353 lines
11 KiB
Rust
353 lines
11 KiB
Rust
//! Stabilizer data stream capabilities
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//!
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//! # Design
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//! Data streamining utilizes UDP packets to send live data streams at high throughput.
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//! Packets are always sent in a best-effort fashion, and data may be dropped.
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//!
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//! Stabilizer organizes livestreamed data into batches within a "Frame" that will be sent as a UDP
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//! packet. Each frame consits of a header followed by sequential batch serializations. The packet
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//! header is constant for all streaming capabilities, but the serialization format after the header
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//! is application-defined.
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//!
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//! ## Frame Header
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//! The header consists of the following, all in little-endian.
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//!
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//! * **Magic word 0x057B** <u16>: a constant to identify Stabilizer streaming data.
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//! * **Format Code** <u8>: a unique ID that indicates the serialization format of each batch of data
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//! in the frame. Refer to [StreamFormat] for further information.
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//! * **Batch Size** <u8>: the number of samples in each batch of data.
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//! * **Sequence Number** <u32>: an the sequence number of the first batch in the frame.
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//! This can be used to determine if and how many stream batches are lost.
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//!
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//! # Example
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//! A sample Python script is available in `scripts/stream_throughput.py` to demonstrate reception
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//! of livestreamed data.
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use heapless::spsc::{Consumer, Producer, Queue};
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use miniconf::MiniconfAtomic;
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use num_enum::IntoPrimitive;
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use serde::Deserialize;
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use smoltcp_nal::embedded_nal::{IpAddr, Ipv4Addr, SocketAddr, UdpClientStack};
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use heapless::pool::{Box, Init, Pool, Uninit};
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use super::NetworkReference;
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const MAGIC_WORD: u16 = 0x057B;
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// The size of the header, calculated in bytes.
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// The header has a 16-bit magic word, an 8-bit format, 8-bit batch-size, and 32-bit sequence
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// number, which corresponds to 8 bytes total.
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const HEADER_SIZE: usize = 8;
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// The number of frames that can be buffered.
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const FRAME_COUNT: usize = 4;
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// The size of each livestream frame in bytes.
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const FRAME_SIZE: usize = 1024 + HEADER_SIZE;
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// The size of the frame queue must be at least as large as the number of frame buffers. Every
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// allocated frame buffer should fit in the queue.
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const FRAME_QUEUE_SIZE: usize = FRAME_COUNT * 2;
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// Static storage used for a heapless::Pool of frame buffers.
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static mut FRAME_DATA: [u8; FRAME_SIZE * FRAME_COUNT] =
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[0; FRAME_SIZE * FRAME_COUNT];
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/// Represents the destination for the UDP stream to send data to.
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///
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/// # Miniconf
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/// `{"ip": <addr>, "port": <port>}`
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///
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/// * `<addr>` is an array of 4 bytes. E.g. `[192, 168, 0, 1]`
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/// * `<port>` is any unsigned 16-bit value.
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///
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/// ## Example
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/// `{"ip": [192, 168,0, 1], "port": 1111}`
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#[derive(Copy, Clone, Debug, MiniconfAtomic, Deserialize, Default)]
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pub struct StreamTarget {
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pub ip: [u8; 4],
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pub port: u16,
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}
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/// Specifies the format of streamed data
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#[repr(u8)]
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#[derive(Debug, Copy, Clone, PartialEq, IntoPrimitive)]
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pub enum StreamFormat {
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/// Reserved, unused format specifier.
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Unknown = 0,
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/// Streamed data contains ADC0, ADC1, DAC0, and DAC1 sequentially in little-endian format.
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///
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/// # Example
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/// With a batch size of 2, the serialization would take the following form:
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/// ```
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/// <ADC0[0]> <ADC0[1]> <ADC1[0]> <ADC1[1]> <DAC0[0]> <DAC0[1]> <DAC1[0]> <DAC1[1]>
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/// ```
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AdcDacData = 1,
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}
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impl From<StreamTarget> for SocketAddr {
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fn from(target: StreamTarget) -> SocketAddr {
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SocketAddr::new(
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IpAddr::V4(Ipv4Addr::new(
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target.ip[0],
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target.ip[1],
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target.ip[2],
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target.ip[3],
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)),
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target.port,
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)
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}
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}
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/// Configure streaming on a device.
