Design dynamic buffer

Signed-off-by: Petr Horacek <[email protected]>

instruments/traky/src/dynamic_buffer.rs

@@ -0,0 +1,116 @@
+//! Manipulate persistent buffers with lengths that are exceeding memory capacity.
+//!
+//! # Requirements
+//!
+//! * Can handle loops from 32 sample length up to tens of minutes.
+//! * Allows simultaneous playback and recording.
+//! * Recorded audio is being saved even while recording is in progress.
+//! * Can immediatelly jump to the beginning of the sample and start playing.
+//! * Saving and loading can be done in another routine.
+//!
+//! # Architecture
+//!
+//! * No pages are owned by the buffer.
+//! * Caller is responsible for:
+//!   * Providing new empty pages on request.
+//!   * Persisting returned buffers.
+//!   * Doing the two listed above with RT guarantees.
+//! * Each of the page contains:
+//!   * Fixed-size array of data.
+//!   * "Dirty" flag.
+//!   * Length of recorded data.
+//!   * Start address, relative to the parent sample.
+//!
+//! # Flow starting from fresh
+//!
+//! 1. Caller initializes empty page on Pool and passes Box to the buffer.
+//! 2. Buffer stores the Box in its struct.
+//! 3. Caller passes input audio, info about armed channels.
+//! 4. Buffer writes the audio into its active page and returns output audio.
+//! 5. Caller asks the buffer whether it is full, if it is, it takes its page and passes
+//!    a fresh one to it again.
+//! 6. Since this was the first page, caller stores it in its cache.
+//! 7. Caller passess the dirty page to SD save queue.
+//! 8. Buffer continues recording, until its full again, swaps the page.
+//! 9. Caller passes the dirty page to save queue.
+//! 10. This continues for some time, until position reset is triggered.
+//! 11. With reset armed, caller will force buffer to return its current buffer,
+//!     and it will pass a clone of the start page to it.
+//! 12. Caller recognizes that the next page is available on SD, it will send
+//!     a request for SD loader to pull it. It should be eventually available
+//!     in a loaded queue.
+//! 13. The loaded page is then passed to buffer instead of empty pages used before.
+//! 14. At some point, midway through the sample, recording stops.
+//! 15. Any new samples will be returned like before, except now they will not
+//!     be dirty and thus just thrown away.
+//!
+//! # Flow starting from a loaded sample
+//!
+//! 1. The caller recognizes there is a sample available and it reads its length.
+//! 2. The caller loads the first page, queues fetching of the second one, if there is one.
+//! 3. The caller passes the first page to the buffer.
+//! 4. Business as usual.
+//!
+//! # Working with samples shorter than a single page
+//!
+//! 1. Buffer gets an inpulse to reset midway through the first page.
+//! 2. The caller takes page from the buffer, clones it for save queue, clones it for
+//!    its own cache and passes it back to the buffer.
+//!
+//! # Optimizations
+//!
+//! * There may be a queue of empty pages, initialized in the background so they
+//!   are readily available.
+
+// const MINIMAL_BLOCK_LENGTH = 32;
+
+// type Frame = ((f32, f32), (f32, f32), (f32, f32), (f32, f32));
+
+struct DynamicBuffer {
+    // first_block: Block,
+    // // TODO: Keep moving blocks outside, so the dynamic buffer can be used
+    // // with reference to populated block while the other one is being populated.
+    // moving_blocks: (Block, Block),
+    // active_block: ActiveBlock,
+    // active_block_position: usize,
+    // sample_length: usize,
+}
+
+impl DynamicBuffer {
+    fn new() -> Self {
+        Self {}
+    }
+
+    fn load(&mut self) {}
+}
+
+// struct Block {
+//     length: (),
+//     buffer: (),
+// }
+
+// enum ActiveBlock {
+//     First,
+//     Low,
+//     High,
+// }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn full_end_to_end() {
+        let mut dynamic_buffer = DynamicBuffer::new();
+
+        let save_exists = true;
+        if save_exists {
+            dynamic_buffer.load();
+        }
+
+        // TODO: play two passes
+        // TODO: start recording while playing, pass input and say to which channels it should go
+        // TODO: stop recording
+        // TODO: play two passes, this time with recorded stuff too
+    }
+}

instruments/traky/src/lib.rs

@@ -1,5 +1,7 @@
 #![no_std]
 
+mod dynamic_buffer;
+
 use core::convert::TryFrom;
 use core::fmt;