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// Copyright © 2017 Mozilla Foundation
//
// This program is made available under an ISC-style license. See the
// accompanying file LICENSE for details
//! `Encoder`s and `Decoder`s from items to/from `BytesMut` buffers.
// The assert in LengthDelimitedCodec::decode triggers this clippy warning but
// requires upgrading the workspace to Rust 2021 to resolve.
// This should be fixed in Rust 1.68, after which the following `allow` can be deleted.
#![allow(clippy::uninlined_format_args)]
use bincode::Options;
use byteorder::{ByteOrder, LittleEndian};
use bytes::{Buf, BufMut, BytesMut};
use serde::de::DeserializeOwned;
use serde::ser::Serialize;
use std::convert::TryInto;
use std::fmt::Debug;
use std::io;
use std::marker::PhantomData;
use std::mem::size_of;
////////////////////////////////////////////////////////////////////////////////
// Split buffer into size delimited frames - This appears more complicated than
// might be necessary due to handling the possibility of messages being split
// across reads.
pub trait Codec {
/// The type of items to be encoded into byte buffer
type In;
/// The type of items to be returned by decoding from byte buffer
type Out;
/// Attempts to decode a frame from the provided buffer of bytes.
fn decode(&mut self, buf: &mut BytesMut) -> io::Result<Option<Self::Out>>;
/// A default method available to be called when there are no more bytes
/// available to be read from the I/O.
fn decode_eof(&mut self, buf: &mut BytesMut) -> io::Result<Self::Out> {
match self.decode(buf)? {
Some(frame) => Ok(frame),
None => Err(io::Error::new(
io::ErrorKind::Other,
"bytes remaining on stream",
)),
}
}
/// Encodes a frame into the buffer provided.
fn encode(&mut self, msg: Self::In, buf: &mut BytesMut) -> io::Result<()>;
}
/// Codec based upon bincode serialization
///
/// Messages that have been serialized using bincode are prefixed with
/// the length of the message to aid in deserialization, so that it's
/// known if enough data has been received to decode a complete
/// message.
pub struct LengthDelimitedCodec<In, Out> {
state: State,
encode_buf: Vec<u8>,
__in: PhantomData<In>,
__out: PhantomData<Out>,
}
enum State {
Length,
Data(u32),
}
const MAX_MESSAGE_LEN: u32 = 1024 * 1024;
const MAGIC: u64 = 0xa4d1_019c_c910_1d4a;
const HEADER_LEN: usize = size_of::<u32>() + size_of::<u64>();
impl<In, Out> Default for LengthDelimitedCodec<In, Out> {
fn default() -> Self {
Self {
state: State::Length,
encode_buf: Vec::with_capacity(crate::ipccore::IPC_CLIENT_BUFFER_SIZE),
__in: PhantomData,
__out: PhantomData,
}
}
}
impl<In, Out> LengthDelimitedCodec<In, Out> {
// Lengths are encoded as little endian u32
fn decode_length(buf: &mut BytesMut) -> Option<u32> {
if buf.len() < HEADER_LEN {
// Not enough data
return None;
}
let magic = LittleEndian::read_u64(&buf[0..8]);
assert_eq!(magic, MAGIC);
// Consume the length field
let n = LittleEndian::read_u32(&buf[8..12]);
buf.advance(HEADER_LEN);
Some(n)
}
fn decode_data(buf: &mut BytesMut, n: u32) -> io::Result<Option<Out>>
where
Out: DeserializeOwned + Debug,
{
let n = n.try_into().unwrap();
// At this point, the buffer has already had the required capacity
// reserved. All there is to do is read.
if buf.len() < n {
return Ok(None);
}
trace!("Attempting to decode");
let msg = bincode::options()
.with_limit(MAX_MESSAGE_LEN as u64)
.deserialize::<Out>(&buf[..n])
.map_err(|e| match *e {
bincode::ErrorKind::Io(e) => e,
_ => io::Error::new(io::ErrorKind::Other, *e),
})?;
buf.advance(n);
trace!("... Decoded {:?}", msg);
Ok(Some(msg))
}
}
impl<In, Out> Codec for LengthDelimitedCodec<In, Out>
where
In: Serialize + Debug,
Out: DeserializeOwned + Debug,
{
type In = In;
type Out = Out;
fn decode(&mut self, buf: &mut BytesMut) -> io::Result<Option<Self::Out>> {
let n = match self.state {
State::Length => {
match Self::decode_length(buf) {
Some(n) => {
assert!(
n <= MAX_MESSAGE_LEN,
"assertion failed: {} <= {}",
n,
MAX_MESSAGE_LEN
);
self.state = State::Data(n);
// Ensure that the buffer has enough space to read the
// incoming payload
buf.reserve(n.try_into().unwrap());
n
}
None => return Ok(None),
}
}
State::Data(n) => n,
};
match Self::decode_data(buf, n)? {
Some(data) => {
// Update the decode state
self.state = State::Length;
// Make sure the buffer has enough space to read the next length header.
buf.reserve(HEADER_LEN);
Ok(Some(data))
}
None => Ok(None),
}
}
fn encode(&mut self, item: Self::In, buf: &mut BytesMut) -> io::Result<()> {
trace!("Attempting to encode");
self.encode_buf.clear();
if let Err(e) = bincode::options()
.with_limit(MAX_MESSAGE_LEN as u64)
.serialize_into::<_, Self::In>(&mut self.encode_buf, &item)
{
trace!("message encode failed: {:?}", *e);
match *e {
bincode::ErrorKind::Io(e) => return Err(e),
_ => return Err(io::Error::new(io::ErrorKind::Other, *e)),
}
}
let encoded_len = self.encode_buf.len();
assert!(encoded_len <= MAX_MESSAGE_LEN as usize);
buf.reserve(encoded_len + HEADER_LEN);
buf.put_u64_le(MAGIC);
buf.put_u32_le(encoded_len.try_into().unwrap());
buf.extend_from_slice(&self.encode_buf);
Ok(())
}
}
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