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///
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/// # Args
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/// * `stack` - A reference to the shared network stack.
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///
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/// # Returns
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/// (generator, stream) where `generator` can be used to enqueue "batches" for transmission. The
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/// `stream` is the logically consumer (UDP transmitter) of the enqueued data.
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pub fn setup_streaming(
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stack: NetworkReference,
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) -> (FrameGenerator, DataStream) {
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// The queue needs to be at least as large as the frame count to ensure that every allocated
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// frame can potentially be enqueued for transmission.
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let queue =
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cortex_m::singleton!(: Queue<StreamFrame, FRAME_QUEUE_SIZE> = Queue::new())
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.unwrap();
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let (producer, consumer) = queue.split();
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let frame_pool =
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cortex_m::singleton!(: Pool<[u8; FRAME_SIZE]>= Pool::new()).unwrap();
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// Note(unsafe): We guarantee that FRAME_DATA is only accessed once in this function.
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let memory = unsafe { &mut FRAME_DATA };
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frame_pool.grow(memory);
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let generator = FrameGenerator::new(producer, frame_pool);
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let stream = DataStream::new(stack, consumer, frame_pool);
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(generator, stream)
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}
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#[derive(Debug)]
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struct StreamFrame {
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buffer: Box<[u8; FRAME_SIZE], Init>,
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offset: usize,
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}
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impl StreamFrame {
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pub fn new(
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buffer: Box<[u8; FRAME_SIZE], Uninit>,
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format: u8,
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buffer_size: u8,
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sequence_number: u32,
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) -> Self {
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let mut buffer = unsafe { buffer.assume_init() };
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buffer[0..2].copy_from_slice(&MAGIC_WORD.to_ne_bytes());
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buffer[2] = format;
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buffer[3] = buffer_size;
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buffer[4..8].copy_from_slice(&sequence_number.to_ne_bytes());
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Self {
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buffer,
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offset: HEADER_SIZE,
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}
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}
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pub fn add_batch<F, const T: usize>(&mut self, mut f: F)
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where
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F: FnMut(&mut [u8]),
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{
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f(&mut self.buffer[self.offset..self.offset + T]);
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self.offset += T;
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}
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pub fn is_full<const T: usize>(&self) -> bool {
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self.offset + T > self.buffer.len()
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}
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pub fn finish(&mut self) -> &[u8] {
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&self.buffer[..self.offset]
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}
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}
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/// The data generator for a stream.
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pub struct FrameGenerator {
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queue: Producer<'static, StreamFrame, FRAME_QUEUE_SIZE>,
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pool: &'static Pool<[u8; FRAME_SIZE]>,
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current_frame: Option<StreamFrame>,
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sequence_number: u32,
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format: u8,
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batch_size: u8,
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}
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impl FrameGenerator {
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fn new(
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queue: Producer<'static, StreamFrame, FRAME_QUEUE_SIZE>,
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pool: &'static Pool<[u8; FRAME_SIZE]>,
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) -> Self {
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Self {
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queue,
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pool,
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batch_size: 0,
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format: StreamFormat::Unknown.into(),
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current_frame: None,
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sequence_number: 0,
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}
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}
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/// Configure the format of the stream.
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///
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/// # Note:
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/// This function shall only be called once upon initializing streaming
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///
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/// # Args
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/// * `format` - The desired format of the stream.
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/// * `batch_size` - The number of samples in each data batch. See
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/// [crate::hardware::design_parameters::SAMPLE_BUFFER_SIZE]
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#[doc(hidden)]
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pub(crate) fn configure(&mut self, format: impl Into<u8>, batch_size: u8) {
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self.format = format.into();
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self.batch_size = batch_size;
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}
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/// Add a batch to the current stream frame.
