74 lines
2.6 KiB
C++
74 lines
2.6 KiB
C++
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// nisps/core/event_queue.hpp — same-thread, batch-drain FIFO for engine
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// output events (NoteOn/NoteOff/Clock/CC, ...).
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//
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// This is NOT a replacement for RingBuffer (nisps/core/ring_buffer.hpp).
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// RingBuffer is an atomics-based SPSC channel for genuine cross-thread /
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// cross-core hand-off (its own header: "the inter-core hand-off can wrap
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// this OR use queue_t directly"). Sequencer engines push events from inside
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// `process()` and the mode layer drains them via `pop_events()` right after
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// — same call chain, same thread, never concurrent — so there is nothing to
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// synchronize. Reusing RingBuffer here would add atomic load/store traffic
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// to the audio-hot `process()` path for no correctness benefit, and would
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// still need a wrapping loop to get the "drain up to N in one call" batch
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// shape `pop_events()` callers rely on (RingBuffer::try_pop is one element
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// at a time). EventQueue is deliberately the plain, non-atomic version of
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// that shape.
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//
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// Extracted from the byte-for-byte-identical event-queue member blocks
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// previously duplicated in nisps/engines/breakor.hpp and
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// nisps/engines/elysiamorf.hpp (2026-07 simplification audit, finding L8).
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#pragma once
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#include <array>
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#include <cstddef>
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#include <span>
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#include <type_traits>
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#include "perf.hpp"
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namespace nisps {
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template <typename T, std::size_t N>
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class EventQueue {
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static_assert(N > 0u, "EventQueue capacity must be > 0");
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static_assert(std::is_trivially_copyable_v<T>,
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"EventQueue element type must be trivially copyable");
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public:
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static constexpr std::size_t capacity() noexcept { return N; }
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// Enqueues one event. Drops silently on overflow (matches the engines'
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// original push_event behaviour — a full event queue on a stalled
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// consumer should not stall or branch the audio-hot producer).
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NISPS_FORCE_INLINE void push(const T& e) noexcept {
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if (count_ >= N) return;
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buf_[write_] = e;
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write_ = (write_ + 1u) % N;
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++count_;
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}
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// Drains up to `out.size()` queued events into `out`. Returns the number
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// actually copied.
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std::size_t pop(std::span<T> out) noexcept {
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std::size_t n = 0u;
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while (n < out.size() && count_ > 0u) {
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out[n++] = buf_[read_];
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read_ = (read_ + 1u) % N;
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--count_;
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}
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return n;
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}
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std::size_t size() const noexcept { return count_; }
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bool empty() const noexcept { return count_ == 0u; }
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private:
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std::array<T, N> buf_{};
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std::size_t read_ = 0u;
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std::size_t write_ = 0u;
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std::size_t count_ = 0u;
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};
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} // namespace nisps
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