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use std::collections::VecDeque;
use std::io::Cursor;
use std::io::Read;
use re_build_info::CrateVersion;
use re_log_types::LogMsg;
use crate::decoder::read_options;
use crate::Compression;
use crate::FileHeader;
use crate::MessageHeader;
use super::{DecodeError, VersionPolicy};
/// The stream decoder is a state machine which ingests byte chunks
/// and outputs messages once it has enough data to deserialize one.
///
/// Chunks are given to the stream via `StreamDecoder::push_chunk`,
/// and messages are read back via `StreamDecoder::try_read`.
pub struct StreamDecoder {
/// The Rerun version used to encode the RRD data.
///
/// `None` until a Rerun header has been processed.
version: Option<CrateVersion>,
/// How to handle version mismatches
version_policy: VersionPolicy,
/// Compression options
compression: Compression,
/// Incoming chunks are stored here
chunks: ChunkBuffer,
/// The uncompressed bytes are stored in this buffer before being read by `rmp_serde`
uncompressed: Vec<u8>,
/// The stream state
state: State,
}
///
/// ```text,ignore
/// StreamHeader
/// |
/// v
/// MessageHeader
/// ^ |
/// | |
/// ---Message<--
/// ```
#[derive(Clone, Copy)]
enum State {
/// The beginning of the stream.
///
/// The stream header contains the magic bytes (e.g. `RRF2`),
/// the encoded version, and the encoding options.
///
/// After the stream header is read once, the state machine
/// will only ever switch between `MessageHeader` and `Message`
StreamHeader,
/// The beginning of a message.
///
/// The message header contains the number of bytes in the
/// compressed message, and the number of bytes in the
/// uncompressed message.
MessageHeader,
/// The message content.
///
/// We need to know the full length of the message before attempting
/// to read it, otherwise the call to `decompress_into` or the
/// MessagePack deserialization may block or even fail.
Message(MessageHeader),
}
impl StreamDecoder {
pub fn new(version_policy: VersionPolicy) -> Self {
Self {
version: None,
version_policy,
compression: Compression::Off,
chunks: ChunkBuffer::new(),
uncompressed: Vec::with_capacity(1024),
state: State::StreamHeader,
}
}
pub fn push_chunk(&mut self, chunk: Vec<u8>) {
self.chunks.push(chunk);
}
pub fn try_read(&mut self) -> Result<Option<LogMsg>, DecodeError> {
match self.state {
State::StreamHeader => {
if let Some(header) = self.chunks.try_read(FileHeader::SIZE) {
// header contains version and compression options
let (version, options) = read_options(self.version_policy, header)?;
self.version = Some(version);
self.compression = options.compression;
// we might have data left in the current chunk,
// immediately try to read length of the next message
self.state = State::MessageHeader;
return self.try_read();
}
}
State::MessageHeader => {
if let Some(mut len) = self.chunks.try_read(MessageHeader::SIZE) {
let header = MessageHeader::decode(&mut len)?;
self.state = State::Message(header);
// we might have data left in the current chunk,
// immediately try to read the message content
return self.try_read();
}
}
State::Message(header) => {
match header {
MessageHeader::Data {
compressed_len,
uncompressed_len,
} => {
if let Some(bytes) = self.chunks.try_read(compressed_len as usize) {
let bytes = match self.compression {
Compression::Off => bytes,
Compression::LZ4 => {
self.uncompressed.resize(uncompressed_len as usize, 0);
lz4_flex::block::decompress_into(bytes, &mut self.uncompressed)
.map_err(DecodeError::Lz4)?;
&self.uncompressed
}
};
// read the message from the uncompressed bytes
let message =
rmp_serde::from_slice(bytes).map_err(DecodeError::MsgPack)?;
self.state = State::MessageHeader;
return if let re_log_types::LogMsg::SetStoreInfo(mut msg) = message {
// Propagate the protocol version from the header into the `StoreInfo` so that all
// parts of the app can easily access it.
msg.info.store_version = self.version;
Ok(Some(re_log_types::LogMsg::SetStoreInfo(msg)))
} else {
Ok(Some(message))
};
}
}
MessageHeader::EndOfStream => {
// We've reached the end of the stream, but there might be concatenated streams
// hence we set the state as if we are about to see another new stream
self.state = State::StreamHeader;
return self.try_read();
}
}
}
}
Ok(None)
}
}
type Chunk = Cursor<Vec<u8>>;
struct ChunkBuffer {
/// Any incoming chunks are queued until they are emptied
queue: VecDeque<Chunk>,
/// This buffer is used as scratch space for any read bytes,
/// so that we can return a contiguous slice from `try_read`.
buffer: Vec<u8>,
/// How many bytes of valid data are currently in `self.buffer`.
buffer_fill: usize,
}
impl ChunkBuffer {
fn new() -> Self {
Self {
queue: VecDeque::with_capacity(16),
buffer: Vec::with_capacity(1024),
buffer_fill: 0,
}
}
fn push(&mut self, chunk: Vec<u8>) {
if chunk.is_empty() {
return;
}
self.queue.push_back(Chunk::new(chunk));
}
/// Attempt to read exactly `n` bytes out of the queued chunks.
