Struct BufferPool 

pub(crate) struct BufferPool {
    pub(crate) bufs: Mutex<Vec<Vec<u8>>>,
    pub(crate) buf_size: usize,
}

Recycles outgoing frame buffers from dropped AudioFrames back to the capture thread, so the steady-state emit path allocates nothing.

INVARIANT: every buffer is born as vec![0u8; buf_size], so bytes [0, buf_size) stay initialized for the allocation’s whole lifetime — truncate only shortens len, never de-initializes memory. That is what makes restore’s set_len back to buf_size sound.

Fields

bufs: Mutex<Vec<Vec<u8>>>

buf_size: usize

Implementations

impl BufferPool

pub(crate) const MAX_POOLED: usize = 16

Cap on pooled buffers. Outstanding frames rarely exceed the delivery-ring capacity plus a few Python-held references; anything past this goes back to the allocator rather than growing the pool unboundedly.

pub(crate) fn new(buf_size: usize) -> Self

Create an empty pool that hands out (and accepts) buf_size-byte buffers.

pub(crate) fn restore(&self, v: Vec<u8>) -> Vec<u8>

Restore a recycled buffer to full buf_size length via set_len.

Sound per the pool invariant: the bytes were written at allocation and truncation does not de-initialize them, so extending len back to buf_size never exposes uninitialized memory.

pub(crate) fn put(&self, v: Vec<u8>)

Return a buffer to the pool, unless it is undersized or the pool is already at MAX_POOLED (in which case it is dropped to the allocator).

pub(crate) fn drain_into(&self, into: &mut Vec<Vec<u8>>)

Move every pooled buffer into into under a single lock — the batched refill for the sole-consumer PoolTaker, whose empty local stash is into.