pub fn parse_packet(input: &[u8]) -> IResult<&[u8], Packet> {
let (remainder, prelude) = parse_prelude(input)?;
// Check the crc of the whole input
let sum = crc32::checksum_ieee(&input[..input.len() - 4]);
let (_, msg_crc) = be_u32(&input[input.len() - 4..])?;
if msg_crc != sum {
return Err(nom::Err::Error(nom::error::Error::new(
b"Prelude CRC doesn't match",
nom::error::ErrorKind::MapRes,
)));
}
let (remainder, header_input) = take(prelude.header_bytes)(remainder)?;
let (_, headers) = many0(parse_header)(header_input)?;
let payload_length = prelude.total_bytes - prelude.header_bytes - 4 - 12;
let (remainder, payload) = take(payload_length)(remainder)?;
// only the message_crc we check before should be remaining now
assert_eq!(remainder.len(), 4);
Ok((
input,
Packet {
prelude,
headers,
payload,
msg_crc,
},
))
}
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