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use nom::{
bits,
bytes::complete::take_while_m_n,
error::{Error, ErrorKind, FromExternalError},
sequence::tuple,
IResult, Parser,
};
use nom_supreme::ParserExt;
use super::{
errors::MPacketHeaderError,
qos::{mquality_of_service, MQualityOfService},
};
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct MPacketHeader {
pub kind: MPacketKind,
pub remaining_length: u32,
}
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum MPacketKind {
Connect,
Connack,
Publish {
dup: bool,
qos: MQualityOfService,
retain: bool,
},
Puback,
Pubrec,
Pubrel,
Pubcomp,
Subscribe,
Suback,
Unsubscribe,
Unsuback,
Pingreq,
Pingresp,
Disconnect,
}
fn mpacketkind(input: &[u8]) -> IResult<&[u8], MPacketKind> {
let (input, (upper, lower)): (_, (u8, u8)) =
bits::<_, _, Error<(&[u8], usize)>, _, _>(tuple((
nom::bits::complete::take(4usize),
nom::bits::complete::take(4usize),
)))(input)?;
let (input, kind) = match (upper, lower) {
(1, 0b0000) => (input, MPacketKind::Connect),
(2, 0b0000) => (input, MPacketKind::Connack),
(3, lower) => {
let dup = lower & 0b1000 != 0;
let retain = lower & 0b0001 != 0;
let qos = match mquality_of_service((lower & 0b0110) >> 1) {
Ok(qos) => qos,
Err(e) => {
return Err(nom::Err::Error(Error::from_external_error(
input,
ErrorKind::MapRes,
e,
)));
}
};
(input, MPacketKind::Publish { qos, dup, retain })
}
(4, 0b0000) => (input, MPacketKind::Puback),
(5, 0b0000) => (input, MPacketKind::Pubrec),
(6, 0b0010) => (input, MPacketKind::Pubrel),
(7, 0b0000) => (input, MPacketKind::Pubcomp),
(8, 0b0010) => (input, MPacketKind::Subscribe),
(9, 0b0000) => (input, MPacketKind::Suback),
(10, 0b0010) => (input, MPacketKind::Unsubscribe),
(11, 0b0000) => (input, MPacketKind::Unsuback),
(12, 0b0000) => (input, MPacketKind::Pingreq),
(13, 0b0000) => (input, MPacketKind::Pingresp),
(14, 0b0000) => (input, MPacketKind::Disconnect),
(inv_type, _) => {
return Err(nom::Err::Error(Error::from_external_error(
input,
ErrorKind::MapRes,
MPacketHeaderError::InvalidPacketType(inv_type),
)))
}
};
Ok((input, kind))
}
pub fn decode_variable_length(bytes: &[u8]) -> u32 {
let mut output: u32 = 0;
for (exp, val) in bytes.iter().enumerate() {
output += (*val as u32 & 0b0111_1111) * 128u32.pow(exp as u32);
}
output
}
pub fn mfixedheader(input: &[u8]) -> IResult<&[u8], MPacketHeader> {
let (input, kind) = mpacketkind(input)?;
let (input, remaining_length) = nom::number::complete::u8
.and(take_while_m_n(0, 3, |b| b & 0b1000_0000 != 0))
.recognize()
.map(decode_variable_length)
.parse(input)?;
Ok((
input,
MPacketHeader {
kind,
remaining_length,
},
))
}
#[cfg(test)]
mod tests {
use crate::v3::{
header::{MPacketHeader, MPacketKind},
qos::MQualityOfService,
};
use super::{decode_variable_length, mfixedheader};
#[test]
fn check_variable_length_decoding() {
let input = &[64];
let output = decode_variable_length(input);
assert_eq!(output, 64);
let input = &[193, 2];
let output = decode_variable_length(input);
assert_eq!(output, 321);
}
#[test]
fn check_header_publish_flags() {
let input = &[0b0011_1101, 0];
let (input, header) = mfixedheader(input).unwrap();
assert_eq!(input, &[]);
assert_eq!(
header,
MPacketHeader {
remaining_length: 0,
kind: MPacketKind::Publish {
dup: true,
qos: MQualityOfService::ExactlyOnce,
retain: true
}
}
);
}
#[test]
fn check_invalid_header_publish_flags() {
let input = &[0b0011_1111, 0];
mfixedheader(input).unwrap_err();
}
}
