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use super::*;
pub struct Decoder {
header_found: bool,
esc_seq: [u8; 4],
esc_seq_len: usize,
}
impl Decoder {
pub fn new() -> Self {
Decoder {
header_found: false,
esc_seq: [0; 4],
esc_seq_len: 0,
}
}
pub fn decode<'a>(&mut self, input: &'a [u8], output: &'a mut [u8])
-> Result<(usize, &'a [u8], bool)>
{
let input_len = input.len();
let mut stream = input;
if !self.header_found {
stream = self.decode_header(stream)?;
}
let res = self.decode_stream(stream, output)?;
Ok((input_len - res.0.len(), res.1, res.2))
}
fn decode_header<'a>(&mut self, input: &'a [u8]) -> Result<&'a [u8]> {
if input.len() < 1 {
return Err(Error::BadHeaderDecode);
}
if input[0] != END {
return Err(Error::BadHeaderDecode);
}
self.header_found = true;
Ok(&input[1..])
}
fn decode_stream<'a>(&mut self, input: &'a [u8], output: &'a mut [u8])
-> Result<(&'a [u8], &'a [u8], bool)>
{
let mut in_byte = 0;
let mut out_byte = 0;
let mut end = false;
loop {
if in_byte == input.len() || out_byte == output.len() {
break;
}
if self.esc_seq_len > 0 {
match input[in_byte] {
ESC_END => {
output[out_byte] = END
}
ESC_ESC => {
output[out_byte] = ESC
}
_ => return Err(Error::BadEscapeSequenceDecode),
}
out_byte += 1;
self.esc_sequence_empty();
} else {
match input[in_byte] {
ESC => {
self.esc_sequence_push(ESC);
}
END => {
in_byte += 1;
end = true;
break;
}
_ => {
output[out_byte] = input[in_byte];
out_byte += 1;
}
}
}
in_byte += 1;
}
Ok((&input[in_byte..], &output[..out_byte], end))
}
fn esc_sequence_push(&mut self, byte: u8) {
self.esc_seq[self.esc_seq_len] = byte;
self.esc_seq_len += 1;
}
fn esc_sequence_empty(&mut self) {
self.esc_seq_len = 0;
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn empty_decode() {
const INPUT: [u8; 2] = [0xc0, 0xc0];
let mut output: [u8; 32] = [0; 32];
let mut slip = Decoder::new();
let res = slip.decode(&INPUT, &mut output).unwrap();
assert_eq!(INPUT.len(), res.0);
assert_eq!(&[0;0], res.1);
assert_eq!(true, res.2);
}
#[test]
fn simple_decode() {
const INPUT: [u8; 7] = [0xc0, 0x01, 0x02, 0x03, 0x04, 0x05, 0xc0];
const DATA: [u8; 5] = [0x01, 0x02, 0x03, 0x04, 0x05];
let mut output: [u8; 32] = [0; 32];
let mut slip = Decoder::new();
let res = slip.decode(&INPUT, &mut output).unwrap();
assert_eq!(INPUT.len(), res.0);
assert_eq!(&DATA, res.1);
assert_eq!(true, res.2);
}
#[test]
fn decode_esc_then_esc_end_sequence() {
const INPUT: [u8; 6] = [0xc0, 0x01, 0xdb, 0xdc, 0x03, 0xc0];
const DATA: [u8; 3] = [0x01, 0xc0, 0x03];
let mut output: [u8; 200] = [0; 200];
let mut slip = Decoder::new();
let res = slip.decode(&INPUT, &mut output).unwrap();
assert_eq!(INPUT.len(), res.0);
assert_eq!(&DATA, res.1);
assert_eq!(true, res.2);
}
#[test]
fn decode_esc_then_esc_esc_sequence() {
const INPUT: [u8; 6] = [0xc0, 0x01, 0xdb, 0xdd, 0x03, 0xc0];
const DATA: [u8; 3] = [0x01, 0xdb, 0x03];
let mut output: [u8; 200] = [0; 200];
let mut slip = Decoder::new();
let res = slip.decode(&INPUT, &mut output).unwrap();
assert_eq!(INPUT.len(), res.0);
assert_eq!(&DATA, res.1);
assert_eq!(true, res.2);
}
#[test]
fn multi_part_decode() {
const INPUT_1: [u8; 6] = [0xc0, 0x01, 0x02, 0x03, 0x04, 0x05];
const INPUT_2: [u8; 6] = [0x05, 0x06, 0x07, 0x08, 0x09, 0xc0];
const DATA_1: [u8; 5] = [0x01, 0x02, 0x03, 0x04, 0x05];
const DATA_2: [u8; 5] = [0x05, 0x06, 0x07, 0x08, 0x09];
let mut output: [u8; 200] = [0; 200];
let mut slip = Decoder::new();
let mut offset = 0;
{
let res = slip.decode(&INPUT_1, &mut output[offset..]).unwrap();
assert_eq!(INPUT_1.len(), res.0);
assert_eq!(&DATA_1, res.1);
assert_eq!(false, res.2);
offset += res.1.len();
}
{
let res = slip.decode(&INPUT_2, &mut output[offset..]).unwrap();
assert_eq!(INPUT_2.len(), res.0);
assert_eq!(&DATA_2, res.1);
assert_eq!(true, res.2);
offset += res.1.len();
}
assert_eq!(10, offset);
}
}