///
/// Returns `None` if there is not enough data to return a slice of `n` bytes.
///
/// NOTE: `try_read` *must* be called with the same `n` until it returns `Some`,
/// otherwise this will discard any previously buffered data.
fn try_read(&mut self, n: usize) -> Option<&[u8]> {
// resize the buffer if the target has changed
if self.buffer.len() != n {
assert_eq!(
self.buffer_fill, 0,
"`try_read` called with different `n` for incomplete read"
);
self.buffer.resize(n, 0);
self.buffer_fill = 0;
}
// try to read some bytes from the front of the queue,
// until either:
// - we've read enough to return a slice of `n` bytes
// - we run out of chunks to read
// while also discarding any empty chunks
while self.buffer_fill != n {
if let Some(chunk) = self.queue.front_mut() {
let remainder = &mut self.buffer[self.buffer_fill..];
self.buffer_fill += chunk.read(remainder).expect("failed to read from chunk");
if is_chunk_empty(chunk) {
self.queue.pop_front();
}
} else {
break;
}
}
if self.buffer_fill == n {
// ensure that a successful call to `try_read(N)`
// followed by another call to `try_read(N)` with the same `N`
// won't erroneously return the same bytes
self.buffer_fill = 0;
Some(&self.buffer[..])
} else {
None
}
}
}
fn is_chunk_empty(chunk: &Chunk) -> bool {
chunk.position() >= chunk.get_ref().len() as u64
}
#[cfg(test)]
mod tests {
use re_chunk::RowId;
use re_log_types::{
ApplicationId, SetStoreInfo, StoreId, StoreInfo, StoreKind, StoreSource, Time,
};
use crate::encoder::Encoder;
use crate::EncodingOptions;
use super::*;
fn fake_log_msg() -> LogMsg {
LogMsg::SetStoreInfo(SetStoreInfo {
row_id: *RowId::ZERO,
info: StoreInfo {
application_id: ApplicationId::unknown(),
store_id: StoreId::from_string(StoreKind::Recording, "test".into()),
cloned_from: None,
is_official_example: false,
started: Time::from_ns_since_epoch(0),
store_source: StoreSource::Unknown,
store_version: Some(CrateVersion::LOCAL),
},
})
}
fn test_data(options: EncodingOptions, n: usize) -> (Vec<LogMsg>, Vec<u8>) {
let messages: Vec<_> = (0..n).map(|_| fake_log_msg()).collect();
let mut buffer = Vec::new();
let mut encoder = Encoder::new(CrateVersion::LOCAL, options, &mut buffer).unwrap();
for message in &messages {
encoder.append(message).unwrap();
}
encoder.finish().unwrap();
(messages, buffer)
}
macro_rules! assert_message_ok {
($message:expr) => {{
match $message {
Ok(Some(message)) => {
assert_eq!(&fake_log_msg(), &message);
message
}
Ok(None) => {
panic!("failed to read message: message could not be read in full");
}
Err(err) => {
panic!("failed to read message: {err}");
}
}
}};
}
macro_rules! assert_message_incomplete {
($message:expr) => {{
match $message {
Ok(None) => {}
Ok(Some(message)) => {
panic!("expected message to be incomplete, instead received: {message:?}");
}
Err(err) => {
panic!("failed to read message: {err}");
}
}
}};
}
#[test]
fn stream_whole_chunks_uncompressed() {
let (input, data) = test_data(EncodingOptions::UNCOMPRESSED, 16);
let mut decoder = StreamDecoder::new(VersionPolicy::Error);
assert_message_incomplete!(decoder.try_read());
decoder.push_chunk(data);
let decoded_messages: Vec<_> = (0..16)
.map(|_| assert_message_ok!(decoder.try_read()))
.collect();
assert_eq!(input, decoded_messages);
}
#[test]
fn stream_byte_chunks_uncompressed() {
let (input, data) = test_data(EncodingOptions::UNCOMPRESSED, 16);
let mut decoder = StreamDecoder::new(VersionPolicy::Error);
assert_message_incomplete!(decoder.try_read());
for chunk in data.chunks(1) {
decoder.push_chunk(chunk.to_vec());
}
let decoded_messages: Vec<_> = (0..16)
.map(|_| assert_message_ok!(decoder.try_read()))
.collect();
assert_eq!(input, decoded_messages);
}
#[test]
fn two_concatenated_streams() {
let (input1, data1) = test_data(EncodingOptions::UNCOMPRESSED, 16);
let (input2, data2) = test_data(EncodingOptions::UNCOMPRESSED, 16);
let input = input1.into_iter().chain(input2).collect::<Vec<_>>();
