frame_store.h

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#pragma once
 
#include <array>
#include <atomic>
#include <cstddef>
#include <cstdint>
#include <optional>
 
#include <freertos/FreeRTOS.h>
#include <freertos/semphr.h>
#include <freertos/task.h>
 
#include "frame_slots.h"
 
struct FrameStoreStats {
    uint32_t published = 0;
    uint32_t dropped_no_slot = 0;
    uint32_t dropped_oversize = 0;
    uint32_t dropped_corrupt = 0;
};
 
class FrameStore final : public frames::SlotReleaser
{
public:
    static constexpr size_t kSlotBytes = 32 * 1024;
 
    bool begin();
 
    // Writer side (camera task only)
    std::optional<size_t> begin_write();
    uint8_t* write_buffer(size_t slot) { return buffers_[slot]; }
    void publish(size_t slot, const frames::FrameMeta& meta);
    void abort_write(size_t slot, frames::AbortReason reason);
 
    // Reader side (any task)
    std::optional<frames::FrameLease> acquire_latest();
    const uint8_t* data(const frames::FrameLease& lease) const { return buffers_[lease.slot()]; }
 
    static constexpr size_t kMaxSubscribers = 2;
 
    bool add_subscriber(TaskHandle_t task);
 
    void remove_subscriber(TaskHandle_t task);
 
    TaskHandle_t start_subscriber_task(TaskFunction_t entry, const char* name, uint32_t stack_bytes,
                                       UBaseType_t priority, BaseType_t core, void* arg);
 
    FrameStoreStats stats();
 
    bool ready() const { return ready_; }
 
    void release_slot(size_t slot) override;
 
private:
    frames::FrameSlots slots_;
    std::array<uint8_t*, frames::kSlotCount> buffers_{};
    SemaphoreHandle_t mutex_ = nullptr;
    std::array<std::atomic<TaskHandle_t>, kMaxSubscribers> subscribers_{};
    bool ready_ = false;
};