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///
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/// # Args
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/// * `f` - A closure that will be provided the buffer to write batch data into. The buffer will
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/// be the size of the `T` template argument.
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pub fn add<F, const T: usize>(&mut self, f: F)
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where
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F: FnMut(&mut [u8]),
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{
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let sequence_number = self.sequence_number;
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self.sequence_number = self.sequence_number.wrapping_add(1);
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if self.current_frame.is_none() {
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if let Some(buffer) = self.pool.alloc() {
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self.current_frame.replace(StreamFrame::new(
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buffer,
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self.format as u8,
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self.batch_size,
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sequence_number,
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));
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} else {
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return;
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}
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}
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// Note(unwrap): We ensure the frame is present above.
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let current_frame = self.current_frame.as_mut().unwrap();
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current_frame.add_batch::<_, T>(f);
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if current_frame.is_full::<T>() {
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// Note(unwrap): The queue is designed to be at least as large as the frame buffer
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// count, so this enqueue should always succeed.
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self.queue
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.enqueue(self.current_frame.take().unwrap())
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.unwrap();
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}
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}
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}
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/// The "consumer" portion of the data stream.
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///
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/// # Note
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/// This is responsible for consuming data and sending it over UDP.
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pub struct DataStream {
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stack: NetworkReference,
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socket: Option<<NetworkReference as UdpClientStack>::UdpSocket>,
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queue: Consumer<'static, StreamFrame, FRAME_QUEUE_SIZE>,
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frame_pool: &'static Pool<[u8; FRAME_SIZE]>,
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remote: SocketAddr,
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}
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impl DataStream {
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/// Construct a new data streamer.
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///
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/// # Args
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/// * `stack` - A reference to the shared network stack.
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/// * `consumer` - The read side of the queue containing data to transmit.
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/// * `frame_pool` - The Pool to return stream frame objects into.
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fn new(
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stack: NetworkReference,
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consumer: Consumer<'static, StreamFrame, FRAME_QUEUE_SIZE>,
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frame_pool: &'static Pool<[u8; FRAME_SIZE]>,
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) -> Self {
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Self {
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stack,
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socket: None,
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remote: StreamTarget::default().into(),
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queue: consumer,
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frame_pool,
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}
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}
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fn close(&mut self) {
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if let Some(socket) = self.socket.take() {
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log::info!("Closing stream");
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// Note(unwrap): We guarantee that the socket is available above.
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self.stack.close(socket).unwrap();
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}
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}
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// Open new socket.
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fn open(&mut self) -> Result<(), ()> {
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// If there is already a socket of if remote address is unspecified,
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// do not open a new socket.
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if self.socket.is_some() || self.remote.ip().is_unspecified() {
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return Err(());
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}
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log::info!("Opening stream");
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let mut socket = self.stack.socket().or(Err(()))?;
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// Note(unwrap): We only connect with a new socket, so it is guaranteed to not already be
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// bound.
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self.stack.connect(&mut socket, self.remote).unwrap();
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self.socket.replace(socket);
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Ok(())
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}
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/// Configure the remote endpoint of the stream.
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///
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/// # Args
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/// * `remote` - The destination to send stream data to.
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pub fn set_remote(&mut self, remote: SocketAddr) {
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// Close socket to be reopened if the remote has changed.
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if remote != self.remote {
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self.close();
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}
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self.remote = remote;
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}
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/// Process any data for transmission.
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pub fn process(&mut self) {
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match self.socket.as_mut() {
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None => {
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// If there's no socket available, try to connect to our remote.
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if self.open().is_ok() {
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// If we just successfully opened the socket, flush old data from queue.
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while let Some(frame) = self.queue.dequeue() {
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self.frame_pool.free(frame.buffer);
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}
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}
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}
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Some(handle) => {
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if let Some(mut frame) = self.queue.dequeue() {
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// Transmit the frame and return it to the pool.
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self.stack.send(handle, frame.finish()).ok();
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self.frame_pool.free(frame.buffer)
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}
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}
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}
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}
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}
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