let mut decoder = StreamDecoder::new(VersionPolicy::Error);
assert_message_incomplete!(decoder.try_read());
decoder.push_chunk(data1);
decoder.push_chunk(data2);
let decoded_messages: Vec<_> = (0..32)
.map(|_| assert_message_ok!(decoder.try_read()))
.collect();
assert_eq!(input, decoded_messages);
}
#[test]
fn stream_whole_chunks_compressed() {
let (input, data) = test_data(EncodingOptions::COMPRESSED, 16);
let mut decoder = StreamDecoder::new(VersionPolicy::Error);
assert_message_incomplete!(decoder.try_read());
decoder.push_chunk(data);
let decoded_messages: Vec<_> = (0..16)
.map(|_| assert_message_ok!(decoder.try_read()))
.collect();
assert_eq!(input, decoded_messages);
}
#[test]
fn stream_byte_chunks_compressed() {
let (input, data) = test_data(EncodingOptions::COMPRESSED, 16);
let mut decoder = StreamDecoder::new(VersionPolicy::Error);
assert_message_incomplete!(decoder.try_read());
for chunk in data.chunks(1) {
decoder.push_chunk(chunk.to_vec());
}
let decoded_messages: Vec<_> = (0..16)
.map(|_| assert_message_ok!(decoder.try_read()))
.collect();
assert_eq!(input, decoded_messages);
}
#[test]
fn stream_3x16_chunks() {
let (input, data) = test_data(EncodingOptions::COMPRESSED, 16);
let mut decoder = StreamDecoder::new(VersionPolicy::Error);
let mut decoded_messages = vec![];
// keep pushing 3 chunks of 16 bytes at a time, and attempting to read messages
// until there are no more chunks
let mut chunks = data.chunks(16).peekable();
while chunks.peek().is_some() {
for _ in 0..3 {
if let Some(chunk) = chunks.next() {
decoder.push_chunk(chunk.to_vec());
} else {
break;
}
}
if let Some(message) = decoder.try_read().unwrap() {
decoded_messages.push(message);
}
}
assert_eq!(input, decoded_messages);
}
#[test]
fn stream_irregular_chunks() {
// this attempts to stress-test `try_read` with chunks of various sizes
let (input, data) = test_data(EncodingOptions::COMPRESSED, 16);
let mut data = Cursor::new(data);
let mut decoder = StreamDecoder::new(VersionPolicy::Error);
let mut decoded_messages = vec![];
// read chunks 2xN bytes at a time, where `N` comes from a regular pattern
// this is slightly closer to using random numbers while still being
// fully deterministic
let pattern = [0, 3, 4, 70, 31];
let mut pattern_index = 0;
let mut temp = [0_u8; 71];
while data.position() < data.get_ref().len() as u64 {
for _ in 0..2 {
let n = data.read(&mut temp[..pattern[pattern_index]]).unwrap();
pattern_index = (pattern_index + 1) % pattern.len();
decoder.push_chunk(temp[..n].to_vec());
}
if let Some(message) = decoder.try_read().unwrap() {
decoded_messages.push(message);
}
}
assert_eq!(input, decoded_messages);
}
#[test]
fn chunk_buffer_read_single_chunk() {
// reading smaller `n` from multiple larger chunks
let mut buffer = ChunkBuffer::new();
let data = &[0, 1, 2, 3, 4];
assert_eq!(None, buffer.try_read(1));
buffer.push(data.to_vec());
assert_eq!(Some(&data[..3]), buffer.try_read(3));
assert_eq!(Some(&data[3..]), buffer.try_read(2));
assert_eq!(None, buffer.try_read(1));
}
#[test]
fn chunk_buffer_read_multi_chunk() {
// reading a large `n` from multiple smaller chunks
let mut buffer = ChunkBuffer::new();
let chunks: &[&[u8]] = &[&[0, 1, 2], &[3, 4]];
assert_eq!(None, buffer.try_read(1));
buffer.push(chunks[0].to_vec());
assert_eq!(None, buffer.try_read(5));
buffer.push(chunks[1].to_vec());
assert_eq!(Some(&[0, 1, 2, 3, 4][..]), buffer.try_read(5));
assert_eq!(None, buffer.try_read(1));
}
#[test]
fn chunk_buffer_read_same_n() {
// reading the same `n` multiple times should not return the same bytes
let mut buffer = ChunkBuffer::new();
let data = &[0, 1, 2, 3];
buffer.push(data.to_vec());
assert_eq!(data, buffer.try_read(4).unwrap());
assert_eq!(None, buffer.try_read(4));
let data = &[4, 5, 6, 7];
buffer.push(data.to_vec());
assert_eq!(data, buffer.try_read(4).unwrap());
assert_eq!(None, buffer.try_read(4));
}
}