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use std::io::{Read, Write};
use crate::{DecodeError, EncodeError, Pack, Unpack};
use crate::ll::marker::Marker;
use byteorder::{WriteBytesExt, ReadBytesExt};
pub trait PackableStructSum: Sized {
fn read_struct_body<T: Read>(size: usize, tag_byte: u8, reader: &mut T) -> Result<Self, DecodeError>;
fn write_struct_body<T: Write>(&self, writer: &mut T) -> Result<usize, EncodeError>;
fn fields_len(&self) -> usize;
fn tag_byte(&self) -> u8;
}
impl PackableStructSum for () {
fn read_struct_body<T: Read>(_: usize, _: u8, _: &mut T) -> Result<Self, DecodeError> {
Ok(())
}
fn write_struct_body<T: Write>(&self, _: &mut T) -> Result<usize, EncodeError> {
Ok(0)
}
fn fields_len(&self) -> usize {
0
}
fn tag_byte(&self) -> u8 {
0x00
}
}
impl<S: PackableStructSum, T: Write> Pack<T> for S {
fn encode(&self, writer: &mut T) -> Result<usize, EncodeError> {
Marker::Structure(self.fields_len()).encode(writer)?;
writer.write_u8(self.tag_byte())?;
Ok(2 + self.write_struct_body(writer)?)
}
}
impl<S: PackableStructSum, T: Read> Unpack<T> for S {
fn decode(reader: &mut T) -> Result<Self, DecodeError> {
let marker = Marker::decode(reader)?;
match marker {
Marker::Structure(sz) => {
let tag_byte = reader.read_u8()?;
S::read_struct_body(sz, tag_byte, reader)
},
_ => Err(DecodeError::UnexpectedMarker(marker))
}
}
}
#[cfg(test)]
pub mod test {
use crate::{PackableStructSum, Pack, Unpack};
use std::fmt::Debug;
pub fn pack_unpack_struct_sum_test<T: PackableStructSum + PartialEq + Debug>(value: &T, expected_size: usize) {
let mut buffer = Vec::new();
let written = T::encode(value, &mut buffer).unwrap();
assert_eq!(expected_size, written);
let res: T = T::decode(&mut buffer.as_slice()).unwrap();
assert_eq!(value, &res, "value '{:?}' got encoded->decoded into '{:?}'", value, res);
}
}